JPH115366A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material having excellent light fastness or particularly light fastness to a basic white, and simultaneously excellent manufacturing suitability by rapid coating suitability. SOLUTION: In the thermal recording material comprising an undercoating layer, thermal recording layer and protective layer sequentially provided on a support, the undercoating layer contains gelatin and water swelling synthetic mica. The mica is desirably water swelling fluoro-mica. And, the recording layer has at least one of a thermal recording layer containing electron donative dye precursor and electron acceptive compound, and a thermal color developing layer containing diazonium salt compound and coupler reacted with the salt compound to color. And, the support is preferably a sheet support laminated with polyethylene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having improved light fastness.

[0002]

2. Description of the Related Art Thermal recording has recently been developed because its recording apparatus is simple, highly reliable, and requires no maintenance. As the heat-sensitive recording material, those utilizing a reaction between an electron-donating dye precursor and an electron-accepting compound,
Those utilizing a reaction between a diazonium salt compound and a coupler are widely known. In recent years, as a heat-sensitive recording material, researches on (1) improvement in characteristics such as color density and color sensitivity (2) robustness of a color former have been earnestly conducted. However, the heat-sensitive recording material has a drawback that when exposed to sunlight for a long time or when posted for a long time in an office or the like, the background portion is colored by the light or the image portion is discolored or faded. I was Various methods have been proposed to improve the coloring of the background portion and the discoloration and fading of the image portion, but a sufficient effect has not always been obtained.

Further, a water-soluble polymer layer such as polyvinyl alcohol is used as an undercoat layer provided between the support and the heat-sensitive recording layer. This water-soluble polymer layer such as polyvinyl alcohol has good oxygen barrier properties, and can be expected to have an effect of reducing photo-coloring of the background. However, since polyvinyl alcohol has high water absorbency and hygroscopicity, the drying load when applying an undercoat layer solution on a support to produce an undercoat layer is large, and it is produced in terms of high-speed applicability of a heat-sensitive recording material. There was a problem with the properties.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material which is excellent in light fastness, especially in a white background, and is excellent in suitability for production by high-speed coating suitability.

[0005]

An object of the present invention is to provide a heat-sensitive recording material comprising a support having thereon an undercoat layer, a heat-sensitive recording layer, and a protective layer in this order, wherein the undercoat layer is gelatin- and water-swellable. This is achieved by a heat-sensitive recording material characterized by containing synthetic mica. Further, the heat-sensitive recording layer is a heat-sensitive recording layer A containing an electron-donating dye precursor and an electron-accepting compound, and a heat-sensitive coloring layer B containing a diazonium salt compound and a coupler that reacts with the diazonium salt compound to form a color. It is desirable to have at least one layer of The aspect ratio of the water-swellable synthetic mica is preferably 100 or more. Further, when a paper support laminated with polyethylene is used as the support, the oxygen barrier properties of the present invention are high, which is preferable.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a heat-sensitive recording material comprising a support having an undercoat layer, a heat-sensitive recording layer, and a protective layer in this order, wherein the undercoat layer comprises gelatin and water-swellable synthetic mica. contains. The support used in the present invention may be transparent or opaque. Examples of the transparent support include, for example, polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate film, polyolefin films such as polystyrene films, polypropylene films, and polyethylene films, polyimide films, and polyvinyl chloride films. And synthetic polymer films such as polyvinylidene chloride film, polyacrylic acid copolymer film and polycarbonate film.

In addition to the above-mentioned synthetic polymer film, paper, synthetic paper, paper having a plastic resin layer, and the like can be used. The undercoat layer containing the water-swellable synthetic mica of the present invention,
When the support is a support having a plastic resin layer, a particularly remarkable effect is exhibited. As the paper having a plastic resin, it is preferable that the thermoplastic resin is formed on both sides of the base paper, or at least the surface on which the recording layer is formed. Examples of such a support include, for example, (1) a base paper having a thermoplastic resin melt-extruded and coated thereon, and (2) a base paper having a melt-extruded thermoplastic resin coated thereon with a gas barrier layer. (3) a base paper to which a plastic film having low oxygen permeability is adhered, (4) a base paper to which a thermoplastic resin is provided by melt extrusion on the surface of the base paper to which the plastic film is adhered, (5) ) A method in which a thermoplastic resin is melt-extruded on a base paper and then coated with a plastic film.

[0008] As the thermoplastic resin to be melt-extruded and coated on the base paper, an olefin resin such as polyethylene,
A homopolymer of α-olefin such as polypropylene and a mixture of these various polymers, or a random copolymer of ethylene and vinyl alcohol are desirable. Examples of polyethylene include LPDE (low density polyethylene),
HDPE (high-density polyethylene), L-LPDE (linear low-density polyethylene) and the like can be used.

As a method of laminating the base paper and the plastic film, a known lamination method as described in "Handbook of New Laminating Processes" edited by Processing Technology Research Group can be appropriately selected and adopted, but what is called Desirable are dry lamination, solvent-free dry lamination, dry lamination using an electron beam or ultraviolet curable resin, or hot dry lamination.

The undercoat layer provided on the support contains at least gelatin and water-swellable synthetic mica. Here, as the water-swellable synthetic mica usable in the present invention,
General formula A (B, C) _2-5 D ₄ O ₁₀ (OH, F, O)
₂ [where A is any of K, Na, and Ca, B and C are any of FeII, FeIII, Mn, Al, Mg, and V, and D is Si or Al. ] Mica group.

In the above mica group, Na tetrasilyl
Kumai Mica NaMg_2.5(Si_FourO _Ten) F_Two, Na or
Li teniolite (Na, Li) Mg_TwoLi (Si_FourO
_Ten) F_Two, Montmorillonite Na or Li hectra
Light (Na, Li)_1/8Mg _{twenty five}Li_1/8(Si
_FourO_Ten) F_TwoWater swellable fluorine mica is useful.

The aspect ratio of the water-swellable synthetic mica used in the present invention is 50 or more, preferably 100 or more, particularly preferably 200 or more. The aspect ratio is the ratio of the thickness to the major axis of the particle. The greater the aspect ratio, the greater the effect of oxygen barrier properties.

The average particle diameter of the water-swellable synthetic mica used in the present invention is 0.3 to 20 μm, preferably 0.5 to 10 μm, and particularly preferably 1 to 5 μm.
The average thickness of the mica particles is 0.1 μm or less, preferably 0.05 μm or less, particularly preferably 0.0 μm or less.
It is 1 μm or less.

As the gelatin used for the undercoat layer, particularly, an alkali-treated gelatin having a low isoelectric point and a gelatin such as a derivative gelatin (for example, phthalated gelatin) having an amino group reacted are desirable.

The content of the water-swellable synthetic mica is 1 to 1000 parts by weight, more preferably 5 to 300 parts by weight, based on 100 parts by weight of gelatin. If the content of the water-swellable synthetic mica is less than 1 part by weight, the undercoat layer will not function sufficiently as an oxygen barrier layer, and if it is more than 1000 parts by weight, the applicability such as applicability will deteriorate. The thickness of the undercoat layer is 0.05 to 5 μm, preferably 0.1 to 2 μm.
It is.

When the undercoat layer contains the water-swellable synthetic mica particles having a high spectral ratio as described above together with gelatin in the undercoat layer, the undercoat layer functions particularly as an oxygen barrier layer, and Is less light colored, the moisture content of the heat-sensitive recording material is low, and the storage stability in a product form is good.

As the color-forming component used in the heat-sensitive recording layer, conventionally known color-forming components can be used. In the heat-sensitive recording material of the present invention, a material utilizing a reaction between a diazonium salt compound and a coupler, and an electron-emitting material, Those utilizing a reaction between a donor colorless dye and an electron accepting compound are also preferable,
The compound used in the heat-sensitive recording layer containing a diazonium salt compound and a coupler which reacts with the diazonium salt compound when heated to form a color, is a diazonium salt compound, a coupler capable of reacting with the diazonium salt compound to form a dye, and Basic substances that promote the reaction between the diazonium salt compound and the coupler are exemplified. The diazonium salt compound is a compound represented by the following, and can control the maximum absorption wavelength depending on the position and type of the substituent in the Ar portion.

[0018]

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[0019] Ar is an aryl group, X ^- represents an acid anion.

Specific examples of the diazonium salt compound 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-octyloxyobenzenediazonium, 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-te
acid anion salts such as rt-amylphenoxy) butyryl) piperazino) benzenediazonium, 2,5-dibutoxy-4-tolylthiobenzenediazonium, 3- (2-octyloxyethoxy) -4-morpholinobenzenediazonium; Diazonium salt compound D-1
~ 5. Particularly, hexafluorophosphate salt, tetrafluoroborate salt and 1,5-naphthalene sulfonate salt are preferable.

[0021]

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Among these diazonium salt compounds, particularly preferred compounds in the present invention are 300 to 400.
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, 2,5-dibutoxy-4- (N- (2-ethylhexanoyl) piperazino) Benzenediazonium, 2,5-diethoxy-4-
(N- (2- (2,4-di-tert-amylphenoxy) butyryl) piperazino) benzenediazonium and the compounds shown in the above specific examples D-3 to D-5. The maximum absorption wavelength of the diazonium salt compound as referred to herein is a spectrophotometer (Shimazu MPS-200) obtained by coating each compound with a coating film of 0.1 g / m ² to 1.0 g / m ^2.
0).

Examples of the couplers used in the present invention, which react with the diazonium salt upon heating to give a color, include resorcinol, flurgurcine, and 2,3-dihydroxynaphthalene-6.
Sodium 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-octylacetate Acetanilide, 1-phenyl-3-methyl-5-pyrazolone, 1-
(2′-octylphenyl) -3-methyl-5-pyrazolone, 1- (2 ′, 4 ′, 6′-trichlorophenyl)
-3-benzamide-5-pyrazolone, 1- (2 ',
4 ', 6'-trichlorophenyl) -3-anilino-5
-Pyralone, 1-phenyl-3-phenylacetamido-5-pyrazolone, and the following compounds C-1 to C-6. These couplers can be used in combination of two or more to obtain a desired color hue.

[0024]

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The basic substance in the heat-sensitive recording layer includes, in addition to an inorganic or organic basic compound, a compound which decomposes upon heating to release an alkaline substance. Representatives are organic ammonium salts, organic amines, amides, ureas and thioureas and their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles , Morpholines,
Examples include nitrogen-containing compounds such as piperidines, amidines, formazines, and pyridines. Specific examples of these include tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine,
Allyl urea, thiourea, methyl thiourea, allyl thiourea, ethylene thiourea, 2-benzylimidazole, 4
-Phenylimidazole, 2-phenyl-4-methylimidazole, 2-undecylimidazoline, 2,4,5
-Trifuryl-2-imidazoline, 1,2-diphenyl-4,4-dimethyl-2-imidazoline, 2-phenyl-2-imidazoline, 1,2,3-triphenylguanidine, 1,2-dicyclohexylguanidine, 1, 2,
3-tricyclohexylguanidine, guanidine trichloroacetate, N, N'-dibenzylpiperazine, 4,
4'-dithiomorpholine, morpholinium trichloroacetate, 2-aminobenzothiazole, 2-benzoylhydrazinobenzothiazole and the like. These can be used in combination of two or more.

As the electron-donating dye used in the present invention, an electron-donating dye precursor can be used. Examples of the precursor include a triarylmethane compound, a diphenylmethane compound, a thiazine compound, a xanthene compound, and spiropyran. And triarylmethane compounds and xanthene compounds are particularly useful because of their high color density. To illustrate some of these,
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-methylindol-3-yl) phthalide, 3- (o-methyl-p
-Diethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 4,4'-bis (dimethylamino) benzhydrin benzyl ether, N-halophenylleucouramine, N-2,4,5 -Trichlorophenylleuco auramine, rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine-B- (p-chloroanilino) lactam, 2-benzylamino-6-diethylaminofluoran, 2-anilino-6 -Diethylaminofluoran, 2
-Anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-cyclohexylmethylaminofluoran, 2-anilino-3-methyl-6
-Isoamylethylaminofluoran, 2- (o-chloroanilino) -6-diethylaminofluoran, 2-octylamino-6-diethylaminofluoran, 2-ethoxyethylamino-3-chloro-2-diethylaminofluoran, 2- Anilino-3-chloro-6-diethylaminofluoran, benzoylleucomethylene blue,
p-Nitrobenzyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-benzylspirodinaphthopyran, 3-propyl-spiro-dibenzopyran And the like.

Examples of the electron accepting compound include a phenol derivative, a salicylic acid derivative, and a hydroxybenzoic acid ester. Particularly, bisphenols and hydroxybenzoates are preferred. Some examples of these include 2,2-bis (p-hydroxyphenyl) propane (ie, bisphenol A), 4,4 ′-(p-phenylenediisopropylidene) diphenol (ie, bisphenol P), 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 salts, 3,5-di (tert-butyl) salicylic acid and its polyvalent metal salts, 3-α, α- Dimethylbenzyl salicylic acid and its polyvalent metal salts, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-hydroxybenzoic acid
2-ethylhexyl, p-phenylphenol, p-cumylphenol and the like can be mentioned.

As the sensitizer, a low-melting organic compound having an aromatic group and a polar group in the molecule is preferable.
benzyl p-benzyloxybenzoate, α-naphthyl benzyl ether, β-naphthyl benzyl ether, β-
Naphthoic acid phenyl ester, α-hydroxy-β-naphthoic acid phenyl ester, β-naphthol- (p-chlorobenzyl) ether, 1,4-butanediol phenyl ether, 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-ethylphenyl ether, 1,4-butanediol-m-methylphenyl ether, 1-phenoxy-2- (p-tolyloxy) ethane, 1-phenoxy-2- (p-ethylphenoxy) ) Ethane, 1-phenoxy-2- (p-chlorophenoxy) ethane, p-benzylbiphenyl and the like.

In the present invention, the above-mentioned diazonium salt compound, a coupler which reacts with the diazonium salt compound when heated to form a color, a basic substance, and a colorless electron-donating dye, an electron-accepting compound, and a sensitizer Is not particularly limited. (1) a method using solid dispersion, (2) a method using emulsification dispersion, (3) a method using polymer dispersion, (4) a method using latex dispersion,
(5) There is a method of microencapsulation and the like, and among these, the method of microencapsulation is particularly preferable from the viewpoint of storage stability. Particularly, in a color system using a reaction between a diazonium salt compound and a coupler, When the diazonium salt compound is microencapsulated, it is preferable to microencapsulate the electron donating colorless dye in a color forming system utilizing the reaction between the electron donating colorless dye and the electron accepting compound.

In the present invention, the above-mentioned heat-sensitive recording layers may be laminated, and a multi-color heat-sensitive recording material can be obtained by changing the hue of each heat-sensitive recording layer. Although the layer configuration is not particularly limited, it is particularly preferable that the layers having different photosensitive wavelengths have different wavelengths.
Thermal recording using two types of diazonium salt compounds, two thermosensitive recording layers combining couplers that react with each diazonium salt compound when heated to develop different colors, and a thermosensitive recording layer combining an electron-donating colorless dye and an electron-accepting compound. A multicolor heat-sensitive recording material in which layers are laminated is preferred. That is, a thermosensitive recording layer A containing an electron-donating colorless dye and an electron-accepting compound on a support, a diazonium salt compound having a maximum absorption wavelength of 360 ± 20 nm, and a coupler which reacts with the diazonium salt compound when heated to give a color. Thermosensitive recording layer B-1 containing a diazonium salt compound having a maximum absorption wavelength of 400 ± 20 nm and a thermosensitive recording layer B-2 containing a coupler which reacts with the diazonium salt compound when heated to form a color. A color heat-sensitive recording material is desirable.

In the recording method of this multicolor heat-sensitive recording material, first, the heat-sensitive recording layer B-2 is heated to develop the diazonium salt compound and the coupler contained in the layer. Then 400 ± 20
After irradiating light of nm to decompose the unreacted diazonium salt compound contained in the heat-sensitive recording layer B-2, sufficient heat is applied to the heat-sensitive recording layer B-1 to develop a color, and The contained diazonium salt compound and the coupler are colored. At this time, the heat-sensitive recording layer B-2 is also strongly heated, but does not develop color because the diazonium salt compound has already been decomposed and the color-forming ability has been lost. 360 ± 20
The diazonium salt compound contained in the heat-sensitive recording layer B-1 is decomposed by irradiating light with a wavelength of nm, and finally, sufficient heat for the heat-sensitive recording layer A to develop color is applied to develop the color. At this time, the heat-sensitive recording layers B-2 and B-1 are also strongly heated at the same time, but do not develop color because the diazonium salt compound has already been decomposed and the coloring ability has been lost.

Further, a multicolor thermosensitive recording in which three thermosensitive recording layers in which three kinds of diazonium salt compounds having different photosensitive wavelengths and a coupler which reacts with each of the diazonium salt compounds upon heating and develops a different hue are combined is laminated. Materials are also preferred. That is, the heat-sensitive recording layer A-1 containing a diazonium salt compound having a maximum absorption wavelength of 350 nm or less, preferably 340 nm or less, and a coupler that reacts with the diazonium salt compound when heated to form a color on the support. A thermosensitive recording layer B-1 containing a diazonium salt compound having a wavelength of 360 ± 20 nm and a coupler which reacts with the diazonium salt compound when heated to form a color, and has a maximum absorption wavelength of 400 ± 2
A multicolor heat-sensitive recording material in which a diazonium salt compound having a thickness of 0 nm and a heat-sensitive recording layer B-2 containing a coupler which reacts with the diazonium salt compound when heated to form a color is preferably laminated.
In these examples, a full-color image can be recorded by selecting the coloring hues of each heat-sensitive recording layer so as to be three primary colors, yellow, magenta, and cyan in the subtractive color mixing.

When laminating thermosensitive coloring layers having different hues, an intermediate layer for preventing color mixing or the like can be provided between the thermosensitive recording layers. In the intermediate layer, as a water-soluble polymer compound, for example, polyvinyl alcohol, modified polyvinyl alcohol, methyl cellulose, sodium polystyrene sulfonate, styrene-maleic acid copolymer,
Those composed of gelatin and / or zetiran derivatives, polyethylene glycol and / or polyethylene glycol derivatives are desirable. In addition, by including an inorganic layered compound in the intermediate layer, mass transfer between layers is suppressed.
Prevention prevents color mixing, and suppresses supply of oxygen, thereby improving raw storability and color image storability.

In the present invention, it is desirable to provide a protective layer containing a pigment, a release agent and the like on the heat-sensitive recording layer in order to protect the heat-sensitive recording layer from sticking and solvents. An inorganic layered compound containing mica or the like may be used as a pigment in the protective layer, but other pigments may be used in combination. Examples of such pigments include calcium oxide, zinc oxide, titanium oxide, aluminum hydroxide, kaolin, synthetic silicate, amorphous silica, and urea formalin resin powder.

In the heat-sensitive recording material of the present invention, a light transmittance adjusting layer can be provided. The light transmittance adjusting layer contains a component that functions as a precursor of an ultraviolet absorber, and does not function as an ultraviolet absorber before irradiation with light having a wavelength in a region necessary for fixing. When the fixing type thermosensitive recording layer is fixed, the wavelength in the region required for fixing is sufficiently transmitted, and the transmittance of visible light is high, so that there is no trouble in fixing the thermosensitive recording layer.

The precursor of the ultraviolet absorber is converted into an ultraviolet absorber by reacting with light or heat after light irradiation of a wavelength necessary for fixing of the light fixing type heat-sensitive recording layer by light irradiation is completed. As a result, most of the light in the wavelength range necessary for fixing in the ultraviolet region is absorbed by the ultraviolet absorber, the transmittance is reduced, and the light resistance of the heat-sensitive recording material is improved. Because there is no absorption effect,
The visible light transmittance is not substantially changed.

At least one light transmittance adjusting layer can be provided in the light-fixing type heat-sensitive recording material. Most preferably, it is formed between the light-fixing type heat-sensitive recording layer and the protective layer. The rate adjusting layer may be used also as the protective layer.

By changing the hue of each heat-sensitive recording layer in the heat-sensitive recording layer, a multi-color heat-sensitive recording material can be obtained.
That is, a full-color image can be recorded by selecting the coloring hues of the respective heat-sensitive recording layers so as to be three primary colors, yellow, magenta, and cyan in the subtractive color mixing. In this case, the coloring mechanism of the heat-sensitive recording layer directly laminated on the support surface (the lowermost layer of the heat-sensitive recording layer) is not limited to the combination of the electron-donating dye and the electron-accepting dye. Any of a diazo coloring system, a base coloring system that forms a color by contacting with a basic compound, a chelating coloring system, and a coloring system that reacts with a nucleophile to cause a desorption reaction to form a color from a coupler that reacts with a diazonium salt to form a color. Alternatively, two heat-fixable heat-sensitive recording layers each containing a diazonium salt compound having a different maximum absorption wavelength and a coupler that reacts with the diazonium salt compound to form a color may be provided on the heat-sensitive recording layer. It is desirable to sequentially provide a transmittance adjusting layer and a protective layer.

In the present invention, as an example of the precursor of the ultraviolet absorber contained in the light transmittance adjusting layer, the following general formula 1 is given.

[0040]

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In the above general formula 1, m represents 1 or 2. A represents —SO ₂ —R, —CO—R, when m = 1 in the general formula (1) and in the general formulas (2) to (4).
_{-CO 2 -R, -CONH-R,} -POR 1 R 2, -C
H ₂ R ₃ or —SiR ₄ R ₅ R ₆ , wherein R
Represents an alkyl group or an aryl group, R ₁ and R ₂ represent an alkoxy group, an aryloxy group, an alkyl group or an aryl group, R ₃ represents a phenyl group substituted by at least one nitro group or methoxy group, R ₄ , R _{4 5} and R ₆ represent an alkyl group or an aryl group, and m = 2 in the general formula (1).
A represents -SO ₂ R ₇ SO _2- , -CO-, -CO
_{CO -, - COR 7 CO -} , - SO 2 - or -SO-
And R ₇ represents an alkylene group or an arylene group.

X is represented by the general formulas (1), (3) and (4).
Hydrogen, alkyl, alkoxy, aryl
In general formula (2),
Alkylene group, -OR₇ O- or -OCOR₇ CO_Two 
Represents-. W is in general formulas (1), (2) and (4)
Represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl
In the general formula (3), the group or the halogen atom is represented by-
OR ₇ O- or -OCOR₇ CO_Two Represents-. Y is one
In general formulas (1), (2) and (3), a hydrogen atom,
Alkyl group, alkoxy group, aryl group or halogen source
Is represented by -OR in the general formula (4).₇O-, -OC
OR₇ CO_Two -, -CH_Two CH_Two CO_Two R₇ OCOCH
_Two CH_Two -, -CH_Two CH_Two OCOR₇ CO_Two CH_Two C
H_Two -Or -CH_Two CH_Two CON (R₈ ) R₇ N (R
₈ ) COCH_Two CH_Two -Is R₈ Is a hydrogen atom or al
Represents a kill group. Z is a hydrogen atom, a halogen atom, an alkyl
Represents a group or an alkoxy group.

Of the above substituents, the alkyl group may be linear or branched, and may have an unsaturated bond.
Further, these alkyl groups may be substituted with an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an aryl group, a hydroxy group, or the like. The aryl group may be further substituted with an alkyl group, an alkoxy group, or a halogen atom.

Of the above substituents, the alkylene group may be linear or branched, and may contain an unsaturated bond, an oxygen atom, a sulfur atom, or a nitrogen atom. The alkylene group may be further substituted with an alkoxy group, a hydroxy group, an aryloxy group, or an aryl group.

Of the above substituents, the arylene group may be further substituted with an alkyl group, an alkoxy group, a halogen atom, or the like.

Among the substituents represented by X, Y and W, a hydrogen atom, an alkyl group having 1 to 18 carbon atoms,
To 18 alkoxy groups, 6 to 18 carbon atoms, aryl groups, fluorine atoms, chlorine atoms, and bromine atoms are preferred. Among them, particularly preferred are a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, and a 1 to 1 carbon atom. Twelve alkoxy groups, phenyl groups or chlorine atoms are preferred.

Among the substituents represented by Z, a hydrogen atom, a chlorine atom, a fluorine atom, an alkyl group having 1 to 12 carbon atoms, and an alkoxy group having 1 to 12 carbon atoms are preferable. , Chlorine atom, 1-6 carbon atoms
And an alkoxy group having 1 to 6 carbon atoms is preferred.

Among the substituents represented by R, those having 1 carbon atom
Preferred are an alkyl group having 18 to 18 carbon atoms and an aryl group having 6 to 18 carbon atoms, and among these, an alkyl group having 1 to 12 carbon atoms and an aryl group having 6 to 12 carbon atoms are particularly preferred.

Of the substituents represented by R ₁ and R ₂ ,
An alkoxy group having 1 to 12 carbon atoms, 6 to 1 carbon atoms
An aryloxy group of 2, an alkyl group having 1 to 12 carbon atoms, and an aryl group having 6 to 12 carbon atoms are preferable.

Among the substituents represented by R ₃ , 2-nitrophenyl, 3,5-dimethoxyphenyl, 3,4,4
A 5-trimethoxyphenyl group is preferred.

Among the substituents represented by R ₄ , R ₅ and R ₆ , an alkyl group having 1 to 12 carbon atoms and a carbon atom having 6 carbon atoms
~ 12 aryl groups are preferred. Among them, an alkyl group having 1 to 8 carbon atoms and a phenyl group are particularly preferable.

The compound represented by the general formula 1 can be used in the following forms: (1) a method of using a solid dispersion, (2) a method of emulsifying and dispersing, (3) a method of dispersing a polymer, (4) Latex dispersed method, (5)
Although there is a method of microencapsulation and the like, it is particularly preferable to use emulsified dispersion or microencapsulation.

As a method of emulsifying and dispersing, first, the compound represented by the general formula 1 is dissolved in oil. The oil may be solid or liquid at room temperature or a polymer. Low-boiling co-solvents such as acetate, methylene chloride, cyclohexanone and / or phosphates, phthalates, acrylates, methacrylates, other carboxylates, fatty acid amides, alkylated biphenyls, alkylated terphenyls, Examples thereof include alkylated naphthalene, diarylethane, chlorinated paraffin, alcohol, phenol, ether, monoolefin, and epoxy. Specific examples include tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, tricyclohexyl phosphate, dibutyl phthalate, dioctyl phthalate, dilaurate phthalate,
Dicyclohexyl phthalate, butyl olefin, diethylene glycol benzoate, dioctyl sebacate, dibutyl sebacate, dioctyl adipate, trioctyl trimellitate, acetyl triethyl citrate, octyl maleate, dibutyl maleate, isoamyl biphenyl, chlorinated paraffin, diisopropyl naphthalene 1,1,1′-ditolylethane, 2,4-dita-
High-boiling oils such as shariamylphenol, N, N-dibutyl-2-butoxy-5-tert-octylaniline, 2-ethylhexyl hydroxybenzoate, and polyethylene glycol, among which alcohols and phosphates are particularly preferred. System, carboxylic acid ester system, alkylated biphenyl, alkylated terphenyl, alkylated naphthalene, and diarylethane are preferred. Furthermore, hindered phenol,
An anti-carbonizing agent such as hindered amine may be added. Further, as the oil using the compound of the general formula 1, oil having an unsaturated fatty acid is particularly desirable, and examples thereof include α-methylstyrene dimer. The α-methylstyrene dimer includes, for example, MSD100 (trade name of Mitsui Toatsu Chemical).

An oil solution containing the compound of the above general formula 1 is added to an aqueous solution of a water-soluble polymer, and emulsified and dispersed using a colloid mill, a homogenizer, or ultrasonic waves. As the water-soluble polymer used at this time, a water-soluble polymer such as polyvinyl alcohol is used, but an emulsion or latex of a hydrophobic polymer may be used in combination. As the water-soluble polymer, polyvinyl alcohol,
Silanol-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amino-modified polyvinyl alcohol, itaconic acid-modified polyvinyl alcohol, styrene-maleic anhydride copolymer, butadiene maleic anhydride copolymer, ethylene maleic anhydride copolymer, isobutylene maleic anhydride copolymer Examples include polymers, polyacrylamide, polystyrenesulfonic acid, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, and gelatin. At this time, a conventionally known surfactant or the like may be added as necessary.

As a method for microencapsulation of the diazonium salt compound or the compound of the general formula 1, a conventionally known microcapsule method can be used. That is, a diazonium salt compound or a compound of the general formula 1 and a microcapsule wall precursor are dissolved in a water-insoluble or insoluble organic solvent, added to an aqueous solution of a water-soluble polymer, and emulsified and dispersed using a homogenizer or the like. Then, the polymer substance which becomes the microcapsule wall when the temperature is raised can be prepared by forming a wall film on the oil / water interface. Specific examples of the high molecular substance serving as the wall film of the microcapsules include, for example, polyurethane resin, polyurea resin, polyamide resin,
Examples include polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-acrylate copolymer resin, styrene-methacrylate copolymer resin, gelatin, and polyvinyl alcohol. Among these, a particularly preferred wall material is a microcapsule having a wall film made of a polyurethane / polyurea resin.

Microcapsules having a wall film made of a polyurethane / polyurea resin are prepared by mixing a microcapsule wall precursor such as polyvalent isocyanate in a core material to be encapsulated, and emulsifying the mixture in an aqueous solution of a water-soluble polymer such as polyvinyl alcohol. It is produced by dispersing, raising the liquid temperature and causing a polymer forming reaction at the oil droplet interface.

Here, some specific examples of the polyvalent isocyanate compound are shown below. For example, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-
Tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,
3'-diphenylmethane-4,4'-diisocyanate, xylene-1,4-diisocyanate, 4,4'-
Diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,
Diisocyanates such as 2-diisocyanate, cyclohexylene-1,2-diisocyanate and cyclohexylene-1,4-diisocyanate; 4,4 ', 4 "-triphenylmethane triisocyanate; toluene-2,
Triisocyanates such as 4,6-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2 ',
Tetraisocyanates such as 5,5'-tetraisocyanate, adducts of hexamethylene diisocyanate and trimethylolpropane, adducts of 2,4-tolylenediisocyanate and trimethylolpropane, and xylylenediisocyanate and trimethylolpropane Isocyanate prepolymers such as adducts and adducts of tolylene diisocyanate and hexanetriol, and the like. If necessary, two or more kinds can be used in combination. Of these, particularly preferred are those having three or more isocyanate groups in the molecule.

In the microencapsulation method, as the organic solvent for dissolving the diazonium salt compound or the compound represented by the general formula 1, oils shown by emulsification and dispersion can be used. The same applies to a water-soluble polymer.

The particle size of the microcapsules is 0.1 to 1.0
μm is preferred, and more preferably in the range of 0.2 to 0.7 μm.

In the present invention, the following known antioxidants can be used in order to further improve the light fastness. For example, EP-A-310551,
German Patent No. 3435443, European Patent No. 310552, Japanese Patent Application Laid-Open No. 3-121449.
JP-A-59-41616, JP-A-2-262654, JP-A-2-71262, JP-A-63-163351, U.S. Pat. No. 4,814,262, and JP-A-54-48535. ,
JP-A-5-61166, JP-A-5-119449
No., US Pat. No. 4,980,275, JP-A-63
JP-A-113536, JP-A-62-262047, EP-A-223239, EP-A-309402, and EP-A-309401.
Specifically, the following are mentioned.

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[0062]

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Further, it is also effective to use various additives already known as heat-sensitive recording materials and pressure-sensitive recording materials. Some of these antioxidants are described in JP-A-60-12.
No. 5,470, JP-A-60-125471, JP-A-60-125472, JP-A-60-2874
No. 85, JP-A-60-287486, JP-A-60-287487, JP-A-62-146680
JP, JP-A-60-287488, JP-A-60-287488
JP-A-282885, JP-A-63-89877, JP-A-63-88380, JP-A-63-08
JP-A-8381, JP-A-01-239282, JP-A-04-291885, JP-A-04-2916
No. 84, JP-A-05-188687, JP-A-05-188686, JP-A-05-110490
JP, JP-A-05-1108437, JP-A-05-1108437
JP-A-5-170361, JP-A-63-203372, JP-A-63-224789, JP-A-63-267594, JP-A-63-182484, JP-A-60-107384 JP-A-60-1
07383, JP-A-61-160287,
JP-A-61-185483, JP-A-61-2111
No. 079, JP-A-63-251282, JP-A-63-051174, JP-B-48-04329.
No. 4, JP-B-48-033212 and the like.

Specific examples include 6-ethoxy-1-phenyl-
2,2,4-trimethyl-1,2-dihydroquinoline,
6-ethoxy-1-octyl-2,2,4-trimethyl-1,2-dihydroquinoline, 6-ethoxy-1-phenyl-2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline, 6-ethoxy-1-octyl-2,
2,4-trimethyl-1,2,3,4-tetrahydroquinoline, nickel cyclohexanoate, 2,2-bis-4
-Hydroxyphenylpropane, 1,1-bis-4-hydroxyphenyl-2-ethylhexane, 2-methyl-
4-methoxy-diphenylamine, 1-methyl-2-phenylindole. These antioxidants are
It can be added to the heat-sensitive recording layer or the intermediate layer, the light transmittance adjusting layer, and the protective layer.

[0066]

EXAMPLES In this example, "parts" means "parts by weight" unless otherwise specified. Example 1 Preparation of Undercoat Layer After mixing 8 parts of water-swellable synthetic mica (trade name: Somasif ME100, manufactured by Corp Chemical) with 92 parts of water, the mixture was wet-dispersed with a biscomil and mica having an average particle diameter of 2.0 μm. A dispersion was obtained. To 100 parts of this dispersion was added 150 parts of water, and the mixture was mixed uniformly. Then, while keeping the temperature at 40 ° C. and stirring, 100 parts of an aqueous 1.5% alkali-treated gelatin solution was added.
20 parts of sodium (4-nonylphenoxytrioxyethylene) butylsulfonate were added to prepare a mica-containing undercoat liquid. The mica-containing undercoat layer is continuously applied onto a photographic paper support obtained by laminating polyethylene on a high-quality paper at a speed of 60 m / min so that the solid content is 2.0 g / m ^2. Was provided.

Preparation of Solution A for Thermosensitive Recording Layer ( Preparation of Capsule Solution for Electron-donating Dye Precursor) Crystal violet lactone as electron-donating dye precursor
0 parts were dissolved in 20 parts of ethyl acetate, and 20 parts of alkylnaphthalene, which is a high boiling point solvent, was added, and the mixture was heated and uniformly mixed. As a capsule wall material, 20 parts of an xylylene diisocyanate / trimethylolpropane adduct was further added to this solution, and the mixture was stirred uniformly. Separately, 54 parts of a 6% by weight aqueous solution of gelatin were prepared, and the above-mentioned electron-donating dye precursor solution was added thereto, followed by emulsification and dispersion with a homogenizer.
After 68 parts of water was added to the obtained emulsion to homogenize it, the temperature was raised to 50 ° C. with stirring, and an encapsulation reaction was performed for 3 hours to obtain a desired capsule liquid. The average particle size of the capsule is 1.6
μm.

(Preparation of Electron-Accepting Compound Dispersion) As an electron-accepting compound, 30 parts of bisphenol A was added to gelatin 4
It was added to 150 parts by weight of an aqueous solution and dispersed by a ball mill for 24 hours to prepare a dispersion. The average particle size of the electron-accepting compound in the dispersion was 1.2 μm.

(Preparation of Coating Liquid) Next, the above-mentioned capsule solution of the electron-donating dye precursor and the dispersion liquid of the electron-accepting compound were adjusted so that the ratio of the electron-donating dye precursor / electron-accepting compound was 1/2. The mixture was mixed to prepare a target coating solution.

Preparation of Solution B for Thermosensitive Recording Layer ( Preparation of Capsule Solution for Diazonium Salt Compound) As the diazonium salt compound, 4- (N- (2- (2,4-di-te) was used.
Dissolve 2.0 parts of rt-amylphenoxy) butyryl) piperazinobenzenediazonium hexafluorophosphate in 20 parts of ethyl acetate, add 20 parts of alkylnaphthalene, which is a high-boiling point solvent, and heat to mix uniformly. did. As a capsule wall material, 15 parts of an adduct of xylylene diisocyanate / trimethylolpropane was further added to this solution, and the mixture was stirred uniformly. Separately, 54 parts of a 6% by weight aqueous solution of gelatin were prepared, the above diazonium salt compound solution was added, and the mixture was emulsified and dispersed with 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 an encapsulation reaction was performed for 3 hours to obtain a desired capsule liquid. The average particle size of the capsule is 1.1 μm
Met.

(Preparation of coupler emulsion) 2 parts of 1- (2′-octylphenyl) -3-methyl-5-pyrazolone, 2 parts of 1,2,3-triphenylguanidine, 1,1- ( 2 parts of p-hydroxyphenyl) -2-ethylhexane, 4 parts of 4,4 ′-(p-phenylenediisopropylidene) diphenol, 2-ethylhexyl-
4-hydroxybenzoate 4 parts, tricresyl phosphate 0.3 part, diethyl maleate 0.1 part, 70%
1 part of a calcium dodecylbenzenesulfonate methanol solution is dissolved in 10 parts of ethyl acetate, and this solution is added to 80 parts of an 8% aqueous gelatin solution and emulsified with a homogenizer for 10 minutes. Then, ethyl acetate is removed to obtain a desired emulsion. Obtained.

(Preparation of Coating Solution) Next, the above-mentioned diazonium salt compound capsule solution and coupler dispersion were mixed so that the ratio of the diazonium salt compound to the coupler was 2/3 to prepare a desired coating solution. Preparation of Sensitizing Recording Layer C Solution ( Preparation of Diazonium Salt Compound Capsule Solution) As a diazonium salt compound, 3.0 parts of 2,5-dibutoxy-4-tolylthiobenzenediazonium hexafluorophosphate was dissolved in 20 parts of ethyl acetate. Further, 20 parts of alkylnaphthalene, which is a high boiling point solvent, was added, and the mixture was heated and uniformly mixed. As a capsule wall material, 15 parts of an adduct of xylylene diisocyanate / trimethylolpropane was further added to this solution, and the mixture was stirred uniformly. Separately, 54 parts of a 6% by weight aqueous solution of gelatin were prepared, the above diazonium salt compound solution was added, and the mixture was emulsified and dispersed with 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 an encapsulation reaction was performed for 3 hours to obtain a desired capsule liquid. The average particle size of the capsule was 1.0 μm.

(Preparation of Coupler Dispersion) 2 parts of 2-chloro-5- (3- (2,4-di-tert-pentyl) phenoxypropylamino) acetoacetanilide as a coupler, 1,2,3-triphenylguanidine Two copies,
1, l- (p-hydroxyphenyl) -2-ethylhexane 2 parts, 4,4 '-(p-phenylenediisopropylidene) diphenol 4 parts, 2-ethylhexyl-4-hydroxybenzoate 4 parts, tricresyl 0.3 part of phosphate, 0.1 part of diethyl maleate and 1 part of a 70% calcium methanol solution of dotesylbenzenesulfonate are dissolved in 10 parts of ethyl acetate, and this solution is added to 80 parts of an 8% aqueous gelatin solution and homogenized. After emulsification for 10 minutes, ethyl acetate was removed to obtain a target emulsion.

(Preparation of Coating Liquid) Next, the above-mentioned diazonium salt compound capsule liquid and coupler dispersion liquid were mixed so that the ratio of diazonium salt compound / coupler became 4/5, to prepare a target coating liquid.

Adjustment of Light Transmittance Adjusting Layer ( Adjustment of Ultraviolet Absorber Precursor Capsule Solution)
0 parts, as an ultraviolet absorber precursor [2-allyl-6-
(2H-benzotriazol-2-yl) -4-t-octylphenyl] benzenesulfonate 10 parts, 2,5
-Di-t-octyl-hydroquinone 3 parts, tricresyl phosphate 2 parts, α-methylstyrene dimer 4
Parts were dissolved. As a capsule wall material, 20 parts of an xylylene diisocyanate / trimethylolpropane adduct was further added to this solution, and the mixture was stirred uniformly. Separately, 200 parts of an 8% aqueous solution of itaconic acid-modified polyvinyl alcohol was prepared, and the ultraviolet absorbent precursor solution was added thereto, followed by emulsification and dispersion with a homogenizer. After 120 parts of water was added to the obtained emulsion to homogenize it, the temperature was raised to 40 ° C. while stirring,
The encapsulation reaction was carried out for a time to obtain a desired capsule liquid.
The average particle size of the capsule was 0.3 μm.

(Preparation of Coating Solution) To 100 parts of the capsule solution of the above-mentioned ultraviolet absorbent precursor was added 10 parts of a 2% aqueous solution of sodium [4-nonylphenoxytrioxyethylene] butylsulfonate. I got Preparation of Intermediate Layer Solution To 100 parts of a 10% aqueous gelatin solution, 2 parts of 2% sodium (4-nonylphenoxytrioxyethylene) butylsulfonate was added to prepare an intermediate layer solution.

Preparation of protective layer solution 5.0% ethylene-modified polyvinyl alcohol aqueous solution 61
2.0 parts by weight of a 20.5% zinc stearate dispersion (Hydrin F115, manufactured by Chukyo Yushi Co., Ltd.)
(4-Nonylphenoxytrioxyethylene) 8.4 parts of an aqueous solution of sodium butyl sulfonate, 8.0 parts of a fluorine-based release agent (ME-313, manufactured by Daikin Co., Ltd.), and 0.5 part of flour starch are added and uniformly stirred. Then, a PVA solution was prepared.
Separately, 20% by weight chaogross (Shiraishi Industry Co., Ltd.) aqueous solution 1
2.5 parts, 10% by weight polyvinyl alcohol (PVA1
05: Kuraray Co., Ltd.) 1.25 parts, 2% by weight aqueous solution of sodium dodecylsulfonate 0:39 parts were mixed and dispersed by Dynomill to prepare a pigment liquid. 4.4 parts of the pigment liquid was added to 80 parts of the PVA liquid to obtain a protective layer liquid.

Coating of heat-sensitive recording layer On a photographic paper support laminated with a polyethylene provided with a mica-containing undercoat layer, a heat-sensitive recording layer A, an intermediate layer, a heat-sensitive recording layer B, an intermediate layer, a heat-sensitive recording layer C, The light transmittance adjusting layer and the protective layer are successively applied in order of 7 layers at a coating speed of 60 m / min in the order of 30 ° C.-30% and 40 ° C.-30%.
And dried under the same conditions to obtain a multicolor heat-sensitive recording material. The coating amount of the solid content was 6.0 g / m ^{2 for} the heat-sensitive recording layer A, and 3 for the intermediate layer.
0 g / m ^2, the heat-sensitive recording layer B6.0g / m ^2, the intermediate layer 3.
0 g / m ^2, the heat-sensitive recording layer C5.0g / m ^2, the light transmittance adjusting layer 3.0 g / m ^2, was coated to a protective layer 1.5 g / m ^2.

Evaluation of performance of heat-sensitive recording material (measurement of moisture content) After application of heat-sensitive recording layer, 10 cm × 5 c
The sample was sampled to a size of m, placed in a weighing bottle, and weighed. After heating at 100 ° C. for 3 hours, it was weighed again, and the moisture content of the heat-sensitive recording material was calculated using the weight loss as the water content. Moisture content (%) = (weight before heating-weight after heating) 重量 weight before heating (Evaluation of storability in product form) A thermosensitive recording material is cut into A5 size, and 20 sheets are made into one set. The sample was placed in an aluminum moisture-proof bag, sealed, and used as a sample for evaluating the storage stability. After treating this sample at 55 ° C. for 24 hours and at 50 ° C. for 10 days, the coloring of the background was measured with an X-rite densitometer. (Evaluation of light resistance) The heat-sensitive recording material was heated to a luminescence center wavelength of 365 n.
After fixing for 15 seconds under an ultraviolet lamp of m, the sample was irradiated with a xenon lamp and a fluorescent lamp (320001 ux) for 48 hours, and the degree of coloring of the background was measured with an X-rite densitometer.

Comparative Example 1 The procedure of Example 1 was repeated except that a photographic paper support laminated with polyethylene without an undercoat layer was used as the support in “Application of the heat-sensitive recording layer” in Example 1.
In the same manner as in the above, a multicolor heat-sensitive recording material was produced.

[Comparative Example 2] Preparation of Undercoat Layer 2% (4%)
10 parts of sodium nonylphenoxytrioxyethylene) butylsulfonate was added to prepare a gelatin undercoating solution. The above gelatin undercoating solution was continuously coated on a photographic paper support obtained by laminating polyethylene on a high-quality paper at a speed of 60 m / min so that the coating amount of solids was 2.0 g / m ² , and a gelatin undercoat layer was formed. Provided. A thermosensitive recording layer was coated on the photographic paper support laminated with polyethylene provided with a gelatin undercoat layer under the same conditions as in Example 1 to obtain a multicolor thermosensitive recording material.

[Comparative Example 3] Preparation of undercoat layer 5% polyvinyl alcohol (PVA117, manufactured by Kuraray)
To 100 parts of the aqueous solution, 10 parts of 2% sodium (4-norylphenoxytrioxyethylene) butylsulfonate was added to prepare a PVA undercoat liquid. The PVA undercoat liquid is continuously applied at a rate of 60 m / min on a photographic paper support obtained by laminating polyethylene on wood free paper at a rate of 60 m / min so that the applied amount of solid content is 2.0 g / m ^2. Provided. A thermosensitive recording layer was applied under the same conditions as in Example 1 on a photographic paper support on which polyethylene having a PVA undercoat layer was laminated to obtain a multicolor thermosensitive recording material.

[Comparative Example 4] "Preparation of undercoat layer" 6% polyvinyl alcohol (PVA)
105, Kuraray Co., Ltd.) and 100 parts of an aqueous solution were mixed with 12 parts of 2% sodium (4-nonylphenoxytrioxyethylene) butylsulfonate to prepare a PVA undercoat liquid.
The above-mentioned PVA undercoating solution was coated on a photographic paper support obtained by laminating polyethylene on wood free paper, and the solid content applied amount was 2.0 g.
/ M ² was continuously applied at a speed of 60 m / min to provide a PVA undercoat layer. A thermosensitive recording layer was applied under the same conditions as in Example 1 on a photographic paper support on which polyethylene having a PVA undercoat layer was laminated to obtain a multicolor thermosensitive recording material.

Comparative Example 5 Preparation of Undercoat Layer 5% Itaconic Acid-Modified Polyvinyl Alcohol (KL-11
8, Kuraray) 3 parts of polyamide ebichlorohydrin resin (Wetmaster 500, manufactured by Toho Chemical) and 10 parts of sodium 2% (4-nonylphenoxytrioxyethylene) butylsulfonate are added to 100 parts of an aqueous solution.
A VA undercoat solution was prepared. The PVA undercoating liquid was applied to a photographic paper support obtained by laminating polyethylene on a high-quality paper so as to have a solid content of 2.0 g / m ² for 60 m.
/ Min., And a PVA undercoat layer was provided. A thermosensitive recording layer was applied on the photographic paper support laminated with polyethylene having the PVA undercoat layer under the same conditions as in Example 1 to obtain a multicolor thermosensitive recording material.

Table 1 summarizes the results of the evaluation of the heat-sensitive recording materials.

[Table 1]

From the results shown in Table 1, the mere gelatin subbing layer does not improve the light coloring of the background. In addition, the undercoat layer of PVA has a sufficient effect of improving the light coloring of the background,
The moisture content of the recording material after application is high, the moisture content does not decrease even if the drying temperature is increased, and the storage stability when packaged in a product form is not good. By providing the mica-containing undercoat layer of the present invention as an oxygen barrier layer, light coloring of the background is small,
In addition, a heat-sensitive recording material having low moisture content of the recording material and good storage stability in a product form can be obtained.

[0087]

As described above, according to the present invention, the dispersibility of gelatin and mica is good, the suitability for high-speed coating of the undercoat layer coating solution is excellent, and the undercoat layer containing gelatin and mica is excellent. The heat-sensitive recording material has good light resistance, no coloring of the background portion, and good storage stability in a product form.

Claims (4)

[Claims] 1. A thermosensitive recording material comprising a support having thereon an undercoat layer, a heat-sensitive recording layer, and a protective layer in this order, wherein the undercoat layer contains gelatin and water-swellable synthetic mica. Heat-sensitive recording material. 2. The heat-sensitive recording material according to claim 1, wherein the water-swellable synthetic mica has an aspect ratio of 100 or more. 3. The heat-sensitive recording layer A comprises a heat-sensitive recording layer A containing an electron-donating dye precursor and an electron-accepting compound, and a diazonium salt compound and a coupler which reacts with the diazonium salt compound to form a color. 3. The image forming apparatus according to claim 1, further comprising at least one thermosensitive coloring layer.
2. The heat-sensitive recording material according to item 1. 4. The heat-sensitive recording material according to claim 1, wherein the support comprises a paper support laminated with polyethylene.