JP2002307827A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material of high quality without material deformation having the capability of preventing a curling due to an environmental change or the application of heat during recording from occurring and making its use applications in a wide range of industrial fields. SOLUTION: This thermal recording material has at least a thermal recording layer formed on one of the surfaces of a support and a back coat layer on the other surface. This back coat layer is of a multi-layer structure with the outermost layer, farthest from the support of the back coat layer, containing a polyvinyl alcohol. In addition, the outermost layer preferably contains a water swelling synthetic mica.

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 excellent curl resistance.

[0002]

2. Description of the Related Art A thermosensitive recording material for recording an image by applying heat with a thermal head or the like is relatively inexpensive, and its recording apparatus is simple and highly reliable, and requires no maintenance. In recent years, in particular, higher performances such as higher image quality and storage stability have been achieved.

On the other hand, the thermosensitive recording material is in a state where the balance of the elongation of the layers on the front and back of the thermosensitive recording material is lost due to an environmental change such as humidity or the application of heat during recording, and the thermosensitive recording material is curled toward one surface. In other words, there is a quality problem of causing curling. In particular, it was remarkably recognized in a multi-layer multi-color heat-sensitive recording material in which a plurality of heat-sensitive recording layers having different coloring hues were laminated. Such curling,
Even if high performance such as high image quality and storage stability is achieved, the product quality as a recording material is significantly impaired.

[0004] In order to prevent the curling as described above, the heat-sensitive recording material includes a heat-sensitive recording layer, a protective layer, and the like.
A back coat layer is provided on the surface (back surface) of the support on the side where the heat-sensitive recording layer and the like are not provided. For example, JP-A-8
JP-A-282112 discloses a technique in which a single-layered backcoat layer is provided on a support, and the layer contains an inorganic layered compound. Indeed, by providing a layer containing an inorganic layered compound on the surface opposite to the side having the heat-sensitive recording layer, curling of the entire recording material is suppressed to some extent, but curling in a low humidity environment cannot be completely prevented, The recording material was deformed in a curl shape, and there was a problem in quality of the recording material. Further, even a multicolor heat-sensitive recording material having a multilayered thick recording layer tends to curl, and there is a problem in maintaining flatness.

[0005] In particular, in recent years, in which various forms of imaging techniques are provided and colorization of images is increasingly regarded as important, along with high performance such as high image quality and storage stability, recording media It is necessary that the quality of the material itself be stable without being impaired. Further, the application range may be limited by curling.

[0006]

As described above, curling due to environmental changes such as humidity during use and the like and heat applied during recording can be avoided, and there is no deterioration in quality due to deformation of the material, so that it can be applied to a wide range of fields. At present, heat-sensitive recording materials have not been provided yet.

An object of the present invention is to solve the above conventional problems and achieve the following objects. That is, the present invention prevents curling due to environmental changes and heat application during recording, and has high quality without material deformation, especially in a multicolor heat-sensitive recording material comprising a sheet material or a multilayer, and is applicable to a wide range of fields. It is an object to provide a heat-sensitive recording material.

[0008]

Means for solving the above problems are as follows. <1> In a heat-sensitive recording material having at least a heat-sensitive recording layer on one surface of a support and a backcoat layer on the other surface, the backcoat layer is composed of multiple layers, and The heat-sensitive recording material is characterized in that the separated outermost layer contains polyvinyl alcohol.

<2> The thermosensitive recording material according to <1>, wherein the outermost layer of the back coat layer farthest from the support further contains an inorganic layered compound. <3> The thermosensitive recording material according to <2>, wherein the inorganic layered compound is synthetic mica. <4> The thermosensitive recording material according to <3>, wherein the synthetic mica is a synthetic mica having an aspect ratio of 100 or more.

<5> The heat-sensitive recording material according to any one of <1> to <4>, wherein the layer located between the outermost layer of the back coat layer and the support contains gelatin.

<6> a recording layer comprising the electron-donating dye precursor and an electron-accepting compound which reacts with the electron-donating dye precursor to form a color, a diazonium salt compound and the diazonium salt The thermosensitive recording material according to any one of <1> to <5>, further comprising: a recording layer containing a compound that reacts with a compound to form a color. <7> The thermosensitive recording material according to any one of <1> to <6>, wherein the support is a paper support on which at least one surface is laminated with polyethylene.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-sensitive recording material of the present invention has a multi-layered back coat layer on the surface of the support on which the heat-sensitive recording layer is not provided, and is most distant from the support of the back coat layer. The outermost layer contains polyvinyl alcohol. Hereinafter, the heat-sensitive recording material of the present invention will be described in detail. In addition, in this specification, polyvinyl alcohol means polyvinyl alcohol and / or modified polyvinyl alcohol.

The heat-sensitive recording material of the present invention has at least a heat-sensitive recording layer on one surface of a support, and may be composed of a single layer or a plurality of layers. Etc., and also has a multi-layered back coat layer on the surface on the other side,
It may have another layer as needed.

(Backcoat layer) The backcoat layer is formed by laminating two or more layers, and the outermost layer farthest from the support (hereinafter, may be simply referred to as the "outermost back layer"). One layer or two or more layers (hereinafter sometimes referred to as “intermediate back layer”) located between the outermost layer and the support.

<Outermost Back Layer> The outermost back layer contains at least polyvinyl alcohol as a binder and, if necessary, other components. For example, in a humidity environment biased to low humidity / high humidity, a large amount of water is easily released or absorbed as water vapor in a layer in contact with the air. In this case, if the expansion and contraction balance of both surfaces of the support is lost, one of the two is lost. The curl tends to occur on the side, especially in the case of a multicolor heat-sensitive recording material composed of multiple layers, the degree of water absorption and release is large between the side having the multilayer heat-sensitive recording layer and the side not having the layer. The contraction balance is more likely to be lost, and may be greatly deformed. However, a multi-layer back coat layer is provided on the surface (rear surface) on the side not having the heat-sensitive recording layer, and polyvinyl alcohol is contained in the outermost layer, so that the moisture retained in the layer adjacent to the outermost layer can be minimized. It can be blocked by the outer layer, which blocks the movement of moisture in the layer due to the change in humidity in the air, and makes it easier to maintain the contraction balance between the front and back. Although this is easily promoted during thermal recording, it is also useful for maintaining the balance of shrinkage between the front and back sides by applying heat.

Examples of the modified polyvinyl alcohol include carbonyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, and ethylene-modified polyvinyl alcohol.

The degree of saponification of the polyvinyl alcohol and / or modified polyvinyl alcohol used in the present invention is preferably at least 88% from the viewpoint of curling prevention.
More preferably, it is 97% or more.

The coating amount of the polyvinyl alcohol in the outermost back layer is preferably from 0.3 to 5.3 g / m ² . By setting the content within the above range, preferable curl characteristics can be obtained.

The outermost back layer preferably further contains an inorganic layered compound. As the inorganic layered compound, the following general formula (1) A (B, C) _2-3 D ₄ O ₁₀ (OH, F, O) ₂ (1) wherein A is K, Na or Ca And B and C independently represent Fe (II), Fe (III), Mn, Al, M
g and V are represented. D represents Si or Al. A talc represented by 3MgO.4SiO ₂ .H ₂ O;
Examples include teniolite, montmorillonite, saponite, hectorite, and zirconium phosphate.

[0020] In micas represented by the general formula (1), as natural mica, for example muscovite, soda mica, phlogopite, biotite, lepidolite, and the like, as synthetic mica, fluorine phlogopite KMg ₃ Non-swelling mica such as (AlSi ₃ O ₁₀ ) F ₂ , potassium tetrasilicic mica KMg _2.5 (Si ₄ O ₁₀ ) F ₂ ,
And Na tetrasilicic mica NaMg _2.5 (Si ₄ O
_{1 0)} F _2, Na or Li taeniolite (Na, L
_{i) Mg 2 Li (Si 4} O 10) F 2, montmorillonite series of Na or Li hectorite _{(Na, Li) 1/3 Mg 2} /3
Swellable mica such as Li _1/3 (Si ₄ O ₁₀ ) F ₂ . Furthermore, synthetic smectites are also useful. In the present invention, among the layered compounds, water-swellable synthetic mica is preferable, and swellable fluorine-based synthetic mica is particularly preferable.

The aspect ratio of the inorganic layered compound is preferably 20 or more, more preferably 100 or more, and particularly preferably 200 or more. When the aspect ratio is 1
If it is less than 00, moisture movement in the layer cannot be shielded and curling may not be effectively prevented. If it is more than 200, a particularly large effect is obtained in terms of curling prevention. Here, the aspect ratio is a ratio of the thickness of the layered compound particle to the major axis.

The average particle diameter of the inorganic layered compound is preferably 0.3 to 20 μm, more preferably 0.5 to 10 μm, and more preferably 1 to 5 μm. Particularly preferred. The average thickness of the layered compound is preferably 0.1 μm or less,
It is more preferably at most 0.05 μm, particularly preferably at most 0.01 μm.

The content of the inorganic layered compound in the outermost back layer is preferably 3 to 30 parts by mass, more preferably 5 to 20 parts by mass, based on 100 parts by mass of polyvinyl alcohol. By setting the content of the inorganic layered compound within the above range, it is possible to maintain the balance of shrinkage between the front and back of the heat-sensitive recording material, sufficiently prevent curling, and have good manufacturing suitability such as applicability. Becomes

In the outermost back layer, the content ratio (mass ratio; x) of the inorganic layered compound (x) to the binder (y)
/ Y) is preferably from 3/100 to 20/100. When the content ratio is within the above range, the balance of shrinkage between the front and back of the heat-sensitive recording material can be maintained, and curling can be sufficiently prevented. Even when a plurality of types of inorganic layered compounds are used, the total amount is preferably within the above range of the mass ratio.

-Other components- The outermost back layer contains a pigment, a metal soap, a wax, a water-proofing agent and the like within a range that does not impair the effects of the present invention in terms of running properties during recording and the like. Is also good. The pigment is not particularly limited, for example, kaolin, calcined kaolin, talc, fluorite, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, zinc oxide, lithopone, amorphous silica, colloidal silica, Calcined stone, silica, magnesium carbonate, titanium oxide, alumina, barium carbonate, barium sulfate, mica, micro balloon,
Examples include urea-formalin fillers, polyester particles, and cellulose fillers.

Examples of the metal soap include higher fatty acid polyvalent metal salts, and specific examples thereof include zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

The wax has a melting point of 40 to 40.
120 ° C., for example, paraffin wax,
Polyethylene wax, carnauba wax, microcrystalline wax, canderia wax, montan wax, fatty acid amide-based wax and the like are preferable, and paraffin wax having a melting point of 50 to 100 ° C, montan wax, and methylol stearamide are more preferable. The content of the wax in the heat-sensitive recording layer is preferably from 5 to 200 parts by weight, more preferably from 20 to 150 parts by weight, per 100 parts by weight of the electron-donating colorless dye.

Examples of the water-proofing agent include water-soluble initial condensates such as N-methylol urea, N-methylol melamine, and urea-formalin; dialdehyde compounds such as glyoxal and glutaraldehyde; and inorganic crosslinking such as boric acid and borax. And heat-treated blends of polyacrylic acid, methyl vinyl ether-maleic acid copolymer, isobutylene-maleic anhydride copolymer, and the like.

When coated on the support, a surfactant may be contained from the viewpoint of obtaining a uniform layer. Examples of the surfactant include a sulfosuccinic acid-based alkali metal salt and fluorine. Preferred surfactants include, for example,
Specifically, sodium salts and ammonium salts such as di- (n-hexyl) sulfosuccinic acid and di- (2-ethylhexyl) sulfosuccinic acid are preferred, and anionic surfactants are preferred.

The thickness of the outermost back layer is 0.3
To 6 μm, more preferably 0.5 to 3 μm.
By setting the thickness of the outermost back layer to 0.3 to 6 μm, the balance of shrinkage between the front and back of the heat-sensitive recording material can be maintained, and curling can be sufficiently prevented.

<Intermediate Back Layer> The intermediate back layer contains at least a water-soluble binder, and may contain other components as necessary. By providing the intermediate back layer, the shrinkage balance is further improved, and curling of the heat-sensitive recording material can be effectively prevented.

As the water-soluble binder, for example,
Vinyl acetate-acrylamide copolymer, silicon-modified polyvinyl alcohol, starch, modified starch, methylcellulose,
Carboxymethylcellulose, hydroxymethylcellulose, gelatin, gum arabic, casein, styrene-maleic acid copolymer hydrolyzate, styrene-maleic acid copolymer half ester hydrolyzate, isobutylene-
Maleic anhydride copolymer hydrolyzate, polyacrylamide derivative, polyvinylpyrrolidone, water-soluble polymers such as polystyrene sodium sulfonate, sodium alginate and styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex And a water-insoluble polymer such as vinyl acetate emulsion, and other components include a latex and a waterproofing agent. Especially, it is preferable to use gelatins.

The thickness of the intermediate back layer is 2 to 1
5 μm is preferable, and 4 to 10 μm is more preferable. By setting the thickness of the intermediate back layer to 2 to 15 μm, the balance of shrinkage between the front and back of the heat-sensitive recording material can be sufficiently maintained, and curling can be sufficiently prevented.

The outermost back layer and the intermediate back layer are prepared by preparing a coating solution for forming the outermost back layer or the intermediate back layer (a coating solution for the outermost back layer and a coating solution for the intermediate back layer), respectively. It can be formed thereon by, for example, coating using a known coating method. In this case, the coating solution for the outermost back layer and the coating solution for the intermediate back layer may be simultaneously applied, or the coating solution for the intermediate back layer may be applied and dried, and then the outermost back layer may be coated on the layer. The liquid may be formed by applying and drying.

Examples of the known coating method include a coating method using an air knife coater, a roll coater, a blade coater, a curtain coater or the like.

(Thermosensitive Recording Layer) The thermosensitive recording layer contains a coloring component and, if necessary, other components such as a binder and a base. As the color-forming component, (1) a combination of a diazonium salt compound and a coupler that forms a color by coupling reaction with the diazonium salt compound, (2) reacting with the electron-donating dye precursor and the electron-donating dye precursor. Suitable examples include a combination with an electron-accepting compound that forms a color.

[Diazonium Salt Compound] Examples of the diazonium salt compound include compounds represented by the following formula (2). Ar—N ₂ ⁺ X ⁻ (2) wherein Ar represents an aromatic moiety, and X ⁻ represents an acid anion. ]

The diazonium salt compound is a compound which undergoes a coupling reaction with a coupler described below by heating to form a color and is decomposed by light. These can control the maximum absorption wavelength depending on the position and type of the substituent in the Ar portion.

Specific examples of the salt-forming diazonium include 4- (p-tolylthio) -2,5-dibutoxybenzenediazonium and 4- (4-chlorophenylthio)-
2,5-dibutoxybenzenediazonium, 4- (N,
N-dimethylamino) benzenediazonium, 4-
(N, N-diethylamino) benzenediazonium, 4
-(N, N-dipropylamino) benzenediazonium, 4- (N-methyl-N-benzylamino) benzenediazonium, 4- (N, N-dibenzylamino) benzenediazonium, 4- (N-ethyl-N -Hydroxyethylamino) benzenediazonium, 4- (N, N-
Diethylamino) -3-methoxybenzenediazonium, 4- (N, N-dimethylamino) -2-methoxybenzenediazonium, 4- (N-benzoylamino)-
2,5-diethoxybenzenediazonium, 4-morpholino-2,5-dibutoxybenzenediazonium, 4-
Anilinobenzenediazonium, 4- [N- (4-methoxybenzoyl) amino] -2.5-diethoxybenzenediazonium, 4-pyrrolidino-3-ethylbenzenediazonium, 4- [N- (1-methyl-2- ( 4-methoxyphenoxy) ethyl) -N-hexylamino]-
2-hexyloxybenzenediazonium, 4- [N-
(2- (4-methoxyphenoxy) ethyl) -N-hexylamino] -2-hexyloxybenzenediazonium, 2- (1-ethylpropyloxy) -4- [di-
(Di-n-butylaminocarbonylmethyl) amino] benzenediazonium, 2-benzylsulfonyl-4-
[N-methyl-N- (2-octanoyloxyethyl)] aminobenzenediazonium and the like.

The maximum absorption wavelength λmax of the diazonium salt compound is preferably 450 nm or less,
440 nm is more preferred. By setting the λmax within the above range, the raw storability, image fixability, image storability, and hue of cyan color can be improved in combination with a coupler described below.

The diazonium salt compound preferably has 12 or more carbon atoms, a solubility in water of 1% or less, and a solubility in ethyl acetate of 5% or more. The diazonium salt compound may be used alone, or two or more diazonium salt compounds may be used in combination depending on the purpose of hue adjustment or the like.

Among the above diazonium salt compounds, diazonium salt compounds represented by the following structural formulas (1) to (4) are more preferable in terms of hue of dye, image storability and image fixability.

[0043]

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In the structural formula (1), Ar represents a substituted or unsubstituted aryl group. As the substituent, an alkyl group, an alkoxy group, an alkylthio group, an aryl group, an aryloxy group, an arylthio group, an acyl group, an alkoxycarbonyl group, a carbamoyl group, a carboxamide group, a sulfonyl group, a sulfamoyl group, a sulfonamide group, a ureido group, Examples thereof include a halogen group, an amino group, and a heterocyclic group, and these substituents may be further substituted.

The aryl group represented by Ar is
An aryl group having 6 to 30 carbon atoms is preferable, for example,
Phenyl group, 2-methylphenyl group, 2-chlorophenyl group, 2-methoxyphenyl group, 2-butoxyphenyl group, 2- (2-ethylhexyloxy) phenyl group, 2
-Octyloxyphenyl group, 3- (2,4-di-t-
Pentylphenoxyethoxy) phenyl group, 4-chlorophenyl group, 2,5-dichlorophenyl group, 2,4,6
-Trimethylphenyl group, 3-chlorophenyl group, 3-
Methylphenyl group, 3-methoxyphenyl group, 3-butoxyphenyl group, 3-cyanophenyl group, 3- (2-ethylhexyloxy) phenyl group, 3,4-dichlorophenyl group, 3,5-dichlorophenyl group, 3,4 -Dimethoxyphenyl group, 3- (dibutylaminocarbonylmethoxy) phenyl group, 4-cyanophenyl group, 4-methylphenyl group, 4-methoxyphenyl group,

4-butoxyphenyl, 4- (2-ethylhexyloxy) phenyl, 4-benzylphenyl, 4-aminosulfonylphenyl, 4-N, N-dibutylaminosulfonylphenyl, 4-ethoxycarbonylphenyl Group, 4- (2-ethylhexylcarbonyl) phenyl group, 4-fluorophenyl group, 3-acetylphenyl group, 2-acetylaminophenyl group, 4-
(4-chlorophenylthio) phenyl group, 4- (4-methylphenyl) thio-2,5-butoxyphenyl group,
-(N-benzyl-N-methylamino) -2-dodecyloxycarbonylphenyl group and the like. However, the present invention is not limited to these. Further, these groups may be further substituted by an alkyloxy group, an alkylthio group, a substituted phenyl group, a cyano group, a substituted amino group, a halogen atom, a heterocyclic group, and the like.

In the structural formula (1), R ²¹ and R ²² each independently represent a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group. R ²¹ and R ²² may be the same or different. Examples of the substituent when substituted include an alkoxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a substituted amino group, a substituted amide group, an aryl group, an aryloxy group, and the like. However, it is not limited to these.

The alkyl group represented by R ²¹ and R ²² is preferably an alkyl group having 1 to 18 carbon atoms, for example, a methyl group, a trifluoromethyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group. Group, sec-butyl group, t-butyl group, pentyl group, isopentyl group, cyclopentyl group, hexyl group, cyclohexyl group, octyl group, t-octyl group, 2-ethylhexyl group, nonyl group, octadecyl group, benzyl group, 4 -Methoxybenzyl group, tolphenylmethyl group, ethoxycarbonylmethyl group, butoxycarbonylmethyl group, 2-ethylhexyloxycarbonylmethyl group, 2 ', 4'-diisopentylphenyloxymethyl group, 2', 4'-di- t-butylphenyloxymethyl group, dibenzylaminocarbonylmethyl group, 2,4 Di -t- amylphenyloxy propyl group, an ethoxycarbonyl propyl group, 1-
(2 ′, 4′-di-t-amylphenyloxy) propyl group, acetylaminoethyl group, 2- (N, N-dimethylamino) ethyl group, 2- (N, N-diethylamino)
Propyl group, methanesulfonylaminopropyl group, acetylaminoethyl group, 2- (N, N-dimethylamino)
Examples include an ethyl group and a 2- (N, N-diethylamino) propyl group.

The aryl group represented by R ²¹ and R ²² is preferably an aryl group having 6 to 30 carbon atoms, for example, phenyl, 2-methylphenyl, 2-chlorophenyl, 2-methoxyphenyl Group, 2-butoxyphenyl group, 2- (2-ethylhexyloxy) phenyl group, 2-octyloxyphenyl group, 3- (2,4-di-t-pentylphenoxyethoxy) phenyl group, 4-
Chlorophenyl group, 2,5-dichlorophenyl group, 2,
4,6-trimethylphenyl group, 3-chlorophenyl group, 3-methylphenyl group, 3-methoxyphenyl group,
3-butoxyphenyl group, 3-cyanophenyl group, 3-
(2-ethylhexyloxy) phenyl group, 3,4-dichlorophenyl group, 3,5-dichlorophenyl group, 3,
4-dimethoxyphenyl group, 3- (dibutylaminocarbonylmethoxy) phenyl group,

4-cyanophenyl, 4-methylphenyl, 4-methoxyphenyl, 4-butoxyphenyl, 4- (2-ethylhexyloxy) phenyl,
-Benzylphenyl group, 4-aminosulfonylphenyl group, 4-N, N-dibutylaminosulfonylphenyl group, 4-ethoxycarbonylphenyl group, 4- (2-ethylhexylcarbonyl) phenyl group, 4-fluorophenyl group, 3- Acetylphenyl group, 2-acetylaminophenyl group, 4- (4-chlorophenylthio) phenyl group, 4- (4-methylphenyl) thio-2,5-butoxyphenyl group, 4- (N-benzyl-N-methyl Amino) -2-dodecyloxycarbonylphenyl group and the like. However, it is not limited to these. Further, these groups may be further substituted by an alkyloxy group, an alkylthio group, a substituted phenyl group, a cyano group, a substituted amino group, a halogen atom, a heterocyclic group and the like.

In the structural formula (2), R^{twenty four}, R^{twenty five}And R²⁶
Is independently a substituted or unsubstituted alkyl group,
Represents a substituted or unsubstituted aryl group;^{twenty four}, R^{twenty five}Passing
And R ²⁶May be the same or different.
Examples of the substituent when it is substituted include, for example, alkyl
Groups, alkoxy groups, alkylthio groups, aryl groups,
Reeloxy group, arylthio group, acyl group, alkoxy
Cicarbonyl group, carbamoyl group, carboamide group,
Ruphonyl group, sulfamoyl group, sulfonamide group, c
Raid group, halogen atom, amino group, heterocyclic group, etc.
I can do it.

The alkyl group represented by R ²⁴ , R ²⁵ and R ²⁶ is preferably an alkyl group having 1 to 18 carbon atoms. For example, the alkyl groups represented by R ²¹ and R ²² in the structural formula (1) And a 1-methyl-2- (4-methoxyphenoxy) ethyl group, a di-n-butylaminocarbonylmethyl group, a di-n-octylaminocarbonylmethyl group, and the like.

The aryl groups represented by R ²⁴ , R ²⁵ and R ²⁶ have the same meanings as the aryl groups represented by R ²¹ and R ²² in the structural formula (1). However, it is not limited to these. Further, these groups may be further substituted by an alkyloxy group, an alkylthio group, a substituted phenyl group, a cyano group, a substituted amino group, a halogen atom, a heterocyclic group and the like.

In the structural formula (2), Y is a hydrogen atom, OR
Represents ²³ group, R ²³ represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group. When substituted, examples of the substituent include an alkyl group, an alkoxy group, an alkylthio group, an aryl group, an aryloxy group, an arylthio group, an acyl group, an alkoxycarbonyl group, a carbamoyl group, a carbamide group, a sulfonyl group, and a sulfamoyl group. , A sulfonamide group, a ureido group, a halogen atom, an amino group, a heterocyclic group and the like. Among the above Y, a hydrogen atom, R ²³
Is preferably an alkyloxy group.

The alkyl group represented by R ²³ has the same meaning as the alkyl group represented by R ²¹ and R ²² in the structural formula (1). However, it is not limited to these. The aryl group represented by R ²³ is a group represented by R in the structural formula (1).
^21, the same meaning as the aryl group represented by R ^22. However, it is not limited to these. Further, these aryl groups further include an alkyloxy group, an alkylthio group, a substituted phenyl group, a cyano group, a substituted amino group, a halogen atom,
It may be substituted by a heterocyclic group or the like.

In the structural formula (3), R ²⁷ and R ²⁸ each independently represent a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and even if R ²⁷ and R ²⁸ are the same, Good or different. Examples of the substituent when it is substituted include, for example, an alkyl group, an alkoxy group, an alkylthio group, an aryl group, an aryloxy group, an arylthio group, an acyl group, an alkoxycarbonyl group, a carbamoyl group, a carbamide group, a sulfonyl group,
Examples include a sulfamoyl group, a sulfonamide group, a ureido group, a halogen atom, an amino group, and a heterocyclic group.

The alkyl group represented by R ²⁷ and R ²⁸ is
It has the same meaning as the alkyl group represented by R ²¹ and R ²² in the structural formula (1). However, it is not limited to these. The aryl groups represented by R ²⁷ and R ²⁸ have the same meanings as the aryl groups represented by R ²¹ and R ²² in the structural formula (1). However, it is not limited to these. Also,
These aryl groups further include an alkyloxy group, an alkylthio group, a substituted phenyl group, a cyano group, a substituted amino group,
It may be substituted by a halogen atom, a heterocyclic group or the like.

[0058] In the structural formula (1) ~ (3), X -
Represents an acid anion, and examples of the acid anion include polyfluoroalkylcarboxylic acids having 1 to 9 carbon atoms, polyfluoroalkylsulfonic acids having 1 to 9 carbon atoms, boron tetrafluoride, tetraphenylboron, and hexafluorophosphoric acid. acid,
Aromatic carboxylic acids, aromatic sulfonic acids and the like can be mentioned.
Among them, hexafluorophosphoric acid is preferable in terms of crystallinity.

The specific examples of the diazonium salt compounds represented by the structural formulas (1) to (3) are shown below, but the present invention is not limited to these.

[0060]

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[0061]

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[0062]

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[0063]

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The diazonium salt compounds represented by the structural formulas (1) to (3) may be used alone or in combination of two or more. Further, the diazonium salt compounds represented by the structural formulas (1) to (3) may be used in combination with other existing diazonium salt compounds according to various purposes such as hue adjustment.

The coating amount of the diazonium salt compound is preferably 0.05 to ² g / m ² in the heat-sensitive recording layer.
0.1-1 g / m < ² > is more preferable. By setting the content within the above range, a sufficient color density can be obtained and the coating suitability of the coating liquid can be improved.

[Coupler] As a coupler which forms a dye by coupling reaction with the above-mentioned diazonium salt compound to form a color, the dye is formed by coupling with a diazonium salt compound under a basic atmosphere and / or a neutral atmosphere. Any compound that can be used can be used.

Used for a silver halide photographic light-sensitive material,
All so-called 4-equivalent couplers can be used as couplers and can be appropriately selected within a range that matches the purpose such as hue. For example, a so-called active methylene compound having a methylene group next to a carbonyl group, a phenol derivative, a naphthol derivative and the like can be mentioned.

Among them, a compound represented by the following formula (3) or a tautomer of the compound is particularly preferable. _{^{E 1 -CH 2 -E 2 ... (}} 3) the formula (3), E ¹ and E ² each independently represents an electron withdrawing group, may be the same or different from each other. The electron-withdrawing group refers to a substituent having a positive Hammett sigma value, for example, acetyl, propionyl, pivaloyl, chloroacetyl, trichloroacetyl, trifluoroacetyl, 1-methylcyclopropylcarbonyl Groups, 1-ethylcyclopropylcarbonyl group, 1-benzylcyclopropylcarbonyl group, benzoyl group, 4-methoxybenzoyl group, acyl group such as tenoyl group, methoxycarbonyl group, ethoxycarbonyl group, 2-methoxyethoxycarbonyl group, 4 Alkoxycarbonyl groups such as -methoxyphenoxycarbonyl group, carbamoyl group, N, N-dimethylcarbamoyl group, N, N-diethylcarbamoyl group, N-phenylcarbamoyl group, N- [2,4-bis (pentyloxy)
Phenyl] carbamoyl group, N- [2,4-bis (octyloxy) phenyl] carbamoyl group, carbamoyl group such as morpholinocarbonyl group, methanesulfonyl group,
Alkylsulfonyl group such as benzenesulfonyl group, toluenesulfonyl group or arylsulfonyl group, phosphono group such as diethylphosphono group, benzoxazole-2
A heterocyclic group such as -yl group, benzothiazol-2-yl group, 3,4-dihydroquinazolin-4-one-2-yl group, 3,4-dihydroquinazolin-4-sulfon-2-yl group, Groups, imino groups and cyano groups.

Further, E ¹ and E ² may be bonded to each other to form a ring. The ring formed by E ¹ and E ^2, are preferred carbocyclic or heterocyclic ring of 5-membered or 6-membered.

Specific examples of the coupler include resorcin, phloroglucin, 2,3-dihydroxynaphthalene, sodium 2,3-dihydroxynaphthalene-6-sulfonate, morpholinopropylamide 1-hydroxy-2-naphthoate, 2-hydroxy Sodium 3-naphthalenesulfonate, 2-hydroxy-3-naphthalenesulfonic acid anilide, 2-hydroxy-3-naphthalenesulfonic acid morpholinopropylamide, 2-hydroxy-3-naphthalenesulfonic acid-2-ethylhexyloxypropylamide, 2 -Hydroxy-3-naphthalenesulfonic acid-2-ethylhexylamide, 5-acetamido-1-naphthol, 1-hydroxy-8-acetamidonaphthalene-3,6-disulfonate sodium, 1-
Hydroxy-8-acetamidonaphthalene-3,6-disulfonic acid dianilide,

1,5-dihydroxynaphthalene, 2-hydroxy-3-naphthoic acid morpholinopropylamide,
2-hydroxy-3-naphthoic acid octylamide, 2-
Hydroxy-3-naphthoic acid anilide, 5,5-dimethyl-1,3-cyclohexanedione, 1,3-cyclopentanedione, 5- (2-n-tetradecyloxyphenyl) -1,3-cyclohexanedione, -Phenyl-4-methoxycarbonyl-1,3-cyclohexanedione, 5- (2,5-di-n-octyloxyphenyl) -1,3-cyclohexanedione, N, N′-dicyclohexylbarbituric acid, N, N'-di-n-dodecyl barbituric acid, Nn-octyl-N'-n-octadecyl barbituric acid, N-phenyl-N'-
(2,5-di-n-octyloxyphenyl) barbituric acid, N, N′-bis (octadecyloxycarbonylmethyl) barbituric acid,

1-phenyl-3-methyl-5-pyrazolone, 1- (2,4,6-trichlorophenyl) -3-anilino-5-pyrazolone, 1- (2,4,6-trichlorophenyl) -3 -Benzamide-5-pyrazolone, 6
-Hydroxy-4-methyl-3-cyano-1- (2-ethylhexyl) -2-pyridone, 2,4-bis- (benzoylacetamido) toluene, 1,3-bis- (pivaloylacetoamidomethyl) benzene, Benzoylacetonitrile, thenoylacetonitrile, acetoacetanilide, benzoylacetanilide, pivaloylacetanilide, 2-chloro-5- (Nn-butylsulfamoyl) -1-pivaloylacetamidebenzene, 1-
(2-ethylhexyloxypropyl) -3-cyano-
4-methyl-6-hydroxy-1,2-dihydropyridin-2-one, 1- (dodecyloxypropyl) -3-
Acetyl-4-methyl-6-hydroxy-1,2-dihydropyridin-2-one, 1- (4-n-octyloxyphenyl) -3-tert-butyl-5-aminopyrazole and the like.

The details of the coupler are described in
-201483, JP-A-7-223667, JP-A-7-223368, JP-A-7-323660, Japanese Patent Application No. 5-278608, Japanese Patent Application No. 5-297024, Japanese Patent Application No. 6-18669, Japanese Patent Application No. 6-18670, Japanese Patent Application No. 7-316280, Japanese Patent Application No. 8-027095, Japanese Patent Application No. 8-027096, Japanese Patent Application No. 8-030799,
Japanese Patent Application No. 8-12610, Japanese Patent Application No. 8-132394,
Japanese Patent Application No. 8-358755, Japanese Patent Application No. 8-358756
And Japanese Patent Application No. 9-069990.

Hereinafter, specific examples of the coupler represented by the formula (3) are shown, but the present invention is not limited thereto.

[0075]

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[0076]

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[0077]

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[0078]

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The content of the coupler in the heat-sensitive recording layer is preferably 0.1 to 1 part by mass of the diazonium salt compound.
1 to 30 parts by mass is preferred.

In the heat-sensitive recording material of the present invention, in addition to the diazonium salt compound and the coupler (diazo-based color former), a combination of an electron-donating dye precursor and an electron-accepting compound (leuco-based color former) is used. Can also. For example,
In a heat-sensitive recording material having a plurality of heat-sensitive recording layers on a support, at least one of the layers can be constituted as a layer containing a leuco-based color former.

[Electron Donating Dye Precursor] Examples of the electron donating dye precursor include triarylmethane compounds, diphenylmethane compounds, thiazine compounds,
Xanthene-based compounds, spiropyran-based compounds, and the like can be mentioned, and among them, a triarylmethane-based compound and a xanthene-based compound are preferable because of high color density.

Specifically, the following compounds can be mentioned. For example, 3,3-bis (p-dimethylaminophenyl)-
6-dimethylaminophthalide (ie, 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-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-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-nitrobenzylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3′- Dichloro-spiro-dinaphthopyran, 3-benzylspirodinaphthopyran, 3-propyl-spiro-dibenzopyran and the like.

The coating amount of the electron donating dye precursor is preferably 0.1 to 1 g / m ² in the heat-sensitive recording layer for the same reason as in the case of the diazonium salt compound described above.

[Electron-Accepting Compound] Examples of the electron-accepting compound include phenol derivatives, salicylic acid derivatives, and hydroxybenzoic acid esters. Of these, bisphenols and hydroxybenzoic acid esters are particularly preferable. Specifically, the following compounds are mentioned.

For example, 2,2-bis (p-hydroxyphenyl) propane (ie, bisphenol A),
4 '-(p-phenylenediisopropylidene) diphenol (that is, 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 polyvalent metal salts thereof, 3,5-di (tert-butyl) ) Salicylic acid and its polyvalent metal salts, 3-α, α-dimethylbenzylsalicylic acid and its polyvalent metal salts, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, 2-ethylhexyl p-hydroxybenzoate, p -Phenylphenol, p-cumylphenol and the like.

The content of the electron-accepting compound in the heat-sensitive recording layer is preferably 0.1 to 30 parts by mass with respect to 1 part by mass of the electron-donating dye precursor.

(Other Components) [Organic Base] In the present invention, it is preferable to add an organic base for the purpose of accelerating the coupling reaction between the diazonium salt and the coupler. The organic base is preferably contained in the light and heat sensitive recording layer together with the diazonium salt compound and the coupler, and may be used alone or in combination of two or more. As the organic base, tertiary amines,
Examples include nitrogen-containing compounds such as piperidines, piperazines, amidines, formamidines, pyridines, guanidines, and morpholines. In addition, Japanese Patent Publication No. 52-46
806, JP-A-62-70082, JP-A-57-169745, JP-A-60-94381, JP-A-57-123086, and JP-A-58-23086.
No. 1347901, JP-A-60-49991, JP-B-2-24916, JP-B-2-2847
9, JP-A-60-165288, JP-A-60-165288
The thing described in 7-185430 can also be used.

Among them, N, N'-bis (3-phenoxy-2-hydroxypropyl) piperazine, N, N '
-Bis [3- (p-methylphenoxy) -2-hydroxypropyl] piperazine, N, N'-bis [3- (p-
Methoxyphenoxy) -2-hydroxypropyl] piperazine, N, N'-bis (3-phenylthio-2-hydroxypropyl) piperazine, N, N'-bis [3-
(Β-naphthoxy) -2-hydroxypropyl] piperazine, N-3- (β-naphthoxy) -2-hydroxypropyl-N′-methylpiperazine, 1,4-bis {[3
Piperazines such as-(N-methylpiperazino) -2-hydroxy] propyloxy} benzene, N- [3- (β
-Naphthoxy) -2-hydroxy] propylmorpholine, 1,4-bis (3-morpholino-2-hydroxy-
Morpholines such as propyloxy) benzene and 1,3-bis (3-morpholino-2-hydroxy-propyloxy) benzene, and piperidines such as N- (3-phenoxy-2-hydroxypropyl) piperidine and N-dodecylpiperidine. And guanidines such as triphenylguanidine, tricyclohexylguanidine and dicyclohexylphenylguanidine.

When an organic base is optionally contained,
The content of the organic base in the heat-sensitive recording layer is preferably from 0.1 to 30 parts by mass based on 1 part by mass of the diazonium salt compound.

[Sensitizer] In addition to the above-mentioned organic base, a sensitizer can be added to the heat-sensitive recording layer for the purpose of accelerating the color-forming reaction. The sensitizer is a substance that increases the color density during heating recording or lowers the minimum color development temperature,
The action of lowering the melting point of the coupler, the organic base, the diazonium salt compound, or the like, or lowering the softening point of the capsule wall, makes the diazonium salt compound, the organic base, the coupler, and the like easily react. Specifically, a low-melting-point organic compound having an aromatic group and a polar group in the molecule is preferable, for example, benzyl p-benzyloxybenzoate, α-naphthylbenzyl 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-chloro Phenoxy)
Ethane, p-benzylbiphenyl and the like.

[Binder] Examples of the binder used in the heat-sensitive recording layer include known water-soluble polymer compounds and latexes. As the water-soluble polymer compound,
Methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, starch derivatives, casein, gum arabic, gelatin, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, polyvinyl alcohol, epichlorohydrin modified polyamide, isobutylene-anhydrous Maleic salicylic acid copolymer, polyacrylic acid, polyacrylamide and the like and modified products thereof, and the like. Examples of the latex include styrene-butadiene rubber latex, methyl acrylate-butadiene rubber latex,
And vinyl acetate emulsion.

[Pigment] For the purpose of adjusting hue, a pigment may be contained in the heat-sensitive recording layer. As the pigment,
Any known organic or inorganic substances can be used,
For example, kaolin, calcined kaolin, talc, fluorite, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, zinc oxide, lithopone, amorphous silica,
Examples include colloidal silica, calcined stone, silica, magnesium carbonate, titanium oxide, alumina, barium carbonate, barium sulfate, mica, microballoons, urea-formalin filler, polyester particles, and cellulose filler.

[Antioxidant, etc.] The following are also shown for the purpose of improving the fastness of the color image to light and heat, or reducing the yellowing due to light in the unprinted portion (non-image portion) after fixing. It is also preferable to use a known antioxidant or the like. As the antioxidant, for example, European published patent,
No. 223739, No. 309401, No. 309402, No. 310510, No. 3
Nos. 10552, 594416, German Patent No. 3,435,443, and JP-A-54-4853.
No. 5, JP-A-62-262047, JP-A-63-11
3536, 63-163351, JP-A-2-262654, JP-A-2-71262, JP-A-3-121449, JP-A-5-611
No. 66, JP-A-5-119449, U.S. Pat. No. 4,814,262, U.S. Pat.
No. 5 and the like.

In the present invention, the diazonium salt compound, a coupler which reacts with the diazonium salt compound when heated to form a color, other components such as an organic base and a sensitizer, an electron-donating dye precursor, an electron-accepting compound There are no particular restrictions on the form of use, and for example, (1) a method of using a solid dispersion, (2) a method of using an emulsified dispersion, (3) a method of using a polymer, and (4) a latex dispersion And (5) a method utilizing microencapsulation. Above all, from the viewpoint of storage stability,
(5) A method utilizing microencapsulation is preferable,
In particular, in a color forming system utilizing a reaction between a diazonium salt compound and a coupler, a form in which the diazonium salt compound is microencapsulated is preferable.In a coloring system utilizing a reaction between an electron donating dye precursor and an electron accepting compound, Preferred is a form in which the electron-donating dye precursor is microencapsulated.

(Method for Producing Microcapsules) In the present invention, the diazonium salt compound and / or the electron-donating dye precursor are preferably encapsulated in microcapsules in order to improve the storage stability of the heat-sensitive recording material. . As a method of microencapsulating the coloring component,
A conventionally known method can be used. For example, an oil phase prepared by dissolving or dispersing a diazonium salt compound (and an electron donating dye precursor), which is one of the coloring components, in an organic solvent that is hardly soluble or insoluble in water, is converted into an aqueous phase in which a water-soluble polymer is dissolved. And emulsified and dispersed by means such as a homogenizer, and then heated to cause a polymer formation reaction at the oil droplet interface to form a microcapsule wall of a polymer substance. . The interfacial polymerization method comprises:
Capsules having a uniform particle size can be formed in a short time, and a recording material having excellent raw preservability can be obtained.

Examples of the organic solvent include low-boiling co-solvents such as acetate, methylene chloride and cyclohexanone, and / or phosphates, phthalates, acrylates, methacrylates and other carboxylic esters. Examples include fatty acid amide, alkylated biphenyl, alkylated terphenyl, alkylated naphthalene, diarylethane, chlorinated paraffin, alcohol solvent, phenol solvent, ether solvent, monoolefin solvent, epoxy solvent and the like.

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, sebacin Dioctyl acid, dibutyl sebacate, dioctyl adipate, trioctyl trimellitate, acetyl triethyl citrate, octyl maleate, dibutyl maleate, isoamyl biphenyl, chlorinated paraffin, diisopropyl naphthalene, 1,1'-
Examples include high boiling solvents such as ditolylethane, 2,4-di-tert-amyl phenol, N, N-dibutyl-2-butoxy-5-tert-octyl aniline, 2-ethylhexyl hydroxybenzoate, and polyethylene glycol. Of these, alcohol solvents, phosphate ester solvents, carboxylate ester solvents, alkylated biphenyls, alkylated terphenyls, alkylated naphthalenes, and diarylethanes are particularly preferred.

Further, an anti-carbonizing agent such as hindered phenol and hindered amine may be added to the high boiling point solvent. As the high boiling point solvent, a solvent having an unsaturated fatty acid is particularly desirable, and examples thereof include α-methylstyrene dimer. The α-methylstyrene dimer includes:
For example, there is "MSD100" manufactured by Mitsui Toatsu Chemicals, Inc.

Examples of the water-soluble polymer include water-soluble polymers such as polyvinyl alcohol. Examples thereof include polyvinyl alcohol, silanol-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amino-modified polyvinyl alcohol, itaconic acid-modified polyvinyl alcohol, and styrene. -Maleic anhydride copolymer, butadiene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer,
Examples thereof include polyacrylamide, polystyrenesulfonic acid, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, and gelatin. Among them, carboxy-modified polyvinyl alcohol is preferable.

The water-soluble polymer may be used in combination with a hydrophobic polymer emulsion or latex.
Examples of the emulsion or latex include a styrene-butadiene copolymer, a carboxy-modified styrene-butadiene copolymer, and an acrylonitrile-butadiene copolymer. At this time, a conventionally known surfactant or the like may be added as necessary.

Examples of the polymer substance constituting the microcapsule wall include polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-acrylate copolymer resin,
Styrene-methacrylate copolymer resin, gelatin, polyvinyl alcohol and the like. Among them, polyurethane / polyurea resins are particularly preferred.

For example, when a polyurethane / polyurea resin is used as a capsule wall material, a microcapsule wall precursor such as polyvalent isocyanate is encapsulated and mixed in an oily medium (oil phase) to be used as a core substance. A second substance (for example, polyol or polyamine) which forms a capsule wall by reacting with a capsule wall precursor is mixed in a water-soluble polymer aqueous solution (aqueous phase), and the oil phase is emulsified and dispersed in an aqueous phase. By heating, a polymer formation reaction occurs at the oil droplet interface, and a microcapsule wall can be formed.

The following are specific examples of the polyvalent isocyanate compound. However, it is not limited to these. 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-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate,

Diisocyanates such as cyclohexylene-1,4-diisocyanate, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, toluene-2,
Triisocyanates such as 4,6-triisocyanate, 4,4′-dimethylphenylmethane-2,2 ′,
Tetraisocyanates such as 5,5′-tetraisocyanate, adducts of hexamethylene diisocyanate with trimethylolpropane, adducts of 2,4-tolylenediisocyanate with trimethylolpropane, and xylylenediisocyanate with trimethylolpropane And isocyanate prepolymers such as adducts and adducts of tolylene diisocyanate and hexanetriol. If necessary, two or more types may be used in combination. Among them, particularly preferable are. It has three or more isocyanate groups in the molecule.

In the microencapsulation method, other components such as a coupler (and an electron-accepting compound), an organic base, and a sensitizer, and an organic solvent for dissolving the microcapsule wall precursor and a second substance that reacts with the precursor Is the same as the organic solvent described above. The particle size of the microcapsules is preferably 0.1 to 1.0 μm, and 0.2 to 0.7 μm.
m is more preferred.

Hereinafter, the specific constitution of the multicolor recording material will be described. The heat-sensitive recording material of the present invention may be either a single-color heat-sensitive recording material having one heat-sensitive recording layer on a support, or a multicolor heat-sensitive recording material having a heat-sensitive recording layer having a laminated structure in which a plurality of single-color recording layers are laminated. It may be. As a multicolor heat-sensitive recording material, an embodiment in which at least one layer constituting the heat-sensitive recording layer is a light fixing type recording layer containing a diazonium salt compound and a coupler which reacts with the diazonium salt compound to form a color is preferred.

In particular, in the case of a full-color heat-sensitive recording layer containing cyan, yellow, and magenta, all the three layers on the support are composed of a diazo-based coloring agent, or the first layer close to the support is the first layer. A heat-sensitive recording material in which the heat-sensitive recording layer is constituted by a leuco-based coloring agent containing an electron-donating dye and an electron-accepting compound, and the second and third heat-sensitive recording layers are constituted by a diazo-based coloring agent. Is preferred. For example, it may be configured in the following modes (a) to (c).

That is, (a) the maximum absorption wavelength 3
A light fixing type recording layer (first recording layer (A layer)) containing a diazonium salt compound having a wavelength of 60 ± 20 nm and a coupler which reacts with the diazonium salt compound to form a color, and has a maximum absorption wavelength of 400 ± 20 nm. A recording layer formed by laminating a light-fixing recording layer (second recording layer (layer B)) containing a diazonium salt compound and a coupler that reacts with the diazonium salt compound to form a color; A recording material provided with a light transmittance adjusting layer and a protective layer as necessary,

(B) On the support, a recording layer containing an electron donating dye and an electron accepting compound (the first recording layer (A
Layer)), a light-fixing type recording layer (second recording layer (layer B)) containing a diazonium salt compound having a maximum absorption wavelength of 360 ± 20 nm and a coupler which reacts with the diazonium salt compound to form a color. An optical fixing type recording layer (third recording layer (C layer)) containing a diazonium salt compound having a maximum absorption wavelength of 400 ± 20 nm and a coupler which reacts with the diazonium salt compound to form a color is laminated in this order. A recording material having a recording layer comprising a light transmittance adjusting layer and a protective layer on the layer, if necessary.

(C) A maximum absorption wavelength of 340 ±
A light-fixing type recording layer (first recording layer (A layer)) containing a diazonium salt compound having a diameter of 20 nm or less and a coupler that undergoes a color reaction with the diazonium salt compound, and a diazonium having a maximum absorption wavelength of 360 ± 20 nm. A light-fixing type recording layer (second recording layer (layer B)) containing a salt compound and a coupler which reacts with the diazonium salt compound to form a color, a diazonium salt compound having a maximum absorption wavelength of 400 ± 20 nm, and the diazonium A light fixing type recording layer (third recording layer (C layer)) containing a coupler that reacts with a salt compound to form a color;
And a recording material in which a light transmittance adjusting layer and a protective layer are provided on the layer as necessary.

The method of multicolor recording will be described below with reference to (b) or (c). First, the third recording layer (C
Layer) is heated to develop the diazonium salt and coupler contained in the layer. Next, after irradiating light having a wavelength of 400 ± 20 nm to decompose and fix the unreacted diazonium salt compound contained in the C layer, the second recording layer (B layer) has sufficient heat to develop color. To develop the diazonium salt compound and the coupler contained in the layer. At this time, the C layer is also heated strongly, but the diazonium salt compound has already been decomposed (fixed by light) and has no color-forming ability, so that no color is formed. Furthermore, the wavelength 360 ± 20n
m, the diazonium salt compound contained in the B layer is decomposed and fixed by light, and finally, the first recording layer (A layer)
The color is developed by applying sufficient heat to develop the color. At this time,
The recording layers C and B are also heated strongly at the same time, but the diazonium salt compound has already been decomposed and has lost its color-forming ability, so that no color is formed.

As for the order of lamination of the layers, the lowermost layer is preferably a yellow layer having low visibility so as to reduce the influence on the image quality due to the roughness on the surface of the support. Useful. In addition, all recording layers (A layer, B layer
Layer and layer C) are diazo-based recording layers, the layers A and B need to be optically fixed after color development, but the layer C for which image recording is performed last is not necessarily required. There is no need to perform light fixing. However, from the viewpoint of improving the storage stability of the formed image, light fixing is preferable.

The fixing light source used for light fixing can be appropriately selected from known light sources, and includes, for example, various fluorescent lamps,
Xenon lamps, mercury lamps and the like can be mentioned. Among them, it is preferable to use a light source whose emission spectrum almost coincides with the absorption spectrum of diazonium chloride used for the recording material in terms of highly efficient light fixing.

-Other layers- In the heat-sensitive recording material of the present invention, an embodiment in which one or more heat-sensitive recording layers are provided on a support, and a light transmittance adjusting layer and a protective layer are preferably provided.

(Light Transmittance Adjusting Layer) The light transmittance adjusting layer contains an ultraviolet absorbent precursor and does not function as an ultraviolet absorbent before irradiation with light having a wavelength in a region necessary for fixing. When fixing the light-fixing type heat-sensitive recording layer, it has sufficient transmittance in the wavelength range necessary for fixing and also has high visible light transmittance, which may hinder the fixing of the heat-sensitive recording layer. Absent. This ultraviolet absorber precursor is preferably contained in microcapsules. Compounds contained in the light transmittance adjusting layer are described in JP-A-9-192.
No. 8 compounds.

The ultraviolet absorber precursor functions as an ultraviolet absorber by reacting with light or heat after light irradiation of a wavelength necessary for fixing the heat-sensitive recording layer by light irradiation is completed. 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 thermosensitive recording material is improved, but there is no visible light absorbing effect. Therefore, the transmittance of visible light does not substantially change. At least one light transmittance adjusting layer can be provided in the heat-sensitive recording material, and is most preferably formed between the heat-sensitive recording layer and the outermost protective layer. You may make it double. The characteristics of the light transmittance adjusting layer can be arbitrarily selected according to the characteristics of the heat-sensitive recording layer.

The coating solution for forming the light transmittance adjusting layer (coating solution for the light transmittance adjusting layer) is obtained by mixing the above-mentioned components.
The light transmittance adjusting layer coating solution can be formed by applying a known coating method such as a bar coater, an air knife coater, a blade coater, and a curtain coater. The light transmittance adjusting layer may be applied simultaneously with the heat-sensitive recording layer or the like.For example, after applying a coating solution for forming the heat-sensitive recording layer and once drying the heat-sensitive recording layer, it may be applied and formed on the layer. Good.

(Protective Layer) The protective layer contains a pigment, a lubricant, a surfactant, a dispersant, a fluorescent brightener, a metal soap, a hardener, an ultraviolet absorber, a cross-linking agent, and the like, together with a binder. . The binder and the pigment can be appropriately selected from the water-soluble binders and pigments that can be used in the back coat layer described above. Examples of other binders include synthetic rubber latex and synthetic resin emulsions, such as styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, and vinyl acetate emulsion. The content of the binder is preferably from 10 to 500% by mass, more preferably from 50 to 400% by mass, based on the pigment in the protective layer.

For the purpose of further improving the water resistance, it is effective to use a cross-linking agent and a catalyst for accelerating the reaction in combination. Examples of the cross-linking agent include an epoxy compound, a blocked isocyanate and a vinyl sulfone compound. Aldehyde compounds, methylol compounds, boric acid, carboxylic anhydrides, silane compounds, chelate compounds, halides and the like, and those which can adjust the pH of the coating solution for forming the protective layer to 6.0 to 7.5 are preferable. . Examples of the catalyst include known acids, metal salts and the like, and those capable of adjusting the pH of the coating solution to 6.0 to 7.5 as described above are preferable.

Examples of the lubricant include zinc stearate, calcium stearate, paraffin wax,
Preferable examples include polyethylene wax. As the surfactant, a sulfosuccinic acid-based alkali metal salt, a fluorine-containing surfactant and the like are preferably mentioned so that a protective layer can be uniformly formed on the heat-sensitive recording layer.
Di- (2-ethylhexyl) sulfosuccinic acid, di- (n
And sodium salts such as -hexyl) sulfosuccinic acid, and ammonium salts.

Coating solution for forming protective layer (coating solution for protective layer)
Is obtained by mixing the above components. Further, a release agent, a wax, a water repellent and the like may be added as necessary. The heat-sensitive recording material of the present invention can be formed by applying a protective layer coating solution on a heat-sensitive recording layer formed on a support by a known coating method. As the known coating method, for example,
Examples include a method using a bar coater, an air knife coater, a blade coater, a curtain coater, and the like.

The dry coating amount of the protective layer is from 0.2 to 7
preferably ^{g / m 2, 1~4g / m} 2 is more preferable. If the dry coating amount is less than 0.2 g / m ² , the water resistance may not be maintained, and if it exceeds 7 g / m ² , the thermal sensitivity may be significantly reduced. After forming the protective layer,
If necessary, a calendering process may be performed.

(Intermediate Layer) When a plurality of heat-sensitive recording layers are laminated, it is preferable to provide an intermediate layer between the heat-sensitive recording layers. In the intermediate layer, similar to the protective layer, in addition to various binders, a pigment, a lubricant, a surfactant, a dispersant, a fluorescent brightener,
Metal soap, ultraviolet absorber and the like can be included. As the binder, the same binder as the protective layer can be used.

(Support) As the support, for example,
Polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate film, polystyrene films, polypropylene films, polyolefin films such as polyethylene films, polyimide films, polyvinyl chloride films, polyvinylidene chloride films,
Examples thereof include a synthetic polymer film such as a polyacrylic acid copolymer film and a polycarbonate film, and paper, synthetic paper, and paper having a plastic resin layer. The supports can be used alone or in combination.

As the paper having the plastic resin layer, it is desirable that the base paper is provided with a layer containing a thermoplastic resin on both surfaces or at least the surface on which the heat-sensitive recording layer is formed. As such a support, for example, a base paper obtained by applying a thermoplastic resin by melt extrusion coating, a base paper obtained by applying a gas barrier layer on a thermoplastic resin applied by melt extrusion coating on a base paper, and A plastic film that has a low permeability film adhered thereto, a thermoplastic resin is provided by melt extrusion on the surface where the plastic film is adhered to the base paper, and the thermoplastic resin is melt extruded and coated on the base paper , And the like.

Examples of the thermoplastic resin to be melt-extruded and coated on base paper include olefin resins, for example, α-olefin homopolymers such as polyethylene and polypropylene, and mixtures of these various polymers, or ethylene and vinyl alcohol. Are preferred. Examples of the polyethylene include LPDE (low density polyethylene), HDPE (high density polyethylene), LL
PDE (linear low density polyethylene) and the like.

The method of laminating the plastic film on the base paper can be appropriately selected from known lamination methods described in "New Laminating Handbook" (edited by the Processing Technology Research Group) and the like. , Dry lamination using an electron beam or ultraviolet curable resin, and hot dry lamination are preferred. Among the various supports described above,
A paper support in which at least one surface of the base paper is laminated with polyethylene is preferable, and is generally laminated on the surface on the side on which the heat-sensitive recording layer is formed. Further, a paper support in which both surfaces of the base paper are laminated with polyethylene is more preferable, and the surface on the side where the heat-sensitive recording layer is formed is laminated for the purpose of increasing flatness, and the opposite side of the surface is opposite to the surface. The surface is laminated for the purpose of adjusting the curl balance.

The synthetic polymer film may be colored to an arbitrary hue. Examples of a method for coloring the polymer film include a method in which a resin is kneaded with a dye before forming the film, and a method in which the dye is formed into a film. A coating solution is prepared by dissolving the coating solution in an appropriate solvent, and is applied to a transparent and colorless resin film by a known coating method, for example, a gravure coating method, a roller coating method, a wire coating method, and the like, and a method of drying. Above all, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate kneaded with a blue dye is formed into a film, which is subjected to heat treatment,
Those subjected to a stretching treatment and an antistatic treatment are preferable.

The thickness of the support is preferably from 25 to 300.
μm is preferable, and 50 to 250 μm is more preferable. The heat-sensitive recording layer, a protective layer, a light transmittance adjusting layer, an intermediate layer, and the like,
It can be formed on a support by a known coating method such as a blade coating method, an air knife coating method, a gravure coating method, a roll coating coating method, a spray coating method, a dip coating method, a bar coating method, and the like, followed by drying. it can.

[0131]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Hereinafter, “parts” and “%” in the examples represent “parts by mass” and “% by mass”, respectively. Hereinafter, the diazonium salt compound may be simply referred to as a diazo compound.

Example 1 (1) Preparation of Support A wood pulp consisting of 100 parts of LBKP was subjected to 300 ml of Canadian freeness using a double disc refiner.
Beated until 0.5 parts of epoxidized behenamide, 1.0 part of anionic polyacrylamide, 0.1 part of polyamide polyamine epichlorohydrin, and 0.5 part of cationic polyacrylamide were added at an absolute dry mass ratio to pulp. A 100 g / m ² base paper was weighed by a fourdrinier paper machine, polyvinyl alcohol was surface-sized at an absolute dry weight of 1.0 g / m ² , and a base paper adjusted to a density of 1.0 by calendering was obtained. Was.

After performing corona discharge treatment on the wire surface (back surface) side of the obtained base paper, high-density polyethylene was coated to a thickness of 30 μm using a melt extruder, and a resin layer consisting of a mat surface was formed. (Hereinafter, the resin layer surface is referred to as a “back surface”). This resin layer on the back side is further subjected to corona discharge treatment, and then, as an antistatic agent,
A dispersion obtained by dispersing aluminum oxide (alumina sol 100, manufactured by Nissan Chemical Industries, Ltd.) and silicon dioxide (Snowtex O, manufactured by Nissan Chemical Industries, Ltd.) in water at a ratio (mass ratio) of 1: 2, Coating was performed so that the dry weight was 0.2 g / m ² .

Further, after a corona discharge treatment was applied to the felt surface (surface) side on which the resin layer was not provided, low-density polyethylene containing 10% of titanium oxide and a small amount of ultramarine blue was melt-extruded. Then, it was melt-extruded so as to have a thickness of 40 μm, and a high-gloss thermoplastic resin layer was formed on the surface side of the base paper (hereinafter, this high-gloss surface is referred to as “front surface”) to obtain a support. Corona discharge treatment was applied to the front polyethylene surface.

(2) Formation of back coat layer-Preparation of coating solution for outermost back layer-100 parts of a 15% aqueous solution of polyvinyl alcohol (PVA105, manufactured by Kuraray Co., Ltd.) was added to 100 parts of sulfosuccinic acid.
-17 parts of a 2% aqueous solution of ethylhexyl ester (Ravizol B90, manufactured by NOF Corporation) and 1 part of a synthetic mica dispersion (Somasif MEB-3, manufactured by Corp Chemical Co., Ltd.)
9 parts and 41 parts of water were added and stirred to obtain a coating solution for the outermost back layer containing synthetic mica and polyvinyl alcohol.

-Preparation of Coating Solution for Intermediate Back Layer- 300 parts of a 15% alkali-treated gelatin aqueous solution, 100 parts of a 2% solution of di-2-ethylhexyl sulfosuccinate, and 1800 parts of water are mixed to form an intermediate back layer. A liquid was obtained.

-Formation of Back Coat Layer- On the surface opposite to the surface of the support obtained above, the coating solution for the intermediate back layer and the coating solution for the outermost back layer were applied from the support side to the solid content after drying. The coating amounts are 9 g / m ² and 1.2 g / m, respectively.
m ² , followed by drying to form a back coat layer consisting of an intermediate back layer and an outermost back layer on the support.

(3) Preparation of Coating Solution for Undercoat Layer Oil-swelling synthetic mica “ME100” (manufactured by Corp Chemical)
97.5 parts of water was added to 2.5 parts, and the mixture was dispersed with a dynamill. This is mixed with a 5% aqueous solution of gelatin at 40 ° C. 200
The mixture was stirred for 30 minutes, and 20 ml of a 5% aqueous solution of the following surfactant-1 was added to prepare a coating solution for an undercoat layer.

[0139]

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(4) Preparation of Coating Solution for Cyan Thermosensitive Recording Layer -Preparation of Microcapsule Solution A Containing Electron Donating Dye Precursor- Solution a 3- (o-methyl-p-dimethylaminophenyl) -3
After dissolving 5 parts of-(1'-ethyl-2'-methylindol-3-yl) phthalide (electron-donating dye precursor) in 20 parts of ethyl acetate, 1-phenyl-1-xylylethane (high 20 parts (boiling point solvent) were added, and the mixture was heated and uniformly mixed. To the obtained solution, 20 parts of a 1/3 adduct of xylylene diisocyanate / trimethylolpropane was added as a capsule wall material, and the mixture was stirred uniformly to obtain a liquid a. Solution b To 54 parts of a 6% aqueous solution of phthalated gelatin, 2 parts of a 2% aqueous solution of sodium dodecylsulfonate were added to obtain a solution b.

The solution a was added to the solution b obtained above and emulsified and dispersed using a homogenizer to obtain an emulsified dispersion. After mixing 68 parts of water with the obtained emulsified dispersion to make it uniform, the mixture is heated to 50 ° C. while stirring, and the encapsulation reaction is performed so that the average particle size of the microcapsules becomes 1.2 μm. The reaction was performed for 3 hours to obtain a microcapsule solution A containing an electron-donating dye precursor.

-Preparation of developer emulsified dispersion B- 2.5 parts of 1,1- (p-hydroxyphenyl) -2-ethylhexane (developer), 0.3 parts of tricresyl phosphate and maleic acid 0.1 part of diethyl was dissolved in 10 parts of ethyl acetate. The resulting solution is mixed with gelatin 6
% Aqueous solution 20 parts and sodium dodecylsulfonate 2
% Aqueous solution was added to the mixed solution, and emulsified for 10 minutes using a homogenizer to obtain a developer emulsified dispersion B.

-Preparation of Coating Solution for Cyan Thermosensitive Recording Layer- To the microcapsule solution C containing the electron-donating dye precursor obtained above, SBR latex (SN-307, manufactured by Sumitomo Nogatack Co., Ltd.) was used as a microcapsule. 40% with respect to the solid content, and then, with respect to the microcapsule liquid C containing the electron-donating dye precursor, the developer emulsified dispersion D
Were mixed so that the mass ratio became 1/4 to obtain a coating solution for a cyan thermosensitive recording layer.

(5) Preparation of coating solution for magenta heat-sensitive recording layer-Preparation of diazo compound-containing microcapsule solution C-The following diazo compound (1) (decomposed by light having a wavelength of 365 nm)
After dissolving 2.8 parts in 20 parts of ethyl acetate, 12 parts of diisopropylnaphthalene was further added, and the mixture was heated and uniformly mixed. To the obtained solution, 15 parts of an adduct of xylylene diisocyanate / trimethylolpropane 1/3 as a capsule wall material was added, and the mixture was uniformly mixed to obtain a liquid I containing a diazo compound.

The obtained solution I was treated with 6% of phthalated gelatin.
The solution was added to a mixed solution of 54 parts of an aqueous solution and 2 parts of a 2% aqueous solution of sodium dodecyl sulfonate, and emulsified and dispersed using a homogenizer. The obtained emulsified dispersion is further treated with water 68
Of the capsules, and the mixture was heated to 40 ° C. with stirring, so that the average particle size of the capsules was 1.2 μm.
The encapsulation reaction was performed for a time to obtain a diazo compound-containing microcapsule liquid C.

[0146]

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-Preparation of Coupler Emulsion Dispersion D- 2 parts of the following coupler (1), 2 parts of 1,2,3-triphenylguanidine, 0.3 part of tricresyl phosphate and 0.1 part of diethyl maleate were added to acetic acid. Dissolved in 10 parts of ethyl. The resulting solution was poured into an aqueous solution obtained by mixing 20 parts of a 6% aqueous solution of gelatin and 2 parts of a 2% aqueous solution of sodium dodecyl sulfonate, and then emulsified for 10 minutes using a homogenizer to obtain a coupler emulsified dispersion D. Was.

[0148]

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-Preparation of coating solution for magenta thermosensitive recording layer- Microcapsule solution C containing diazo compound obtained above
Then, SBR latex (SN-307, manufactured by Sumitomo Nogatack Co., Ltd.) was added to the solid content of the microcapsules at 40%.
%, And then the coupler emulsion D was mixed with the diazo compound-containing microcapsule solution C at a mass ratio of 3/2 to obtain a coating liquid for a magenta thermosensitive recording layer.

(6) Preparation of coating solution for yellow thermosensitive recording layer Preparation of diazo compound-containing microcapsule solution E 2,5-dibutoxy-4-tolylthiobenzenediazonium hexafluorophosphate (diazo compound: light having a wavelength of 420 nm) After dissolving 3.0 parts in 20 parts of ethyl acetate, 7 parts of tricresyl phosphate and 4 parts of monoisopropylbiphenyl as a high boiling point solvent were added thereto, and the mixture was heated and uniformly mixed. In the resulting solution,
As a capsule wall material, 15 parts of a 1/3 adduct of xylylene diisocyanate / trimethylolpropane was added and uniformly mixed to obtain a liquid II containing a diazo compound.

The obtained solution II was treated with 6% of phthalated gelatin.
54 parts of aqueous solution and sodium dodecyl sulfonate aqueous solution 2
The mixture was added to the mixed solution, and emulsified and dispersed using a homogenizer. A solution obtained by adding 68 parts of water to the obtained emulsified dispersion and uniformly mixing the mixture was heated to 40 ° C. with further stirring, and the mixture was adjusted to a particle size of 1.3 μm with an average particle size of 1.3 μm.
The encapsulation reaction was performed for a time to obtain a diazo compound-containing microcapsule liquid E.

Preparation of Coupler Emulsion Dispersion F 2-Chloro-5- (3- (2,4-di-tert-pentyl) phenoxypropylamino) acetoacetanilide 2 parts, 1,2,3-triphenylguanidine 1 part, tricresyl phosphate 0.3 part and diethyl maleate 0.1 part are dissolved in ethyl acetate 10 parts, 6% aqueous solution of gelatin 20 parts and sodium dodecyl sulfonate 2 parts
% Aqueous solution, and emulsified for 10 minutes using a homogenizer.
I got

-Preparation of Yellow Thermosensitive Recording Layer Coating Solution- The coupler emulsified dispersion F obtained above was mixed with the diazo compound-containing microcapsule solution E so that the weight ratio thereof was 3/2, and the mixture was mixed with yellow. A coating solution for a heat-sensitive recording layer was obtained.

(7) Preparation of coating solution for intermediate layer 15% of gelatin (# 750, manufactured by Nitta Gelatin Co., Ltd.)
In 10 parts of the aqueous solution, add polyacrylic acid (Dulima AC-1).
(0 L, 3 parts of a 15% aqueous solution of Nippon Junyaku Co., Ltd.) were added and mixed uniformly to obtain a coating solution for an intermediate layer.

(8) Preparation of coating solution for light transmittance adjusting layer 1.5 parts of the following compound and compound R- as a reducing agent
6 was sufficiently dissolved by mixing 0.5 part of ethyl acetate, 6.0 parts of ethyl acetate, and 0.8 parts of tricresyl phosphate. Xylylene diisocyanate / capsule wall solution was added to this solution.
Trimethylolpropane (Takenate D110N, 75
% Ethyl acetate solution, manufactured by Takeda Pharmaceutical Co., Ltd.) was further added and stirred uniformly. To this, 29.7 parts of an 8% aqueous solution of carboxy-modified polyvinyl alcohol (KL-318, manufactured by Kuraray Co., Ltd.) was added, and emulsified and dispersed using a homogenizer. The obtained emulsion was added to 40 parts of ion-exchanged water and stirred at 40 ° C. for 3 hours to carry out an encapsulation reaction. Thereafter, 7.0 parts of an ion exchange resin Amberlite MB-03 (manufactured by Organo Co., Ltd.) was added, and the mixture was further stirred for 1 hour to prepare a coating solution for a light transmittance adjusting layer. The average particle size of the microcapsules was 0.35 μm.

[0156]

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(9) Preparation of Coating Solution for Protective Layer A coating solution for a protective layer was prepared by mixing the following components. -EP130 (7%) ... 100 g (dodecyl-modified polyvinyl alcohol, manufactured by Denki Kagaku Kogyo KK)-Water-50 g-Varifine BF21 dispersion (20%)-10 g (Barium sulfate ultrafine particles, Sakai Chemical Industry Co., Ltd.) -Surfactant-1 (2%): 5 ml-Surfactant-2 (5%): 5 ml

[0158]

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(10) Preparation of Thermosensitive Recording Material The undercoat layer coating solution, the cyan thermosensitive recording layer coating solution, and the intermediate layer were applied from the support side to the corona discharge-treated polyethylene surface of the front surface of the support obtained above. Coating solution for magenta heat-sensitive recording layer, coating solution for intermediate layer, coating solution for yellow heat-sensitive recording layer, coating solution for light transmittance adjustment layer, and coating solution for protective layer in this order, and dried. Thus, a multicolor heat-sensitive recording material (1) of the present invention was produced. The application amount of each coating solution is
In terms of solid content after drying, in order from the support side, the undercoat layer was 1.0 g / m ² , the cyan thermosensitive recording layer was 7.2 g / m ² , the intermediate layer was 2.0 g / m ² , and the magenta thermosensitive recording layer was 7.8 g / m ² . m ² ,
Intermediate layer 2.0 g / m ² , yellow heat-sensitive recording layer 5.0 g / m ²
m ² , light transmittance adjusting layer 2.5 g / m ² , protective layer 1.2 g /
It was m ^2.

(Example 2) In forming the back coat layer in Example 1, the polyvinyl alcohol used was changed to carbonyl-modified polyvinyl alcohol (KL-118, manufactured by
A multicolor heat-sensitive recording material (2) was produced in the same manner as in Example 1 except that the material was replaced with Kuraray.

Example 3 In forming the back coat layer in Example 1, the applied amount of the solid content after drying the outermost back layer coating solution was 1.2 g / m ² without using the synthetic mica dispersion. In the same manner as in Example 1, except that
A multicolor heat-sensitive recording material (3) of Example 3 was produced.

(Comparative Example 1) In forming the back coat layer of Example 1, the applied amount of the solid content after drying the intermediate back layer coating solution was 10.2 g without using the outermost back layer coating solution.
/ M ² , except that the multicolor heat-sensitive recording material (4) of Comparative Example 1 was prepared in the same manner as in Example 1.

(Evaluation of Curling) The multicolor thermosensitive recording materials (1) to (4) obtained above were evaluated as follows. The evaluation results are shown in Table 1 below. FUJIX digital color printer NC370D was applied to each sheet of heat-sensitive recording material under environmental conditions of 23 ° C. and 20% RH.
Using Fuji Photo Film Co., Ltd., print in A6 size in a gray solid state, and the curl amount immediately after printing and one day after printing (the amount of curl from the flat surface when left on a flat surface) (Average lift [mm] at four corners of each thermal recording material)
Was measured and used as an index indicating the degree of curling (curling). In the measurement, the amount of curl on the side having the heat-sensitive recording layer (front side) and the amount lifted up are represented by “+”, and the amount of curl on the side having the back coat layer (back side) is “−”. ".

[0164]

[Table 1]

From the results shown in Table 1, in the case of the thermosensitive recording material (3) having two layers and the outermost layer having a back coat layer containing polyvinyl alcohol, the material deformation immediately after printing under low humidity could be suppressed. . Further, in the heat-sensitive recording materials (1) and (2), which are composed of two layers and the outermost layer has a back coat layer containing an inorganic layered compound (synthetic mica) and polyvinyl alcohol, immediately after printing in a low humidity environment and after printing Material deformation (curling) after one day had elapsed was able to be suppressed. On the other hand, in the case of the heat-sensitive recording material (4) containing no polyvinyl alcohol in the outermost layer, the material was greatly deformed immediately after printing and one day after printing, and curling could not be sufficiently prevented.

[0166]

According to the present invention, curling due to environmental changes and heat application during recording is prevented, and high quality without material deformation is provided, especially in a multicolor heat-sensitive recording material comprising a sheet material or a multilayer. It is possible to provide a heat-sensitive recording material applicable to various fields.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B41M 5/18 THF term (Reference) 2H026 AA07 AA14 BB01 BB41 DD01 DD32 DD48 DD58 EE01 FF07 FF17 4F100 AA01B AC05B AC05E AH03D AJ04 AJ09C AJ09E AK04A AK05 AK06 AK21B AL05B AT00A BA03 BA04 BA05 BA07 CA13D DE02B DG10A EH23A GB90 HB00D JA20B JL00D JL04 JL10D

Claims (7)

[Claims] 1. A thermosensitive recording material having at least a heat-sensitive recording layer on one surface of a support and a backcoat layer on the other surface, wherein the backcoat layer comprises a multilayer, A thermosensitive recording material, wherein the outermost layer furthest from the recording layer contains polyvinyl alcohol. 2. The heat-sensitive recording material according to claim 1, wherein the outermost layer of the back coat layer farthest from the support further contains an inorganic layered compound. 3. The heat-sensitive recording material according to claim 2, wherein the inorganic layered compound is synthetic mica. 4. The heat-sensitive recording material according to claim 3, wherein the synthetic mica is a synthetic mica having an aspect ratio of 100 or more. 5. The heat-sensitive recording material according to claim 1, wherein the layer located between the outermost layer of the back coat layer and the support contains gelatin. 6. A recording layer comprising an electron-donating dye precursor and an electron-accepting compound which reacts with the electron-donating dye precursor to form a color, a diazonium salt compound and the diazonium salt compound. The recording material according to any one of claims 1 to 5, further comprising: a recording layer containing a coupler that reacts with the coupler to form a color. 7. The heat-sensitive recording material according to claim 1, wherein the support is a paper support having at least one surface laminated with polyethylene.