JP2002321455A - Heat sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording material, with which an image having high lustrous properties can be formed, at the same time, a high image quality image with uniform density can be formed by reducing a load change through the reduction of a printing torque. SOLUTION: In the heat sensitive recording material, printing is performed with a thermal head and a heat sensitive recording layer and a protective layer is provided in the order named on a support, a thermally soft film layer, the hardness of which is lower than that of the protective layer at the printing, is provided on the surface at the heat sensitive recording layer side of the protective layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermosensitive recording material for recording an image using a thermal head.

[0002]

2. Description of the Related Art The needs of thermal recording systems are increasing in various fields such as facsimile machines, printers, labels, and the like, and accordingly, higher performance thermosensitive recording materials are required. However, in thermal recording, in which the image is recorded by heating the image likewise with a thermal head, the shape of the surface of the thermal recording material, the state of the molten component, and the physical properties of the film change due to the change in printing energy during printing. As a result, load fluctuation occurs. Such a load variation during printing / transportation causes uneven image density, and the load variation is greater as the torque is larger. That is, as the torque is larger, the density unevenness of the image due to the load fluctuation becomes larger, which is one of the causes of the deterioration of the image quality of the thermosensitive recording material. In particular, in the case of a full-color heat-sensitive recording material, heat of a considerably high energy level is applied to a layer close to the support, so that the change in energy is large and the movement of the thermal head is repeated. .

[0003] As a countermeasure for eliminating the load fluctuation, a torque difference due to printing energy is preliminarily estimated from the apparatus and the correction is performed to reduce the load fluctuation, but the effect is limited. is there. Therefore, in order to make a fundamental improvement, it is necessary to reduce the torque at the time of printing of the heat-sensitive recording material itself and to minimize the torque difference (load fluctuation) due to a change in printing energy. In order to reduce the printing torque, it is preferable to apply a matting agent in a low to medium printing energy range to increase the unevenness of the surface of the heat-sensitive recording material and reduce the contact area with the head. It is preferable to improve the lubricity between the head and the surface of the heat-sensitive recording material by increasing the amount of the lubricant in the middle to high regions.

However, applying a large amount of a matting agent impairs the smoothness of the surface of a heat-sensitive recording material, and applying a large amount of a lubricant plasticizes and deforms the surface of the heat-sensitive recording material. In either case, there is a problem that the glossiness of the surface of the heat-sensitive recording material is reduced. Furthermore,
Simply increasing the amount of the lubricant causes a decrease in the quality of the exposed skin color and the like.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems, and it is possible to form an image having high glossiness, reduce a printing torque, and reduce a load fluctuation. To provide a thermosensitive recording material capable of forming a high-quality image without density unevenness,
It is an object to achieve the object.

[0006]

<1> A thermosensitive recording material which is printed using a thermal head and has a thermosensitive recording layer and a protective layer on a support in order, wherein the protective layer is on the thermosensitive recording layer side. A heat-sensitive recording material characterized by having on its surface a thermo-soft film layer whose hardness at the time of printing is lower than the hardness of the protective layer. <2> The protective layer contains inorganic ultrafine particles, and the glossiness at 20 ° of the printed image after printing is 40 or more <1>
2. The heat-sensitive recording material according to item 1. <3> The heat-sensitive recording material according to <1> or <2>, wherein the protective layer has a dynamic hardness at 120 ° C of 30 or more, and the thermal soft film layer has a dynamic hardness at 120 ° C of 10 or less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermal recording material of the present invention is to be printed by a thermal head. Further, the thermosensitive recording material has a thermosensitive recording layer and a protective layer sequentially on a support, and a thermosoft layer having a hardness at the time of printing lower than the hardness of the protective layer on the thermosensitive recording layer side surface of the protective layer. Have. Note that, between the support and the thermosoftening layer, other layers appropriately selected according to the purpose, for example, an undercoat layer provided between the support and the thermosensitive recording layer, It may have an intermediate layer provided therebetween, a light transmittance adjusting layer provided between the heat-sensitive recording layer and the thermal soft film layer, and the like.

Hereinafter, the heat-sensitive recording material of the present invention will be described in detail. (Protective layer) The protective layer is a layer provided for sticking the thermal recording layer and protecting the thermal recording layer from solvents and the like. The protective layer has a small contact area with the thermal head to reduce the printing torque. In order to achieve this, it is preferable to include inorganic ultrafine particles. The protective layer preferably has a dynamic hardness at 120 ° C. of 30 or more, more preferably 35 or more, even more preferably 35 to 45. If the dynamic hardness is less than 30, the protective layer surface will be deformed during printing,
Image quality is likely to deteriorate, and if it exceeds 45, streak-like unevenness may easily occur on the printing screen.

The dynamic hardness is a value measured by a dynamic hardness tester of Shimadzu Corporation. All the dynamic hardnesses in the present specification were measured in the same manner. In addition to the inorganic ultrafine particles (pigments), it is also preferable to include other pigments, waxes, a cross-linking agent, a catalyst, a release agent, a surfactant, a water repellent, and the like as necessary.

The inorganic ultrafine particles are inorganic fine particles having an average primary particle size of 0.5 μm or less, preferably 0.2 μm or less, and more preferably 0.15 μm or less. However, the maximum particle size of the dispersion (the threshold value at the larger particle size distribution in the dispersion) is preferably 0.5 μm or less, more preferably 0.4 μm or less, and 0.35 μm or less. Particularly preferred. Also,
The frequency of (agglomerated) particles having a particle size of 0.35 μm or more in the dispersion is 5% or less, preferably 1% or less, and 0.25% or less.
It is particularly preferred that the frequency of (agglomerated) particles of μm or more is 5% or less. The particle size can be determined by a known method, for example, CO 2
It can be measured by an ULTER N4 type submicron particle size analyzer (Nikkaki) or the like.

The inorganic ultra-fine particles are preferably at least one selected from the group consisting of barium sulfate, zinc oxide, magnesium oxide, lead oxide, zirconium oxide, colloidal silica, and alumina. Colloidal silica, barium sulfate And alumina are even more preferred. Among them, barium sulfate is particularly preferred.

The above-mentioned inorganic ultrafine particles may be used alone or in combination of two or more. When colloidal silica is used as the inorganic ultrafine particles, since the colloidal silica has a particularly high activity, depending on the combination when performing multi-layer simultaneous coating, the interaction with the compound of the other layer may cause uneven coating, resulting in thermal recording. The surface smoothness of the material may be impaired. Therefore, when using colloidal silica, it is preferable to use colloidal silica and other inorganic ultrafine particles in combination, and the mixing ratio (colloidal silica / other inorganic ultrafine particles) is 1/9 to 6/4 by mass ratio.
Is preferred, and a blend ratio of 2/8 to 5/5 is more preferred. Further, as a combination of the inorganic ultrafine particles to be used in combination, a combination of colloidal silica and barium sulfate is preferable,
It is more preferable to use colloidal silica and barium sulfate in a combination ratio of 2/8 to 5/5.

As the inorganic ultrafine particles having an average particle diameter of 0.5 μm or less which can be suitably used in the present invention, specifically, for example, barium sulfate (trade name: BARILINE BF)
-21, BF-20, manufactured by Sakai Chemical Industry), zirconium oxide (trade name: NZR-A, manufactured by Nissan Chemical), zinc oxide (trade name: FINEX-75, manufactured by Sakai Chemical Industry), titanium oxide (TTO-55) And Ishihara Sangyo) and silica (Nippon Aerosil).

These inorganic ultrafine particles are JIS Z-coated so as to maintain the glossiness of the printing screen (solid black portion) after printing.
It is added to the protective layer considering that the glossiness at 20 ° specified by 8741 is 40 or more, preferably 45 or more, more preferably 50 or more.

As a method of adding the inorganic ultrafine particles, an aqueous dispersion resin such as carboxymethylcellulose, gelatin, or polyvinyl alcohol is used in order to prevent aggregation of the fine particles and achieve uniform adsorption on the surface of the resin particles. It is preferable from the viewpoint of effect and production to adopt a method of adding as a resin solution, a method of adding a colloidal dispersion after preparing the colloidal dispersion by various mills or the like, and the like.

Other pigments to be added to the protective layer include inorganic laminar compounds including mica, calcium oxide, zinc oxide, titanium oxide, aluminum hydroxide, kaolin, synthetic silicate, amorphous silica, and the like. Urea formalin resin powder and the like. As the waxes to be added to the protective layer, polyolefin waxes, ester waxes, amide waxes, fatty acids, natural waxes and the like can be used. Among them, carnauba wax is preferred. The emulsified particle size of the carnauba wax particles in the protective layer coating liquid is preferably 1 to 10 μm.

As the binder for the protective layer, a water-soluble binder is preferable, and long-chain alkyl ether-modified polyvinyl alcohol, silicone-modified polymer, gelatin, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, starch, agar, κ-carrageenan, gum arabic, Casein, styrene-maleic anhydride copolymer hydrolyzate, ethylene-maleic anhydride copolymer hydrolyzate, isobutylene-maleic anhydride copolymer hydrolyzate, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylamide and the like. Can be

Of these water-soluble binders, silicone-modified aqueous polymers and ethylene-modified polyvinyl alcohol are preferred. Specific examples of the silicone-modified aqueous polymer include those described in Japanese Patent Application No. 9-7060. Among them, a silicone block-modified polyvinyl alcohol using polyvinyl alcohol for the trunk polymer is particularly preferable.

Among them, a water-soluble polymer which can be set and dried is preferable in that it has a high surface smoothness in the background portion and the printing screen and is excellent in glossiness. The set-dryable water-soluble polymer exhibits a predetermined viscosity when heated (for example, around 40 ° C.) and can be applied, and then cools (for example, 5 ° C. to 15 ° C.) to increase the viscosity and the fluid state. Means a water-soluble polymer that stops and gels. Suitable polymers as the set-dryable water-soluble polymer include proteins such as gelatin, polysaccharides such as carrageenan and agar, and polyvinyl alcohol-based compounds.In the case of polyvinyl alcohol-based compounds, gelation with polyvinyl alcohol-based compounds is possible. When used in combination with boric acid or a salt thereof as an agent, it can be used as a water-soluble polymer that can be set and dried.

As the water-soluble binder, a synthetic rubber latex or a synthetic resin emulsion may be used. Examples of monomers constituting latex and emulsion of these polymers include acrylates, methacrylates, crotonic esters, vinyl esters, maleic diesters, fumaric diesters, itaconic diesters, acrylamides, and methacrylic acid. Examples include amides, vinyl ethers, styrenes, and acrylonitrile.

Specific examples of these monomers are shown below. As the acrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate,
Isopropyl acrylate, n-butyl acrylate,
Isobutyl acrylate, tert-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, acetoxyethyl acrylate, phenyl acrylate, 2-methoxy acrylate, 2-ethoxy acrylate, 2- (2-methoxy ethoxy) ethyl acrylate, and the like.

Examples of the methacrylate include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, tert-
Butyl methacrylate, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate, 2-ethoxyethyl methacrylate and the like.

Examples of the crotonate include butyl crotonate and hexyl crotonate. As vinyl esters, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl methoxy acetate,
And vinyl benzoate.

Examples of the maleic acid diester include diethyl maleate, dimethyl maleate, dibutyl maleate and the like. Examples of the fumaric acid diester include diethyl fumarate, dimethyl fumarate, dibutyl fumarate and the like. Examples of the itaconic acid diester include diethyl itaconate, dimethyl itaconate, and dibutyl itaconate.

The acrylamides include acrylamide, methyl acrylamide, ethyl acrylamide, propyl acrylamide, n-butyl acrylamide, t
tert-butylacrylamide, cyclohexylacrylamide, 2-methoxyethylacrylamide, dimethylacrylamide, diethylacrylamide, phenylacrylamide and the like.

Examples of the methacrylamides include methyl methacrylamide, ethyl methacrylamide, n-butyl methacrylamide, tert-butyl methacrylamide,
2-methoxy methacrylamide, dimethyl methacrylamide, diethyl methacrylamide and the like.

Examples of vinyl ethers include methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxyethyl vinyl ether, dimethylamino vinyl ether and the like. As styrenes,
Styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, butyl styrene, chloromethyl styrene, methoxy styrene, butoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, vinyl benzoate methyl ester, 2- Methylstyrene and the like can be mentioned.

The polymer composed of these monomers may be a homopolymer or a copolymer. Binary or ternary copolymers of acrylic esters, methacrylic esters, styrenes, acrylic acid and methacrylic acid; copolymers of styrenes and butadiene are preferably used.

The Tg of the polymer constituting the aqueous binder
(Glass transition point) is 150 ° C. or less, preferably 0 ° C.
130 ° C, particularly preferably 40 ° C to 100 ° C.

It is desirable to use a crosslinking agent which undergoes a crosslinking reaction with the silicone-modified polymer and / or the aqueous binder.
Or the aqueous binder is a carboxy group as a functional group,
Amino group, ammonium base, hydroxy group, sulfinic acid (or salt thereof) group, sulfonic acid (or salt thereof) group,
Alternatively, it is desirable to have at least one functional group selected from glycidyl groups.

Examples of the cross-linking agent include vinyl sulfone compounds, aldehyde compounds (formaldehyde, glutaraldehyde, etc.), epoxy compounds,
Oxazine-based compounds, triazine-based compounds,
Polymer hardeners described in JP-A-234157, methylated melamine, blocked isocyanates, methylol compounds, carbodiimide resins and the like can be used.

Among these crosslinking agents, vinyl sulfone compounds, aldehyde compounds, epoxy compounds, oxazine compounds, triazine compounds,
The polymer hardener described in JP-A-234157 is preferred.

Of the modified polyvinyl alcohols, silanol-modified polyvinyl alcohol is particularly preferable, which itself can improve water resistance and the like. However, in order to further improve water resistance, it is crosslinked with silanol-modified polyvinyl alcohol. It is effective to use an agent and a catalyst for accelerating the reaction.

Specific examples of the crosslinking agent include the following. As the epoxy compound, those having two or more functions can be used. For example, dibromophenyl glycidyl ether, dibromoneopentyl glycol diglycidyl ether, an emulsion of epoxy cresol novolak resin, a modified bisphenol A type epoxy emulsion,
Adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, hydroquinone diglycidyl ether, bisphenol S glycidyl ether, terephthalic acid diglycidyl ether, glycidyl phthalimide, propylene polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, allyl glycidyl Ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, phenol (EO) 5 glycidyl ether, p-tert-butylphenyl glycidyl ether, lauryl alcohol (EO) 15 glycidyl ether, carbon number 12 to 1
Glycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether,
1,6-hexanediol diglycidyl ether, ethylene polyethylene glycol diglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl-tris ( 2-hydroxyethyl) isocyanurate and the like. Among these epoxy compounds, glycidyl ethers are particularly preferable.

The epoxy compound effective for the present invention preferably has an epoxy equivalent of 70 to 1000 WPE. When the epoxy equivalent exceeds 1000 WPE, it becomes difficult to impart water resistance, which is not preferable.

The term "blocked isocyanate" refers to a compound obtained by masking the terminal isocyanate group of an isocyanate with a blocking agent. Examples of the blocked isocyanate include (a) an isocyanate compound in which a block of a hydrophilic group comprising a carbamoyl sulfonate group (—NHCOSO ₃ ⁻ ) is formed at the terminal of the isocyanate compound to block an active isocyanate group, and (b) isopropyl Blocking active isocyanate groups using lidenmalonate (this blocked isocyanate is obtained by reacting HDI isocyanurate, isopropylidene malonate and triethylamine), and (c) blocking active isocyanate groups with phenols And the like. Such a blocked isocyanate is mixed with a silanol-modified polyvinyl alcohol and heated to cross-link and modify the silanol-modified polyvinyl alcohol, thereby achieving water resistance of the silanol-modified polyvinyl alcohol.

As the vinyl sulfone compound, those described in JP-A-53-57257, JP-A-53-41221, JP-B-49-13563, JP-B-47-24259, and the like can be used. It is.

Examples of the aldehyde compounds include monoaldehydes such as formaldehyde and acetaldehyde, and polyvalent aldehydes such as glyoxal, glutaraldehyde and dialdehyde starch (dialdehyde starch). Examples of the methylol compound include methylol melamine and dimethylol urea. And the like. In the case of silanol-modified polyvinyl alcohol, an aldehyde compound is particularly preferred as the crosslinking agent.

The amount of the crosslinking agent used for the water-soluble polymer, polymer latex or polymer emulsion is 1 to 50 parts by weight based on 100 parts by weight of the water-soluble polymer, polymer latex or polymer emulsion. It is desirable to mix. When the amount of the crosslinking agent is less than 1 part by mass, the degree of crosslinking modification is low, and the water resistance and chemical resistance become insufficient. On the other hand, when the amount exceeds 50 parts by mass, the liquid stability is reduced, which is preferable. Absent.

The protective layer is formed by applying a protective layer coating solution comprising a (water-soluble) binder and inorganic ultrafine particles on the thermal soft film layer using a bar coater, an air knife coater, a blade coater, a curtain coater or the like, and drying. Get it. However, the protective layer may be applied at the same time as the thermal soft film layer by the superposition method, or after the thermal soft film layer is applied, the thermal soft film layer may be dried once and then applied thereon. The dry coating amount of the protective layer is preferably 0.1 to 3 g / m ² , and 0.3 to ² g / m ² .
0 g / m ² is more preferred. If the coating amount is large, the thermal sensitivity is remarkably lowered, and if the coating amount is too low, the function as a protective layer (friction resistance, lubricity, scratch resistance, etc.) cannot be exhibited. After the application of the protective layer, a calendering treatment may be performed if necessary.

(Thermo-softening layer) The thermo-softening layer is a layer having a hardness lower than that of the protective layer at the time of printing by a thermal head, and is provided adjacent to the surface of the protective layer on the heat-sensitive recording layer side. . By providing this thermal soft film layer, the thermal soft film layer is softened more than the protective layer by the heat of the thermal head and is effectively deformed to perform the function of a cushion layer, thereby reducing the printing torque without deforming the smooth protective layer. Can be reduced. Therefore, the load fluctuation is reduced due to the decrease in the printing torque, and it is possible to form a high-quality image without density unevenness while maintaining the high gloss protective layer.

The thermal soft film layer functions if the hardness at the time of printing with a thermal head is lower than the hardness of the protective layer.
Usually, the dynamic hardness at 120 ° C. of the thermal soft film layer is preferably 20 or less, more preferably 15 or less, and even more preferably 3 to 10. In particular, when the dynamic hardness at 120 ° C. of the protective layer is 30 or more, the dynamic hardness at 120 ° C. of the thermal soft film layer is preferably 10 or less, more preferably 7 or less, and 3 to 7 Is more preferable. If the dynamic hardness exceeds 10, the function may not be exhibited. If the dynamic hardness is less than 3, the film may be too soft, and color misregistration may occur during yellow and magenta printing.

The dynamic hardness of the protective layer at 120 ° C. is in the range of 30 to 45,
When the dynamic hardness at ℃ is in the range of 3 to 20, the difference in the dynamic hardness is preferably 20 or more, more preferably 30 or more.

Examples of the binder for the thermosoftening layer include:
Styrene-acrylic copolymer, styrene-butadiene copolymer, acryl-styrene-butadiene copolymer, vinyl acetate copolymer, acrylic-epoxy copolymer, acrylic-silicone copolymer, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, silicone Modified polymers, cellulose and the like can be mentioned. Examples of the additive include inorganic fine particles such as colloidal silica, zirconia oxide, aluminum oxide, and zinc oxide. By adding these inorganic fine particles, the cushioning property of the thermal soft film layer can be improved.

The amount of the inorganic fine particles to be added is preferably from 10 to 50, more preferably from 10 to 30, based on the binder 1 in terms of mass ratio. When the addition amount is less than 10, the thermal buffy coat layer becomes too soft,
In some cases, an appropriate cushioning property cannot be obtained, and when it exceeds 50, the protective layer becomes too hard, and uneven printing may occur due to uneven hitting of the head. If necessary, a polyhydric aldehyde such as boric acid, glyoxal, or dialdehyde starch may be added to adjust the film hardness.

The thickness of the thermal soft film layer is 1.0 to 1.0.
It is preferably 10 μm, more preferably 1.0 to 5.0 μm, and even more preferably 1.5 to 3.0 μm. When the layer thickness is less than 1.0 μm,
The effect of reducing the printing torque as the cushion layer may be reduced, and if it exceeds 10 μm, the thermal sensitivity of the heat-sensitive recording layer may decrease.

(Thermal Recording Layer) The thermal recording layer may have a single-layer structure or a multilayer structure, and may have a layer structure appropriately selected according to the purpose. The heat-sensitive recording layer contains a coloring component and is designed so that a desired color image can be formed by a coloring reaction of the coloring component. The coloring component is not particularly limited, and conventionally known components can be suitably used. The color-forming reaction is not particularly limited, and examples thereof include a color-forming reaction between a diazonium salt compound and a coupler and a color-forming reaction between an electron-donating colorless dye and an electron-accepting compound.

In the case where the heat-sensitive recording layer contains the diazonium salt compound and a coupler which reacts with the diazonium salt compound when heated to form a color, the heat-sensitive recording layer contains the diazonium salt compound and the coupler. A basic substance or the like which promotes a color forming reaction is suitably added.

The diazonium salt compound is a compound represented by the following general formula (B), whose maximum absorption wavelength can be controlled by the position and type of the substituent in the Ar portion. Formula ^{(B): Ar-N 2+} X - In the general formula (B), Ar represents an aryl group. X ^- represents an acid anion.

Specific examples of the diazonium salt compound include 4- (N- (2- (2,4-di-tert-amylphenoxy) butyryl) piperazino) benzenediazonium, 4-dioctylaminobenzenediazonium,
-(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-tert-amylphenoxy) butyryl) piperazino) benzene Diazonium, 2,5-dibutoxy-4-tolylthiobenzenediazonium, 3- (2-octyloxyethoxy) -4-
Acid anion salts such as morpholinobenzenediazonium and the following diazonium salt compounds (D-1 to 5). These may be used alone or in combination of two or more. Among these, hexafluorophosphate salts, tetrafluoroborate salts, 1,5-
Naphthalene sulfonate salts are particularly preferred.

[0051]

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Among these diazonium salt compounds,
4-decomposes with light having a wavelength of 300 to 400 nm;
(N- (2- (2,4-di-tert-amylphenoxy) butyryl) piperazino) benzenediazonium,
-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, diazonium salts shown in the above specific examples D-3 to 5 Compounds are particularly preferred. Here, the maximum absorption wavelength of the diazonium salt compound is measured by a spectrophotometer (Shimazu MPS-2000) obtained by coating each diazonium compound with a coating amount of 0.1 to 1.0 g / m ^2. It was done.

Examples of couplers which react with the diazonium salt compound when heated to produce a color include, for example, resorcinol, furruglucin, sodium 2,3-dihydroxynaphthalene-6-sulfonate, and morpholinopropylamide 1-hydroxy-2-naphthoate. 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, Benzoylacetoanilide, 2-chloro-5-octylacetoacetoanilide,
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, a compound represented by the following (C-1 to 6),
And the like. These couplers may be used alone or in combination of two or more.

[0054]

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[0055]

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The basic substance is not particularly limited and can be appropriately selected from known ones according to the purpose. In addition to the inorganic or organic basic compound, an alkaline substance which decomposes upon heating and produces an alkaline substance can be used. Such compounds include those which release such compounds, and typical examples thereof include organic ammonium salts, organic amines, amides, ureas and thioureas and derivatives thereof, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indole , Imidazoles, imidazolines, triazoles, morpholines,
Examples include nitrogen-containing compounds such as piperidines, amidines, formazines, and pyridines.

Specific examples thereof include tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine, allylurea, thiourea,
Methylthiourea, allylthiourea, ethylenethiourea,
2-benzylimidazole, 4-phenylimidazole, 2-phenyl-4-methylimidazole, 2-undecylimidazoline, 2,4,5-trifuryl-2-imidazoline, 1,2-diphenyl-4,4-dimethyl-
2-imidazoline, 2-phenyl-2-imidazoline,
1,2,3-triphenylguanidine, 1,2-dicyclohexylguanidine, 1,2,3-tricyclohexylguanidine, guanidine trichloroacetate, N, N ′
-Dibenzylpiperazine, 4,4'-dithiomorpholine, morpholinium trichloroacetate, 2-aminobenzothiazole, 2-benzoylhydrazinobenzothiazole and the like. These may be used alone or in combination of two or more.

The colorless electron donating dye is not particularly limited and can be appropriately selected from known ones according to the purpose. In the present invention, a precursor of the colorless electron donating dye can be used. .

The electron-donating colorless dye precursor includes:
For example, triarylmethane compounds, diphenylmethane compounds, thiazine compounds, xanthene compounds,
And spiropyran compounds. They are,
One type may be used alone, or two or more types may be used in combination. Among them, a triarylmethane-based compound and a xanthene-based compound are preferable because of high color density and usefulness. Examples of these include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (ie, crystal violet lactone), 3,3-bis (p
-Dimethylamino) phthalide, 3- (p-dimethylaminophenyl) -3- (1,3-dimethylindole-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-halophenylleuco auramine, 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-nitrobenzylleucomethylene 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 phenol derivatives, salicylic acid derivatives, and hydroxybenzoic acid esters. Among these, bisphenols and hydroxybenzoates are particularly preferred, and specifically, 2,2-bis (p-hydroxyphenyl) propane (that is, bisphenol A), 4,4′-
(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 salt, 3-α, α-dimethylbenzylsalicylic acid and its polyvalent metal salt, butyl p-hydroxybenzoate, p
Benzyl hydroxybenzoate, 2-ethylhexyl p-hydroxybenzoate, p-phenylphenol, p
-Cumylphenol and the like are particularly preferred.

In the present invention, the heat-sensitive recording layer preferably contains a sensitizer, and the sensitizer may be a low-sensitizer having an aromatic group and a polar group in the molecule. Melting point organic compounds are preferred, specifically, benzyl p-benzyloxybenzoate, α-naphthyl benzyl ether,
β-naphthylbenzyl ether, β-naphthoic acid phenyl ester, α-hydroxy-β-naphthoic acid phenyl ester, β-naphthol- (p-chlorobenzyl) ether, 1,4-butanediol phenyl ether,
1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-ethylphenyl ether, 1,4-butanediol-m-methylphenyl ether, 1-phenoxy-2- (p-tolyloxy) Ethane, 1-phenoxy-2- (p-ethylphenoxy)
Ethane, 1-phenoxy-2- (p-chlorophenoxy) ethane, p-benzylbiphenyl, and the like.

The thermosensitive recording layer preferably contains a compound represented by the following general formula (A) in an amount of 0.05 g / m ² or more. When the heat-sensitive recording layer is composed of a plurality of layers, the layer containing the compound represented by the general formula (A) is not particularly limited and may be appropriately selected depending on the purpose.
It is preferably a layer composed of a solid dispersion.

Formula (A): R—SO ₃ M In the above formula (A), R represents an alkyl group, an aryl group, an alkoxyl group, an aryloxy group, a polyoxyethylene aryl group, or a polyoxyethylene alkyl. Represents a group, preferably an alkyl group having 1 to 20 carbon atoms,
An aryl group having 1 to 30 carbon atoms is preferable, and an aryl group having 1 to 2 carbon atoms.
An alkoxyl group having 0 carbon atoms is preferable, an aryloxy group having 1 to 30 carbon atoms is preferable, a polyoxyethylene aryl group having 1 to 30 carbon atoms is preferable, and a polyoxyethylene alkyl group having 1 to 20 carbon atoms is preferable. M represents an alkali metal, and is preferably sodium, potassium, or the like.

Specific examples of the compound represented by the general formula (A) include sodium lauryl sulfate, sodium higher alcohol sulfate, sodium dodecylbenzenesulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, and alkyldiphenyl ether disulfonic acid. Sodium, sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium alkane sulfonate, sodium salt of condensate of β-naphthalenesulfonic acid formalin, special aromatic formalin sulfonate And sodium salts of condensates. These may be used alone or in combination of two or more. In the present invention, among these, sodium dodecylbenzenesulfonate represented by the following formula is preferable in that it can improve the exposure coloration of the background.

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The content of the compound represented by formula (A) in the heat-sensitive recording layer is 0.05 g / m ^2.
Or more, preferably 0.05 to 0.50 g / m ² ,
0.05 to 0.20 g / m ² is preferred. When the content is less than 0.05 g / m ² , the light resistance of the heat-sensitive recording material is not sufficient, and it is not preferable in that the surface is colored by exposure to light. On the other hand, when the content is 0.05 g / m ² , This is preferable because the weather resistance of the heat-sensitive recording material is remarkably improved, and the background exposure coloring is effectively suppressed.

In the thermosensitive recording layer, the diazonium salt compound, the coupler which reacts with the diazonium salt compound when heated to form a color, the basic substance, the electron-donating colorless dye, the electron-accepting compound, There are no particular restrictions on the mode of inclusion of the sensitizer and the like, and it can be appropriately selected according to the purpose. For example, (1) a method of containing these by solid dispersion, and (2) a method of containing them by emulsion dispersion (3) a method of containing by polymer dispersion,
(4) a method of containing by latex dispersion, and (5) a method of containing by microencapsulation.

Among these, the method of microencapsulation and inclusion is preferable from the viewpoint of storage stability. In the case of utilizing the color development reaction between the diazonium salt compound and the coupler, the diazonium salt compound is microencapsulated. The thermosensitive recording layer is preferably contained in the heat-sensitive recording layer, and in the case of utilizing a color-forming reaction between the electron-donating colorless dye and the electron-accepting compound, the electron-donating colorless dye is microencapsulated to form the heat-sensitive recording layer. It is preferable to contain them.

When the heat-sensitive recording layer has a multilayer structure, a multicolor heat-sensitive recording material can be obtained by changing the hue of each heat-sensitive recording layer. The layer structure in this case is as follows:
There is no particular limitation, and it can be appropriately selected according to the purpose. In the present invention, two kinds of diazonium salt compounds having different photosensitive wavelengths and each of the diazonium salt compounds react with heat to develop a different hue. It is preferable to form a multicolor heat-sensitive recording layer by laminating two heat-sensitive recording layers combining a coupler and a heat-sensitive recording layer combining an electron-donating colorless dye and an electron-accepting compound. That is, on the support, a heat-sensitive recording layer A containing an electron-donating colorless dye and an electron-accepting compound, a diazonium salt compound having a maximum absorption wavelength of 360 ± 20 nm and a hot reaction with the diazonium salt compound are presented. A thermosensitive recording layer B-1 containing a coloring coupler; and a thermosensitive recording layer B- containing a diazonium salt compound having a maximum absorption wavelength of 400 ± 20 nm and a coupler which reacts with the diazonium salt compound when heated to give a color. 2 are laminated in this order, and a multicolor heat-sensitive recording material is preferable.

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

Further, in the present invention, three types of heat-sensitive recording layers each comprising a combination of three kinds of diazonium salt compounds having different photosensitive wavelengths and a coupler which reacts with each of the diazonium salt compounds when heated and develops a different hue are used. It is also preferable to form a laminated multicolor heat-sensitive recording layer. That is, on the support, the maximum absorption wavelength is 350 nm or less, preferably 34 nm or less.
Heat-sensitive recording layer A-1 containing a diazonium salt compound having a wavelength of not more than 0 nm and a coupler which reacts with the diazonium salt compound when heated to form a color, and has a maximum absorption wavelength of 360 ± 20 nm
Heat-sensitive recording layer A-2 containing a diazonium salt compound which is a coupler which reacts with the diazonium salt compound when heated to give a color, a diazonium salt compound having a maximum absorption wavelength of 400 ± 20 nm, and a heat-sensitive layer. Heat-sensitive recording layer A-3 containing a coupler which forms a color upon reaction
Are preferably stacked in this order.

In the case of the multicolor heat-sensitive recording layer described above,
If the color hue of each heat-sensitive recording layer is selected so as to be three primary colors, yellow, magenta, and cyan in subtractive color mixing,
Full-color image recording becomes possible. As described above, according to the heat-sensitive recording material of the present invention, even in the case where high energy is applied and the movement of the thermal head is repeated to form a multi-color or full-color image with the heat-sensitive recording layer having a multilayer structure, the printing torque can be reduced. Since the load fluctuation is reduced by the decrease in the image density, it is possible to form an image without density unevenness.

(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,
In addition to a plastic film such as a polyacrylic acid copolymer film and a polycarbonate film, paper, synthetic paper, paper having a plastic resin layer, and the like can be mentioned, and a support having the plastic film layer is preferable. These may be transparent or opaque, and may be used alone or in combination of two or more.

As the support having the plastic layer, a support in which a layer made of a thermoplastic resin is formed on both sides of the base paper or at least on the side on which the recording layer is formed, is preferably mentioned. (1) base paper coated with a thermoplastic resin by melt extrusion coating, (2) base paper coated with a gas barrier layer on a thermoplastic resin coated by melt extrusion,
(3) a base paper having a plastic film having low oxygen permeability bonded thereto, (4) a base paper having a thermoplastic resin provided by melt extrusion on a surface where the plastic film is bonded to the base paper, and (5) a thermoplastic having a base paper having thermoplastic resin. After melt-extrusion coating a resin, a plastic film is adhered, and the like.

Examples of the thermoplastic resin to be melt-extruded on the base paper include olefin polymers such as α-olefin homopolymers such as polyethylene and polypropylene, and mixtures of these various polymers; Suitable examples include a random copolymer with vinyl alcohol. Examples of the polyethylene include LDPE
(Low density polyethylene), HDPE (high density polyethylene), L-LDPE (linear low density polyethylene) and the like.

The method of bonding the plastic film to the base paper is not particularly limited, and may be appropriately selected from known lamination methods as described in “Handbook of New Laminating Processes” edited by Processing Technology Research Group. Suitable examples include so-called dry lamination, solvent-free dry lamination, dry lamination using an electron beam or ultraviolet curable resin, or hot dry lamination. In the present invention, among the above supports, those obtained by coating both sides of a base paper mainly composed of natural pulp with an olefin polymer are particularly preferable.

(Undercoat Layer) In the present invention, it is preferable to have an undercoat layer between the support and the thermosensitive recording layer. The undercoat layer is not particularly limited and may be appropriately selected from known ones according to the purpose. Gelatin having a PAGI viscosity of 10 to 30 mP and a PAGI jelly strength of 15 to 70 g is preferred. It is particularly preferable to contain a "gelatin") and a layered inorganic compound. In the present invention, it is also preferable to have such a layer as an intermediate layer described later.

The viscosity of the above-mentioned PAGI method and the jelly strength of the above-mentioned PAGI method are described in Pagii Method: Photographic Gelatin Test Method, 7th Edition (1992)
2 years version). The gelatin can be obtained by reducing the molecular weight of a known gelatin produced by a usual method (hereinafter, referred to as “normal gelatin”). However, the term "normal gelatin" used herein refers to, for example, "raw glue and gelatin (edited by Abiko Yoshihiro, published by Nippon Nippon, Gelatin Industry Association, 1987), such as cow bone, cow hide, and pig hide. Is processed by lime, acid or the like, and has a much higher viscosity and jelly strength than the gelatin.

The above-mentioned ordinary gelatin is characterized by conditions such as raw materials, processing methods (eg, lime treatment, acid treatment) and extraction conditions (temperature, number of extractions). The gelatin may be obtained by reducing the molecular weight based on any gelatin.However, the number of extractions is small, and the one extracted at a low temperature can achieve both low viscosity and jelly strength within the above numerical range. Is preferred. Examples of the method for reducing the molecular weight include a method using an enzyme and a method using heat, and among these, the method using an enzyme is preferable. In the case of the method using heat, when the viscosity is reduced to a preferable value, the jelly strength may be reduced. In addition, as said enzyme, papain is mentioned suitably, for example.

In the gelatin, the viscosity according to the PAGI method is 10 to 30 mP, and the jelly strength according to the PAGI method is 15 to 70 g. If the viscosity according to the PAGI method is less than 10 mP, the viscosity of the coating solution decreases. Becomes larger,
In some cases, the dispersion state of the pigment (mica) in the coating liquid is deteriorated, and when it exceeds 30 mP, the viscosity of the coating liquid increases, and coating failure may easily occur. Further, when the jelly strength of the PAGI method is less than 15 g, the strength of the coating film decreases, and the adhesive strength with the support may decrease. When the jelly strength of the PAGI method is greater than 70 g, the coating strength may decrease. The curl of the film may increase due to environmental changes.

The gelatin may be cross-linked by using a hardening agent, if necessary. In this case, examples of the hardening agent include known ones used as hardening agents for gelatin. For example, a vinyl sulfone compound, an active halogen compound, an isocyanate compound, an epoxy compound and the like can be mentioned. Among these, epoxy compounds are particularly preferred, and as the epoxy compound, for example, the following compounds are suitably mentioned.

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The coating amount of the gelatin in the undercoat layer is preferably 0.5 g / m ² or more from the viewpoint of suppressing Plister (a fine swelling phenomenon due to the heat of the printer thermal head during printing).

The layered inorganic compound is preferably a swellable inorganic layered compound. Specific examples of the swellable inorganic layered compound include bentonite, hectorite, saponite, beaderite, nontronite, stevensite, beidellite, swellable viscosity minerals such as montmorillonite, swellable synthetic mica, swellable synthetic smectite, and the like. No.

These swellable inorganic layered compounds have a laminated structure composed of unit crystal lattice layers having a thickness of about 10 to 15 Å, and the substitution of metal atoms in the lattice is significantly larger than that of other clay minerals. As a result, the lattice layer suffers from a lack of positive charge, and Na ⁺ , C
Cations such as a ²⁺ and Mg ²⁺ are adsorbed. The cations interposed between these layers are called "exchangeable cations" and exchange with various cations. In particular, when the cation between the layers is Li ⁺ , Na ^+, etc., since the ionic radius is small, the bond between the layered crystal lattices is weak, and the layer swells greatly with water. When shear is applied in this state, it is easily cleaved and forms a stable sol in water. Among the specific examples of the swellable inorganic layered compound, bentonite and swellable synthetic mica are preferable because of their strong tendency, and swellable synthetic mica is particularly preferable.

As the swellable synthetic mica, for example, the following compounds are preferably exemplified. Na tetrathick mica NaMg _2.5 (Si ₄ O ₁₀ ) F ₂ , Na or Li teniolite (NaLi) Mg ₂ (Si ₄ O ₁₀ ) F ₂ , Na or Li hectorite (NaLi) _{/ 3} Mg _2/3 Li _{1 / 3} (Si
4O ₁₀ ) F ₂ , and the like.

The swellable synthetic mica has a thickness of 1 to 50 nm and a plane size of 1 to 20 μm. The thickness is preferably as thin as possible in terms of diffusion control, and the plane size is preferably as large as possible without deteriorating the smoothness and transparency of the coated surface. The aspect ratio of the swellable synthetic mica is usually 100 or more, preferably 200 or more, and more preferably 500 or more.

In the case where the above-mentioned ordinary gelatin is used, when the ratio of mica (to gelatin is 1.5 to 10 or more) increases, the viscosity and gelation progress at a certain solid content concentration (for example, 5 to 10%). , It is necessary to lower the viscosity. To lower the viscosity, there is a method of lowering the concentration. However, lowering the concentration increases the drying load of the coating film and deteriorates the coated surface state due to thick coating. There is also a method of adding urea, salt, or the like to the coating solution, but the viscosity cannot be sufficiently reduced, and the surface after coating is poor. On the other hand, the gelatin is capable of remarkably reducing the thickening and gelation without causing such adverse effects, and can significantly reduce the thickening and gelation even when used in combination with mica. Is advantageous.

The content of the water-swellable synthetic mica in the undercoat layer was 1/100 by mass ratio of mica / gelatin.
20 to 1/2 is preferred. When the content of the water-swellable synthetic mica is less than 1/20, the undercoat layer may not function sufficiently as an oxygen barrier layer. May worsen.

The coating amount of mica in the undercoat layer is usually 0.01 g / m ² or more, and 0.02 g / m ² or more.
/ M ² or more. When the coating amount of the mica is 0.01
If it is less than g / m ² , the oxygen-blocking ability of the undercoat layer is reduced, and the property of preventing the background portion from being colored may not be able to be exhibited.

(Intermediate Layer) In the present invention, when the thermosensitive recording layer has a laminated structure of thermosensitive coloring layers having different hues, an intermediate layer for preventing color mixing or the like is provided between the thermosensitive recording layers. Is preferred. The intermediate layer is not particularly limited and may be appropriately selected depending on the intended purpose. The intermediate layer can be formed using a water-soluble polymer compound or the like.

Examples of the water-soluble polymer compound include polyvinyl alcohol, modified polyvinyl alcohol, methyl cellulose, sodium polystyrene sulfonate, styrene-maleic acid copolymer, gelatin and / or
Alternatively, those composed of a zetirane derivative, polyethylene glycol and / or a polyethylene glycol derivative are preferred.

The inorganic layer compound can be suitably added to the intermediate layer. When the intermediate layer contains the inorganic layered compound, color mixing can be prevented by suppressing and preventing mass transfer between layers, and raw storage and color image storage are improved by suppressing the supply of oxygen. Can be done.

(Light Transmittance Adjusting Layer) In the present invention, a light transmittance adjusting layer can be suitably provided. It is preferable that at least one light transmittance adjusting layer is provided in the thermosensitive recording material, and it is more preferable that the light transmittance adjusting layer is formed between the thermosensitive recording layer and the protective layer. Note that the light transmittance adjusting layer may be designed so as to double as the protective layer. 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 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 the fixing of the heat-sensitive recording layer does not hinder.

The component functioning as a precursor of the ultraviolet absorber absorbs ultraviolet light 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. Began to function as an agent,
Most of the light in the wavelength range necessary for fixing in the ultraviolet region is absorbed by the ultraviolet absorber, and the transmittance is reduced.
Although the light resistance of the heat-sensitive recording material is improved, the visible light transmittance is not substantially changed because there is no visible light absorbing effect.

Preferred examples of the component functioning as a precursor of the ultraviolet absorbent include a compound represented by any of the following formulas (1) to (4).

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In the general formulas (1) to (4), m is 1
Or 2 is represented. A is the general formula (1) when m = 1, and
And in the general formulas (2) to (4), -SO_Two-R, -C
OR, -CO_Two-R, -CONH-R, -POR
¹R^Two, -CH _TwoR^ThreeOr -SiR^FourR^FiveR⁶Represents Also,
A is -SO in the general formula (1) when m = 2._Two
R⁷SO_Two-, -CO-, -COCO-, -COR⁷CO
-, -SO_Two-Or -SO-.

X represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group or a halogen atom in the general formulas (1), (3) and (4). X is an alkylene group, —OR ⁷ O— or —O in the general formula (2).
Represents COR ⁷ CO ₂ —. W represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group or a halogen atom in the general formulas (1), (2) and (4). W is
In the general formula (3), -OR ⁷ O- or -OCOR ⁷ C
Represents O ₂ —.

Y represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group or a halogen atom in the general formulas (1), (2) and (3). Further, Y is represented by the general formula (4)
^{In, -OR 7 O -, - OCOR} 7 CO 2 -, - CH 2
_{^{CH 2 CO 2 R 7 OCOCH 2}} CH 2 -, - CH 2 CH 2 OC
OR ⁷ CO ₂ CH ₂ CH ₂ — or —CH ₂ CH ₂ CON (R
⁸ ) represents R ⁷ N (R ⁸ ) COCH ₂ CH ₂ —.

Z represents a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group. Here, R represents an alkyl group or an aryl group. R ¹ and R ² are an alkoxy group,
Represents an aryloxy group, an alkyl group or an aryl group.
R ³ represents a phenyl group substituted with at least one nitro group or methoxy group. R ⁴ , R ⁵ and R ⁶ represent an alkyl group or an aryl group. R ⁷ represents an alkylene group or an arylene group. R ⁸ represents a hydrogen atom or an alkyl group.

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

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

The arylene group further includes an alkyl group,
It may be substituted with an alkoxy group, a halogen atom or the like.

The substituents represented by X, Y and W include an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, a fluorine atom and a chlorine atom. , A bromine atom or a hydrogen atom is preferable, and among them, an alkyl group having 1 to 12 carbon atoms,
Particularly preferred are 12 alkoxy groups, phenyl groups, or hydrogen and chlorine atoms.

As the substituent represented by Z, a hydrogen atom,
A chlorine atom, a fluorine atom, an alkyl group having 1 to 12 carbon atoms,
An alkoxy group having 1 to 12 carbon atoms is preferable, and among these, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydrogen atom, and a chlorine atom are particularly preferable.

The substituent represented by R has 1 to 1 carbon atoms.
Preferred are an alkyl group having 18 and an aryl group having 6 to 18 carbon atoms, and among these, an alkyl group having 1 to 12 carbon atoms,
An aryl group having 6 to 12 carbon atoms is particularly preferred.

The substituents represented by R ¹ and R ² include an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, and a
Twelve aryl groups are preferred.

Examples of the substituent represented by R ³ include a 2-nitrophenyl group, a 3,5-dimethoxyphenyl group,
A 4,5-trimethoxyphenyl group is preferred.

The substituent represented by R ⁴ , R ⁵ and R ⁶ is preferably an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and is preferably an alkyl group having 1 to 8 carbon atoms or phenyl. Groups are particularly preferred.

In a so-called bis-form having two benzotriazole rings in one molecule, the substituent represented by R ⁷ is an alkylene group having 1 to 12 carbon atoms or a substituent having 6 to 6 carbon atoms.
A 12 arylene group is preferable, and a substituent represented by R ⁸ is preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

As the substituent represented by A, -SO ₂ R
Is particularly preferred.

The specific examples of the substituents are described below, but the present invention is not limited to these. X, Y, and W
Among the substituents represented by are monovalent, a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, Pentyl group, hexyl group, octyl group, decyl group, dodecyl group, allyl group, 2-butenyl group, benzyl group, α-dimethylbenzyl group, methoxy group, ethoxy group, propyloxy group, butyloxy group,
Octyloxy group, dodecyloxy group, methoxyethoxy group, phenoxyethoxy group, methoxycarbonylethyl group, ethoxycarbonylethyl group, propyloxycarbonylethyl group, butyloxycarbonylethyl group,
Examples thereof include an octyloxycarbonylethyl group, a phenoxycarbonylethyl group, a phenyl group, a tolyl group, a chlorine atom, a fluorine atom, and a bromine atom. Examples of the divalent group include the following.

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As the substituent represented by Z, a hydrogen atom,
Examples include a chlorine atom, a methyl group, an ethyl group, a propyl group, a hexyl group, a methoxy group, an ethoxy group, a propyloxy group, and an octyloxy group.

Examples of the monovalent substituent represented by A include methanesulfonyl, ethanesulfonyl, butanesulfonyl, benzenesulfonyl, 4-methylbenzenesulfonyl, 2-mesitylenesulfonyl,
-Methoxybenzenesulfonyl group, 4-octyloxybenzenesulfonyl group, 2,4,6-triisopropylbenzenesulfonyl group, β-styrenesulfonyl group, vinylbenzenesulfonyl group, 4-chlorobenzenesulfonyl group, 2,5-dichlorobenzenesulfonyl Group, 2,
4,5-trichlorobenzenesulfonyl group, 1-naphthalenesulfonyl group, 2-naphthalenesulfonyl group, quinolinesulfonyl group, thiophenesulfonyl group, acetyl group, propionyl group, butyryl group, pivaloyl group, lauroyl group, stearoyl group, benzoyl group, Cinnamoyl group, furoyl group, nicotinoyl group, methoxycarbonyl group, ethoxycarbonyl group, phenoxycarbonyl group, hexylaminocarbonyl group, phenylaminocarbonyl group, diphenylphosphoryl group, diethylphosphoryl group, 2-nitrobenzyl group, 3,5-dimethoxy Benzyl group, 3,4,5-trimethoxybenzyl group, trimethylsilyl group, triethylsilyl group, t-butyldimethylsilyl group, diethylisopropylsilyl group, dimethylphenylsilyl group, Phenylmethyl silyl group, and the like triphenylsilyl group are given below in as divalent.

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When A is —SiR ⁴ R ⁵ R ^6, a photoacid generator such as an ammonium salt, a diazonium salt, an iodonium salt, a sulfonium salt, a phosphonium salt or an onium salt is used in combination for the purpose of improving photoreactivity. May be. Specific examples of these photoacid generators include “Organic Materials for Imaging” (edited by the Research Group for Organic Electronics Materials, 199).
3 years).

The compounds represented by the general formulas (1) to (4) can be easily synthesized by a conventionally known method. These may be used alone or in combination of two or more. You may use together.

The manner in which the compounds represented by the general formulas (1) to (4) are contained in the light transmittance adjusting layer is not particularly limited and may be appropriately selected depending on the intended purpose. These are (1) a method of containing them by solid dispersion, (2) a method of containing them by emulsification dispersion,
(3) a method of containing by polymer dispersion, (4) a method of containing by latex dispersion, and (5) a method of containing by microencapsulation. Among these, the method of containing by emulsification and dispersion and the method of containing by microencapsulation are preferable.

In the emulsification and dispersion method, first, the compounds represented by the general formulas (1) to (4) are dissolved in oil. The oil may be solid or liquid at room temperature, or may be a polymer, and may be a low-boiling auxiliary solvent such as acetate, methylene chloride, cyclohexanone and / or a phosphate, or phthalic acid. Esters, acrylic esters, methacrylic esters, other carboxylic esters, fatty acid amides, alkylated biphenyls, alkylated terphenyls, alkylated naphthalenes, diarylethanes, chlorinated paraffins, alcohols, phenols, ethers, monoolefins system,
Epoxy type, 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, dioctyl sebacate,
Dibutyl sebacate, dioctyl adipate, trioctyl trimellitate, acetyl triethyl citrate, octyl maleate, dibutyl maleate, isoamyl biphenyl, chlorinated paraffin, diisopropyl naphthalene, 1,1'-ditolyl ethane, 2,4-dita-shalia Milphenol, N, N-dibutyl-2-butoxy-
And high-boiling oils such as 5-tert-octylaniline, 2-ethylhexyl hydroxybenzoate, and polyethylene glycol. These may be used alone or in combination of two or more,
Of these, alcohols, phosphates, carboxylic esters, alkylated biphenyls, alkylated terphenyls, alkylated naphthalenes, and diarylethanes are preferred. In the present invention, the oil
An anti-carbonizing agent such as hindered phenol or hindered amine may be added.

The oil containing the compounds represented by the general formulas (1) to (4) is added to an aqueous solution of a water-soluble polymer, and emulsified and dispersed by a colloid mill, a homogenizer, or ultrasonic waves.

Examples of the water-soluble polymer include 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, polyacrylamide, polystyrenesulfonic acid, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, gelatin and the like can be mentioned. In the present invention, a surfactant or the like may be added to the water-soluble polymer, if necessary, or an emulsion or latex of a hydrophobic polymer may be used in combination.

When the diazonium salt compound or the compounds represented by the general formulas (1) to (4) are microencapsulated, a conventionally known microencapsulation method can be used. For example, the diazonium salt compound or the general formula (1) to
The compound represented by (4) and the microcapsule wall precursor are dissolved in a water-insoluble or insoluble organic solvent, added to an aqueous solution of a water-soluble polymer, emulsified and dispersed using a homogenizer or the like, and By forming a wall film at the oil / water interface of a polymer substance which becomes a microcapsule wall when heated, the microcapsules of the diazonium salt compound or the compounds represented by the general formulas (1) to (4) can be prepared. Can be prepared.

Specific examples of the microcapsule wall film include, for example, polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin, melamine resin, polystyrene resin, styrene-acrylate copolymer resin, and styrene resin. And a wall film made of a methacrylate copolymer resin, gelatin, polyvinyl alcohol, or the like. Among these, a wall film made of a polyurethane / polyurea resin is preferable.

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

Specific examples of the polyvalent isocyanate compound include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate and diphenylmethane-isocyanate. 4,
4'-diisocyanate, 3,3'-diphenylmethane-4,4'-diisocyanate, xylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2- Diisocyanates such as diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, toluene-2, Triisocyanates such as 4,6-triisocyanate; tetraisocyanates such as 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate; hexamethylene diisocyanate; Adduct of trimethylolpropane,
Isocyanate prepolymers such as adducts of 2,4-tolylene diisocyanate and trimethylolpropane, adducts of xylylene diisocyanate and trimethylolpropane, and adducts of tolylene diisocyanate and hexanetriol. These may be used alone or in combination of two or more. Among them, those having three or more isocyanate groups in the molecule are particularly preferable.

In the method of microencapsulation,
The diazonium salt compound, or the general formula (1) to
As the organic solvent for dissolving the compound represented by (4), the oil described in the emulsification and dispersion method can be used. The same applies to a water-soluble polymer.

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

In the present invention, the following known antioxidants can be added to the heat-sensitive recording material in order to further improve the light resistance. Such antioxidants include, for example, EP-A-310551, DE-A-3435443, EP-A-310552 and JP-A-3-121.
No. 449, EP-A-594416, JP-A-2-262654, JP-A-2-712.
No. 62, JP-A-63-163351, U.S. Pat. No. 4,814,262, JP-A-54-48535, JP-A-5-61166, JP-A-5-119
No. 449, U.S. Pat. No. 4,980,275, JP-A-63-113536, JP-A-62-26204.
7, European Patent No. 223739,
Examples include antioxidants described in European Patent Publication No. 309402 and European Patent Publication No. 309401, and specific examples include the following.

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[0136]

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[0137]

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[0138]

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Further, Japanese Patent Application Laid-Open No. Sho 60-125470,
JP-A-60-125471, JP-A-60-125
472, JP-A-60-287485, JP-A-60-287486, and JP-A-60-28748.
7, JP-A-62-146680, and JP-A-6-146680.
JP-A-0-287488, JP-A-62-282885, JP-A-63-89877, JP-A-63-8
JP-A-8380, JP-A-63-088381, JP-A-01-239282, JP-A-04-2916
No. 85, JP-A-04-291684, JP-A-05-188687, JP-A-05-188686
JP, JP-A-05-110490, JP-A-05-110490
-1108437, JP-A-05-170361, JP-A-63-203372, JP-A-63-203372
JP-A-224889, JP-A-63-267594, JP-A-63-182484, JP-A-60-1
No. 07384, JP-A-60-107383,
JP-A-61-160287, JP-A-61-185
483, JP-A-61-211079, JP-A-63-251282, JP-A-63-05117
No. 4, JP-B-48-043294, JP-B-4
8-033212, 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 and the like. These antioxidants can be added to the heat-sensitive recording layer, the intermediate layer, the light transmittance adjusting layer, and the protective layer.

[0141]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. In the following, “parts” means “parts by mass” unless otherwise specified.

(Example 1) <Undercoat layer> -Preparation of gelatin solution- Enzymatically degraded gelatin (average molecular weight: 10,000, PAGI
Method viscosity: 15 mP, PAGI method jelly strength: 20 g) 4
0 parts were added to 60 parts of water and dissolved by stirring at 40 ° C. to prepare a gelatin solution. -Preparation of mica dispersion liquid- 8 parts of water-swellable synthetic mica (aspect ratio: 1000, trade name: Somasif ME100, manufactured by Corp Chemical) and water 9
After mixing with 2 parts, the mixture was wet-dispersed with a biscomil to obtain a mica dispersion having an average particle size of 2.0 μm. Water was added to the mica dispersion so that the mica concentration was 5% by mass, and the mixture was uniformly mixed to prepare a desired mica dispersion.

—Formation of Undercoat Layer— 40 parts by weight of 40% by mass of the gelatin solution at 40 ° C.
After 20 parts and 556 parts of methanol were added and sufficiently stirred and mixed, 208 parts of the mica dispersion liquid of 5% by mass was added, sufficiently mixed and stirred, and 9.8 parts of 1.66% by mass of an ethylene oxide surfactant was added. Was. Then, the liquid temperature is changed from 35 ° C. to 4
6. The gelatin hardener represented by E-1 was maintained at 0 ° C.
3 parts were added to prepare an undercoat layer coating solution (5.7% by mass).

This undercoat layer coating solution was applied onto a support obtained by laminating a polyester film on both sides of high-quality paper so that the amount of mica applied was 0.2 g / m ² .
An undercoat layer was formed.

<Preparation of Coating Solution for Thermosensitive Recording Layer A> Preparation of Electron-donating Colorless Dye Precursor Microcapsule Solution 3.0 parts of crystal violet lactone as an electron-donating colorless dye precursor was added to 20 parts of ethyl acetate. After dissolving, 20 parts of alkylnaphthalene, which is a high boiling point solvent, was added, and the mixture was heated and uniformly mixed. 20 parts of an xylylene diisocyanate / trimethylolpropane adduct was further added to this solution as a microcapsule wall agent, and the mixture was stirred uniformly to obtain an electron-donating colorless dye precursor solution. Separately, 54 parts of a 6% by mass aqueous solution of gelatin were prepared, and the above-mentioned electron-donating colorless 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. while stirring, and a microencapsulation reaction was performed for 3 hours to prepare an electron-donating colorless dye precursor microcapsule liquid. . The average particle size of the microcapsules was 1.6 μm.

—Preparation of Electron-Accepting Compound Dispersion— An electron-accepting compound dispersion was obtained by adding 30 parts of bisphenol A as an electron-accepting compound to 150 parts of a 4% by mass aqueous solution of gelatin and dispersing it in a ball mill for 24 hours. Was. The average particle size of the electron accepting compound in the electron accepting compound dispersion was 1.2 μm.

—Preparation of Coating Solution for Thermosensitive Recording Layer A— Next, the above-mentioned electron-donating dye precursor microcapsule solution and the above-mentioned electron-accepting compound dispersion were mixed with an electron-donating dye precursor / electron-accepting compound. Of the thermosensitive recording layer A formed by coating the coating solution for the thermosensitive recording layer A with sodium dodecylbenzenesulfonate represented by the structural formula (1). Was added so that the coating amount in Example 1 was 0.1 g / m ² to prepare the intended coating solution for the heat-sensitive recording layer A.

<Preparation of Coating Solution for Heat-Sensitive Recording Layer B> Preparation of Diazonium Salt Compound Microcapsule Solution 4- (N- (2- (2,4
Dissolve 2.0 parts of -di-tert-amylphenoxy) butyryl) piperazinobenzenediazonium hexafluorophosphate in 20 parts of ethyl acetate, add 20 parts of alkylnaphthalene which is a high-boiling point solvent, and heat. Mix evenly. 15 parts of an xylylene diisocyanate / trimethylolpropane adduct as a microcapsule wall agent was further added to this solution, and the mixture was stirred uniformly. Separately, 54 parts of a 6% by mass 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. while stirring, and a microencapsulation reaction was performed for 3 hours to prepare a desired diazonium salt compound microcapsule liquid. The average particle size of the microcapsules was 1.1 μm.

—Preparation of Coupler Emulsion— 1- (2′-octylphenyl) -3- as a coupler
Methyl-5-pyrazolone 2 parts, 1,2,3-triphenylguanidine 2 parts, l, 1- (p-hydroxyphenyl) -2-ethylhexane 2 parts, 4,4 ′-(p-phenylenediisopropylidene ) 4 parts of diphenol, 4 parts of 2-ethylhexyl-4-hydroxybenzoate, 0.3 part of tricresyl phosphate, 0.1 part of diethyl maleate and 1 part of a 70% calcium dodecylbenzenesulfonate methanol solution in acetic acid This solution was dissolved in 10 parts of ethyl, and this solution was added to 80 parts of an 8% aqueous gelatin solution, emulsified with a homogenizer for 10 minutes, and then ethyl acetate was removed to prepare a desired coupler emulsion.

—Preparation of Coating Solution for Thermosensitive Recording Layer B— Next, the diazonium salt compound microcapsule solution and the coupler dispersion were mixed with a diazonium salt compound /
The mixture was mixed such that the ratio of the couplers became 2/3 to prepare the intended coating solution for the heat-sensitive recording layer B.

<Coating solution for heat-sensitive recording layer C> -Preparation of microcapsule solution of diazonium salt compound- As a diazonium salt compound, 2,5-dibutoxy-4-
Dissolve 3.0 parts of tolylthiobenzenediazonium hexafluorophosphate in 20 parts of ethyl acetate, and further add 20 parts of alkylnaphthalene, which is a high boiling point solvent,
Heat to mix evenly. 15 parts of an xylylene diisocyanate / trimethylolpropane adduct as a microcapsule wall agent was further added to this solution, and the mixture was stirred uniformly. Separately, 54 parts of a 6% by mass 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 a microencapsulation reaction was performed for 3 hours to obtain a desired diazonium salt compound microcapsule liquid. The average particle size of the microcapsules was 1.0 μm.

-Preparation of Coupler Dispersion- As a coupler, 2-chloro-5- (3- (2,4-di-
tert-pentyl) phenoxypropylamino) acetoacetanilide 2 parts, 1,2,3-triphenylguanidine 2 parts, 1,1- (p-hydroxyphenyl) -2
-2 parts of ethylhexane, 4 parts of 4,4 '-(p-phenylenediisopropylidene) diphenol, 4 parts of 2-ethylhexyl-4-hydroxybenzoate, 0.3 part of tricresyl phosphate, 0.1 part of diethyl maleate Department,
Then, 1 part of a 70% calcium dotesylbenzenesulfonate methanol solution was dissolved in 10 parts of ethyl acetate, and this solution was added to 80 parts of an 8% aqueous gelatin solution, emulsified with a homogenizer for 10 minutes, and then ethyl acetate was removed. Thus, the desired coupler dispersion was prepared.

—Preparation of Coating Solution for Thermosensitive Recording Layer C— Next, the diazonium salt compound microcapsule solution and the coupler dispersion were mixed with a diazonium salt compound /
The mixture was mixed so that the ratio of the couplers became 4/5 to prepare the intended coating solution for the heat-sensitive recording layer C.

<Light Transmittance Adjusting Layer> —Preparation of Microcapsule Solution of Ultraviolet Absorber Precursor— 30 parts of ethyl acetate was used as an ultraviolet absorber precursor [2-
Allyl-6- (2H-benzotriazol-2-yl)
-4-t-octylphenyl] benzenesulfonate 1
0 parts, 2,5-di-t-octyl-hydroquinone 3
Parts, 2 parts of tricresyl phosphate and 4 parts of α-methylstyrene dimer were dissolved. As a microcapsule 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. with stirring, and an encapsulation reaction was performed for 3 hours to prepare a desired ultraviolet absorbent precursor microcapsule solution. The average particle size of the microcapsules was 0.3 μm.

-Preparation of Coating Solution for Light Transmittance Adjusting Layer- 2% [4-nonylphenoxytrioxyethylene] was added to 100 parts of the ultraviolet absorbent precursor microcapsule solution.
10 parts of an aqueous solution of sodium butylsulfonate was added to prepare a coating solution for a light transmittance adjusting layer.

<Preparation of Coating Solution for Intermediate Layer> To 100 parts of a 10% aqueous gelatin solution, 2 parts of 2% sodium (4-nonylphenoxytrioxyethylene) butylsulfonate was added to prepare a coating solution for an intermediate layer.

<Preparation of Coating Solution for Protective Layer> -Preparation of Pigment Dispersion for Protective Layer- An anionic special polycarboxylic acid was added to 4 parts of barium sulfate (trade name: BF-21F, manufactured by Sakai Chemical Industry Co., Ltd.). Type polymer activator (trade name: Poise 532A (40% by mass aqueous solution), manufactured by Kao Corporation) 0.1 part, ion-exchanged water 15.9
The parts were mixed and dispersed with a Dynomill to prepare a barium sulfate dispersion. This dispersion was subjected to particle size measurement (LA-91
0, carried out by Horiba, Ltd.) as a result, the median diameter was 0.15 μm or less. Barium sulfate dispersion 4
4 parts of colloidal silica (trade name: Snowtex O (20% by mass aqueous dispersion), manufactured by Nissan Chemical Co., Ltd.) was added to 6 parts to obtain the intended dispersion for protective layer.

-Preparation of Matting Agent Dispersion for Protective Layer- Wheat starch (particle size: 10 μm) (trade name: wheat starch S, manufactured by Shinshin Food Industry Co., Ltd.) (Product name: PROXELB.D,
I. C. 3.5 parts, ion-exchanged water 1950
The parts were mixed and uniformly dispersed to obtain a protective layer matting agent dispersion.

-Preparation of Coating Blend for Protective Layer- 4% by mass of vinyl alcohol-alkyl vinyl ether copolymer (trade name: EP-130, manufactured by Denki Kagaku Kogyo KK)
30 parts of sodium (4-nonylphenoxytrioxyethylene) butylsulfonate (manufactured by Sankyo Chemical Co., Ltd. (2.0% by mass aqueous solution)) in 1000 parts of an aqueous solution, N- (perfluoro-1-octanesulfonyl) -N-propylaminoacetic acid potassium salt (trade name: Megafac F-120)
(2% by mass aqueous solution) Dainippon Ink and Chemicals, Inc. 30
Parts, 90 parts of the pigment dispersion for the protective layer, 16 parts of the matting agent dispersion for the protective layer, and zinc stearate dispersion (trade name:
L111 (21% by mass aqueous solution) manufactured by Chukyo Yushi Co., Ltd.) 45
The parts were uniformly mixed to obtain a coating blend liquid for a protective layer.

<Preparation of Thermal Soft Film Layer Coating Solution> Colloidal silica-containing acrylic polymer (trade name: Movinyl 8020)
(40 mass% aqueous solution), 5 parts by Hoechst Synthesis Co., Ltd.
Sodium (4-nonylphenoxytrioxyethylene) butylsulfonate (manufactured by Sankyo Chemical Co., Ltd. (2.0% by mass)
(Aqueous solution)) 1 part of ion-exchanged water was uniformly mixed with 4 parts to obtain a heat-softening layer coating blend liquid.

<Coating of Coating Solution for Each Thermosensitive Recording Layer> On the undercoat layer, the coating solution for the thermosensitive recording layer A, the coating solution for the intermediate layer, the coating solution for the thermosensitive recording layer B, and the coating solution for the intermediate layer. Liquid, the coating solution for the heat-sensitive recording layer C, the coating solution for the light transmittance adjusting layer, the coating solution for the thermal soft film layer, and the coating solution for the protective layer in this order, with a coating speed of 60 m / min and a continuous application of 8 layers. And
Drying was performed at 30 ° C. and a humidity of 30%, and at a temperature of 40 ° C. and a humidity of 30%, to obtain a multicolor heat-sensitive recording material.

The amount of the solid content applied was 6.0 g for the heat-sensitive recording layer A.
/ M ² , the intermediate layer is 3.0 g / m ² , and the heat-sensitive recording layer B is 6.0.
g / m ² , the intermediate layer is 3.0 g / m ² , and the heat-sensitive recording layer C is 5.0 g / m ² .
0 g / m ² , the light transmittance adjusting layer was adjusted to 3.0 g / m ² , the thermal soft film layer was adjusted to 2.0 g / m ² , and the protective layer was adjusted to 1.5 g / m ² .

(Example 2) The thermosoftening layer was applied to 15 parts of polyvinyl alcohol (trade name: Gosefimer Z210 (7% by mass aqueous solution, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)).
Example 1 was repeated except that 1 part of sodium (nonylphenoxytrioxyethylene) butylsulfonate (manufactured by Sankyo Chemical Co., Ltd. (2.0% by mass aqueous solution)) was uniformly mixed to obtain a blended solution for a thermal soft film layer. Same as above.

Comparative Example 1 The procedure of Example 1 was repeated, except that seven layers other than the thermal soft film layer were sequentially coated on the undercoat layer. (Comparative Example 2) The same procedure as in Comparative Example 1 was carried out except that 48 parts of a matting agent dispersion liquid was added at the time of preparing the blend liquid for coating the protective layer.

(Comparative Example 3) In preparing a protective layer matting agent dispersion, corn starch (particle size: 15 μm) was obtained from wheat starch (particle size: 10 μm) (trade name: wheat starch S, manufactured by Shinshin Food Industry Co., Ltd.).
(Product name: Eclipse Cornstarch, Nippon Shokuhin Kako Co., Ltd.)
Ex. (Comparative Example 4) A comparison was made except that the amount of the zinc stearate dispersion (trade name: L111, (21% by mass aqueous solution), manufactured by Chukyo Yushi Co., Ltd.) was changed to 90 parts at the time of preparing the coating blend liquid for the protective layer. Same as Example 1.

The following measurements were performed. (Hardness of the protective layer and heat buffy coat layer) - Preparation of samples - solid coating amount of the protective layer or heat buffy coat layer coating blend solution PET base having a thickness of 175μm is to be 3.0 g / m ² It was prepared by applying and drying with a coating bar. —Measurement of Dynamic Hardness— The above coated sample was heated to 120 ° C. and measured with a Shimadzu Dynamic Ultra Micro Hardness Tester DUH-200 using a triangular pyramid indenter with a 115 ° edge angle.

(Glossiness) Printed by a digital printer "NC-300" manufactured by Fuji Photo Film Co., Ltd., and the specular glossiness of the printed solid black portion was measured by a digital variable angle glossmeter manufactured by Suga Test Instruments Co., Ltd. It was measured at an incident angle of 20 ° with “UGV-5D”. (Printing torque) Platen meter 12φ, hardness 40 °, pressure 6
Jig printer of kg / cm (Machiles Corporation G)
X-3 machine)) and A5 thermal head (manufactured by TDK, model L
V4403), and a line cycle of 5.29 ms,
Power 0.32w, maximum printing energy 105.6mj /
mm ^2, performs gradation printing by the printing condition of the conveying speed 16 mm / s, the printing energy 17 mJ / mm ² (low energy), 40 mJ / mm @ 2 (medium energy), and 95m
The torque generated between the sample and the platen roll at j / mm ² (high energy) was measured and converted to a kinetic friction coefficient.

<Evaluation of Image Quality> Digital printer (NC
(-300D), a gray solid image was printed, and the degree of density unevenness was visually evaluated. Table 1 shows the above results.
Shown in

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[Table 1]

As is clear from Table 1, none of Comparative Examples 1 to 4 in which the thermal soft film layer was provided provided low torque while maintaining high gloss. Had become. On the other hand, in Examples 1 and 2, high gloss and low torque were realized, and the image quality was also very good. In particular, in Example 1 using a thermal soft film layer having a dynamic hardness of 3 at 120 ° C.,
The improvement in image quality was remarkable.

[0171]

According to the heat-sensitive recording material of the present invention, an image having high gloss can be formed, and printing torque is reduced to reduce load fluctuation unevenness, thereby forming a high-quality image without density unevenness. be able to.

Claims (3)

[Claims] 1. A heat-sensitive recording material which is printed using a thermal head and has a heat-sensitive recording layer and a protective layer sequentially on a support, wherein a hardness at the time of printing is formed on the surface of the protective layer on the side of the heat-sensitive recording layer. Has a thermal soft film layer lower than the hardness of the protective layer. 2. The heat-sensitive recording material according to claim 1, wherein the protective layer contains inorganic ultrafine particles, and has a gloss of 20 ° on a printed image after printing of 40 or more. 3. The heat-sensitive recording material according to claim 1, wherein the dynamic hardness at 120 ° C. of the protective layer is 30 or more, and the dynamic hardness at 120 ° C. of the thermal soft film layer is 10 or less.