JP2000118139A - Fine particle dispersion method and thermal recording material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material in which both adhesion and sticking of tailings in a thermal recording head or the like are prevented and flaw resistance is excellent by providing a protective layer having excellent transparency, glossy properties, heat resistance and light resistance and also having excellent frictional resistance and lubricating properties for the thermal recording head. SOLUTION: In the thermal recording material in which a thermal recording layer and a protective layer are provided successively on a supporting body, the protective layer contains inorganic ultrafine particles. These inorganic ultrafine particles are produced by previously dispersing the inorganic ultrafine particles in existence of a silicone modified polymer and/or silanol modified polyvinyl alcohol. Furthermore, the dispersed ultrafine particles are agitated and mixed together with the other component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dispersing fine particles and a heat-sensitive recording material using the same. A heat-sensitive recording material containing ultra-fine inorganic particles, which has excellent transparency, gloss, heat resistance, and light resistance, and has a protective layer with excellent friction resistance with the heat-sensitive recording head and lubricity. The present invention relates to a heat-sensitive recording material which is excellent in scratch resistance and free from adhesion and residue on a heat-sensitive recording head.

[0002]

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

[0003] On the other hand, needs for thermal recording systems are expanding in various fields such as facsimile machines, printers and labels. Along with this, excellent printing suitability without contamination and sticking of the thermal recording head is required. Therefore, in order to meet these demands, conventionally, inorganic fine particles such as kaolin have been added to a protective layer which is the outermost surface layer of the heat-sensitive recording material. However, if the dispersibility of the inorganic fine particles in the protective layer is poor, the transparency and glossiness of the heat-sensitive recording material are reduced (when the heat-sensitive recording material is a transmission material, the haze is increased). was there.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a dispersion method capable of stably dispersing fine particles and finer dispersion, and a heat-sensitive recording material containing inorganic ultrafine particles finely dispersed by this method. There is no sticking or scum sticking on thermal recording heads etc. by having a protective layer with excellent transparency, glossiness, heat resistance, light resistance, and excellent friction resistance with thermal recording head, excellent lubricity Another object of the present invention is to provide a heat-sensitive recording material having excellent scratch resistance.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above-mentioned object, and as a result, have found that a silicone-modified polymer or silanol-modified polyvinyl alcohol can stably disperse inorganic fine particles. The invention has been completed. That is, the method for dispersing fine particles of the present invention comprises a dispersion stabilizing step of previously dispersing fine particles in the presence of a silicone-modified polymer and / or a silanol-modified polyvinyl alcohol, and a dispersing step of stirring and mixing the previously dispersed fine particles together with other components. And a liquid adjusting step. This dispersion method is effectively applied to inorganic fine particles, and is particularly effective for inorganic ultrafine particles which are relatively difficult to stabilize.

The heat-sensitive recording material of the present invention is a heat-sensitive recording material having a heat-sensitive recording layer and a protective layer provided on a support, wherein the protective layer contains inorganic ultra-fine particles, Are dispersed by the fine particle dispersion method of the present invention. That is, the method is characterized in that inorganic ultrafine particles are previously dispersed in the presence of a silicone-modified polymer and / or silanol-modified polyvinyl alcohol, and the previously dispersed inorganic ultrafine particles are stirred and mixed with other components. It is preferable that the inorganic ultrafine particles are at least one selected from the group consisting of barium sulfate, zinc oxide, magnesium oxide, lead oxide, zirconium oxide, colloidal silica, and alumina.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the heat-sensitive recording material of the present invention will be described below. The heat-sensitive recording material of the present invention is a heat-sensitive recording material in which a heat-sensitive recording layer and a protective layer are provided on a support, wherein the protective layer contains inorganic ultrafine particles, and the inorganic ultrafine particles are a silicone-modified polymer. And / or dispersed by silanol-modified polyvinyl alcohol.

In the present invention, the ultrafine particles mean particles having an average primary particle size of 0.2 μm or less, and have an average primary particle size of 0.1 μm or less.
There is no particular limitation as long as it is 2 μm, but the average primary particle size is 0.1 μm.
The case of 1 μm is preferred. Further, 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 particularly preferably 0.3 μm or less. . The frequency of (agglomerated) particles having a particle diameter of 0.3 μm or more in the dispersion is 5%.
Or less, preferably 1% or less, and particularly preferably, the frequency of (agglomerated) particles of 0.35 μm or more is 5% or less. In addition,
The particle size can be measured by a known method, for example, a COULTER N4 type submicron particle size analyzer (Nikkaki).

Inorganic ultrafine particles of barium sulfate, zinc oxide, magnesium oxide, lead oxide, zirconium oxide, colloidal silica or alumina are preferred, of which barium sulfate and colloidal silica are preferred, and barium sulfate is particularly preferred. As the inorganic ultrafine particles having an average particle diameter of 0.2 μm or less that can be suitably used in the present invention, for example, those shown in Table 1 are also available as commercial products.

[0010]

[Table 1]

In the present invention, the amount of the inorganic ultrafine particles added to the protective layer is 0.01 to 1 g / m ² . 0.01 g /
If it is less than m ^{2, the} effect of adding the inorganic ultrafine particles will be insufficient, and if it exceeds 1 g / m ² , the gloss may be reduced.

In the present invention, the dispersion of the inorganic ultrafine particles is performed by the fine particle dispersion method of the present invention. The fine particle dispersion method of the present invention has a dispersion stabilizing step and a dispersion liquid adjusting step. The dispersion stabilizing step is a step of previously dispersing the fine particles in the presence of the silicone-modified polymer and / or the silanol-modified polyvinyl alcohol, and the dispersion adjusting step is a step of stirring and mixing the previously dispersed fine particles with other components. This is the step of performing In preparing the fine particle dispersion, the silicone-modified polymer and / or the silanol-modified polyvinyl alcohol are added to the inorganic ultrafine particles in an amount of 1%.
Preferably, it is added in an amount of from 30 to 30% by weight, more preferably from 2 to 20% by weight, particularly preferably from 3 to 15% by weight.

The protective layer coating solution of the present invention comprises, as other components, an aqueous binder, and optionally a crosslinking agent, a catalyst, a release agent, a surfactant, a wax, in addition to the dispersion of the fine particles. And a water repellent may be added. When the previously dispersed fine particles are stirred and mixed with other components, shock aggregation during mixing can be avoided by adding the fine particle dispersion little by little while sufficiently stirring the liquid of the other components.

The method for dispersing fine particles of the present invention can be applied not only to the dispersion of inorganic ultrafine particles but also to the dispersion of fine particles in general. For example, in order to improve friction resistance and lubricity, calcium carbonate, aluminum hydroxide, barium sulfate, titanium oxide, talc, wax, kaolin, calcined kaolin,
The present invention can be applied to a case where a general organic or inorganic pigment such as amorphous silica, urea formalin resin powder, polyethylene resin powder, and benzoguanamine resin powder is added.

The silicone-modified polymer used in the dispersion stabilization step is preferably a silicone graft polymer, a silicone block polymer, a silicone-modified acrylic polymer, a silicone-modified polyvinyl alcohol, or the like. Further, as the silicone graft polymer, a silicone graft acrylic polymer and a silicone graft modified polyvinyl alcohol are preferable, and as the silicone block polymer, a silicone block acrylic polymer and a silicone block modified polyvinyl alcohol are preferable.

The characteristic feature of the trunk polymer of the silicone-modified polymer is that any resin may be used as long as it is a resin having excellent film forming properties, heat resistance and light resistance, and high Tg (glass transition point) having high film strength. In particular, acrylic resins and polyvinyl alcohol resins are preferably used.

The monomers constituting such an acrylic resin include acrylic resins such as methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and glycidyl (meth) acrylate. Monomers. Further, non-acrylic copolymerizable monomers such as styrene, acrylonitrile, vinyl acetate, N-vinylpyrrolidone, and Nt-butylacrylamide may be copolymerized. In the case of a water-soluble type, as a water-solubility imparting unit, and in the case of an emulsion type or latex type, as a dispersion stability imparting unit, (meth) acrylic acid (or a salt thereof), maleic acid (or a salt thereof), Itaconic acid (or its salt), styrenesulfonic acid (or its salt), 2-acrylamide-2
-Methylpropanesulfonic acid (or a salt thereof), 2-hydroxyethyl (meth) acrylate, acrylamide,
It is preferable to include a monomer such as dimethylacrylamide, dimethylaminoethyl (meth) acrylate (or a salt thereof), or polyethylene glycol monomethyl ether mono (meth) acrylate.

As the branch polymer of the silicone-modified polymer, any silicone may be used, but polydimethylsiloxane is preferably used. Polydimethylsiloxane has excellent properties in terms of water repellency and lubricity.

Therefore, a copolymer having a unit derived from the above-mentioned acrylic monomer and a polydimethylsiloxane unit is excellent in film-forming properties, heat resistance and light resistance, excellent in film strength, and also excellent in water repellency and lubricity. Are better.

As the silicone-modified polymer in the present invention, a silicone graft polymer is preferable. Among the silicone graft polymers, a copolymer of a silicone macromonomer represented by the general formula (1) and a monomer copolymerizable therewith is preferred. Among them, those represented by the general formula (2) are particularly preferred.

[0021]

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In the general formula (2), R ¹ is an alkyl group having 1 to 6 carbon atoms, R ² is —COOR ⁷ , an aryl group, a cyano group, an imidazole group, a triazole group, a pyrrolidone group,
—OCOR ⁷ (R ⁷ represents an alkyl group, an aryl group, or an aralkyl group), R ³ , R ⁴ , R ⁵ , and R ⁶ each represent hydrogen or a methyl group, X represents a hydrophilic group, and Y represents a reactive group. ,
n is a positive integer, m is 2 to 6, a, b, c, d (however,
c may be 0. ) Represents the degree of polymerization.

In the general formula (2), examples of the hydrophilic group (X) include a polyethylene oxide group, a polypropylene oxide group, a carboxy (or salt thereof) group, a hydroxy group, a sulfonic acid (or salt thereof) group and an amino group. Group,
Amide group, substituted amide group, an ammonium base and groups having these functional groups (e.g., -COOCH ₂ CH ₂ O
_{H, -COO (CH 2 CH 2} O) n H), and the like. Further, as the reactive group (Y), a group capable of reacting with a crosslinking agent and / or a binder, for example, an amino group, a carboxyl (or salt thereof) group, a hydroxy group, a sulfinic acid (or salt thereof) group, a glycidyl group And groups having these functional groups.

Depending on the composition of the monomers, these silicone-grafted acrylic polymers may be solution-polymerized with an azobis-based compound or an organic peroxide in an organic solvent such as isopropyl alcohol, toluene, or xylene, or may be nonionic-based. It is manufactured by emulsion polymerization using potassium persulfate or the like in the presence of anionic and cationic surfactants.

The silicone-modified polyvinyl alcohol derivative is a polymer having a repeating unit (polysiloxane chain) of the general formulas (3) and (4).

[0026]

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In the general formula (4), R ¹ and R ² are each an alkyl group having 6 or less carbon atoms or an aryl group. Examples of the substituent on the polysiloxane chain include a methyl group, an ethyl group, and a phenyl group. Of these, polymethylsiloxane is particularly preferable from the viewpoint of availability of raw materials.

Conventionally, polyvinyl alcohol derivatives containing silicon are well known. For example, JP-A-63-1
JP-A-96603, JP-A-58-79003, and JP-A-58-59203 describe examples of polyvinyl alcohol derivatives containing silicon. The use of such a compound on a heat-sensitive coloring layer of a heat-sensitive recording material or on the layer is described in JP-A-58-193189, JP-A-1-204785, JP-A-2-22646, It is described in Japanese Patent Publication No. Hei 4-32745. However, all of the compounds shown therein are those in which silicon has a reactive substituent such as an alkoxy group, an acyloxy group, a hydroxyl group (or an alkali metal salt), and for a polyvinyl alcohol derivative having a polysiloxane chain, There is no description.

As an example of the synthesis of a polyvinyl alcohol derivative containing a polysiloxane chain, Makromol,
Chem. 186 (4) 685 (1985); Co
lloid. Interface, Sci. 114
(1) 16 (1986), polymer processing 34 (11) 52
2 (1985) and others describe a method of synthesizing a polyvinyl alcohol derivative having polydimethylsiloxane by hydrolyzing a copolymer of polydimethylsiloxane having vinyl groups and vinyl acetate. However, in these documents, no mention is made of the application to heat-sensitive recording materials.

JP-A-63-256629 discloses a synthesis example using a reaction between an isocyanate group-containing polysiloxane and an active hydrogen-containing resin.
No. 361 describes a synthesis example by a reaction between an epoxy group-containing polysiloxane and polyvinyl alcohol. However, there is no mention of the use for a heat-sensitive recording material.

A method of hydrolyzing a copolymer of a monomer having a polysiloquine chain and vinyl acetate, or a polysiloxane compound or a polyvinyl alcohol containing a reactive functional group such as an epoxy group, an isocyanate group, a carboxylic acid, or a carboxylic halide. Silicone graft polyvinyl alcohol having a polysiloxane chain as a graft chain (or a derivative thereof) is reacted with a hydroxyl group (or a COOH group which can be contained in polyvinyl alcohol as a copolymer component) of the (or derivative thereof). Derivatives thereof).

Further, a silicone block polyvinyl alcohol (or a derivative thereof) can be obtained by subjecting a monomer containing a polysiloxane chain to radical polymerization from a terminal SH group of a polyvinyl alcohol derivative having a terminal SH group. Such a method of synthesizing a block polymer by radical polymerization using a terminal SH group is disclosed in JP-A-59-189133, Journal of High Polymers 49.
(11) 885 (1992). However, there is no description of an example of synthesizing a silicone block polyvinyl alcohol derivative using a monomer containing polysiloxane. Also, a silicone block polyvinyl alcohol (derivative) can be obtained by adding a polysiloxane compound containing an epoxy group to a terminal SH group of a polyvinyl alcohol derivative having a terminal SH group.
Is obtained. Examples of the monomer containing a polysiloxane chain used in these syntheses include a compound represented by the above general formula (3).

As the silanol-modified polyvinyl alcohol used in the dispersion stabilization step, a commercially available product can be used. For example, "R1130" and "R2106" manufactured by Kuraray Co., Ltd. can be mentioned.

The aqueous binder used for the protective layer is not particularly limited. As the aqueous binder, for example, in addition to the silicone-modified polymer described above, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose,
Starch, agar, κ-carrageenan, gelatin, gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, ethylene-maleic anhydride copolymer hydrolyzate, isobutylene-maleic anhydride copolymer hydrolysis Products, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylamide and the like.

Among these polymers, a water-soluble polymer which can be set and dried is preferable. The set-dryable water-soluble polymer exhibits a predetermined viscosity at the time of heating (for example, about 40 ° C.) and can be applied, and then becomes viscous when cooled (for example, 5 ° C. to 15 ° C.).

In the present invention, polymers suitable as a set-dryable water-soluble polymer include proteins such as gelatin, polysaccharides such as carrageenan and agar, and polyvinyl alcohol compounds. In the case of a polyvinyl alcohol compound, When used in combination with a polyvinyl alcohol-based compound and boric acid or a salt thereof as a gelling agent, it can be used as a set-dryable water-soluble polymer.

As the aqueous binder used for the protective layer,
Water-soluble types of silicone-modified polymers are preferred. By using a silicone-modified polymer for the protective layer, printing characteristics, transparency, and glossiness can be improved. In addition, the silicone-modified polymer is prepared when preparing a coating liquid from a water-soluble type, an emulsion type, a latex type, a solvent miscible with water such as alcohol, or a type dissolved in a mixed solvent of these solvents and water. Any of the types excluding the solvent may be used before, but when preparing a coating liquid from a water-soluble type, a solvent miscible with water such as alcohol, or a type dissolved in a mixed solvent of these solvents and water. A type in which the solvent is removed before the preparation is preferable.

When these silicone-modified polymers are used for the protective layer, the Tg (glass transition point) of the polymer is at least 60 ° C., preferably at least 80 ° C., particularly preferably at least 100 ° C. When the Tg (glass transition point) of the silicone-modified polymer is lower than 60 ° C., the slipperiness with the head during printing decreases, which is not preferable.

When a silicone-modified polymer is used for the protective layer, it is preferably used in combination with another aqueous binder. As the other aqueous 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.

It is desirable to add a crosslinking agent which undergoes a crosslinking reaction with the silicone-modified polymer and / or the aqueous binder to the protective layer, and the silicone-modified polymer and / or the aqueous binder has a carboxyl group, an amino group as the functional group. It is preferable to have at least one functional group selected from a group, an ammonium base, a hydroxy group, a sulfinic acid (or a salt thereof) group, a sulfonic acid (or a salt thereof) group, and a glycidyl group.

Examples of the crosslinking 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.

Among the modified polyvinyl alcohols, ethylene-modified polyvinyl alcohol is particularly preferable, which itself can improve the water resistance and the like. However, in order to further improve the water resistance, it is crosslinked with ethylene-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, glycidyl ether of an alcohol mixture having 12 to 13 carbon atoms, 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 equivalent of the epoxy compound effective in the present invention is desirably 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 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. By mixing and heating such a blocked isocyanate with ethylene-modified polyvinyl alcohol, the ethylene-modified polyvinyl alcohol is cross-linked and reformed, thereby making the ethylene-modified polyvinyl alcohol water-resistant.

Further, 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 compound include monoaldehydes such as formaldehyde and acetaldehyde, and polyhydric 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 ethylene-modified polyvinyl alcohol, an aldehyde compound is particularly suitable as a 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 compounding amount of the crosslinking agent is less than 1 part by weight, the degree of crosslinking modification is low, and the water resistance and chemical resistance become insufficient. On the other hand, when it exceeds 50 parts by weight, the liquid stability decreases, and Absent.

Next, the heat-sensitive recording layer of the present invention may be a full-color heat-sensitive recording layer or a monocolor heat-sensitive recording layer. The heat-sensitive recording layer may include a diazo compound and a coupler which reacts with the diazo compound on a support. It is desirable to have at least one heat-sensitive recording layer containing a binder as a main component. In particular, it is desirable that the heat-sensitive recording layer has a heat-sensitive recording layer formed of a diazo system for each of cyan, yellow, and magenta.

A heat-sensitive recording material in which a transparent heat-sensitive recording layer is coated on a transparent support is a preferable system for exhibiting the effects of the present invention. In the case of a full-color heat-sensitive recording layer, the light-sensitive type heat-sensitive recording layer is provided on a support with a light transmittance adjusting layer whose light transmittance in a wavelength region where light is fixed is reduced after fixing, and a heat-sensitive layer having a protective layer thereon. Recording materials are preferred.

The light-fixing type thermosensitive recording layer further comprises a heat-sensitive recording layer 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, and a maximum absorption wavelength of 400 ± 20 nm. And a photo-fixing thermosensitive recording layer containing a diazonium salt compound and a coupler which reacts with the diazonium salt compound to form a color.

Further, a heat-sensitive recording layer containing an electron donating dye and an electron accepting compound is provided on a support.
A light-fixing type thermosensitive recording layer containing a diazonium salt compound having a wavelength of 00 ± 20 nm and a coupler which reacts with the diazonium salt compound to form a color, and a maximum absorption wavelength of 360 ± 20 nm
And a light-fixing type heat-sensitive recording layer containing a diazonium salt compound and a coupler which reacts with the diazonium salt compound to form a color, and a light transmittance adjusting layer and a protective layer are preferably provided on this layer. .

Further, on the support, a maximum absorption wavelength of 34
A light-fixing type thermosensitive recording layer containing a diazonium salt compound having a diameter of 0 ± 20 nm or less and a coupler that undergoes a color reaction with the diazonium salt compound, and a maximum absorption wavelength of 360 ± 20 nm
And a photo-fixing type thermosensitive recording layer containing a coupler which reacts with the diazonium salt compound to form a color, and a color which reacts with the diazonium salt compound having a maximum absorption wavelength of 400 ± 20 nm and the diazonium salt compound. And a light-fixing type heat-sensitive recording layer containing a coupler, and a light transmittance adjusting layer and a protective layer provided on this layer.

In the present invention, the light transmittance adjusting layer contains a component functioning as a precursor of an ultraviolet absorber.
Before the light irradiation of the wavelength of the region required for fixing does not function as an ultraviolet absorber, the light transmittance is high, and when fixing the light fixing type thermosensitive recording layer, the wavelength of the region required for fixing is sufficiently transmitted, In addition, the transmittance of visible light is high, and there is no problem in fixing the heat-sensitive recording layer.

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

At least one light transmittance adjusting layer can be provided in the light fixing type thermosensitive recording material, and most preferably, it is formed between the light fixing type thermosensitive recording layer and the outermost protective layer. The light transmittance adjusting layer may be used also as the protective layer. The characteristics of the light transmittance adjusting layer can be arbitrarily selected according to the characteristics of the light fixing type thermosensitive recording layer.

Particularly, a heat-sensitive recording material which is effective for applying the present invention is provided on a support with at least a maximum absorption wavelength of 360.
A photo-fixing type thermosensitive recording layer containing a diazonium salt compound having a wavelength of ± 20 nm and a coupler which reacts with the diazonium salt compound to form a color, and reacts with the diazonium salt compound having a maximum absorption wavelength of 400 ± 20 nm and the diazonium salt compound. It is desirable to have a light-fixing type heat-sensitive recording layer containing a color coupler and to provide a light transmittance adjusting layer on these layers. In the case of such a thermosensitive recording material, the light transmittance of the light transmittance adjusting layer in the wavelength region where light is fixed is 360.
65% or more in nm, and the light transmittance after fixing is 36%.
It is desirable that it is 20% or less at 0 nm. in this case,
Light irradiation refers to performing light irradiation of 13 kJ / m ² at a wavelength of 420 nm using a xenon lamp forced tester. Specifically, WeatherOmeter Ci6
5 (manufactured by Atlas Electric Co.) 0.9
Light irradiation at W / m ² for 4.0 hours.

Further, according to the present invention, the maximum absorption wavelength is 340n.
m, a photo-fixing type thermosensitive recording layer containing a diazonium salt compound and a coupler which reacts with the diazonium salt compound to form a color, and reacts with the diazonium salt compound having a maximum absorption wavelength exceeding 420 nm and the diazonium salt compound to form a color. The present invention is also applicable to a case where a light-fixing type heat-sensitive recording layer containing a coupler is provided.

In the thermosensitive recording layer, a multicolor thermosensitive recording material can be obtained by changing the hue of each thermosensitive recording layer. That is, a full-color image can be recorded by selecting the coloring hues of the respective heat-sensitive recording layers so as to be three primary colors, yellow, magenta, and cyan in the subtractive color mixing. In this case, the color-forming mechanism of the heat-sensitive recording layer directly laminated on the support surface (the lowermost layer of the heat-sensitive recording layer) is a color-forming system composed of an electron-donating dye and an electron-accepting dye, for example, a diazonium salt and a diazonium salt. Any of a diazo coloring system, a base coloring system that forms a color by contacting with a basic compound, a chelate coloring system, a coloring system that reacts with a nucleophile to cause a elimination reaction to form a color may be used. Preferably, a diazo coloring system is provided, and two layers of light-fixing type thermosensitive recording layers each containing a diazonium salt compound having a different maximum absorption wavelength and a coupler reacting with the diazonium salt compound to form a color are provided on the thermosensitive recording layer. It is desirable to provide a light transmittance adjusting layer and an outermost protective layer on the layer.

In the present invention, as the compound contained in the light transmittance adjusting layer, the compounds described in JP-A-9-1928 can be used.

In the present invention, as the color-forming component used in the heat-sensitive recording layer, conventionally known color-forming components can be used. In particular, those utilizing a reaction between a diazonium salt compound and a coupler, or an electron-donating colorless dye and an electron-accepting dye are used. Compounds utilizing a reaction with a hydrophilic compound are preferred. Examples of the compound used in the heat-sensitive recording layer containing a diazonium salt compound and a coupler that reacts with the diazonium salt compound when heated to form a color include a diazonium salt compound and the diazonium salt. In addition to a coupler capable of forming a dye by reacting with a compound, a basic substance that promotes a reaction between the diazonium salt compound and the coupler and the like can be mentioned. The diazonium salt compound is a compound represented by the following, and can control the maximum absorption wavelength depending on the position and type of the substituent in the Ar portion.

[0063]

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[0064] Ar is an aryl group, X ^- represents an acid anion.

Specific examples of the diazonium salt compound in the present invention include 4- (N- (2- (2,4-di-
tert-amylphenoxy) butyryl) piperazino)
Benzenediazonium, 4-dioctylaminobenzenediazonium, 4- (N- (2-ethylhexanoyl)
Piperazino) benzenediazonium, 4-dihexylamino-2-hexyloxybenzenediazonium, 4-
N-ethyl-N-hexadecylamino-2-ethoxybenzodiazonium, 3-chloro-4-dioctylamino-2-octyloxyobenzenediazonium, 2,5
-Dibutoxy-4-morpholinobenzenediazonium,
2,5-octoxy-4-morpholinobenzenediazonium, 2,5-dibutoxy-4- (N- (2-ethylhexanoyl) piperazino) benzenediazonium, 2,
5-diethoxy-4- (N- (2- (2,4-di-te
acid anion salts such as rt-amylphenoxy) butyryl) piperazino) benzenediazonium, 2,5-dibutoxy-4-tolylthiobenzenediazonium, 3- (2-octyloxyethoxy) -4-morpholinobenzenediazonium and the following diazonium salts Compound D-1
To D-5. Further, as the diazonium salt compound, a hexafluorophosphate salt, a tetrafluoroborate salt, and a 1,5-naphthalene sulfonate salt are particularly preferable.

[0066]

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Among these diazonium salt compounds, particularly preferred compounds in the present invention are 300 to 40.
4- (N- (2-
(2,4-di-tert-amylphenoxy) butyryl) piperazino) benzenediazonium, 4-dioctylaminobenzenediazonium, 4- (N- (2-ethylhexanoyl) piperazino) benzenediazonium,
4-dihexylamino-2-hexyloxybenzenediazonium, 4-N-ethyl-N-hexadecylamino-2-ethoxybenzodiazonium, 2,5-dibutoxy-4- (N- (2-ethylhexanoyl) piperazino) Benzenediazonium, 2,5-diethoxy-4-
(N- (2- (2,4-di-tert-amylphenoxy) butyryl) piperazino) benzenediazonium and the compounds shown in the specific examples D-3 to D-5. The maximum absorption wavelength of the diazonium salt compound referred to herein is a spectrophotometer (Shimazu MPS-200) obtained by coating each compound with a coating film of 0.1 g / m ² to 1.0 g / m ^2.
0).

Examples of the couplers used in the present invention, which react with the diazonium salt upon heating to give a color, include resorcinol,
Fluluglucin, 2,3-dihydroxynaphthalene-6
Sodium sulfonate, 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-octyl Acetoacetanilide, 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
-Pyrazolone, 1-phenyl-3-phenylacetamido-5-pyrazolone, and the following C-1 to C-6 compounds. By using two or more of these couplers together, a desired color hue can be obtained.

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Examples of the basic substance include an inorganic or organic basic compound, and a compound which decomposes upon heating to release an alkaline substance. Representatives include organic ammonium salts, organic amines, amides, ureas and thioureas and their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines,
Nitrogen-containing compounds such as triazoles, morpholines, piperidines, amidines, formazines, pyridines and the like can be mentioned. Specific examples of these include tricyclohexylamine, tribenzylamine, octadecylbenzylamine, stearylamine, allylurea, thiourea,
Methylthiourea, allylthiourea, ethylenethiourea,
2-benzylimidazole, 4-phenylimidazole, 2-phenyl-4-methylimidazole, 2-undecylimidazoline, 2,4,5-trifuryl-2-imidazoline, 1,2-diphenyl-4,4-dimethyl-
2-imidazoline, 2-phenyl-2-imidazoline,
1,2,3-triphenylguanidine, 1,2-dicyclohexylguanidine, 1,2,3-tricyclohexylguanidine, guanidine trichloroacetate, N, N ′
-Dibenzylpiperazine, 4,4'-dithiomorpholine, morpholinium trichloroacetate, 2-aminobenzothiazole, 2-benzoylhydrazinobenzothiazole and the like. These can be used in combination of two or more.

Examples of the electron-donating dye precursor used in the present invention include triarylmethane compounds, diphenylmethane compounds, thiazine compounds, xanthene compounds, spiropyran compounds, and the like. Xanthene compounds are useful because they have a high coloring density. To illustrate some of these,
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (that is, crystal violet lactone), 3,3-bis (p-dimethylamino) phthalide, 3- (p-dimethylaminophenyl) -3 − (1,
3-dimethylindol-3-yl) phthalide, 3-
(P-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (o-methyl-p
-Diethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 4,4'-bis (dimethylamino) benzhydrin benzyl ether, N-halophenylleucouramine, N-2,4,5 -Trichlorophenylleuco auramine, rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine-B- (p-chloroanilino) lactam, 2-benzylamino-6-diethylaminofluoran, 2-anilino-6 -Diethylaminofluoran, 2
-Anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-cyclohexylmethylaminofluoran, 2-anilino-3-methyl-6
-Isoamylethylaminofluoran, 2- (o-chloroanilino) -6-diethylaminofluoran, 2-octylamino-6-diethylaminofluoran, 2-ethoxyethylamino-3-chloro-2-diethylaminofluoran, 2- Anilino-3-chloro-6-diethylaminofluoran, benzoylleucomethylene blue,
p-Nitrobenzyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-benzylspirodinaphthopyran, 3-propyl-spiro-dibenzopyran And the like.

Examples of the electron-accepting compound include phenol derivatives, salicylic acid derivatives, and hydroxybenzoic acid esters. Particularly, bisphenols and hydroxybenzoates are preferred. Some examples of these include 2,2-bis (p-hydroxyphenyl) propane (ie, bisphenol A), 4,4 ′-(p-phenylenediisopropylidene) diphenol (ie, bisphenol P), 2,2-bis (p-hydroxyphenyl) pentane, 2,2-bis (p-hydroxyphenyl) ethane, 2,2-bis (p-hydroxyphenyl)
Butane, 2,2-bis (4'-hydroxy-3 ', 5'
-Dichlorophenyl) propane, 1,1- (p-hydroxyphenyl) cyclohexane, 1,1- (p-hydroxyphenyl) propane, 1,1- (p-hydroxyphenyl) pentane, 1,1- (p-hydroxyphenyl) ) -2-Ethylhexane, 3,5-di (α-methylbenzyl) salicylic acid and its polyvalent metal salts, 3,5-di (tert-butyl) salicylic acid and its polyvalent metal salts, 3-α, α- Dimethylbenzyl salicylic acid and its polyvalent metal salts, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-hydroxybenzoic acid
2-ethylhexyl, p-phenylphenol, p-cumylphenol and the like can be mentioned.

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

In the present invention, use forms of the above-mentioned diazonium salt compound, a coupler, a basic substance, a colorless electron-donating dye, an electron-accepting compound, and a sensitizer which react with the diazonium salt compound to give a color when heated. Is not particularly limited. That is, (1) a method of using a solid dispersion, (2) a method of using an emulsified dispersion, (3) a method of using a polymer dispersed, (4) a method of using a latex dispersed, and (5) a micro method. Although there is a method of encapsulation and the like, among them, the method of microencapsulation is particularly preferable from the viewpoint of storage stability, and particularly in a color forming system utilizing a reaction between a diazonium salt compound and a coupler, a diazonium salt compound is used. In the case of microencapsulation, it is preferable to microencapsulate the electron donating colorless dye in a color forming system utilizing the reaction between the electron donating colorless dye and the electron accepting compound.

As a method of microencapsulation, a conventionally known microcapsule method can be used.
That is, the coloring agent, the additive 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 heated. Thus, it can be adjusted by forming a polymer substance to be the microcapsule wall as a wall film at the oil / water interface.

Examples of the organic solvent include low-boiling auxiliary solvents such as acetate, methylene chloride, and cyclohexanone and / or phosphates, phthalates, acrylates, methacrylates, other carboxylic esters, fatty acid amides, and the like. Alkylated biphenyl, alkylated terphenyl, alkylated naphthalene,
Diarylethane, chlorinated paraffin, alcoholic,
Phenol type, ether type, monoolefin type, epoxy type and the like can be mentioned. 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'-ditolylethane, 2,4-ditertiaryamylphenol, N, N-dibutyl-2-butoxy-5
Tert-octylaniline, hydroxybenzoic acid 2-
Ethylhexyl ester, high-boiling oils such as polyethylene glycol, and among them, alcohols, phosphates, carboxylic esters,
Preferred are alkylated biphenyls, alkylated terphenyls, alkylated naphthalenes, and diarylethanes. Further, an anti-carbonizing agent such as hindered phenol and hindered amine may be added to the high boiling point oil. Further, as the oil, those having an unsaturated fatty acid are particularly desirable,
α-methylstyrene dimer and the like.
Examples of the α-methylstyrene dimer include “MSD100” manufactured by Mitsui Toatsu Chemicals, Inc.

As the water-soluble polymer, a water-soluble polymer such as polyvinyl alcohol is used, but a hydrophobic polymer emulsion or latex may be used in combination. 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, and ethylene. -Maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyacrylamide, polystyrene sulfonic acid, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, gelatin and the like, among which carboxy-modified polyvinyl alcohol is particularly preferred. preferable. Examples of the hydrophobic polymer 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. Specific examples of the polymer substance serving as the wall film of the microcapsules include, for example, 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 these, a particularly preferred wall agent is a polyurethane / polyurea resin. Microcapsules having a wall film made of polyurethane / polyurea resin, a microcapsule wall precursor such as polyvalent isocyanate is mixed in a core material to be encapsulated, and emulsified and dispersed in an aqueous solution of a water-soluble polymer such as polyvinyl alcohol. It is produced by raising the liquid temperature and causing a polymer forming reaction at the oil droplet interface.

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

In the microencapsulation method, the oil shown by emulsification and dispersion can be used as an organic solvent for dissolving the colorant, additives and microcapsule wall precursor. The same applies to a water-soluble polymer. The particle size of the microcapsules is preferably from 0.1 to 1.0 μm, more preferably from 0.2 to 0.7 μm.

In the present invention, the above-described heat-sensitive recording layers may be laminated, and a multi-color heat-sensitive recording material can be obtained by changing the hue of each heat-sensitive recording layer. Although the layer configuration is not particularly limited, it is particularly preferable that the layers having different photosensitive wavelengths have different wavelengths.
Thermal recording using two types of diazonium salt compounds, two thermosensitive recording layers combining couplers that react with each diazonium salt compound when heated to develop different colors, and a thermosensitive recording layer combining an electron-donating colorless dye and an electron-accepting compound. And a multi-color thermosensitive recording material in which three layers are laminated, and three thermosensitive recording layers in which three kinds of diazonium salt compounds having different photosensitive wavelengths are combined with couplers which react with the respective diazonium salt compounds when heated to develop different colors. The multicolor heat-sensitive recording material described above is preferable, and the latter is more preferable.

That is, a support comprising a colorless electron-donating dye and an electron-accepting compound or a diazonium salt compound having a maximum absorption wavelength of 340 nm or less and a coupler which reacts with the diazonium salt compound upon heating to form a color on a support. A heat-sensitive recording layer, a second heat-sensitive recording layer containing a diazonium salt compound having a maximum absorption wavelength of 360 ± 20 nm and a coupler which reacts with the diazonium salt compound when heated to form a color, and has a maximum absorption wavelength of 400 ± 20 nm. This is a third heat-sensitive recording layer containing a certain diazonium salt compound and a coupler which reacts with the diazonium salt compound when heated to give a color. In this example, a full-color image can be recorded by selecting the coloring hues of the respective heat-sensitive recording layers so as to be three primary colors, yellow, magenta, and cyan in the subtractive color mixing.

In the recording method of the multicolor heat-sensitive recording material, first, the third heat-sensitive recording layer is heated, and the diazonium salt compound and the coupler contained in the layer are colored. Then 400 ± 20
After irradiating light of nm to decompose the unreacted diazonium salt compound contained in the third heat-sensitive recording layer,
The heat is applied to the heat-sensitive recording layer in order to develop color to cause the diazonium salt compound and the coupler contained in the layer to develop color. At this time, the third heat-sensitive recording layer is also heated strongly, but does not develop color because the diazonium salt compound has already been decomposed and the color-forming ability has been lost. 360 ± 20
The second heat-sensitive recording layer is irradiated with light of nm to decompose the diazonium salt compound contained in the second heat-sensitive recording layer, and finally, heat is applied to the first heat-sensitive recording layer to develop color. At this time, the third and second heat-sensitive recording layers are also heated strongly 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.

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

[0084]

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[0085]

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[0086]

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In the present invention, at least one of the light transmission control layer and the protective layer, preferably a protective layer in which a random copolymer having a vinyl ester unit represented by the following general formula is saponified (ethylene-modified polyvinyl alcohol) ).

[0088]

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(Wherein R¹, R^Two, R^ThreeIs a hydrogen atom or
Represents a hydrocarbon group;^TwoAnd R^ThreeAre connected to each other to form a ring
May form a hydrocarbon group of¹, R^TwoPassing
And R ^ThreeAre bonded to each other to form a cyclic hydrocarbon group.
Good. ]

Among the ethylene-modified polyvinyl alcohols, particularly, the ratio of the vinyl alcohol monomer component of the polyvinyl alcohol to the ethylene monomer is 80:20 to 9: 9.
Ethylene-modified polyvinyl alcohol, which is a 9: 1 random copolymer, is desirable. In the case of ethylene-modified polyvinyl alcohol, in order to have water solubility and sufficient water resistance, the ethylene modification rate must be 20 mol% (that is, the ratio of the vinyl alcohol monomer component to the ethylene monomer is 80:20). １1 mol% (99: 1 in the ratio of vinyl alcohol monomer component to ethylene monomer) is desirable, and more desirably, the ethylene modification ratio is 5 to 10 mol%. In the case of non-ethylene-modified polyvinyl alcohol, sufficient water resistance and chemical resistance cannot be obtained, and if the ethylene modification ratio exceeds 20 mol%, the solubility in water is undesirably reduced.

The ethylene-modified polyvinyl alcohol desirably has a saponification degree of 80 mol% or more. If the saponification degree is less than 80 mol%, the solubility is insufficient, and it is difficult to prepare a predetermined coating solution. It is. These ethylene-modified polyvinyl alcohols may be further modified with other functional groups within a range that does not adversely affect performance and coating solution stability. Specific examples include a carboxyl group, a terminal alkyl group, an amino group, a sulfonic acid group, a terminal thiol group, a silanol group, and an amide group. For imparting the solubility of ethylene-modified polyvinyl alcohol, carboxyl group-modified, amino group-modified sulfonic acid groups and the like are effective.

It is also effective to use various additives already known as heat-sensitive recording materials and pressure-sensitive recording materials. Of these, some of the antioxidants are described in JP-A-60-125470, JP-A-60-125471, JP-A-60-125472, and JP-A-60-2.
87485, JP-A-60-287486,
JP-A-60-287487, JP-A-62-146
680, JP-A-60-287488, JP-A-62-282885, JP-A-63-89877
JP, JP-A-63-88380, JP-A-63-088381, JP-A-01-239282, JP-A-04-291885, JP-A-04-2
No. 91684, Japanese Unexamined Patent Publication No. 05-188687,
JP-A-05-188686, JP-A-05-110
490, JP-A-05-1108437, JP-A-05-170361, JP-A-63-2033
No. 72, JP-A-63-2241989, JP-A-63-267594, JP-A-63-182484
JP, JP-A-60-107384, JP-A-60-107384
-107383, JP-A-61-160287, JP-A-61-185483, JP-A-61-2
No. 11079, JP-A-63-251282,
JP-A-63-051174, JP-B-48-043
No. 294, JP-B-48-033212 and the like.

Specific examples include 6-ethoxy-1-phenyl-
2,2,4-trimethyl-1,2-dihydroquinoline,
6-ethoxy-1-octyl-2,2,4-trimethyl-1,2-dihydroquinoline, 6-ethoxy-1-phenyl-2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline, 6-ethoxy-1-octyl-2,
2,4-trimethyl-1,2,3,4-tetrahydroquinoline, nickel cyclohexanoate, 2,2-bis-4
-Hydroxyphenylpropane, 1,1-bis-4-hydroxyphenyl-2-ethylhexane, 2-methyl-
Examples include 4-methoxy-diphenylamine, 1-methyl-2-phenylindole and the compounds shown below.

[0094]

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[0095]

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[0096]

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[0097]

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These antioxidants can be added to the heat-sensitive recording layer or intermediate layer, the light transmittance adjusting layer, and the protective layer. When these antioxidants are used in combination, for example, specific examples (Q-7), (Q-45), (Q-4)
6) or a combination of compound (Q-10) and compound (Q-13).

As the support in the present invention, a plastic film, paper, plastic resin laminated paper, synthetic paper, or the like can be used.

In the present invention, when laminating thermosensitive coloring layers having different hues, an intermediate layer can be provided to prevent color mixing and the like. When a substrate having a high O ₂ transmittance such as a laminated paper is used as the support, an undercoat layer may be provided as an O ₂ cut layer to improve light resistance. A water-soluble polymer compound is used for the intermediate layer and the undercoat layer. For example, polyvinyl alcohol, modified polyvinyl alcohol,
Examples include methylcellulose, sodium polystyrene sulfonate, styrene-maleic acid copolymer, and gelatin. Prevent color mixing with a thinner layer for the intermediate layer and undercoat layer,
It is effective to include a swellable inorganic layered compound described in Japanese Patent Application No. Hei 7-113825 in order to improve light resistance.

The protective layer coating liquid of the present invention is applied onto the heat-sensitive recording layer using an apparatus such as a bar coater, an air knife coater, a blade coater, and a curtain coater, and dried to obtain a protective layer of the present invention. However, the protective layer may be applied at the same time as the recording layer, or after the thermal recording layer is applied, the thermal recording layer may be dried once and then applied thereon.
Dry coating amount of the protective layer is preferably from 0.1 to 3 g / m ^2, more preferably from 0.3 to 1.5 g / m ^2.
If the coating amount is large, the thermal sensitivity is significantly reduced, and if the coating amount is too low, the function as a protective layer (friction resistance,
Lubricity, scratch resistance, etc.). After the application of the protective layer, a calendering treatment may be performed if necessary. In the above-described example, the description has been made particularly with respect to the full-color heat-sensitive recording layer. However, the heat-sensitive recording material of the present invention may be a heat-sensitive recording material having a monocolor heat-sensitive recording layer.

The monocolor heat-sensitive recording layer contains at least a substantially colorless color-forming component A and a substantially colorless color-forming component B which reacts with the color-forming component A to form a color. The color-forming component A and the color-forming component B are components that cause a color-forming reaction when they come into contact with each other. Examples of combinations of these components include the following (A) to (W).

(A) Combination of a photodegradable diazo compound and a coupler. (B) A combination of an electron-donating dye precursor and an electron-accepting compound. (C) A combination of an organic metal salt such as silver behenate and silver stearate with a reducing agent such as protocatechinic acid, spiroindane and hydroquinone. (D) A combination of a long-chain fatty acid salt such as ferric stearate and ferric myristate and a phenol such as tannic acid, gallic acid and ammonium salicylate.

(E) Organic acid heavy metal salts such as nickel, cobalt, lead, copper, iron, mercury and silver salts such as acetic acid, stearic acid and palmitic acid; and alkalis such as calcium sulfide, strontium sulfide and potassium sulfide. A combination with an earth metal sulfide or a combination of the organic acid heavy metal salt and an organic chelating agent such as s-diphenylcarbazide or diphenylcarbazone. (F) A combination of a heavy metal sulfate such as a sulfate of silver, lead, mercury or sodium and a sulfur compound such as Na-tetrathionate, sodium thiosulfate or thiourea.

(G) A combination of a ferric fatty acid salt such as ferric stearate and an aromatic polyhydroxy compound such as 3,4-hydroxytetraphenylmethane. (H) A combination of an organic acid metal salt such as oxalate and mercury oxalate and an organic polyhydroxy compound such as polyhydroxy alcohol, glycerin and glycol. (Ii) A combination of a ferric fatty acid salt such as ferric pelargonic acid or ferric laurate, and a thiocesylcarbamide or isothiocesylcarbamide derivative.

(Nu) Lead salts of organic acids such as lead caproate, lead pelargonate and lead behenate, ethylene thiourea, N
-In combination with a thiourea derivative such as dodecylthiourea. (L) A combination of a heavy metal salt of a higher fatty acid such as ferric stearate and copper stearate with zinc dialkyldithiocarbamate. (Ii) Those that form an oxazine dye, such as a combination of resorcinol and a nitroso compound. (W) A combination of a formazan compound and a reducing agent and / or a metal salt.

Among them, in the present invention, (a)
A combination of a photodegradable diazo compound and a coupler, a combination of an electron-donating dye precursor and an electron-accepting compound (b),
A combination of the organic metal salt of (c) and a reducing agent is preferable,
The cases (a) and (b) are more preferable, and the case (a) is particularly preferable.

[0108]

[Example 1]

[Preparation of coating solution for protective layer] To 3667 ml of water, 333 g of an aqueous solution containing 30% by weight of a silicone graft acrylic polymer "CYMAC US450" (manufactured by Toagosei Co., Ltd.) was added.
In addition, barium sulfate ultrafine particles "Varifine BF21"
After adding 1000 g (manufactured by Sakai Chemical Industry Co., Ltd.) and roughly dispersing,
By a Dynomill (TYPE KDL-PILOT), the dispersion was performed in 6 passes at a circulation speed of 0.32 kg / min to obtain a fine particle dispersion A. This dispersion was analyzed using a laser diffraction / scattering particle size distribution analyzer “LA-910” (manufactured by Horiba, Ltd.).
The particle size distribution was measured. The average particle size was 0.148 and the maximum particle size was 0.296. In the fine particle dispersion A, each component is stirred and mixed in accordance with the following recipe. While sufficiently stirring with a stirring blade, the mixture was added little by little to obtain a coating liquid for a protective layer. When the particle size distribution in this protective layer coating solution was measured, the average particle size was 0.15 μm and the maximum particle size was 0.296 μm. Gelatin (15 wt%) 17 g Water 35 g X-22-8053 (40 wt% IPA solution) 20 g Ultrafine particle dispersion A 10 g Surfactant-1 (2 wt%) 3 ml Surfactant-2 (5 wt%) 3 ml Surflon S-131 (30% by weight) 0.5 ml (fluorinated surfactant; manufactured by Asahi Glass Co., Ltd.) However, X-22-8053 is a silicone-grafted acrylic polymer having the following structural formula (Tg = 110 ° C.)
(Made by Shin-Etsu Chemical Co., Ltd.).

[0109]

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The structural formulas of Surfactant-1 and Surfactant-2 are shown below.

[0111]

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[Preparation of Coating Solution for Light Transmittance Control Layer] The following compound (1.5 parts), R-6 as a reducing agent (0.5 parts), ethyl acetate (6.0 parts) and tricresyl phosphate (0.8 part) were used. Mix and dissolve well. Xylylene diisocyanate / trimethylolpropane (75% ethyl acetate solution: manufactured by Takeda Pharmaceutical Co., Ltd .; trade name: Takenate D11) as a capsule wall material
0N ") was added to this solution and stirred to homogeneity. 8% by weight of carboxy-modified polyvinyl alcohol (Kuraray Co., Ltd .; trade name "KL-318")
29.7 parts of an aqueous solution was prepared, added to the above solution, and emulsified and dispersed with a homogenizer. The obtained emulsion was treated with 40
The mixture was added to a portion of ion-exchanged water and stirred at 40 ° C. for 3 hours to perform an encapsulation reaction. Thereafter, 7.0 parts of an ion exchange resin "Amberlite MB-03" (manufactured by Organo Corporation) was added, and the mixture was further stirred for 1 hour. Thus, a target coating solution was prepared. The average particle size of the capsule is 0.35
μm.

[0113]

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[Preparation of Thermosensitive Recording Layer Solution] (Preparation of Diazonium Salt Compound Capsule Solution) As a diazonium salt compound, 2.8 parts of a compound represented by a-1 having a maximum absorption wavelength of decomposition at 365 nm, 2.8 parts of dibutyl sulfate are used.
Part, 2,2-dimethoxy-1,2-diphenylethane-
0.56 parts of 1-one (manufactured by Ciba-Geigy; trade name “Irgacure 651”) was dissolved in 19.0 parts of ethyl acetate. Further, 5.9 parts of isopropyl biphenyl which is a high boiling point solvent and 2.5 parts of tricresyl phosphate were added to the above solution, and the mixture was heated and uniformly mixed. As a capsule wall material, xylylene diisocyanate / trimethylolpropane adduct (75% ethyl acetate solution :: manufactured by Takeda Pharmaceutical Company;
7.6 parts of trade name “Takenate D110N”) was further added to this solution, and the mixture was stirred uniformly. Separately, 6% by weight gelatin (manufactured by Nippi Gelatin Industries Co., Ltd .; trade name “MG”) added with 2.0 parts of a 10% by weight aqueous sodium dodecyl sulfonate solution
P-9066 ") 64 parts of an aqueous solution was prepared, the above diazonium salt compound solution was added, and the mixture was emulsified and dispersed with a homogenizer. After 20 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. Thereafter, the liquid temperature was lowered to 35 ° C., and the ion exchange resin “Amberlite IRA68” (manufactured by Organo Corporation) was used.
6.5 parts and 13 parts of “Amberlite IRC50” (manufactured by Organo) are added, and the mixture is further stirred for one hour. Thereafter, the ion exchange resin was filtered to obtain a desired capsule liquid. The average particle size of the capsule was 0.64 μm.

[0115]

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(Preparation of Coupler Emulsion Dispersion) As a coupler, 3.0 parts of the compound b-1 shown below, 4.0 parts of triphenylguanidine, and 1,1- (p-hydroxyphenyl) -2-ethylhexane were used. 4.0 parts, 4,4 '-(p
-Phenylenediisopropylidene) diphenol to 8.
0 parts, 8.0 parts of 2-ethylhexyl-4-hydroxybenzoate, 2.0 parts of b-2 as an antioxidant,
1,1,3-tris (2-methyl-4-hydroxy-5
(T-butylphenyl) butane (2.0 parts) was dissolved in ethyl acetate (10.5 parts), and a high boiling solvent tricresyl phosphate (0.48 part) and diethyl maleate (0.24 part) were further dissolved.
After adding 1.27 parts of "Pionin A41C" (manufactured by Takemoto Yushi), the mixture was heated and uniformly mixed. Separately, it was added to 93 parts of an aqueous 8% by weight gelatin (manufactured by Nitta Gelatin Co .; trade name "# 750 gelatin"), and emulsified and dispersed by a homogenizer. The remaining ethyl acetate was evaporated from this emulsion to obtain a target emulsified dispersion.

[0117]

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(Preparation of coating liquid) The above-mentioned diazonium salt compound capsule liquid, coupler emulsified dispersion, and styrene-
Butadiene rubber (SBR: manufactured by Sumitomo Nogatack Co .; trade name "SN307") was prepared such that the ratio of diazonium salt compound / coupler was 1/2, and the ratio of diazonium salt compound / styrene-butadiene rubber was 1 /.
The resulting mixture was mixed so as to obtain a coating solution of 6.4.

[Preparation of heat-sensitive recording material] On a photographic paper support obtained by laminating polyethylene on high-quality paper, a heat-sensitive recording layer, a light transmittance adjusting layer, and a protective layer are sequentially coated and dried by a wire bar in the stated order. A heat-sensitive recording material 101 was obtained. The application amount as solids is 8.33 g per 1 m ² ,
2.50 g and 1.23 g.

Examples 2 to 6, Comparative Examples 1 to 4 Heat-sensitive recording materials 102 to 110 were produced in the same manner as in Example 1 except that the fine particles and the dispersant were changed as shown in Table 2. In Table 2, “AEROSIL200” is manufactured by Nippon Aerosil, “Aluminum oxide C” is manufactured by Degussa, and “R1130” is silanol-modified polyvinyl alcohol manufactured by Kuraray.

<Evaluation method> Each of the heat-sensitive recording materials 101 to 11
Table 2 shows the average particle size and the maximum particle size of the fine particles in the fine particle dispersion liquid and the coating liquid used for No. 0. Further, the thermosensitive recording materials 101 to 110 were printed with a digital printer "NC-300D" manufactured by Fuji Photo Film Co., Ltd., and the mirror gloss of the unprinted portion and the printed gray portion were measured by Suga Test Machine Co., Ltd. It was measured at an incident angle of 20 ° using a digital variable gloss meter “UGV-5D”. The higher the number, the better the gloss. Table 2 shows the results.

[0122]

[Table 2]

The fine particle dispersions used in the examples were all stably dispersed without any aggregation. Therefore, there was no need for redispersion and handling was easy. Further, in the heat-sensitive recording material using this ultrafine particle dispersion, compared to the comparative example, no paper feeding failure occurred, the paper feeding property was good, the gloss was good, and the friction resistance was good. The printing was good without friction with the thermal head during printing. (If the friction with the head during printing is large, abnormal noise occurs during printing and printing position shift occurs.)

[0124]

As described above, according to the present invention, a dispersion method capable of stably dispersing fine particles and finely dispersing the same, and having excellent transparency, gloss, heat resistance, light resistance and heat sensitivity By providing a protective layer having excellent friction resistance and lubricity with the recording head, it is possible to provide a heat-sensitive recording material which is free from sticking and scum adherence to a heat-sensitive recording head and has excellent scratch resistance.

Claims (5)

[Claims] 1. A dispersion stabilizing step of previously dispersing fine particles in the presence of a silicone-modified polymer and / or a silanol-modified polyvinyl alcohol; and a dispersion liquid adjusting step of stirring and mixing the previously dispersed fine particles together with other components.
And a method for dispersing fine particles. 2. The method according to claim 1, wherein the fine particles are inorganic fine particles. 3. The method according to claim 2, wherein the inorganic fine particles are inorganic ultrafine particles. 4. A heat-sensitive recording material comprising a support having thereon a heat-sensitive recording layer and a protective layer, wherein the protective layer contains inorganic ultra-fine particles, and the inorganic ultra-fine particles are the method according to claim 3. A thermosensitive recording material characterized by being dispersed by: 5. The inorganic ultrafine particle is at least one selected from the group consisting of barium sulfate, zinc oxide, magnesium oxide, lead oxide, zirconium oxide, colloidal silica, and alumina.
2. The heat-sensitive recording material according to item 1.