JPH06104383B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material having high film strength and high transparency.

<< Prior Art >> In the thermal recording method, (1) development is not necessary, (2) when the support is paper, the quality of the paper is close to that of ordinary paper, (3) easy handling, (4) color density It has the advantages of high cost, (5) simple and inexpensive recording device, and (6) no noise at the time of recording. is doing.

Against such a background, in recent years, in order to adapt to multiple colors or to be used for an overhead projector (abbreviated as OHP), a transparent thermal recording material that can be directly recorded by a thermal head. Is desired to be developed.

In order to meet such a demand, the present inventors have provided on a support, a microcapsule containing a colorless or light-colored basic dye precursor, and a developer dissolved in an organic solvent that is sparingly soluble or insoluble in water. A heat-sensitive recording material having a substantially transparent heat-sensitive layer obtained by coating and drying a coating solution comprising an emulsion dispersion of (1) was proposed (Japanese Patent Application No. 62-88197).

<Problems to be Solved by the Invention> However, the surface of the heat-sensitive layer of the above-mentioned transparent heat-sensitive recording material has a weak film strength and is easily scratched by a hard object such as a nail when scratched.

Therefore, it is an object of the present invention to provide a heat-sensitive recording material having a transparent heat-sensitive layer with improved scratch resistance.

<< Means for Solving the Problem >> The above-mentioned various objects of the present invention include a microcapsule containing a colorless or light-colored basic dye precursor, and a color developer dissolved in a water-insoluble or insoluble organic solvent. In a heat-sensitive recording material having a heat-sensitive layer formed by emulsifying and dispersing a developer solution, and applying and drying a coating solution containing the obtained emulsified dispersion on the heat-sensitive layer. It has been achieved by a heat-sensitive recording material characterized in that it contains a filler having a refractive index ratio of 0.95 to 1.05 with a colorant solution and an average particle size of 3 μm or less.

As the basic dye precursor used in the present invention, a colorless or light-colored one is appropriately selected from known compounds which develop a color by donating an electron or accepting a proton such as an acid. Such a compound has a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, amide, etc., and these partial skeletons are ring-opened or cleaved upon contact with a color developing agent. Examples thereof include triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, spiropyran compounds, and the like.

Particularly preferred compounds are compounds represented by the following general formula.

In the formula, R ₁ is an alkyl group having 1 to 8 carbon atoms, R ₂ is an alkyl group having 4 to 18 carbon atoms, an alkoxyalkyl group or a tetrahydrofurfuryl group, and R ₃ is a hydrogen atom or 1 to 15 carbon atoms. Is an alkyl group or a halogen atom, and R ₄ is a substituted or unsubstituted aryl group having 6 to 20 carbon atoms.
As the substituent of R ₄ , an alkyl group having 1 to 5 carbon atoms,
Alkoxy groups, halogenated alkyl groups and halogen atoms are preferred.

In the present invention, by encapsulating the above-mentioned color former in microcapsules, it is possible to prevent fogging during the production of the heat-sensitive material, and at the same time improve the raw storage stability and the record storage stability of the heat-sensitive material. In this case, the image density during recording can be increased by selecting the wall material and manufacturing method of the microcapsules. The amount of the color former used is preferably 0.05 to 5.0 g / m ² .

Examples of the wall material of the microcapsule include polyurethane, polyurea, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer, gelatin, polyvinylpyrrolidone, polyvinyl alcohol and the like. . In the present invention, two or more of these polymer substances may be used in combination.

In the present invention, among the above polymeric substances, polyurethane, polyurea, polyamide, polyester, polycarbonate and the like are preferable, and polyurethane and polyurea are particularly preferable.

The microcapsules used in the present invention are preferably microencapsulated by emulsifying a core substance containing a reactive substance such as a color former, and then forming a wall of a polymer substance around the oil droplets. In this case, the reactant forming a polymer substance is added inside the oil droplet and / or outside the oil droplet. Details of the microcapsules that can be preferably used in the present invention, such as the preferred method for producing the microcapsules, are described in, for example, JP-A-59-222716.

Here, the organic solvent for forming the oil droplets can be appropriately selected from those generally used as pressure sensitive oils. Among them, preferred oils include compounds represented by the following general formulas (I) to (III), triallylmethane (eg, tritoluylmethane, toluyldiphenylmethane), terphenyl compounds (eg, terphenyl), alkylated diphenyls. Phenyl ether (eg,
Examples include propyl diphenyl ether, hydrogenated terphenyl (eg, hexahydroterphenyl), diphenyl ether, and the like.

In the present invention, it is particularly preferable to use esters among these from the viewpoints of solubility of the developer and emulsion stability of the emulsion dispersion of the developer.

In the formula, R ¹ represents hydrogen or an alkyl group having 1 to 18 carbon atoms, and R ² represents an alkyl group having 1 to 18 carbon atoms. p ¹ and q ¹ represent an integer of ¹ to 4, and the total sum of alkyl groups is 4 or less.

The alkyl group of R ¹ and R ² is preferably an alkyl group having 1 to 8 carbon atoms.

In the formula, R ³ is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, R ⁴
Represents an alkyl group having 1 to 12 carbon atoms, and n represents 1 or 2.

p ² and q ² represent an integer of 1 to 4. When n = 1, the total number of alkyl groups is 4 or less, and when n = 2, the total number of alkyl groups is 6 or less.

In the formula, R ⁵ and R ⁶ represent a hydrogen atom or the same or different alkyl group having 1 to 18 carbon atoms. m represents an integer of 1 to 13. p ³ and q ³ represent an integer of 1 to 3, and the total sum of alkyl groups is 3 or less.

In addition, the alkyl group of R ⁵ and R ⁶ is particularly preferably an alkyl group having 2 to 4 carbon atoms.

Examples of the compound represented by the formula (I) include dimethylnaphthalene, diethylnaphthalene and diisopropylnaphthalene.

Examples of the compound represented by the formula (II) include dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl and diisobutylbiphenyl.

Examples of the compound represented by the formula (III) include 1-methyl-1-dimethylphenyl-1-phenylmethane, 1-ethyl-1-dimethylphenyl-1-phenylmethane, and 1-methyl-1-dimethylphenyl-1-phenylmethane.
-Propyl-1-dimethylphenyl-1-phenylmethane.

The preferred microcapsules produced as described above are not destroyed by heat or pressure as used in conventional recording materials, and the reactive substances contained in the core and outside of the microcapsules do not permeate the microcapsule wall. And can react.

In the present invention, the wall material of the microcapsule is selected,
If necessary, a glass transition point adjusting agent (for example, Japanese Patent Application No. 60-11
No. 9862), microcapsules composed of walls having different glass transition points are prepared, and a combination of basic colorless dye precursors having different hues and their developers can be used to increase the It is possible to realize intermediate colors. Therefore, the present invention is not limited to a monochromatic thermal paper, but can be applied to a bicolor or multicolor thermal paper and a thermal paper suitable for image recording with gradation.

In addition, if necessary, for example, Japanese Patent Application Nos. 60-125470 and 60-
The photobleaching inhibitors described in 125471 and 60-125472 can be added as appropriate.

As the color developing agent that causes a color-forming reaction in the thermal melting with the basic colorless dye used in the present invention, a known developer can be appropriately used. For example, the developer for the leuco dye includes a phenol compound, a sulfur-containing phenol compound, a carboxylic acid compound, a sulfone compound, a urea compound or a thiourea compound, and the details thereof are, for example, paper pulp technology. Times (1985) pages 49-54 and 65
-Page 70. Among these, especially the melting point
A substance having a temperature of 50 ° C to 250 ° C is preferable, and a phenol and an organic acid having a low water solubility of 60 ° C to 200 ° C are preferable. When two or more developers are used in combination, the solubility increases, which is preferable.

Among the developers used in the present invention, particularly preferable ones are represented by the following general formulas [IV] to [VII].

R ⁷ is an alkyl group, an aryl group, an aryloxyalkyl group or an aralkyl group, and a methyl group and a butyl group are particularly preferable.

R ⁸ is an alkyl group, particularly preferably a butyl group, a pentyl group, a heptyl group and an octyl group.

R ⁹ is a hydrogen atom or a methyl group, and n is 0-2.

R ¹⁰ is an alkyl group, an aralkyl group or an aryloxyalkyl group.

In the present invention, after the developer is dissolved in a poorly water-soluble or insoluble organic solvent, it is mixed with an aqueous phase containing a surfactant and having a water-soluble polymer as a protective colloid, and emulsified and dispersed. Used in the form of a dispersion.

The organic solvent that dissolves the developer can be appropriately selected from organic solvents that are sparingly soluble or insoluble in water, but in particular, the boiling point
When an organic solvent having a temperature of 150 ° C. or lower is used, the thermal sensitivity is good, which is preferable. As these organic solvents, for example,
Examples thereof include ethyl acetate, isopropyl acetate, butyl acetate and methylene chloride.

In the present invention, esters having a high boiling point and these pressure-sensitive oils can be appropriately mixed with these organic solvents and used, but in particular, esters are used from the viewpoint of the stability of the color developer emulsion dispersion. It is preferable.

Examples of the high boiling point esters include phosphoric acid esters (eg, triphenyl phosphate, tricresyl phosphate, butyl phosphate, octyl phosphate, cresyl diphenyl phosphate), phthalic acid esters (dibutyl phthalate, 2-ethylhexyl phthalate, phthalic acid). Ethyl, octyl phthalate, butylbenzyl phthalate) dioctyl tetrahydrophthalate,
Benzoic acid esters (ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate, benzyl benzoate), abietic acid esters (ethyl abietic acid, benzyl abietic acid), dioctyl adipate,
Isodecyl succinate, dioctyl azelate, oxalate (dibutyl oxalate, dipentyl oxalate), diethyl malonate, maleate (dimethyl maleate, diethyl maleate, dibutyl maleate), tributyl citrate, sorbate ( Methyl sorbate, ethyl sorbate, butyl sorbate), sebacate ester (dibutyl sebacate, dioctyl sebacate), ethylene glycol esters (formic acid monoester and diester, butyric acid monoester and diester, lauric acid monoester and diester, Palmitic acid monoesters and diesters, stearic acid monoesters and diesters, oleic acid monoesters and diesters), triacetin, diethyl carbonate, diphenyl carbonate, ethyl carbonate. Emissions, propylene carbonate,
Examples thereof include boric acid esters (tributyl borate, tripentyl borate) and the like. Among these, when tricresyl phosphate is mixed and used, the emulsion dispersion stability of the color developer is particularly good, which is preferable.

The water-soluble polymer to be contained as a protective colloid in the aqueous phase in which the developer is mixed with the dissolved oil phase can be appropriately selected from known anionic polymers, nonionic polymers and amphoteric polymers. However, polyvinyl alcohol, gelatin, cellulose derivatives and the like are preferable.

As the surfactant to be contained in the aqueous phase, it is possible to appropriately select and use anionic or nonionic surfactants that do not cause precipitation or aggregation by acting on the protective colloid. . Preferred surfactants include sodium alkylbenzene sulfonate (eg, sodium dodecylbenzene sulfonate), sodium alkyl sulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonylphenyl ether), and the like. .

The emulsified dispersion of the developer in the present invention is a means used for ordinary fine particle emulsification such as high speed stirring and ultrasonic dispersion of an oil phase containing a developer and an aqueous phase containing a protective colloid and a surfactant. Can be easily obtained by mixing and dispersing.

To this emulsified dispersion, a melting point depressant for a color developer can be added as appropriate. Some of these melting point depressants are
It also has the function of a glass transition point regulator of the capsule wall. Examples of such a compound include a hydroxy compound, a carbamic acid ester compound, a sulfonamide compound, an aromatic methoxy compound, and the details thereof are described, for example, in Japanese Patent Application No. 59-244190.

These melting point depressants can be appropriately used in the range of 0.1 to 2 parts by weight, preferably 0.5 to 1 part by weight, relative to 1 part by weight of the color-developing agent that lowers the melting point. It is preferable to use the color developing agent and the like that drop in the same place at the same place. When adding to different places, it is preferable to add 1 to 3 times the above addition amount.

A filler is added to the heat-sensitive layer of the heat-sensitive recording material of the present invention in order to increase the film strength or prevent sticking. It is essential that this filler is a filler having a refractive index ratio with the developer solution of 0.95 to 1.05 in order to prevent deterioration of transparency.

Examples of such fillers include inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, rouxite, kaolin, aluminum hydroxide, amorphous silica and colloidal silica, and polystyrene,
Vinyl acetate resin, polymethylmethacrylate, styrene-methacrylate copolymer, vinylidene chloride, polystyrene, polyurea, melamine-organic pigments such as formaldehyde, zinc stearate, calcium stearate, metal soap such as aluminum stearate and paraffin wax, There are waxes such as microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, and silicone.

In order not to reduce the transparency, the particle size of these fillers needs to be 3 μm or less, and more preferably 1.5 μm or less.

These fillers may be used alone or in combination of two or more kinds.

The total amount of these fillers added is usually 0.1 to 100%, preferably 10 to 50% based on the weight of the heat-sensitive layer.

<< Function >> In the present invention, the addition of the filler to the heat-sensitive layer improves the film strength and scratch resistance of the heat-sensitive layer, but as described above, the refractive index of the filler and the developer The ratio of the refractive index to the solution is 0.95 to 1.05, and the particle size of the filler is 3 μm or less, which is extremely fine. Therefore, even if the filler is added, light scattering hardly occurs. Almost not impaired by the addition of filler.

In the heat-sensitive recording material of the present invention, it is preferable to provide a protective layer on the heat-sensitive layer by a known method for the purpose of preventing sticking to the thermal head and improving the writability.
Details of the protective layer are described, for example, in "Paper and Pulp Technology Times" (September 1985, September issue), pages 2 to 4.

The heat-sensitive recording material of the present invention can be coated using a suitable binder.

As the binder, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, arabic rubber, gelatin, polyvinyl pyrrolidone, casein, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate, polyacrylic acid ester, ethylene-vinyl acetate copolymer. It is possible to use various emulsions such as The amount used is 0.5 to 5 g / m ² as solid content.

The heat-sensitive recording material of the present invention is prepared by preparing a coating liquid containing microcapsules containing a color-forming agent and a main component of a dispersion in which at least a color-developing agent is emulsified and dispersed, and other additives such as a binder, paper or a synthetic resin film. Bar coating, blade coating, air knife coating, gravure coating, etc. on a support such as
The solid content is 2.5 to 25 g / m ² after coating and drying by a coating method such as roll coating, spray coating or dip coating.
It is manufactured by providing a heat-sensitive layer. The heat-sensitive layer of the heat-sensitive material produced in this way has extremely good transparency.

As the support of the heat-sensitive recording material of the present invention, both a transparent support and an opaque support such as paper are used depending on the purpose and application.

The paper used for the support is heat-extracted pH 6 to 6 sized with a neutral sizing agent such as alkyl ketene dimer.
Use of 9 neutral paper (described in JP-A-55-14281) is advantageous in terms of storage stability over time.

In order to prevent the coating from penetrating into the paper and to improve the contact between the thermal recording head and the thermal recording layer, it is described in JP-A-57-116687. Moreover, paper having a Bekk smoothness of 90 seconds or more is advantageous.

Matatoku HirakiAkira optical surface roughness as described in JP 58-136492 is 8μ or less, and the thickness is 40~75μ paper, and optical contact at the following densities 0.9 g / cm ³ described in JP 58-69097 Paper with a rate of 15% or more, Canadian standard freeness (JIS JIS 58-69097)
Paper made from pulp beaten to 400 cc or more with P8121) to prevent the penetration of coating liquid, JP-A-58-65695
In order to improve the color density and resolution by using the glossy surface of the base paper produced by the Yankee machine as the coating surface,
It is described in JP-A-59-35985. Papers obtained by subjecting the base paper to corona discharge treatment to improve the coating suitability are also used in the present invention and give good results. In addition to these, any of the supports generally used in the field of heat-sensitive recording paper can be used as the support of the present invention.

A transparent support may be used in the heat-sensitive recording material of the present invention. By using the transparent support, the recorded matter after recording can be used as an OHP sheet or the like.

Examples of the transparent support include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose triacetate films, polypropylene films, polyolefin films such as polyethylene, and the like, and these may be used alone or in combination. it can.

In the present invention, an undercoat layer may be provided between the transparent support and the heat-sensitive layer in order to enhance the adhesion between the two layers. As a material for the undercoat layer, gelatin, synthetic polymer latex, nitrocellulose or the like is used. 0.1 g of undercoat layer
/ m ^{2 to} 2.0 g / m ² is preferable, especially 0.2 g / m
The range of ^{2 to} 1.0 g / m ² is preferable.

If it is less than 0.1 g / m ² , the adhesion between the support and the heat-sensitive layer is not sufficient, and even if it is increased to 2.0 g / m ² or more, the adhesion between the support and the heat-sensitive layer reaches saturation, so the cost is low. Will be disadvantageous.

As the undercoat layer, when the heat-sensitive layer is coated thereon, the image quality of the heat-sensitive layer may deteriorate if the undercoat layer swells from the water contained in the heat-sensitive layer. It is desirable to cure.

The following hardeners can be used in the present invention.

Divinylsulfone-N, N'-ethylenebis (vinylsulfonylacetamide), 1,3-bis (vinylsulfonyl) -2-propanol, methylenebismaleimide, 5
-Acetyl-1,3-diacryloyl-hexahydro-s
-Triazine, 1,3,5-triacryloyl-hexahydro-s-triazine, 1,3,5-trivinylsulfonyl-
Active vinyl compounds such as hexahydro-s-triazine.

2,4-dichloro-6-hydroxy-s-triazine
Sodium salt, 2,4-dichloro-6-methoxy-s-triazine, 2,4-dichloro-6- (4-sulfoanilino) -s-triazine sodium salt, 2,4-dichloro-6- (2-sulfo Ethylamino) -s-triazine,
Active halogen compounds such as NN'-bis (2-chloroethylcarbamyl) piperazine.

Bis (2,3-epoxypropyl) methylpropylammonium.p-toluenesulfonate, 1,4-bis (2 ', 3'-epoxypropyloxy) butane, 1,3,5
An epoxy compound such as triglycidyl isocyanurate, 1,3-diglycidyl-5- (γ-acetoxy-β-oxypropyl) isocyanurate.

Ethyleneimino compounds such as 2,4,6-triethylene-s-triazine, 1,6-hexamethylene-N, N'-bisethyleneurea and bis-β-ethyleneiminoethylthioether.

Methanesulfonic acid ester compounds such as 1,2-di (methanesulfonoxy) ethane, 1,4-di (methanesulfonoxy) butane, and 1,5-di (methanesulfonoxy) pentane.

Dicyclohexylcarbodiimide, 1-cyclohexyl-3- (3-trimethylaminopropyl) carbodiimide-p-trienesulfonate, 1-ethyl-3-
Carbodiimide compounds such as (3-dimethylaminopropyl) carbodiimide hydrochloride.

2,5-dimethylisoxazole / perchlorate, 2-
Isoxazole compounds such as ethyl-5-phenylisoxazole-3'-sulfonate and 5,5 '-(paraphenylene) bisisoxazole.

Inorganic compounds such as chromium alum, chromium acetate, zirconium salts and boric acid.

N-carbethoxy-2-isopropoxy-1,2-dihydroquinoline, N- (1-morpholinocarboxy)-
Dehydration condensation type peptide reagents such as 4-methylpyridinium chloride; active ester compounds such as N, N'-adipoyldioxydisuccinimide and N, N'-terephthaloyldioxydisuccinimide.

Isocyanates such as toluene-2,4-diisocyanate and 1,6-hexamethylene diisocyanate.

Dialdehydes such as glutaraldehyde, glyoxal, dimethoxyurea and 2,3-dihydroxy-1,4-dioxane.

Of these, glutaraldehyde, dialdehydes such as 2,3-dihydroxy 1,4-dioxane, and boric acid are particularly preferable.

The amount of these hardeners added is based on the weight of the base coating material.
An appropriate addition amount can be selected in the range of 0.20% by weight to 3.0% by weight according to the coating method and the desired degree of curing.

If the amount added is less than 0.2% by weight, the degree of curing will be insufficient regardless of the time, and the undercoat layer will swell when the heat-sensitive layer is applied. And the adhesion between the undercoat layer and the support deteriorates, and the undercoat layer becomes a film and peels off from the support.

Depending on the hardening agent used, if necessary, caustic soda or the like may be further added to bring the pH of the solution to the alkaline side, or the pH of the solution may be brought to the acidic side with citric acid or the like.

It is also possible to add an antifoaming agent to eliminate bubbles generated during coating, or to add an activator to improve the leveling of the liquid and prevent the generation of coating streaks.

Further, it is desirable to activate the surface of the support by a known method before applying the undercoat layer. As a method of activation treatment, etching treatment with acid, flame treatment with a gas burner, or corona discharge treatment, glow discharge treatment or the like is used, but in terms of cost or simplicity, U.S. Pat.No. 2,715,075, No. 2,846,727, No. 3,
The corona discharge treatment described in No. 549,406 and No. 3,590,107 is most preferably used.

The heat-sensitive recording material of the present invention may have the above-mentioned substantially transparent heat-sensitive layer formed on at least one surface of the support,
In addition to providing one layer of the heat-sensitive layer on one surface of the transparent or opaque support, it is also possible to prepare a double-sided heat-sensitive recording material by providing one layer of the heat-sensitive layer having the same structure on both sides of the opaque support, respectively. The transparent support may be provided on both sides with substantially transparent heat-sensitive layers described in the present specification capable of developing different colors, and one layer may be provided for each layer, or a known heat-sensitive layer may be laminated. Various modes are possible according to the application, purpose.

<< Examples >> The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 4, Comparative Examples 1 to 3 [Preparation of Capsule Liquid] Crystal violet lactone 14 g (leuco dye),
Takenate D-110N (Takeda Pharmaceutical Co., Ltd. capsule wall material)
60 g and 2 g of Sumisorb 200 (UV absorber manufactured by Sumitomo Chemical Co., Ltd.) were added to a mixed solvent of 55 g of 1-phenyl-1-xylylethane and 55 g of methylene chloride and dissolved.
This leuco dye solution was mixed with 100 g of an 8% aqueous solution of polyvinyl alcohol, 40 g of water and 1.4 g of a 2% sodium salt of dioctyl sulfosuccinate (dispersant) and mixed with an ace homogenizer manufactured by Nippon Seiki Co., Ltd. 10,000 rpm
Was emulsified for 5 minutes, 150 g of water was further added, and the mixture was reacted at 40 ° C. for 3 hours to prepare a capsule liquid having a capsule size of 0.7 μm.

[Preparation of color developer emulsion]

Developers (a) 8g, (b) 4g and (c) 30g represented by the following structural formulas were dissolved in 1-phenyl-1-xylylethane 8.0g and ethyl acetate 30g. The resulting developer solution is
100g of 8% aqueous solution of polyvinyl alcohol, 150g of water, and 0.5g of sodium dodecylbenzene sulfonate were mixed and emulsified for 5 minutes at 10,000rpm room temperature using an ace homogenizer manufactured by Nippon Seiki Co., Ltd. to obtain a particle size of 0.5. An emulsified dispersion of μ was obtained.

[Preparation of heat-sensitive recording material] 5.0 g of the above-mentioned capsule liquid, 10.0 g of the developer emulsion dispersion, 4.5 g of 20% dispersion liquid of the filler shown in Table 1 and 5 g of water were stirred and mixed,
75μ thick transparent polyethylene terephthalate (PET)
A heat-sensitive layer was formed by coating one surface of the support so that the solid content was 10 g / m ² and drying.

Further, a protective layer having the following composition is formed on the heat-sensitive layer so that the solid content is
A heat-sensitive recording material was obtained by coating and drying so as to obtain 3 g / m ² .

Silicon modified polyvinyl alcohol (Kuraray PVAR210
5) 2 parts by weight colloidal silica (Nissan Chemical Snowtex 30) 3
1 part by weight Paraffin wax emulsion (Chukyo Yushi Cerosol 428) 1 part by weight Zinc stearate emulsion (Chukyo Yushi Hydrin Z-7) 0.1 parts by weight The transparency of the heat-sensitive recording material thus obtained was measured with an integrating sphere photometer ( It was measured with a haze meter. Also, the film strength was evaluated from the ease of scratching when the surface was lightly rubbed with a nail. The results are as shown in Table 2.

From the results shown in Table 2, the heat-sensitive layer of the heat-sensitive recording material of the present invention was
It was demonstrated that both transparency and scratch resistance were good.

Claims (1)

[Claims] 1. A microcapsule containing a colorless or light-colored basic dye precursor, and a color developer solution obtained by dissolving a color developer in a water-insoluble or insoluble organic solvent.
In a heat-sensitive recording material having a heat-sensitive layer formed by coating and drying a coating liquid containing the obtained emulsified dispersion on a support,
The heat sensitive layer has a refractive index ratio of 0.95 to 1.
A heat-sensitive recording material characterized by containing a filler having an average particle size of 05 and an average particle size of 3 μm or less.