JP2002178647A - Heat sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording material, matching of which with a thermal head is excellent, with which a favorable image gloss is obtained and haze of a non-image part of which is a few. SOLUTION: This heat sensitive recording material has a heat sensitive recording layer including a substantially non-photosensitive organic silver salt on a transparent support, and a protective layer including a matting agent dispersed in a binder on the farther side of the support than the heat sensitive recording layer under the condition that the average particle diameter of the matting agent is below 0.7 times as much as the thickness of the protective layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material capable of forming an image by heating with a thermal head. And a heat-sensitive recording material having a small haze.

[0002]

2. Description of the Related Art As a high quality image recording method, an image forming method of a wet process using silver halide has been generally used for a long time. However, because of wet processing,
An image forming method that does not use these processing solutions has been desired because of waste liquid treatment of processing chemicals and restrictions on installation of facilities such as piping. As a result, application of an image forming system such as an ink jet printer, electrophotography, dye thermal transfer, and direct thermal method is currently being studied as a hard copy material. However, none of these dry image forming methods is quite satisfactory in fields requiring excellent granularity, high space and density resolution, such as medical images.

Under such circumstances, a heat-sensitive recording material comprising a substantially non-photosensitive organic silver salt and an organic reducing agent, which has been known for a long time in US Pat. Nos. 3,074,809 and 3,080,254, is disclosed. As described in JP-A-8-505579 and JP-A-9-504752, when used for direct thermal image recording by a printer equipped with a thermal head, the maximum density and smooth gradation that cannot be obtained by other recording methods This is suitable for application to the field of medical imaging. Further, the recording material is non-photosensitive, and is excellent in handleability for the user.

[0004] Usually, the recorded medical image is observed on the Schaukasten and used for diagnosis. However, if the image is glare, the diagnosis may be difficult due to the reflection of room light or the like. Extremely low gloss is not preferred because it gives an impression lacking sharpness. Therefore, an image having an appropriate gloss is required, and a matting agent such as clay, talc, or silica is generally used in the protective layer.

However, Japanese Unexamined Patent Publication No. Hei 8-503175 (WO94 / 1119)
As described in 8), when a matting agent having a size that at least partially protrudes from the protective layer is used, the haze of the non-image portion increases to obtain a necessary matting effect, and irregular reflection occurs. There was a problem that the Schaukasten light made it difficult to diagnose low-concentration areas. Further, the contact with the thermal head is hindered, and a failure may occur in an image in a pinhole shape, which is a problem.

Another purpose of these matting agents is to impart abrasion resistance to a printed image. If the amount of addition is insufficient, sticking to a thermal head occurs at the time of printing. Therefore, there has been a strong demand for a protective layer that simultaneously solves these problems.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a recording material which is excellent in matching with a thermal head, can obtain a preferable gloss of an image, and has a small haze in a non-image portion.

[0008]

The heat-sensitive recording material of the present invention for solving the above-mentioned problems comprises a heat-sensitive recording layer containing a substantially non-photosensitive organic silver salt on a transparent support, On the side farther from the heat-sensitive recording layer, a protective layer containing a matting agent dispersed in a binder is provided, and the average particle size of the matting agent is less than 0.7 times the thickness of the protective layer. And
Further, it is desirable that the matting agent is wet silica particles, and that wet silica and fumed silica, or wet silica and colloidal silica are used in combination.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in more detail.

As the matting agent used in the present invention, fine particles of known organic or inorganic compounds which are insoluble in the solvent of the coating solution are used. For example, organic compounds include polymethyl acrylate, polymethyl methacrylate, polystyrene, and polytetrafluoroethylene, and inorganic compounds include silica (silicon dioxide), titanium dioxide, talc (magnesium silicate), and alumina. Among these, it is preferable to use wet silica for the heat-sensitive recording material of the present invention formed on a transparent support.

The wet-process silica in the present invention is defined as primary particles obtained by polymerization of a silica sol obtained by hydrolyzing sodium silicate with an inorganic acid such as sulfuric acid.
It is obtained by pulverizing the three-dimensionally agglomerated material and having a secondary particle diameter of a micron size. The average particle size in the present invention refers to this secondary particle size. When a plurality of types of matting agents are used, the largest one among the average particle diameters is used. Such wet-process silica having various particle sizes is commercially available from Nippon Silica Industry Co., Ltd., Fuji Silysia Chemical Ltd., and the like, and can be easily obtained.

The thickness of the protective layer can vary widely depending on the type of binder used, the required thermal sensitivity, and the matching property with the thermal head, but is generally 0.1 to 10 microns, preferably 0.5 to 5 microns. Selected from a range. The amount of the matting agent added to the protective layer to obtain a preferable glossiness can vary widely depending on the type of binder and matting agent, the particle size, the thickness of the protective layer, but in the case of wet-process silica, The binder is selected from 0.5 to 15 parts, preferably 2 to 7 parts, per 100 parts of the binder.

In the present invention, the average particle diameter of the wet-processed silica is less than 0.7 times the thickness of the protective layer.
Less than a micron. As a matter of course, in order to sufficiently obtain the effects of the present invention, it is preferable that the particle size distribution is as narrow as possible. The particle diameter is measured by various methods, but in the present invention, it means an average particle diameter measured by a Coulter counter method.

The dispersion of the wet-process silica in the present invention includes:
A high-speed stirrer such as a homodisper is suitable. Also, if necessary, it can be crushed to a smaller particle size by a ball mill, sand mill, high-pressure homogenizer, etc., but the matting effect depends on the thickness and the particle size of the protective layer. Grinding to an extremely small particle size is not preferred for keeping. Specifically, the particle size of the matting agent is less than 0.7 times, 0.05 times or more, more preferably less than 0.65 times and 0.3 times or more the thickness of the protective layer.

Furthermore, in the present invention, it is preferable to use fumed silica in combination. This fumed silica is also called dry silica as opposed to wet (precipitation) silica, and is generally produced by a flame hydrolysis method. Specifically, a method of burning silicon tetrachloride together with hydrogen and oxygen is generally known, but instead of silicon tetrachloride, silanes such as methyltrichlorosilane and trichlorosilane may be used alone or silicon tetrachloride. And can be used in a mixed state. Such fumed silica is commercially available from Nippon Aerosil Co., Ltd., Tokuyama Co., and the like, and can be easily obtained.

Solid fine particles such as fumed silica are loosely agglomerated in a slurry state in a dispersion medium, and are used after being dispersed by a ball mill, a high-pressure homogenizer, or the like.
In this case, they may be dispersed alone and added as a dispersion, or may be dispersed together with the wet-process silica or the resin forming the protective layer. Thus, in the present invention, by using a fumed silica dispersed to a size of 1/10 or less as compared with a wet fumed silica, a protective layer having excellent heat resistance and less sticking, the glossiness is significantly reduced. Can be obtained without having to. The finely dispersed fumed silica has different purposes and effects from wet silica as a matting agent.

In the present invention, it is also preferable to use colloidal silica in combination. This colloidal silica is a colloid solution in which ultrafine silica particles are dispersed in water.
The particle size of the ultrafine particles is generally 10 to 50 nm. Such colloidal silica can be easily obtained, for example, commercially available from Nissan Chemical Industries, Ltd. as "Snowtex". In the present invention, the colloidal silica has a low haze when used in combination, and a protective layer having high scratch resistance can be obtained without lowering the glossiness, and has the same effect as the wet process silica as a matting agent. Are also different.

The organic silver salt used in the heat-sensitive recording layer of the present invention is a substantially non-photosensitive, colorless or white silver salt, which is reduced by heating with a reducing agent described below to convert silver. What happens. Specifically, Research Disclosure No. 17029 on photothermographic materials
Organic salts of gallic acid, oxalic acid, behenic acid, stearic acid, palmitic acid, lauric acid and the like as described in section (II) and section 29996 (XVI); 1- (3-carboxypropyl) thio Urea, silver salts of carboxyalkylthioureas such as 1- (3-carboxypropyl) -3,3-dimethylthiourea; aldehydes such as formaldehyde, acetaldehyde, butyraldehyde and salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, Complex of silver with a polymer reaction product with an aromatic carboxylic acid such as 5,5-thiodisalicylic acid; 3- (2-carboxyethyl) -4-hydroxymethyl-4-thiazoline-2-thione; Carboxymethyl-4-methyl-4-thiazoline-2-
Silver salts or complexes of thiones such as thione; imidazole,
Pyrazole, urazole, 1,2,4 triazole and 1H-
Silver salts or complexes of nitrogen acids selected from tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benzotriazole; silver salts such as saccharin and 5-chlorosalicylaldoxime; silver salts of mercaptides Is raised. Among these, fatty acid silver having 10 or more carbon atoms is preferable, and silver stearate, silver behenate and the like are particularly preferably used.

These organic silver salts or complexes are dissolved in or dispersed in a suitable solvent such as water, aliphatic hydrocarbons, esters, alcohols, ethers or the like, or in a suitable solvent. It can be easily obtained by mixing a dissolved or dispersed silver salt such as silver nitrate. It is preferable to remove extraneous salts from the obtained crystals by washing with water or the like. Since the obtained crystals are insoluble in water, in the present invention, it is preferable to use a high-speed stirrer, a ball mill, a sand mill, a colloid mill, a vibration mill, an ultrasonic disperser, a homogenizer or the like to disperse the crystals and use them as a stable dispersion. At this time, if necessary, a surfactant may be used as a dispersing aid, and a polymer compound may be used as a protective colloid.

The amount of silver in the above-mentioned reducible silver source used in the present invention is determined by the maximum density required, but is generally 3 g / m ² or less, preferably 0.5 to 2.0 g, as silver.

In the heat-sensitive recording material of the present invention, US Pat.
U.S. Patents such as pyrogallol, 4-stearoylpyrogallol, isopropyl gallate, ethyl 3,4-dihydroxybenzoate, and 2,5-dihydroxybenzoic acid according to 074,809
3,440,049 and polyhydroxyindanes described in JP-A-6-317870. Patent application 2000-214
Compounds represented by the following general formulas [I] to [III] described in 76 are particularly preferable as the reducing agent used in the present invention.

[0022]

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In the general formula [I], R ¹ and R ² are substituents having a positive Hammett's substituent constant σ. In the general formula [II], Z represents an atom group necessary for forming a ring structure. In the general formula [III], R ³ and R ⁴ are a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group, an aryl group, an acyl group, an ester group, an amide group,
Represents a cyano group, a nitro group, a sulfonyl group, R ³ and R ⁴
May combine with each other to form a ring structure. General formulas [I] to [I
In II], the benzene ring having a dihydroxy group may optionally have a substituent.

Specific examples of the compounds represented by formulas [I] to [III] are shown below, but the reducing agents used in the present invention are not limited to these.

[0025]

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[0026]

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The addition amount of these reducing agents can vary widely depending on the type of reducing agent and the type of organic silver salt, but is generally about 0.1 to 3 mol, preferably about 0.1 to 3 mol, per mol of organic silver salt.
0.3 mol to 2 mol. For various purposes, two or more of the above reducing agents may be used in combination.

The reducing agent used in the present invention can be prepared by various methods known to those skilled in the art, for example, by dissolving in a suitable organic solvent.
It is added as a solid dispersion using a ball mill or the like, or emulsified and dispersed together with other additives to form an emulsion. The reducing agent does not necessarily need to be added to the layer containing the organic silver salt, but may be added to another layer or may be added separately.

It is preferable to use a color tone agent because the reduced silver image formed in the heat-sensitive recording material of the present invention shows a cool black. Examples of the toning agent include the above-mentioned Research Disclosure on Photothermographic Materials, Item 17029 (V) and Item 2996.
Known in Section 3 (XXII) and the like, specifically, imides such as phthalimide, mercapto compounds such as 3-mercapto-1,2,4-triazole, phthalazine, phthalazinone, 4-methylphthalic acid, and tetrachlorophthalic acid And benzoxazine derivatives such as 1,3-benzoxazine-2,4-dione.

In the heat-sensitive recording material of the present invention, various accelerators, stabilizers and precursors thereof may be used for the purpose of suppressing or promoting the formation of image silver by reduction, and improving the preservability before and after printing. Good. Specifically, photographic stabilizers, benzotriazole, 5-methylbenzotriazole, 5-chlorobenzotriazole, well-known as an inhibitor,
2-mercaptobenzotriazole, 2-mercaptomensimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 4-hydroxy-6-methyl-1,
3,3a, 7-tetrazaindene, 1-phenyl-5-mercaptotetrazole, 2-amino-5-mercapto-1,3,4-thiadiazole, 3-mercapto-5-phenyl-1,2,4-triazole ,
It can be selected from 4-benzamide-3-mercapto-5-phenyl-1,2,4-triazole and the like.

A thermoplastic resin is used as a binder for the heat-sensitive recording layer of the present invention. For example, there are synthetic resins such as polyvinyl alcohol, cellulose derivatives such as hydroxyethyl cellulose and hydroxypropyl cellulose, polysaccharides such as dextran, acrylic resin, polyester resin, polyurethane resin, vinyl chloride resin, vinyl acetate resin, polyolefin resin, and polyvinyl acetal resin. . The resin may be used by dissolving it in an organic solvent or water, or may be a latex in which a hydrophobic polymer solid is dispersed in the form of fine particles or a resin in which polymer molecules form micelles and are dispersed. In the present invention, among these, those which form a transparent film after coating and drying are preferable. If necessary, two or more resins compatible with each other may be used in combination.

The binder used in the heat-sensitive recording layer preferably contains as little free halide ions as possible, such as chloride ions and bromide ions. These halide ions react with silver ions during long-term storage to form photosensitive silver halide, which causes a reduction in light resistance of the recording material. Specifically, the content is preferably 100 ppm or less based on the resin solid content.

The coating liquid for forming the heat-sensitive recording layer of the present invention includes:
In addition, pigments, waxes, thickeners, coating aids, and the like may be added as necessary.

The protective layer of the present invention uses a binder that can withstand heating during printing by a thermal head. Generally, natural or synthetic resins are crosslinked to improve heat resistance.Specifically, gelatin, polyvinyl alcohol, acrylic resin, polyester resin, polyurethane resin, vinyl chloride resin, vinyl acetate resin, polyolefin resin, It is preferable to select from polyvinyl acetal resins and the like, and aqueous dispersions of these resins and resins are also commercially available and easily available.

The crosslinking agent for the layer obtained by coating and drying these resin dispersions and polymer solutions is selected from aldehydes, methylol compounds, epoxy compounds, amino resins such as melamine and benzoguanamine, and isocyanate compounds, depending on the polymer. It is. In the present invention, the type and amount of the cross-linking agent must be selected so that the cross-linking can proceed rapidly at room temperature without practically causing a problem such as an increase in the minimum concentration.

A protective layer made of a polymer cross-linked by radiation such as an electron beam or light is particularly preferable in terms of room temperature curing and high productivity. Generally, such a layer is obtained by applying a photocurable resin containing a polymerizable oligomer, a monomer, and in the case of photocrosslinking, a photoinitiator and the like, and radiating ultraviolet rays or electron beams to cure the layer.

Examples of the polymerizable oligomer include epoxy acrylate, urethane acrylate and polyester acrylate obtained by reacting various polyols, organic isocyanate and hydroxyl group-containing acrylate. Monomers are used to lower the viscosity of the coating liquid and to improve the adhesiveness and properties of the cured film.Specifically, monofunctional alkylene oxide-modified acrylates, N-vinylpyrrolidone, acryloylmorpholine, N-vinylcaprolactone Polyalkylene glycol acrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, and the like.

In the present invention, it is particularly preferable that these polymerizable oligomers are dispersed in water by emulsification or the like, and are combined with a water-soluble or water-dispersible monomer for the purpose of improving the properties of a cured film. A protective layer obtained by preparing an aqueous coating liquid, drying the coating, and then irradiating ultraviolet rays or electron beams to cure the coating.

Specific examples of the photoinitiator include benzophenone, methyl orthobenzoyl benzoate and 2-hydroxy-2.
-Methyl-1-phenyl-propan-1-one, 1-hydroxycyclohexylphenyl ketone, and the like. Further, as other additives, a polymerization inhibitor such as p-methoxyphenol may be contained. In the case of an aqueous coating liquid,
These photoinitiators and additives are preferably added after emulsification using a surfactant or the like.

In order to improve the matching property with the thermal head, the protective layer of the present invention may contain a slipping agent such as zinc stearate and calcium stearate, if necessary, in addition to the matting agent. Is also good. In this case, it is preferable that these are added as a water dispersion in the case of aqueous coating and dispersed in a suitable monomer or the like by a known method in the case of radiation curable resin coating. Further, a surfactant may be contained for improving coatability. The surfactant is not particularly limited, and any nonionic, anionic or cationic surfactant may be used.

The heat-sensitive recording material of the present invention can be coated on various supports. For example, resin films such as polyethylene terephthalate, polyethylene naphthalate, cellulose nitrate, and polycarbonate, resin-coated paper, baryta paper, synthetic paper, glass, and metal can be used. The support may be transparent or opaque, but is preferably transparent in the present invention. These supports may be processed for easy adhesion. Further, a colored support may be used to improve the visibility as a transmission image.

The coating method of the heat-sensitive recording material of the present invention is not particularly limited, and is described in E. Cohen, E. Gutoff, "Modern Coati
ng and Drying Technology ", VCH Publishers, Inc. Ne
w York, 1992. Further, simultaneous application of a plurality of layers is particularly preferable from the viewpoint of improving productivity.

The heat-sensitive recording material of the present invention may be provided with an intermediate layer, an undercoat layer, an antistatic layer and the like, if necessary, in addition to the heat-sensitive recording layer and the protective layer.

[0044]

EXAMPLES The present invention will be described below in detail with reference to examples, but is of course not limited thereto. Example 1 <Preparation of silver behenate> 34 g of behenic acid was added to 960 g of water at 90 ° C, 100 ml of a 1N aqueous sodium hydroxide solution was added dropwise with vigorous stirring over about 30 minutes, and the temperature was lowered to 40 ° C. A solution of 15.3 g of silver nitrate in 220 g of water to which 22.5 ml of 1N-phosphoric acid was added was added dropwise over about 60 minutes. The obtained crystals are taken out by suction filtration, washed with water until the conductivity of the washing water is 30 μS / cm or less,
Drying yielded 90% converted silver behenate crystals.

<Preparation of silver behenate dispersion> 20 g of the above silver behenate crystals and polyvinyl butyral (“But” manufactured by Sorcia)
8 g of var "B-79) was added to 92 g of 2-butanone, and a silver behenate dispersion having an average particle size of 1 micron or less was obtained using a bead mill.

<Preparation and coating of heat-sensitive recording layer coating liquid> In 100 g of 2-butanone, 15 g of polyvinyl butyral (“Butvar” B-79 manufactured by Sorcia), 1.3 g of the exemplary compound (R-2), tetrachlorophthalic anhydride 0.15 g, 0.14 g of 5-methylbenzotriazole, 0.26 g of phthalazinone, 0.35 g of adipic acid, and 35 g of the above-mentioned silver behenate dispersion were added to prepare a thermosensitive recording layer coating solution. This heat-sensitive layer coating liquid was applied to a 175-micron-thick PET base so as to have a silver amount of 1.3 g / m ² and dried to obtain a heat-sensitive layer.

<Preparation and application of protective layer coating liquid> In 100 g of 2-propanol, 30 g of a urethane acrylate oligomer (non-yellowing, viscosity 5000 mPa · s), 50 g of 1,6-hexanediol diacrylate, 50 g of 2-hydroxy-2- Methyl-1-phenyl-
3.2 g of propan-1-one, fumed silica (manufactured by Nippon Aerosil Co., Ltd., R972, primary particle diameter about 16 nm, amount is described in Table 1)
Was dispersed in a bead mill, 3 g of wet silica (particle size is described in Table 1) and 1 g of zinc stearate were added, and the mixture was dispersed with a disper at 8000 rpm for 20 minutes to obtain a protective layer coating liquid. This was applied onto the already obtained heat-sensitive recording layer, dried, and irradiated with a high-pressure mercury lamp (80 W / cm) at an irradiation distance of 10 cm and a speed of 10 cm.
It was cured under the conditions of m / min. According to electron microscopic observation, the thickness of the protective layer was about 2.5 microns.

Thermal recording is performed using a thermal head (TDK Corporation).
(LH4409 model) and the applied voltage and pulse width are changed to change the color density.
The reciprocal of the applied energy of the portion was compared as a thermal sensitivity by a relative value. The haze value was measured by Nippon Mikko Co., Ltd.
The POIC HAZEMETER SEP-HS-D1 was used to measure the non-printing area, and the gloss was measured at the 60% reflectance at the highest density area. In medical image observation, the haze value is preferably 30% or less and the glossiness is preferably in the range of 65 to 85% in the measurement method of the present embodiment.

[0049]

[Table 1]

In the table, sticking was evaluated in five stages depending on the degree. As for the standard of each stage, 5 is the best, quiet and smooth printing, 4 is greater than 5 sound at the time of printing, and 3 is sticking to reduce the image by 5% or less in the paper feed direction. 2, the further reduction occurs,
Reference numeral 1 denotes a state in which printing cannot be performed at all.

From Table 1, it is clear that the heat-sensitive recording material of the present invention has an image having low haze and preferable gloss. When the fumed silica was used in combination, the matching property with the thermal head was particularly good.

Example 2 <Preparation of Aqueous Aqueous Silver Behenate Dispersion> 20 g of the silver behenate crystals prepared in Example 1 and 32 g of 5% by weight polyvinyl alcohol (PVA203 manufactured by Kuraray Co., Ltd.) were added to 48 g of water. Using a bead mill, a 20% by weight silver behenate dispersion having an average particle size of 1 micron or less was obtained.

<Preparation of Reducing Agent / Additive Dispersion> 10% by Weight
58 g of polyvinyl alcohol (PVA203), 10 g of 5 wt% sodium dodecylbenzenesulfonate, Exemplified compound (R-2)
50 g, tetrachlorophthalic anhydride 7.6 g, 2-mercapto-
6 g of 5-methylbenzimidazole, 10 g of phthalazinone, 250 g by adding water were dispersed using a bead mill,
A reducing agent / additive dispersion was obtained.

<Preparation and application of coating solution for aqueous thermal recording layer>
Hydran HW-950 (Polyurethane dispersion manufactured by Dainippon Ink and Chemicals, Inc.) 50 g, ion-exchanged water 14.3
g, 29.2 g of the above-mentioned aqueous dispersion of silver behenate and 6.5 g of a reducing agent / additive dispersion, to give an aqueous heat-sensitive recording layer coating liquid. 1.3 g of this heat-sensitive layer coating solution as silver on a 175 micron thick PET base
/ m ² and dried to obtain a heat-sensitive layer.

<Water-based protective layer coating solution> Superflex®
175 g of 5100 (a UV-curable urethane acrylate aqueous dispersion manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 40%), 10.5 g of pentaerythritol triacrylate, 2-hydroxy-2-methyl
3.5 g of 1-phenyl-propan-1-one (dispersed with a nonionic surfactant having an HLB of 15) and 3 g of silica fine particles (particle diameter is described in Table 2) were added, and the dispersion was performed at 8000 rpm and 20 rpm.
After dispersing, Snowtex C (colloidal silica,
Particle size 10 to 20 nm, solid content about 20%: The amount is described in Table 2.) Zinc stearate fine particle dispersion (average particle size 0.3
3.5 g, micron, solid content 20%) and water to make 280 g. This was applied onto the already obtained water-based heat-sensitive recording layer, dried, and irradiated with a high-pressure mercury lamp (80 W / cm) at an irradiation distance of 10 cm.
The composition was cured at a speed of 7 m / min. According to electron microscopic observation, the thickness of the protective layer was about 2.8 microns.

[0056]

[Table 2]

In the table, the scratch strength was measured using a HEIDON-18 type continuous load-type scratch strength tester manufactured by Shinto Kagaku Co., Ltd., at 0.05 mmR and 90 °, while changing the load. Scratching with a sapphire needle, evaluation was made based on the weight at which scratches began to form.

From Table 2, it is apparent that the heat-sensitive recording material of the present invention gives an image having a low haze and a favorable gloss, and particularly when colloidal silica is used in combination, the transparency is improved and the scratch resistance is high. It is.

[0059]

According to the present invention, it is possible to provide a recording material which does not cause sticking with a thermal head, has excellent friction resistance, obtains a preferable gloss of an image, and has a small haze in a non-image portion. .

Claims (4)

[Claims] 1. A heat-sensitive recording layer containing a substantially non-photosensitive organic silver salt on a transparent support, and a matte dispersed in a binder on a side farther from the heat-sensitive recording layer as viewed from the support. A thermosensitive recording material having a protective layer containing an agent, wherein the average particle size of the matting agent is less than 0.7 times the thickness of the protective layer. 2. The heat-sensitive recording material according to claim 1, wherein the matting agent is a wet-processed silica particle. 3. The heat-sensitive recording material according to claim 2, wherein wet-process silica and fumed silica are used in combination. 4. The heat-sensitive recording material according to claim 2, wherein a wet process silica and a colloidal silica are used in combination.