JPH06336084A - Thermal recording material and production thereof - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material excellent not only in chemical resistance but also in sticking preventing properties and imparting good image quality. CONSTITUTION:In a thermal recording material wherein a thermal recording layer containing at least a color former and a developer forming a color upon the contact with the color former and a protective layer are successively provided on a support, the protective layer is formed by applying a coating soln. containing at least a binder and 0.01-10wt.% of alkylnaphthalenesulfonate and drying the formed coating soln. 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, and more particularly to a heat-sensitive recording material which is excellent in recorded image and background chemical resistance and is capable of recording a high quality image.

[0002]

2. Description of the Related Art Thermal recording methods have been used in various fields in recent years, such as facsimiles and printers, because they are highly reliable and require no maintenance despite the simple recording apparatus used. However, since the thermal recording material has poor resistance to chemicals such as oil and plasticizer, the density of the recorded image decreases when the recorded image is stored in contact with a plastic film containing the plasticizer for a long period of time. was there.

As a method for solving such a drawback, a method of providing a protective layer containing a specific amount of a fluorosurfactant on the color forming layer (Japanese Patent Laid-Open No. 107884/1982) or a thermosensitive recording layer is used. A method of providing a water-soluble resin layer containing a specific amount of alkyl sulfosuccinate on the substrate
No. 17479) is known. However, in any of the above methods, although the chemical resistance is improved, the protective layer coating solution is repelled on the heat-sensitive recording layer at the time of coating, which makes it difficult to uniformly coat the protective layer. Therefore, when an image is recorded using such a thermosensitive recording material, there is a drawback that the recorded image suffers from density unevenness due to the repelling and the quality of the recorded image becomes poor. In addition, when the coating solution for the protective layer is applied using a hopper type coating apparatus, the coating property is inferior and an uncoated portion is produced, so that the sticking prevention is not sufficient.

[0004]

The inventors of the present invention have made extensive studies to solve the above-mentioned drawbacks, and as a result, provided a polymer binder layer containing a specific amount of alkylnaphthalene sulfonate as a protective layer. It was found that a good heat-sensitive recording material can be obtained in the case of the above, and the present invention was reached.

Therefore, the first object of the present invention is not only excellent in chemical resistance but also excellent in sticking resistance.
It is to provide a heat-sensitive recording material having excellent image quality.
A second object of the present invention is to provide a method for producing a heat-sensitive recording material which is excellent not only in chemical resistance and sticking resistance but also in which excellent image quality can be provided.

[0006]

The above-mentioned various objects of the present invention provide a heat-sensitive recording layer containing at least a color-forming agent and a color-developing agent which develops a color on contact with the color-forming agent, and a protective layer on a support. A heat-sensitive recording material which is sequentially provided, wherein the protective layer is formed by applying and drying a coating solution containing at least a binder and 0.01 to 10% by weight of alkylnaphthalene sulfonate. Achieved by a heat-sensitive recording material and its manufacturing method.

In the heat-sensitive recording material of the present invention, an image is recorded by heating a color-developing agent and a color-developing agent which are separated from each other at room temperature to bring them into contact with each other to develop a color. As a color former and a color developer, a combination of an electron-donating dye precursor (color former) and an electron accepting compound (color former), or a combination of a diazo compound (color former) and a coupling compound (color former) It is preferable to use, and particularly when the former combination is adopted, the effect of the present invention of significantly improving the stability of the printed image is remarkable.

The electron-donating dye precursor used in the present invention is not particularly limited, but it has a property of developing a color by donating an electron or accepting a proton such as an acid, and a lactone. Compounds having a partial skeleton such as lactam, sultone, spiropyran, ester, amide, etc., which are ring-opened or cleaved upon contact with a color developer, are generally colorless compounds.

As a concrete example, Japanese Patent Laid-Open No. 55-2272.
Examples include those described in No. 53 and the like. If some of these are shown, the triarylmethane-based compound is 3,3-bis (p-dimethylaminophenyl) -6.
-Dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,3dimethylindole-3-
Yl) phthalide, 3- (p-dimethylaminophenyl)
-3- (2-methylindol-3-yl) phthalide and the like;

The diphenylmethane compound is 4,
4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leuco auramine, N-
2,4,5-trichlorophenyl leuco auramine and the like;

Examples of the xanthene compound include rhodamine-B-anilinolactam, rhodamine- (p-nitrino) lactam, 2- (dibenzylamino) fluorane,
2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluorane, 2-anilino
3-Methyl-6-N-methyl-N-cyclohexylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-anilino-3-methyl-6-
N-ethyl-N-isobutylaminofluorane, 2-anilino-6-dibutylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-tetrahydrofurfurylaminofluorane, 2-anilino-3 -Methyl-
6-piperidinoaminofluorane, 2- (o-chloroanilino) -6-diethylaminofluorane, 2- (3,
4-dichloroanilino) -6-diethylaminofluorane and the like;

Examples of thiazine compounds include benzoyl leuco methylene blue, p-nitrobenzyl leuco methylene blue and the like; examples of spiro compounds include 3-methyl-spiro-dinaphthopyran and 3-ethyl-spiro-dinaphthopyran 3,3'-dichloro-spiro- Jinaftpyran, 3
-Benzylspiro-dinaphthopyran, 3-methyl-naphtho- (3-methoxy-benzo) -spiropyran, 3-propyl-spiro-dibenzopyran and the like.

As the electron-accepting compound (developing agent) for these color-forming agents, phenol compounds, organic acids or metal salts thereof, and acidic substances such as oxybenzoic acid esters are used. Particularly, phenolic compounds or salicylic acid derivatives are used. And polyvalent metal salts thereof are preferred.

Examples of the phenolic compound include 2,
2'-bis (4-hydroxyphenyl) propane, 4-
t-butylphenol, 4-phenylphenol, 4-
Hydroxydiphenoxide, 1,1′-bis (3-chloro-4-hydroxyphenyl) cyclohexane, 1,
1'-bis (3-chloro-4-hydroxyphenyl)-
2-ethylbutane, 4,4'-sec-isooctylidene diphenol, 4,4'-sec-butylidene diphenol, 4-tert-octylphenol, 4-p-
There are methylphenylphenol, 4,4'-methylcyclohexylidenephenol, 4,4'-isopentylidenephenol, benzyl p-hydroxybenzoate and the like.

Examples of salicylic acid derivatives include 4-
Pentadecylsalicylic acid, 3,5-di (α-methylbenzyl) salicylic acid, 3,5-di (ter-octyl) salicylic acid, 5-octadecylsalicylic acid, 5-α- (p
-Α-methylbenzylphenyl) ethylsalicylic acid, 3
-Α-methylbenzyl-5-ter-octylsalicylic acid, 5-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4
-Decyloxysalicylic acid, 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid, 4-octadecyloxysalicylic acid and the like, and zinc, aluminum, calcium, copper and lead salts thereof.

In particular, when a phenolic compound is used, the effect of suppressing background fogging is remarkable. Examples of the heat-sensitive recording material in which such an electron-donating dye precursor (color former) and an electron-accepting compound (developing agent) are combined include:
U.S. Pat. Nos. 4,771,034 and 4,839,332
No. 6, JP-A-63-22682, 63-2656.
82, 63-227375, JP-A-1-10.
It is described in detail in Japanese Patent No. 5782.

The diazo compound that can be used in the present invention is a compound that reacts with a color developer called a coupling component described below to develop a desired hue, and emits light of a specific wavelength before the reaction. It is a photodecomposable diazo compound that decomposes when received and no longer has the ability to develop color even when the coupling component acts.

The hue in this coloring system is mainly determined by the diazo dye produced by the reaction of the diazo compound and the coupling component. Therefore, as is well known,
By changing the chemical structure of the diazo compound or the chemical structure of the coupling component, the coloring hue can be easily changed, and almost any coloring hue can be obtained depending on the combination.

The photodecomposable diazo compound in the present invention mainly means an aromatic diazo compound, and more specifically, a compound such as an aromatic diazonium salt, a diazosulfonate compound, a diazoamino compound or the like. Details of these diazo compounds are described in, for example, JP-A-2-136286.

The coupling component for forming a dye by coupling with a diazo compound (diazonium salt) used in the present invention includes, for example, 2-hydroxy-3-naphthoic acid anilide, resorcin and the like. -14
The thing described in 6678 can be mentioned. Further, an image having an arbitrary color tone can be obtained by using two or more of these coupling components in combination.

Since the coupling reaction between the diazo compound and the coupling component easily occurs in a basic atmosphere, it is preferable to add a basic substance in the layer. Specific examples of these basic substances are described in, for example, JP-A-61-29.
1183. Two or more basic substances may be used in combination. A heat-sensitive recording material using a combination of the above-mentioned diazo compound (color former) and coupling compound (developer) is disclosed in, for example, Japanese Patent Publication No. 28479/1990.
It is described in JP-A-2-31674 and JP-A-2-20434.

The color former or developer used in the present invention can be usually used as a solid dispersion, but from the viewpoint of raw storability of the thermosensitive recording layer such as preventing contact between the color former and the developer at room temperature. From the viewpoints of (fog prevention) and the control of color development sensitivity of color development with desired thermal energy, in the present invention, either a color former or a developer is used, especially a color former is encapsulated in microcapsules. It is preferable.

Any of an interfacial polymerization method, an internal polymerization method, and an external polymerization method can be adopted for producing the microcapsules which can be used in the present invention. In particular, a core containing a color former is used. It is preferable to employ an interfacial polymerization method in which a substance is emulsified in an aqueous solution in which a water-soluble polymer is dissolved and then a wall of the polymer substance is formed around the oil droplets.

The reactant forming the polymer substance is added inside the oil droplet and / or outside the oil droplet. Specific examples of the polymer substance include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer and the like. Preferred polymeric substances are polyurethanes, polyureas, polyamides, polyesters and polycarbonates, particularly preferably polyurethanes and polyureas. Two or more polymer substances can be used in combination.

Specific examples of the water-soluble polymer include gelatin, polyvinylpyrrolidone, polyvinyl alcohol and the like. Details of the method for producing the microcapsule composite wall are described in, for example, Japanese Patent Application Laid-Open No. 58-66948. In order to microencapsulate the color former, it is preferable to dissolve the color former in an organic solvent before use.

Examples of such organic solvents include low-boiling solvents such as ethyl acetate, methyl acetate, carbon tetrachloride, chloroform, methanol, ethanol, n-butanol, dioxane, acetone and benzene, and phosphoric acid esters and phthalic acid esters. High boiling point solvents such as carboxylic acid esters, fatty acid amides, alkylated biphenyls, alkylated terphenyls, chlorinated paraffins, alkylnaphthalenes, and diarylethanes can be mentioned. Such an organic solvent is described in detail in JP-A-4-19778.

In the case of microcapsules containing a color-forming agent, a solid sensitizer for swelling the walls of the microcapsules when heated can be further added. As the solid sensitizer, those which are solid at room temperature and have a melting point of 50 ° C. or higher, preferably 120 ° C. or lower can be selected and used from among the plasticizers of polymers used for the microcapsule wall. For example, when the wall material is made of polyurea or polyurethane, a hydroxy compound, a carbamic acid ester compound, an aromatic alkoxy compound, an organic sulfonamide compound, an aliphatic amide compound, an arylamide compound and the like are preferably used.

In the present invention, when a diazo compound is used as the color former, a color former may be used. The coloring aid that can be used in the present invention is a substance that increases the coloring density during heating printing or lowers the minimum coloring temperature, lowers the melting point of the coupling component or the diazo compound, or capsule wall. This is to create a situation in which the diazo compound and the coupling component easily react with each other by the action of lowering the softening point of.

In the present invention, when the color developer is not microencapsulated, the transparency of the heat-sensitive recording layer is improved to improve the light transmittance of the heat-sensitive recording material to obtain a heat-sensitive recording material used for OHP. Or, from the viewpoint of laminating multiple heat-sensitive layers to form a multicolor heat-sensitive recording material, after dissolving it in an organic solvent that is sparingly soluble or insoluble in water, it contains a surfactant and protects the water-soluble polymer. It can also be used in the form of a dispersion obtained by mixing and emulsifying with an aqueous phase having a colloid.

The organic solvent used in this case can be appropriately selected from high boiling point oils. Among them, preferable oils include dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene, dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, diisobutylbiphenyl, 1-methyl-1-dimethylphenyl-1-phenylmethane, and 1 in addition to esters.
-Ethyl-1-dimethylphenyl-1-phenylmethane, 1-propyl-1-dimethylphenyl-1-phenylmethane, triallylmethane (eg, tritoluylmethane, toluyldiphenylmethane), terphenyl compound (eg, terphenyl) , Alkyl compounds, alkylated diphenyl ethers (eg propyl diphenyl ether), hydrogenated terphenyls (eg hexahydroterphenyl), diphenyl ethers and the like.

Of these, the use of esters is particularly preferable from the viewpoint of emulsion stability of the emulsion dispersion. Examples of the esters include phosphoric acid ester, phthalic acid ester, dioctyl tetrahydrophthalate, benzoic acid ester, abietic acid ester, dioctyl adipate, isodecyl succinate, dioctyl azelate acid, oxalic acid ester, diethyl malonate, maleic acid ester. , Tributyl citrate, sorbate ester, sebacate ester, ethylene glycol esters, triacetin, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, borate ester and the like.

Specific examples of these esters are, for example,
It is described in JP-A-4-371887. In particular, the use of tricresyl phosphate alone or in combination is preferable because the emulsion dispersion stability of the color developer is particularly good. It is also possible to use the above oils in combination, or to use in combination with other oils. In the present invention, an auxiliary solvent may be added to the above organic solvent as a low boiling point dissolution aid. As such an auxiliary solvent, for example, ethyl acetate, isopropyl acetate, butyl acetate, methylene chloride and the like can be mentioned as particularly preferable ones.

The water-soluble polymer to be contained as a protective colloid in the aqueous phase mixed with the oil phase containing these components is appropriately selected from known anionic polymers, nonionic polymers and amphoteric polymers. However, polyvinyl alcohol, gelatin, cellulose derivatives and the like are preferable. The surfactant contained in the aqueous phase may be appropriately selected from anionic or nonionic surfactants that do not cause precipitation or aggregation by acting on the protective colloid. As a preferred surfactant,
Examples thereof include sodium alkylbenzene sulfonate, sodium alkyl sulfate, dioctyl sodium sulfosuccinate, and polyalkylene glycol (eg, polyoxyethylene nonylphenyl ether).

The emulsified dispersion of the present invention comprises an oil phase containing the above-mentioned components, a protective colloid, and an aqueous phase optionally containing a surfactant.
It can be easily obtained by mixing and dispersing using a means usually used for emulsification of fine particles. The ratio of the oil phase to the water phase (oil phase weight / water phase weight) is 0.0
2 to 0.6 is preferable, and 0.1 to 0.4 is particularly preferable.
Is preferred. If it is 0.02 or less, the amount of the aqueous phase is too large to be diluted and sufficient color developability cannot be obtained, and if it is 0.6 or more, the viscosity of the liquid is increased, which causes inconvenience in handling and a decrease in coating liquid stability.

In the present invention, a heat-fusible substance may be contained in the heat-sensitive color forming layer in order to improve the heat response of the heat-sensitive recording material. Examples of preferable heat-fusible substances include benzyl p-benzyloxybenzoate, β-naphthyl-benzyl ether, stearamide, stearyl urea, p-benzylbiphenyl, di (2-methylphenoxy) ethane, di (2 -Methoxyphenoxy) ethane, β-naphthol- (p-methylbenzyl) ether, α-naphthylbenzyl ether, 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-tert-octylphenyl ether,
1-phenoxy-2- (4-ethylphenoxy) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1,4-butanediol phenyl ether, diethylene glycol-bis (4-methoxyphenyl) ether and the like can be mentioned. To be

The heat-fusible substances may be used alone or as a mixture. In order to obtain a sufficient thermal response, it is preferable to use the heat-fusible substance in an amount of 10 to 200% by weight, particularly preferably 20 to 150% by weight, based on the developer. If necessary, the thermal recording layer may further include
Pigments, metal soaps, waxes, antistatic agents, ultraviolet absorbers, surfactants, defoamers, conductive agents, fluorescent paints and the like may be added.

As the pigment, calcium carbonate, barium sulfate, lithopone, wax, kaolin, silica, amorphous silica, aluminum hydroxide and the like are used. As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, and aluminum stearate.

As the wax, paraffin wax,
Microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, polystyrene wax, fatty acid amide wax, etc. may be used alone or in combination. As a surfactant,
A sulfosuccinic acid-based alkali metal salt and a fluorine-containing surfactant are used. The coating amount of the thermosensitive coloring layer is not particularly limited, but is usually 1 to 10 g / dry weight.
m ² , preferably in the range of ^{2 to} 8 g / m ² .

The greatest feature of the heat-sensitive recording material of the present invention is that a protective layer containing an alkylnaphthalene sulfonate is provided on the heat-sensitive recording layer. As such an alkylnaphthalene sulfonate, an alkali metal salt, ammonium salt or triethanolamine salt of alkylnaphthalene sulfonic acid represented by the following chemical formula 1 is particularly preferable.

[0040]

[Chemical 1] R in Chemical formula 1 represents an alkyl group. As R, C _{3 to} C ₂₀
Are preferred, and C _{4 to} C ₁₂ alkyl groups are particularly preferred.

The amount of alkylnaphthalene sulfonate added to the protective layer liquid is 0.01 to 1 in terms of solid content.
It is 0% by weight, preferably 1 to 8% by weight. If it is less than 0.01% by weight, a uniform protective layer cannot be formed, and the print quality and anti-sticking performance become insufficient. On the other hand, if the addition amount is more than 10% by weight, the foaming becomes large and the permeation of the protective layer liquid into the heat-sensitive recording layer becomes large, resulting in a non-uniform protective layer.

The binder for the protective layer containing an alkylbenzene sulfonate in the present invention includes polyvinyl alcohol, carboxy-modified polyvinyl alcohol, gelatin or its derivatives, starch and its derivatives, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose and the like. Cellulose derivative, casein, sodium alginate, sodium polyacrylate, polyacrylamide, styrene-maleic acid copolymer salt, self-crosslinking acrylic resin emulsion, polyurethane resin, styrene / butadiene / acrylic copolymer latex, etc. are used. To be In this case, it is possible to use a waterproofing agent together. In the present invention, it is particularly preferable to use a fluorosurfactant in combination.

In the protective layer, for the purpose of improving matching property with a thermal head at the time of thermal recording and improving water resistance,
Pigments, metal soaps, waxes, crosslinking agents, etc. are added. Details of these pigments, metal soaps, waxes, cross-linking agents and the like are described in, for example, JP-A-2-141279. Examples of the pigment include calcium carbonate, zinc oxide, titanium oxide, aluminum hydroxide, kaolin, talc, clay and the like. Among them, the oil absorption is 50 ml /
Pigments up to 100 g are preferred.

The protective layer liquid containing the alkylnaphthalene sulfonate is, if necessary, sufficiently mixed and dispersed by stirring, mixing, and dispersing devices such as a mixer, a dissolver, an attritor, and a sand mill, and then, is dispersed on the heat-sensitive recording layer. Is applied. When the protective layer solution or the heat-sensitive layer solution prepared as described above is applied on the support or the heat-sensitive recording layer, known coating means using a water-based or organic solvent-based coating solution is used.

The coating amount of the protective layer is not particularly limited, but if it is less than 0.1 g / m ² , the desired effect cannot be obtained, and if it exceeds 10 g / m ² , the recording sensitivity may be significantly lowered. Is generally 0.1 to 10 g / m due to
² , preferably in the range of 1 to 5 g / m ² .

The protective layer, like the heat-sensitive recording layer, is a conventionally known coating method, for example, air knife coating,
It is applied by blade coating, gravure coating, bar coating, spray coating, dip coating, curtain coating, etc. Among them, the curtain coating method of forming a free-fall curtain film and applying it to the running support to be applied is It is preferable because a surface defect due to bubbles does not occur and a uniform protective layer can be formed. The applied heat-sensitive recording material is dried, treated with a calendar or the like, and then used.

The support used in the present invention may be transparent or opaque. Examples of opaque supports include paper, coated paper, synthetic paper, paper laminated with polymer film, aluminum vapor deposition base, polymer film coated with white pigment, etc., but improved thermal sensitivity Therefore, it is preferable to provide an undercoat layer containing a pigment and a binder as main components.

Examples of the transparent support include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate film, polystyrene films, polypropylene films, polyolefin films such as polyethylene films, polyimide films and polychlorinated films. Vinyl film, polyvinylidene chloride film, polyacrylic acid copolymer film, polycarbonate film and the like can be mentioned, and these can be used alone or by laminating, but especially polyester film which has been subjected to heat treatment and antistatic treatment. Is preferred. A support having a thickness of 20 to 200 μm is used, and particularly 50 to 1
It is preferably 00 μm.

[0049]

Since the heat-sensitive recording material of the present invention has a protective layer containing an alkylnaphthalene sulfonate on the heat-sensitive recording layer, it has improved storage stability and sticking resistance and excellent head-matching property. It is a material.
Further, by forming the protective layer by the curtain coating method, it is possible to improve the printing quality.

[0050]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Unless otherwise specified, the parts and percentages described below
Indicates parts by weight and% by weight, respectively.

Example 1. (Formation of Thermosensitive Recording Layer) Preparation of Liquid A 10 parts of 3-butylamino-6-methyl-7-anilinofluorane and 5% solution of polyvinyl alcohol (PVA
-105: trade name of Kuraray Co., Ltd.) A liquid having a composition of 50 parts was used, and the average particle size was 1.0 μm in a sand mill.
A dispersion liquid of was obtained.

Preparation of Solution B 20 parts of bisphenol A, naphthyl benzyl ether 2
A liquid having a composition of 0 part and 200 parts of polyvinyl alcohol was used to obtain a dispersion liquid having an average particle diameter of 1.0 μm by a sand mill.

Preparation of Liquid C A liquid having a composition of 40 parts of light calcium carbonate, 1 part of sodium polyacrylate and 60 parts of water was used to obtain a pigment dispersion liquid having an average particle diameter of 2.0 μm by a sand mill. Liquid A above 6
0 parts, B solution 240 parts, C solution 101 parts and zinc stearate 21% dispersion liquid 25 parts were mixed to obtain a thermal recording layer coating solution. The obtained heat-sensitive recording layer coating liquid was applied to an undercoat base paper of 50 g / m ² having an undercoat layer mainly composed of a pigment and a binder by air knife coating so that the coating amount was 5 g / m ^2. It was dried to obtain a heat sensitive recording layer.

(Formation of thermosensitive recording material) Preparation of protective layer liquid 200 parts of 10% oxidized starch aqueous solution, 20 parts of aluminum hydroxide, 19 parts of zinc stearate 21% dispersion, 2 parts of sodium butylnaphthalene sulfonate and 65 parts of water. A protective layer liquid consisting of The resulting protective layer liquid was applied onto the above-mentioned thermosensitive recording layer by an air knife coat so as to be 3 g / m ² and dried to obtain a thermosensitive recording material.

Example 2. Instead of the protective layer solution used in Example 1, 200 parts of 10% aqueous solution of oxidized starch, 20 parts of aluminum hydroxide, 21% of zinc stearate Dispersion 1
A thermosensitive recording material was obtained in exactly the same manner as in Example 1 except that the protective layer liquid consisting of 9 parts, 2 parts of ammonium butylnaphthalenesulfonate and 65 parts of water was used.

Example 3. Instead of the protective layer solution used in Example 1, 200 parts of 10% aqueous solution of oxidized starch, 20 parts of aluminum hydroxide, 21% of zinc stearate Dispersion 1
A thermosensitive recording material was obtained in exactly the same manner as in Example 1 except that the protective layer liquid consisting of 9 parts, 2 parts of ammonium butylnaphthalenesulfonate and 65 parts of water was used.

Comparative Example 1. Instead of the protective layer solution used in Example 1, 200 parts of 10% aqueous solution of oxidized starch, 20 parts of aluminum hydroxide, 21% of zinc stearate Dispersion 1
A thermosensitive recording material was obtained in the same manner as in Example 1 except that the protective layer liquid consisting of 9 parts and 65 parts of water was used.

Comparative Example 2. Instead of the protective layer liquid used in Example 1, 200 parts of a 10% aqueous solution of oxidized starch, 20 parts of aluminum hydroxide, 2 parts of a sodium salt of a β-naphthalenesulfonic acid formalin condensate, zinc stearate 21
% A thermosensitive recording material was obtained in exactly the same manner as in Example 1 except that the protective layer liquid consisting of 19 parts of the dispersion liquid and 65 parts of water was used.

Comparative Example 3. Instead of the protective layer solution used in Example 1, 200 parts of 10% aqueous solution of oxidized starch, 20 parts of aluminum hydroxide, 2 parts of polyoxyethylene lauryl ether, 19 parts of 21% zinc stearate dispersion and 65 parts of water. A thermosensitive recording material was obtained in the same manner as in Example 1 except that the protective layer liquid was used. The evaluation results of the thermal recording materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1 below.

[0060]

[Table 1] The dynamic sensitivity, image quality, sticking and chemical resistance in the table were measured as follows.

Method of measuring sensitivity Thermal head manufactured by Kyocera Corporation (KLT-216-
8MPD1) and a thermal printing device having a pressure of 100 kg / cm ² immediately before the head, print with a pulse width of 1.2 ms while using a pressure roll under the conditions of a head voltage of 24 V and a pulse cycle of 10 ms. Was measured with a Macbeth reflection densitometer RD-918.

Evaluation Method of Image Quality The above print samples were visually evaluated, and the judgment criteria were as follows. ⊚--Excellent. ○ --- It is excellent. Δ −−−−− Inferior. × −−−−− Very poor.

Sticking Evaluation Method Printing was performed with Xerox-TC7005, and whiteout and print sound were evaluated according to the following criteria. ○ ------ No white noise occurs and print noise is low. △ ----- Slightly overexposure occurred and printing sound was present (usable in practice). × −−−−− The amount of blown-out highlights is very large and the printing sound is loud.

Evaluation method of chemical resistance Writing with a highlighter pen (Zebra highlighter 2-pink) was performed, and the fogging on the surface of the heat-sensitive recording material was visually evaluated. The judgment criteria are as follows. ○ ----- No fog is seen. △ ---- Slight fogging is observed. × −−−−− Fog is clearly seen. As is clear from the results of Table 1, the heat-sensitive recording materials obtained in the examples of the present invention have improved storage stability and sticking resistance, and also have excellent head matching properties and high image quality. there were.

Claims (3)

[Claims] 1. A heat-sensitive recording layer containing, on a support, at least a color-forming agent and a color-developing agent that develops a color by contacting the color-forming agent.
And a protective layer sequentially provided, wherein the protective layer is formed by applying and drying a coating solution containing at least a binder and 0.01 to 10% by weight of alkylnaphthalene sulfonate. A heat-sensitive recording material characterized by: 2. The heat-sensitive recording material according to claim 1, wherein the alkylnaphthalenesulfonic acid salt is at least one selected from alkali metal salts, triethanolamine salts and ammonium salts of alkylnaphthalenesulfonic acid. 3. A thermosensitive recording layer containing at least a color-forming agent and a color-developing agent which develops a color when contacted with the color-forming agent is provided on a support, and then at least 0.01 to 1
A method for producing a heat-sensitive recording material, which comprises applying a protective layer liquid containing 0% by weight of an alkylnaphthalene sulfonate and a water-soluble resin as a binder, wherein the protective layer is applied by a free-fall curtain coating method. And a method for producing a heat-sensitive recording material.