JP3324872B2 - Thermal recording material and method for producing the same - Google Patents

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 excellent in image quality, stamp ink drying property, scratch resistance and chemical resistance.

[0002]

2. Description of the Related Art In recent years, thermal recording methods have been used in various fields such as facsimile machines and printers, because they have high reliability and do not require maintenance, despite the simple use of a recording apparatus. I have. Along with this, the use of various stationery, such as markers, for example, in the thermal recording material has increased, and the use of stationery, such as markers, has no effect on the recorded image, as in the case of PPC paper. There is an increasing demand for developing thermal recording materials. From such a viewpoint, a protective layer is provided on the thermosensitive coloring layer to improve chemical resistance and scratch resistance. As such a heat-sensitive recording material, for example, a material in which starch and polyvinyl alcohol are used in combination as a binder in a protective layer (JP-A-4-110188)
No.), and those using an acrylic resin as a binder in the protective layer (Japanese Patent Application Laid-Open No. 4-341886) have been proposed.

[0003] However, these heat-sensitive recording materials have improved chemical resistance and scratch resistance, but dry slowly when they are stamped with stamp ink and vermilion or when stationery such as a ballpoint pen is used. However, there is a disadvantage that the recording paper may be stained or the hands may be stained. In addition, when the coating liquid for the protective layer is applied using a hopper type coating device, the coating property is poor and uncoated portions are generated, so that sticking is not sufficiently prevented or density unevenness occurs in a recorded image. Also occurs.

[0004]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned drawbacks. As a result, a self-crosslinkable acrylic resin, starch and fully saponified polyvinyl alcohol were used as a binder in the protective layer. It has been found that a good heat-sensitive recording material with the above-mentioned disadvantages improved can be obtained. Accordingly, a first object of the present invention is to provide a heat-sensitive recording material which is excellent not only in image quality, chemical resistance and scratch resistance but also in stationery suitability. A second object of the present invention is to provide a method for producing a thermosensitive recording material which is excellent not only in image quality, chemical resistance, scratch resistance and head matching but also in stationery suitability.

[0005]

The above objects of the present invention are attained in a heat-sensitive recording material comprising a support and a heat-sensitive recording layer and a protective layer successively provided on a support. The present invention has been attained by a heat-sensitive recording material comprising an acrylic resin, starch, and polyvinyl alcohol, and having a self-crosslinkable acrylic resin content of 20 to 60% by weight in a protective layer binder, and a method for producing the same.

In the heat-sensitive recording material of the present invention, an image is recorded by causing a color developer and a developer, which are isolated from each other at room temperature, to come into contact with each other by heating to form 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 developer), or a combination of a diazo compound (color former) and a coupling compound (color developer) Is preferable, and when the former combination is employed, the effect of the present invention of greatly improving the stability of a printed image is remarkable.

[0007] The electron-donating dye precursor used in the present invention is not particularly limited, but has a property of donating electrons or accepting a proton such as an acid to develop a color, and is preferably a lactone. , Lactams, sultones, spiropyrans, esters, amides, etc., are generally colorless compounds which have a partial skeleton which is opened or cleaved upon contact with a color developing agent.

A specific example is disclosed in Japanese Patent Application Laid-Open No. 55-2272.
No. 53 and the like. For example,
As a triarylmethane compound, 3,3-bis (p
-Dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3-
(1,3 dimethylindol-3-yl) phthalide, 3
-(P-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide and the like; as diphenylmethane compounds, 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucoura Min, N-2,4,5-trichlorophenylleuco auramine and the like;

As a xanthene compound, rhodamine-
B-anilinolactam, rhodamine- (p-nitrino)
Lactam, 2- (dibenzylamino) fluoran, 2-
Anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-dibutylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluoran, 2- Anilino-3
-Methyl-6-N-methyl-N-cyclohexylaminofluoran, 2-anilino-3-chloro-6-diethylaminofluoran, 2-anilino-3-methyl-6-N
-Ethyl-N-isobutylaminofluoran, 2-anilino-6-dibutylaminofluoran, 2-anilino-
3-methyl-6-N-methyl-N-tetrahydrofurfurylaminofluoran, 2-anilino-3-methyl-6
-Piperidinoaminofluoran, 2- (o-chloroanilino) -6-diethylaminofluoran, 2- (3,4
-Dichloroanilino) -6-diethylaminofluoran and the like;

Examples of the thiazine compound include benzoyl leucomethylene blue and p-nitrobenzyl leucomethylene blue; examples of the spiro compound include 3-methyl-spiro-dinaphthopyran and 3-ethyl-spiro-dinaphthopyran 3,3'-dichloro-spiro- Zinaphthopyran, 3
-Benzylspiro-dinaphthopyran, 3-methyl-naphtho- (3-methoxy-benzo) -spiropyran, 3-propyl-spiro-dibenzopyran and the like. Two or more of these color formers may be used in combination.

As the electron-accepting compound (developing agent) for these coloring agents, phenol compounds, organic acids or metal salts thereof, and acidic substances such as oxybenzoic acid esters are used. In particular, phenolic compounds or salicylic acid derivatives are used. And polyvalent metal salts thereof. Examples of the phenolic compound include 2,2′-bis (4-hydroxyphenyl) propane, 4-t-butylphenol,
-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-methylphenylphenol, 4,4'-methylcyclohexylidenephenol, 4,4'-isopentylidenephenol, benzyl p-hydroxybenzoate and the like.

Examples of the salicylic acid derivative include, for example, 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,
-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 fog is remarkable. Examples of such a heat-sensitive recording material in which an electron-donating dye precursor (color former) and an electron-accepting compound (color developer) are combined include, for example,
U.S. Pat. Nos. 4,771,034 and 4,839,332
JP-A-63-22682, JP-A-63-2656
No. 82, 63-227375, JP-A-1-10
No. 5782 discloses this in detail.

The diazo compound that can be used in the present invention is a compound that develops a desired hue by reacting with a developer called a coupling component described later, and emits light of a specific wavelength before the reaction. It is a photo-decomposable diazo compound that decomposes when it receives it and no longer has a color-forming ability even when a coupling component acts. The hue in this color forming system is mainly determined by the diazo dye formed by the reaction between the diazo compound and the coupling component. Therefore, as is well known, the color hue can be easily changed by changing the chemical structure of the diazo compound or the chemical structure of the coupling component, and it is possible to obtain almost any color hue depending on the combination. it can.

The photo-decomposable diazo compound in the present invention mainly refers to an aromatic diazo compound, and more specifically, to compounds such as aromatic diazonium salts, diazosulfonate compounds, and diazoamino compounds. Details of these diazo compounds are described in, for example, JP-A-2-136286. Coupling components that form a dye by coupling with a diazo compound (diazonium salt) used in the present invention include, for example, 2-hydroxy-3-naphthoic acid anilide and resorcinol, as well as JP-A-62-146.
No. 678 can be mentioned.
An image of any color tone can be obtained by using two or more of these coupling components.

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 into the layer. Specific examples of these basic substances are described, for example, in JP-A-61-29
No. 1183. Two or more basic substances may be used in combination. Thermal recording materials using a combination of the above diazo compound (color former) and coupling compound (color developer) are described in, for example, JP-B-2-28479 and JP-B-2-28479.
Nos. 31,674 and 2,020,434.

The color former or developer used in the present invention can be usually used in the form of a solid dispersion. However, from the viewpoint of raw storage stability of the heat-sensitive recording layer, such as preventing contact between the color developer and the developer at room temperature. In the present invention, one of the color former and the developer, particularly the color former is used by being encapsulated in a microcapsule from the viewpoints of (fogging prevention) and control of the color development sensitivity of causing color development with desired thermal energy. Is preferred.

For the production of the microcapsules usable in the present invention, any of an interfacial polymerization method, an internal polymerization method and an external polymerization method can be employed. In particular, a core containing a color former is preferably 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 walls of the polymer substance are formed around the oil droplets.

The reactant forming the polymer substance is added to the inside of the oil droplet and / or to the outside of 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, 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, and polyvinyl alcohol. The details of the method for producing the microcapsule composite wall are described in, for example, JP-A-58-66948. In order to microencapsulate the color former, it is preferable to use the color former dissolved in an organic solvent.

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 phosphate esters and phthalate esters. Examples include high-boiling solvents such as carboxylic acid esters, fatty acid amides, alkylated biphenyls, alkylated terphenyls, chlorinated paraffins, alkylnaphthalenes, and diarylethanes. Such an organic solvent is described in detail in JP-A-4-19778.

In the case of a microcapsule containing a color former, a solid sensitizer for swelling the microcapsule wall during heating can be further added. As the solid sensitizer, those which have a melting point of 50 ° C. or higher, preferably 120 ° C. or lower and are solid at ordinary temperature can be selected from those called polymer plasticizers used as microcapsule walls. For example, when the wall material is made of polyurea or polyurethane, a hydroxy compound, a carbamate compound, an aromatic alkoxy compound, an organic sulfonamide compound, an aliphatic amide compound, an arylamide compound, or the like is preferably used.

In the present invention, when a diazo compound is used as a color former, a color former may be used. The color-forming auxiliary that can be used in the present invention is a substance that increases the color density at the time of heating printing or lowers the minimum color-forming temperature, lowers the melting point of a coupling component or a diazo compound, or reduces the capsule wall. The purpose is to create a situation in which the diazo compound and the coupling component easily react by the action of lowering the softening point.

In the present invention, when the developer is not microencapsulated, the transparency of the heat-sensitive recording layer is improved, the light transmittance of the heat-sensitive recording material is improved, and the heat-sensitive recording material is used for OHP. Or, from the viewpoint of laminating multiple heat-sensitive layers into a multicolor heat-sensitive recording material, after dissolving in a water-insoluble or insoluble organic solvent, this contains a surfactant and protects the water-soluble polymer. It can also be used in the form of a dispersion which is mixed with an aqueous phase having a colloid and emulsified and dispersed.

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

Among these, esters are particularly preferred from the viewpoint of the emulsion stability of the emulsified dispersion. Esters include phosphates, phthalates, dioctyl tetrahydrophthalate, benzoates, abietic esters, dioctyl adipate, isodecyl succinate, dioctyl azelate, oxalate, diethyl malonate, maleate , Tributyl citrate, sorbate, sebacate, ethylene glycol esters, triacetin, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, borate and the like.

Specific examples of these esters include, for example,
It is described in JP-A-4-371887. In particular, when tricresyl phosphate is used alone or as a mixture, it is preferable because the emulsification and dispersion stability of the developer is good. The above oils can be used together or in combination with other oils. In the present invention, an auxiliary solvent may be further added to the above-mentioned organic solvent as a low boiling point dissolution aid.
As such co-solvents, 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. As the surfactant to be contained in the aqueous phase, a surfactant which does not cause precipitation or aggregation by acting with the protective colloid can be appropriately selected from anionic or nonionic surfactants. Preferred surfactants include sodium alkylbenzene sulfonate, sodium alkyl sulfate, dioctyl sulfosuccinate sodium salt,
Polyalkylene glycol (for example, polyoxyethylene nonylphenyl ether) and the like can be mentioned.

The emulsified dispersion of the present invention is prepared by mixing an oil phase containing the above-mentioned components, a protective colloid, and, if necessary, an aqueous phase further containing a surfactant, with ordinary fine particles such as high-speed stirring and ultrasonic dispersion. It can be easily obtained by mixing and dispersing using means used for emulsification.
The ratio of the oil phase to the water phase (oil phase weight / water phase weight) is
0.02 to 0.6, preferably 0.1 to 0.6
Preferably it is 0.4. If it is less than 0.02, the aqueous phase is too large to be diluted, and sufficient color development cannot be obtained. If it is more than 0.6, the viscosity of the liquid becomes higher, which causes inconvenience in handling and lowers the stability of the coating liquid.

In the present invention, in order to improve the thermal response of the heat-sensitive recording material, a heat-fusible substance can be contained in the heat-sensitive coloring layer. Examples of preferred heat-fusible materials 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

The heat-fusible substance is used alone or as a mixture. In order to obtain sufficient thermal responsiveness, 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. The heat-fusible substance is added to one or both of the color former and the developer, and dispersed at the same time, or a heat eutectic with the color former or the developer is prepared in advance and then cooled, and then cooled. It may be dispersed. Further, the thermosensitive recording layer may further include, if necessary,
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 or the like is used alone or in combination.

As the surfactant, a sulfosuccinic acid-based alkali metal salt and a fluorine-containing surfactant are used. The thermosensitive coloring layer liquid of the present invention using these materials is, if necessary, a mixer, a dissolver, an attritor,
After being sufficiently mixed and dispersed by a stirring, mixing, and dispersing device such as a sand mill, it is applied to a support. The coating amount of the heat-sensitive coloring layer is not particularly limited, usually, 1 to 10 g / m ² in dry weight, preferably from 2 to 8 g / m ^2.

The most significant feature of the heat-sensitive recording material of the present invention resides in that a protective layer containing a self-crosslinkable acrylic resin, starch, and fully saponified polyvinyl alcohol as a pigment binder is provided on the heat-sensitive recording layer. In the present invention,
The composition ratio of self-crosslinkable acrylic resin / starch / polyvinyl alcohol in the protective layer is 20 to 60% by weight / 20 to
It is preferably 60% by weight / 5 to 40% by weight, and especially the above composition ratio is 30 to 50% by weight / 30 to 50% by weight.
/ 5 to 30% by weight.

The self-crosslinkable acrylic resin in the present invention includes N-methylolamide and hydroxyethyl methacrylate or acrylic acid, glycidyl methacrylate and acrylic acid or dimethylaminoethyl acrylate, hydroxyethyl methacrylate and acrylic acid or acrolein, etc. Are copolymerized with a combination having a reactive group. Among them, a copolymer having a Tg (glass transition point) of 20 ° C. or more is preferable, and a copolymer having a Tg of 40 ° C. or more is particularly preferably used.

Specific examples include an acrylic set SC series and a SA series manufactured by Nippon Shokubai Kagaku Co., Ltd. and a Jurimar series manufactured by Nippon Pure Chemical Co., Ltd. The starch that can be used in the present invention is not particularly limited, and examples thereof include oxidized starch, esterified starch, etherified starch, and crosslinked starch. These may be used alone or in combination of two or more.
Preferably, the viscosity of a 20% solution at 0 ° C. is 100 cp or less.

The polyvinyl alcohol which can be used in the present invention includes any commonly used or commercially available polyvinyl alcohol, carboxylic acid-modified polyvinyl alcohol, silicon-containing polyvinyl alcohol, cation-modified polyvinyl alcohol, ternary Modified polyvinyl alcohol, such as copolymer polyvinyl alcohol, terminal alkyl group-modified polyvinyl alcohol, terminal thiol group-modified polyvinyl alcohol, and sulfonic acid-modified polyvinyl alcohol, and the like, and the degree of polymerization is 3
It is preferable that the saponification degree is not less than 00 to 2400 and the degree of saponification is not less than 87 mol%, and particularly preferably the degree of polymerization is not less than 300 to 1700 and the saponification degree is not less than 98 mol%.

As the pigment that can be used in the present invention, all general organic or inorganic pigments can be used.
Specifically, calcium carbonate, zinc oxide, titanium oxide,
Examples include aluminum hydroxide, kaolin, talc, fluorite, synthetic silicate, amorphous silica, urea formalin resin powder, and the like. Particularly, the oil absorption degree specified in JIS-K5101 is 5
Pigments of 0 ml / 100 g or less are preferred. The amount of the binder used in the protective layer is 10 to 500 with respect to the above pigment.
% By weight, preferably 50 to 300% by weight, particularly preferably 100 to 200% by weight.

The coating solution for the protective layer in the present invention can be obtained by mixing a pigment with the solution of the binder, and improves the head matching with a thermal head during thermal recording.
Lubricants and dispersants such as zinc stearate, calcium stearate, paraffin wax, polyethylene wax, etc., fluorescent brighteners, crosslinking agents, ultraviolet absorbers, surfactants, etc. May be further appropriately added. The protective layer liquid is coated on the heat-sensitive recording layer after being sufficiently mixed and dispersed by a stirring, mixing, and dispersing device such as a mixer, dissolver, attritor, or sand mill, if necessary.

When the protective layer solution or the heat-sensitive layer solution prepared as described above is coated on the support or the heat-sensitive recording layer, a known aqueous or organic solvent-based coating solution is used. . The coating amount of the protective layer is 0.5 to 2.5 g
/ M ² , particularly preferably 1.0 to 2.0 g /
m ² is preferred. If it is less than 0.5 g / m ² , the scratch resistance and the chemical resistance deteriorate. Also, 2.
If it exceeds 5 g / m ² , the recording sensitivity is reduced, the drying of the stamp ink and vermilion is deteriorated, and the ink is stained after writing with a ballpoint pen, so that the desired effect cannot be obtained.

The protective layer is formed by a known coating method, for example, air knife coating, similarly to the heat-sensitive recording layer.
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-falling curtain film and applying it to a running support to be applied, This is preferable because a defective surface due to bubbles does not occur and a uniform protective layer can be formed. Similarly, it is preferable to apply a layer other than the protective layer by the curtain coating method, since the surface state becomes better and the head matching property and the density unevenness become better. The applied heat-sensitive recording material is dried, subjected to a treatment such as a calender, and provided for use.

The support used in the present invention may be transparent or opaque. Opaque supports include paper, coated paper, synthetic paper, paper laminated with polymer film, aluminum vapor-deposited base, polymer film coated with white pigment, etc. For this purpose, 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; polyolefin films such as polystyrene film, polypropylene film and polyethylene film; polyimide films; Examples include a vinyl film, a polyvinylidene chloride film, a polyacrylic acid copolymer film, and a polycarbonate film, and these can be used alone or in combination, and particularly those obtained by subjecting a polyester film to a heat treatment and an antistatic treatment. Is preferred. The support has a thickness of 20 to 200 μm, and particularly preferably 50 to 1 μm.
Those having a size of 00 μm are preferred.

[0044]

The heat-sensitive recording material of the present invention has a protective layer containing a self-crosslinkable acrylic resin, starch and polyvinyl alcohol on the heat-sensitive recording layer, and therefore is excellent only in image quality, chemical resistance and scratch resistance. It is also excellent in stationery suitability. In addition, by forming the protective layer by a free-fall curtain coating method, the printing quality can be further improved and the head matching property can be improved.

[0045]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Unless otherwise specified, parts and% described below
Represents parts by weight and% by weight, respectively, and the viscosity represents a value at 25 ° C.

Embodiment 1 (Formation of Thermosensitive Recording Layer) Preparation of Solution A 10 parts of 3-dibutylamino-6-methyl-7-anilinofluoran and polyvinyl alcohol (PVA-10)
5: 40 parts of a 5% solution of Kuraray Co., Ltd.) was mixed, and a dispersion having an average particle diameter of 1.0 μm was obtained using a sand mill. Preparation of solution B 2,2'-bis (4-hydroxyphenyl) propane 2
0 parts, 30 parts of naphthylbenzyl ether and 200 parts of polyvinyl alcohol were mixed, and a dispersion having an average particle diameter of 1.0 μm was obtained using a sand mill.

Preparation of Liquid C 30 parts of light calcium carbonate, 1 part of sodium polyacrylate and 50 parts of water were mixed, and a pigment dispersion having an average particle diameter of 2.0 μm was obtained using a sand mill. 50 parts of liquid A, B
240 parts of the liquid, 71 parts of the liquid C and 25 parts of a 21% zinc stearate dispersion were mixed to obtain a coating solution for a thermosensitive recording layer. The obtained coating solution for a heat-sensitive recording layer was applied to a 50 g / m ² undercoat base paper provided with an undercoat layer mainly composed of a pigment and a binder in advance by a free-fall curtain coating method so that the coating amount was 4 g / m ^2. And dried to obtain a heat-sensitive recording layer.

(Formation of Thermosensitive Recording Material) Preparation of Protective Layer Solution 25% self-crosslinkable acrylic resin emulsion (FC6
0: 80 parts of Nippon Junyaku), 150 parts of a 20% aqueous solution of phosphate esterified starch (viscosity: 70 cp), 100 parts of a 10% aqueous solution of polyvinyl alcohol (degree of saponification: 98.5 mol%, polymerization degree: 500) , 40 parts of aluminum hydroxide, 46 parts of a 21% zinc stearate dispersion, 2 parts of sodium dodecylbenzenesulfonate, and 202 parts of water to obtain a protective layer liquid. The obtained protective layer liquid was applied on the above-mentioned heat-sensitive recording layer by an air knife coating method at 1.5 g / m ² and dried to obtain a heat-sensitive recording material.

Embodiment 2 FIG. (Formation of heat-sensitive recording material) Preparation of protective layer liquid 25% self-crosslinkable acrylic resin emulsion (FC6
0: 80 parts of Nippon Junyaku), 125 parts of a 20% aqueous solution of oxidized starch (viscosity: 90 cp), 150 parts of a 10% aqueous solution of polyvinyl alcohol (saponification degree: 98.5 mol%, polymerization degree: 500), hydroxylation 40 parts of aluminum, 46 parts of a 21% zinc stearate dispersion, 2 parts of sodium dodecylbenzenesulfonate, and 177 parts of water were mixed to obtain a protective layer liquid. The obtained protective layer liquid was applied onto the heat-sensitive recording layer of Example 1 by an air knife coating method at 1.5 g / m ² and dried to obtain a heat-sensitive recording material.

Embodiment 3 FIG. (Formation of heat-sensitive recording material) Preparation of protective layer liquid 25% self-crosslinkable acrylic resin emulsion (FC6
0: 120 parts of Nippon Junyaku) 125 parts of a 20% aqueous solution of oxidized starch (viscosity: 90 cp), 50 parts of a 10% aqueous solution of polyvinyl alcohol (saponification degree: 98.5 mol%, polymerization degree: 500), hydroxylation 40 parts of aluminum, 46 parts of a 21% zinc stearate dispersion, 2 parts of sodium dodecylbenzenesulfonate, and 237 parts of water were mixed to obtain a protective layer liquid. The obtained protective layer liquid was applied onto the heat-sensitive recording layer of Example 1 by an air knife coating method at 1.5 g / m ² and dried to obtain a heat-sensitive recording material.

Embodiment 4 FIG. (Formation of heat-sensitive recording material) Preparation of protective layer liquid 25% self-crosslinkable acrylic resin emulsion (FC6
0: 80 parts of Nippon Junyaku), 100 parts of a 20% aqueous solution of oxidized starch (viscosity: 90 cp), 200 parts of a 10% aqueous solution of polyvinyl alcohol (saponification degree: 98.5 mol%, polymerization degree: 500), hydroxylation 40 parts of aluminum, 46 parts of a 21% zinc stearate dispersion, 2 parts of sodium dodecylbenzenesulfonate, and 152 parts of water were mixed to obtain a protective layer liquid. The obtained protective layer liquid was applied onto the heat-sensitive recording layer of Example 1 by an air knife coating method at 1.5 g / m ² and dried to obtain a heat-sensitive recording material.

Embodiment 5 FIG. (Formation of heat-sensitive recording material) Preparation of protective layer liquid 25% self-crosslinkable acrylic resin emulsion (FC6
0: 80 parts of Nippon Junyaku) 100 parts of a 20% aqueous solution of phosphate esterified starch (viscosity: 70 cp), 200 parts of a 10% aqueous solution of polyvinyl alcohol (saponification degree: 98.5 mol%, polymerization degree: 500) , 40 parts of aluminum hydroxide, 46 parts of a 21% dispersion of zinc stearate, 2 parts of sodium dodecylbenzenesulfonate, and 152 parts of water to obtain a protective layer liquid. The obtained protective layer liquid was applied onto the heat-sensitive recording layer of Example 1 by an air knife coating method at 1.5 g / m ² and dried to obtain a heat-sensitive recording material.

Embodiment 6 FIG. (Formation of heat-sensitive recording material) The protective layer liquid obtained in Example 2 was applied onto the heat-sensitive recording layer of Example 1 at 2.3 g / m ² by an air knife coating method and dried. I got Embodiment 7 FIG. (Formation of heat-sensitive recording material) The protective layer liquid obtained in Example 2 was applied onto the heat-sensitive recording layer of Example 1 so as to be 0.8 g / m ² by an air knife coating method and dried. I got

Embodiment 8 FIG. The protective layer liquid obtained in Example 2 was applied onto the heat-sensitive recording layer of Example 1 by a free-fall curtain coating method at 1.5 g / m ² and dried to obtain a heat-sensitive recording material. Comparative Example 1 (Formation of heat-sensitive recording material) Preparation of protective layer liquid 25% self-crosslinkable acrylic resin emulsion (FC6
0: trade name, manufactured by Nippon Pure Chemical Co., Ltd.) 240 parts, aluminum hydroxide 40 parts, zinc stearate 21% dispersion liquid 46 parts,
Sodium dodecylbenzenesulfonate 2 parts, water 292
The parts were mixed to obtain a protective layer liquid. The obtained protective layer liquid was applied onto the heat-sensitive recording layer of Example 1 by an air knife coating method at 1.5 g / m ² and dried to obtain a heat-sensitive recording material.

Comparative Example 2 (Formation of thermosensitive recording material) Preparation of protective layer liquid 300 parts of a 20% aqueous solution of starch oxide (viscosity: 90 cp), 40 parts of aluminum hydroxide, and 21% of zinc stearate
46 parts of the dispersion, 2 parts of sodium dodecylbenzenesulfonate, and 232 parts of water were mixed to obtain a protective layer liquid. 1.5 g / m ^{2 of the} obtained protective layer liquid was applied on the heat-sensitive recording layer of Example 1.
Was applied by an air knife coating method and dried to obtain a heat-sensitive recording material.

Comparative Example 3 (Formation of Thermal Recording Material) A 20% aqueous solution of polyvinyl alcohol (degree of saponification: 98.5 mol%, degree of polymerization: 500) 300
, 40 parts of aluminum hydroxide, 46 parts of a 21% dispersion of zinc stearate, 2 parts of sodium dodecylbenzenesulfonate, and 232 parts of water to obtain a protective layer liquid. 1.5 g of the obtained protective layer liquid was applied on the heat-sensitive recording layer of Example 1.
/ M ² by an air knife coating method and dried to obtain a heat-sensitive recording material.

Comparative Example 4 (Formation of heat-sensitive recording material) Preparation of protective layer liquid 25% self-crosslinkable acrylic resin emulsion (FC6
0: 120 parts of Nippon Junyaku), 150 parts of a 20% aqueous solution of starch oxide (viscosity: 90 cp), 40 parts of aluminum hydroxide, 46 parts of a zinc stearate 21% dispersion, sodium dodecylbenzenesulfonate 2 And 262 parts of water were mixed to obtain a protective layer liquid. The obtained protective layer liquid was applied onto the heat-sensitive recording layer of Example 1 by an air knife coating method at 1.5 g / m ² and dried to obtain a heat-sensitive recording material.

Comparative Example 5 (Formation of heat-sensitive recording material) Preparation of protective layer liquid 25% self-crosslinkable acrylic resin emulsion (FC6
0: 120 parts of Nippon Junyaku), 300 parts of a 10% aqueous solution of polyvinyl alcohol (degree of saponification: 98.5 mol%, polymerization degree: 500), 40 parts of aluminum hydroxide, and 46 parts of a 21% dispersion of zinc stearate. , 2 parts of sodium dodecylbenzenesulfonate and 112 parts of water were mixed to obtain a protective layer solution. The obtained protective layer liquid was applied onto the heat-sensitive recording layer of Example 1 by an air knife coating method at 1.5 g / m ² and dried to obtain a heat-sensitive recording material.

Comparative Example 6 (Formation of heat-sensitive recording material) Preparation of protective layer solution 150 parts of a 20% aqueous solution of starch oxide (viscosity: 90 cp), polyvinyl alcohol (saponification degree: 98.5 mol%, polymerization degree: 50)
0) 300 parts of a 10% aqueous solution of aluminum hydroxide 40
, A 21% dispersion of zinc stearate, 46 parts of sodium dodecylbenzenesulfonate and 82 parts of water were mixed to obtain a protective layer liquid. The obtained protective layer liquid was applied onto the heat-sensitive recording layer of Example 1 by an air knife coating method at 1.5 g / m ² and dried to obtain a heat-sensitive recording material. Table 1 shows the evaluation results of the heat-sensitive recording materials obtained in Examples 1 to 8 and Comparative Examples 1 to 3.

[0060]

[Table 1] The dynamic sensitivity, dryness, scratch resistance, and chemical resistance of the stamp ink in the table were measured as follows.

Method of measuring sensitivity Thermal head (KLT-216- manufactured by Kyocera Corporation)
8MPD1) and a thermal printing apparatus provided with a pressure applying means of 100 kg / cm ² immediately before the head, the head voltage 2
Printing was performed with a pulse width of 1.8 ms under the conditions of 4 V and a pulse period of 10 ms using a pressure roll, and the print density was measured with a Macbeth reflection densitometer RD-918.

Dryness ( Stamping Property) of Stamp Ink A stamp was printed using a Shachihata stamp (red), and the dry level after one minute was evaluated based on the state of transfer of the ink when the stamped portion was overlaid on high quality paper. The criteria were as follows. A: No adhesion. −---Although thin adhesion is observed, it is practically good as ink stain. Δ −−−−− Adhesion is observed and stains occur. X: Extremely large amount of adhesion, and adhesion after 5 minutes.

The surface of the heat-sensitive recording material was scratched with a fingernail of a scratch-resistant finger, and the level of coloring stain was evaluated according to the following criteria. ○----There is no coloring stain due to scratching. O *-Some color stains due to scratching are present, but they are almost inconspicuous and practically good. Δ −−−− Color stain due to scratching is noticeable. × −−−− Coloring stains due to scratching are dark and conspicuous.

Evaluation Method for Chemical Resistance Writing was performed with a fluorescent pen (pilot fluorescent pen-pink), and the fog on the surface of the heat-sensitive recording material was visually evaluated. The criteria were as follows. ○----No fog is observed. ○ * ---- Some fog is observed but good. Δ −−−− Fogging is observed, but at a practical level. X: Fogging is remarkably observed. The results in Table 1 demonstrate the effectiveness of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-341886 (JP, A) JP-A-6-234275 (JP, A) JP-A-3-256788 (JP, A) JP-A-61- 202886 (JP, A) JP-A-4-345887 (JP, A) JP-A-4-110188 (JP, A) JP-A-7-314914 (JP, A) JP-A-7-228047 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) B41M 5/28-5/34

Claims (5)

(57) [Claims] 1. A thermosensitive recording material comprising a support, on which a thermosensitive recording layer and a protective layer are sequentially provided, wherein the binder in the protective layer comprises a self-crosslinkable acrylic resin, starch, and polyvinyl alcohol. The content of the self-crosslinkable acrylic resin in the binder is 20 to 60% by weight.
A heat-sensitive recording material, characterized in that: 2. The heat-sensitive recording material according to claim 1, wherein the content of starch in the binder for the protective layer is 20 to 60% by weight. 3. The composition ratio of self-crosslinkable acrylic resin / starch / polyvinyl alcohol is 20 to 60% by weight / 2.
3. The composition of claim 2, wherein the composition is selected from 0 to 60% by weight / 5 to 40% by weight.
Heat-sensitive recording material described in 1. 4. The coating amount of the protective layer is 0.5 to 2.5 g / m.
4. The heat-sensitive recording material according to claim 1, which is ² . 5. The method for producing a heat-sensitive recording material according to claim 1, wherein at least the protective layer is provided by being applied and dried by a free-fall curtain coating method. Manufacturing method of thermal recording material.