JPH111063A - Heat-sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To have a sufficient antistatic ability for overcoming static obstacles even under low moisture conditions, and use even in the case of requiring a transparency and coloring property. SOLUTION: This includes a carrier, a heat-sensitive coloring layer, and a conductive layer, and the conductive layer is a heat-sensitive recording body containing conductive polymer. Also, the conductive layer is formed between the carrier and the heat-sensitive coloring layer, or on the opposite surface of a heat-sensitive coloring layer forming surface of the carrier. The conductive layer is of a type having a sulfonated polyaniline and sulfonic acid group- containing copolymeric polyester. The surface resistive value becomes 10<6> -10<12> Ω/square at 25 deg.C, 15% RH in this conductive 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 medium, and more particularly, to a heat-sensitive plotter for outputting a drawing created by a CAD system and a heat-sensitive image for outputting a CRT image for medical measurement as a hard copy. The present invention relates to a negative film sheet for image formation for an overhead projector (OHP) excellent in suitability for a printer and a thermal head, and further relates to a heat-sensitive recording material suitable for use in multicolor printing and the like.

[0002]

2. Description of the Related Art Conventionally, a thermosensitive recording medium is generally provided on one side of a support made of paper, synthetic paper, plastic film, or the like, with a colorless or pale-colored color-forming substance such as an electron-donating leuco dye and an electron-accepting substance. A heat-sensitive coloring layer containing an organic acid developer such as a phenolic compound and an adhesive as main components, and reacting these coloring dyes and the developer with heat energy to record a color. Images can be obtained.

Such a thermosensitive recording medium has advantages such as a compact and inexpensive recording apparatus and easy maintenance, and is used only as a recording medium for facsimile machines, automatic ticket vending machines, and scientific measuring machines. Not POS label, CA
It is widely used as an output medium for various printers and plotters for medical images such as D and CRT.

However, in the case of a thermosensitive recording medium using a synthetic paper or a plastic film as a support, dust or dust adheres to the film surface due to static electricity during processing steps such as winding, finishing, laminating, etc. or during thermosensitive recording. hand,
There has been a problem that the image quality is deteriorated or a process trouble is caused.

[0005] In order to solve these problems, there has been proposed a heat-sensitive recording material in which a surfactant is blended in a heat-sensitive recording layer as an antistatic agent. However, surfactants not only do not provide a sufficiently low surface resistance (10 ¹⁰ Ω / □ or less) to suppress adhesion of dust and dirt to the film surface, but also have an antistatic ability that reduces the amount of moisture and It is easy to change under the influence of moisture. In particular, there is a disadvantage that a desired antistatic property cannot be obtained under low humidity.

It has also been proposed to laminate metal and carbon. Such a thermosensitive recording medium exhibits sufficient antistatic performance even under low humidity, but has a problem that it is difficult to use it in applications requiring transparency and coloring.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of earnest research focusing on the above problems, and an object of the present invention is to make use of the excellent points of a structural molded article such as an original plastic film. It is an object of the present invention to provide a thermosensitive recording medium which has a sufficient antistatic ability to overcome static electricity damage even under low humidity and can be used in applications requiring transparency and coloring.

[0008]

The present invention has the following features. (1) A thermosensitive recording medium comprising a support, a thermosensitive coloring layer, and a conductive layer, wherein the conductive layer contains a conductive polymer. (2) The thermosensitive recording medium according to the above (1), wherein the conductive layer is formed between the support and the thermosensitive coloring layer. (3) The heat-sensitive recording material according to the above (1), wherein the conductive layer is formed on the surface of the support opposite to the surface on which the heat-sensitive coloring layer is formed. (4) The thermosensitive recording medium according to (1), wherein the thermosensitive coloring layer contains a coloring dye, a developer, and an adhesive. (5) The surface resistance of the conductive layer is 10 at 25 ° C. and 15% RH.
The heat-sensitive recording material according to the above (1), which has a resistance of ⁶ to 10 ¹² Ω / □. (6) The thermosensitive recording material according to the above (1), wherein the conductive polymer is polyaniline or a derivative thereof. (7) The thermosensitive recording material according to the above (6), wherein the polyaniline or a derivative thereof is a sulfonated polyaniline containing an alkoxy group-substituted aminobenzenesulfonic acid as a main component. (8) The heat-sensitive recording material according to (7), wherein the alkoxy-substituted aminobenzenesulfonic acid is aminoanisolesulfonic acid. (9) The thermosensitive recording medium according to the above (1), wherein the conductive layer further contains a water-soluble or water-dispersible resin. (10) The heat-sensitive recording material according to the above (9), wherein the water-soluble or water-dispersible resin is a copolymerized polyester. (11) The copolymer polyester described above, wherein the copolymer polyester contains 2 to 10 mol% of 5-sulfoisophthalic acid units.
The thermal recording medium according to (10). (12) The heat-sensitive recording material according to the above (1), wherein the support is a thermoplastic film. (13) The thermosensitive recording material according to the above (12), wherein the thermoplastic film is a polyester film. (14) The thermosensitive recording material according to the above (13), wherein the polyester film is a void-containing polyester film obtained by at least uniaxially stretching a film made of a mixture of polyester and a thermoplastic resin incompatible with the polyester.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The thermosensitive recording medium of the present invention includes a support, a thermosensitive coloring layer, and a conductive layer.

(Support) As the support in the present invention, translucent or opaque synthetic paper produced by heating and kneading a polyester resin or polyolefin resin and a white inorganic pigment, extruding from a die, and stretching; Thermoplastic resin such as polypropylene, ethylene-vinyl acetate copolymer resin, polyvinyl chloride, polystyrene, polyester, polyamide, etc. or a mixture of two or more kinds thereof is heated and kneaded, extruded from a die, and biaxially stretched. Mixing a white inorganic pigment with these resins,
Axial stretched opaque film; other high quality paper, medium quality paper,
Paper manufactured from pulp fibers such as roll paper, recycled paper, and coated paper is used. When a support made of pulp fibers is used, it is preferable to form a conductive layer or a thermosensitive coloring layer after forming a coating layer in advance in order to improve image uniformity.

In the present invention, the support is preferably a polyester film in terms of stiffness, heat resistance, shrinkage resistance, cost, etc., and particularly, polyester film in terms of lightness, workability, etc. It is preferable to use a void-containing polyester film obtained by at least uniaxially stretching a film made of a mixture of a thermoplastic resin incompatible with the polyester. Examples of the thermoplastic resin incompatible with the polyester include polystyrene, polypropylene, and polyethylene. Examples of such a void-containing polyester film include Krispar (manufactured by Toyobo Co., Ltd.) and Papillar (manufactured by Toray Industries, Inc.).

The thickness of the support is usually from 10 to 250
μm, preferably 20 to 200 μm.

(Conductive Layer) The conductive layer in the present invention is a layer containing a conductive polymer. Since the conductive layer contains a conductive polymer, the antistatic performance is improved even under low humidity, and since the conductive layer is transparent, the color of the conductive layer is transparent to the thermosensitive coloring layer, making it difficult to see an image. (This is also one type of image unevenness) can be prevented.

The conductive polymer used in the present invention includes, for example, polyaniline or a derivative thereof, polypyrrole or a derivative thereof, polyacetylene or a derivative thereof, and among them, polyaniline or a derivative thereof, particularly, an alkoxy-substituted aminobenzene Sulfonated polyaniline containing sulfonic acid as a main component is preferred in that it is water-soluble.

As the alkoxy-substituted aminobenzenesulfonic acid, for example, 2-aminoanisole-3-sulfonic acid, 2-aminoanisole-4-sulfonic acid, 2-aminoanisole-4-sulfonic acid,
Aminoanisole-5-sulfonic acid, 2-aminoanisole-6-sulfonic acid, 3-aminoanisole-2-sulfonic acid, 3-aminoanisole-4-sulfonic acid, 3
-Aminoanisole-5-sulfonic acid, 3-aminoanisole-6-sulfonic acid, 4-aminoanisole-2-
Aminoanisolesulfonic acids such as sulfonic acid and 4-aminoanisole-3-sulfonic acid; compounds in which the methoxy group of these aminoanisolesulfonic acids is substituted with an alkoxy group other than a methyl group such as an ethoxy group or an iso-propoxy group; No. Among these, aminoanisolesulfonic acid is preferred in terms of simplicity of polymerization, cost, etc., and particularly, 2-aminoanisole-3-sulfonic acid,
2-aminoanisole-4-sulfonic acid, 2-aminoanisole-5-sulfonic acid, 2-aminoanisole-6
-Sulfonic acid, 3-aminoanisole-2-sulfonic acid, 3-aminoanisole-4-sulfonic acid, and 3-aminoanisole-6-sulfonic acid are preferred.

The sulfonated polyaniline may contain components other than the above-mentioned alkoxy-substituted aminobenzenesulfonic acid.

In the sulfonated polyaniline, the sulfonic acid group is preferably at least 70 mol%, more preferably at least 80 mol%, particularly preferably 100 mol%, based on the aromatic ring. Further, aromatic rings containing a sulfonic acid group and aromatic rings not containing a sulfonic acid group may be mixed or alternately arranged.

When the sulfonic acid group content of the sulfonated polyaniline is less than 70 mol%, the solubility or dispersibility of the sulfonated polyaniline in water, alcohol or a mixed solvent system thereof during preparation of the coating solution for the conductive layer. Is insufficient, and as a result, the applicability and spreadability of the coating solution containing the same to the support are deteriorated, the conductivity of the obtained conductive layer is reduced, and the antistatic ability tends to be reduced. Not preferred.

The number average molecular weight of the sulfonated polyaniline is preferably from 300 to 500,000, particularly
A value of 00 or more is preferable in terms of solubility (or dispersibility) in a solvent as described above and the strength of the obtained conductive layer.

The content of the above conductive polymer is preferably 5 to 70% by weight, more preferably 8 to 30% by weight in the conductive layer in view of the conductivity and mechanical properties of the obtained conductive layer.

In addition to the above-mentioned conductive polymer, the conductive layer of the present invention may be water-soluble or water-dispersible from the viewpoint of improving the coating properties and spreadability of the conductive layer coating solution and the hardness of the obtained conductive layer. It is preferable to contain a copolymerized polyester resin. In particular, in view of compatibility with the above-mentioned sulfonated polyaniline, a water-soluble or water-dispersible copolymerized polyester having a sulfonic acid group (hereinafter, a sulfonic acid group-containing copolymerized polyester) ).

The sulfonic acid group-containing copolyester is a polyester using a dicarboxylic acid component and / or a glycol component having a sulfonic acid group and / or an alkali metal base thereof as a part of a dicarboxylic acid component and / or a glycol component. Say. Above all, an aromatic dicarboxylic acid component having a sulfonic acid group and / or an alkali metal base thereof is blended in a proportion of 2 to 10 mol% with respect to all the acid components in that the transparency of the conductive layer is increased. Polymerized copolyesters are preferred. As the aromatic dicarboxylic acid component having a sulfonic acid group and / or an alkali metal base, 5-sodium sulfoisophthalic acid is preferable.

Other dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalenedicarboxylic acid,
4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, cyclohexane-1,
4-dicarboxylic acid and the like. From the viewpoint of improving the surface hardness of the obtained conductive layer, terephthalic acid and isophthalic acid are preferred.

As the glycol component, ethylene glycol is mainly used. In addition, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexane dimethanol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and poly (ethylene glycol) Tetramethylene glycol and the like can be used. Among them, polyesters containing propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexane dimethanol, or the like as a copolymer component are preferred in that compatibility with sulfonated polyaniline is improved.

In addition, the copolymer component may contain a small amount of a dicarboxylic acid component having an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like, or a glycol component. Also, in order to further improve the surface hardness of the conductive layer, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, polycarboxyl group-containing monomers such as pyromellitic anhydride, among all dicarboxylic acid components,
It can be used as a copolymer component at a ratio of 5 mol% or less. When it exceeds 5 mol%, the obtained sulfonic acid group-containing copolymerized polyester becomes thermally unstable,
It is easy to gel and is not preferable as a component of the conductive layer of the present invention.

The sulfonic acid group-containing copolyester is prepared, for example, using the above-mentioned dicarboxylic acid component, the above-mentioned glycol component and, if necessary, the above-mentioned polycarboxyl group-containing monomer, by a transesterification reaction and a polycondensation. It can be obtained by performing a reaction or the like. The obtained sulfonic acid group-containing copolymerized polyester is heated and stirred with a solvent such as n-butyl cellosolve, and can be used as an aqueous solution or aqueous dispersion by gradually adding water while stirring.

The content of the sulfonic acid group-containing copolymerized polyester is 50 to 2 parts per 100 parts by weight of the conductive polymer, based on the conductivity and mechanical properties of the obtained heat-sensitive recording material.
000 parts by weight, more preferably 100 to 1
500 parts by weight, most preferably 200 to 1000 parts by weight.

The conductive layer is formed, for example, as follows. First, a coating solution is prepared by dissolving or dispersing a conductive polymer and a water-soluble or water-dispersible copolymerized polyester in a solvent. Here, the amount of the conductive polymer used is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the solvent. When the amount of the conductive polymer used is less than 0.01 part by weight, the long-term storage stability of the solution is deteriorated, and the obtained conductive layer tends to have pinholes, which tends to cause poor conductivity, and conversely, If the amount used exceeds 10 parts by weight, the solubility or dispersibility of the sulfonated polyaniline in water or a water / organic solvent system and the applicability of a coating solution tend to deteriorate, which is not preferable.

The water-soluble or water-dispersible copolymerized polyester is used in an amount of 50 to 50 parts by weight based on 100 parts by weight of the conductive polymer, depending on the conductivity and mechanical properties of the obtained conductive layer.
2000 parts by weight is preferable, and 100 to 100 parts by weight is more preferable.
It is 1500 parts by weight, most preferably 200 to 1000 parts by weight.

As the solvent to be used, any organic solvent can be used as long as it does not dissolve or swell a support such as a polyester film. However, water or a mixed solvent with an organic solvent such as water / alcohol is used in an environment in which the solvent is used. This is not only preferable in terms of surface properties, but also improves coatability and conductivity on the support in some cases. Examples of the organic solvent include alcohols such as methanol, ethanol, propanol, and propyl alcohol; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; cellosolves such as methyl cellosolve and ethyl cellosolve; and methyl propylene glycol and ethyl propylene glycol. Amides such as propylene glycols, dimethylformamide and dimethylacetamide, and pyrrolidones such as N-methylpyrrolidone and N-ethylpyrrolidone are preferably used. These organic solvents are used by being mixed with water at an arbitrary ratio. Specific examples include water / methanol, water / ethanol, water / propanol, water / isopropanol, water / methyl propylene glycol, water / ethyl propylene glycol, and the ratio thereof is water / organic solvent = 1 /
10 to 10/1 is preferred.

Although the amount of the solvent used is not particularly limited, it is generally 1000 to 2 parts by weight based on 100 parts by weight of the conductive polymer.
0000 parts by weight. When the amount of the solvent used is extremely large, the applicability of the obtained conductive layer may be deteriorated. Therefore, pinholes are easily generated in the conductive layer, and the conductivity may be reduced, that is, the antistatic property may be reduced. When the amount of the solvent used is extremely small, the solubility or dispersibility of the conductive polymer in the solvent becomes insufficient, and the surface of the obtained conductive layer may not be easily flattened.

The conductive layer coating solution has excellent coatability and spreadability even with only the above-mentioned components, and has a good surface hardness of the obtained conductive layer, but has a surfactant and / or polymer soluble in the above-mentioned solvent. By further using the compound, application to a thermoplastic film having poor wettability becomes possible.

Examples of the surfactant include nonionic surfactants such as polyoxyethylene octyl phenyl ether, polyoxyethylene alkyl ether and polyoxyethylene sorbitan fatty acid ester, and fluoroalkyl carboxylic acids, perfluoroalkyl carboxylic acids, and the like. Fluorinated surfactants such as perfluoroalkylbenzenesulfonic acid, perfluoroalkylquaternary ammonium, and perfluoroalkylpolyoxyethyleneethanol are used.

The content of the surfactant is determined by the amount of the conductive polymer 10
0 parts by weight, preferably 0.001 part by weight or more and 1 part by weight
0 parts by weight or less. If the content exceeds 10 parts by weight, the surfactant in the conductive layer is set off, which may cause a problem in secondary processing or the like.

Examples of the high molecular compound include a water-soluble resin such as polyacrylamide and polyvinylpyrrolidone; a water-soluble or water-dispersible copolymerized polyester having a hydroxyl group or a carboxylic acid group; and an acrylic resin such as polyacrylic acid and polymethacrylic acid. Acid resin; acrylic acid resin such as polyacrylic acid ester and polymethacrylic acid ester; ester resin such as polyethylene terephthalate and polybutylene terephthalate; polystyrene and poly-α-
Styrene resins such as methyl styrene, polychloromethyl styrene, polystyrene sulfonic acid and polyvinyl phenol; vinyl ether resins such as polyvinyl methyl ether and polyvinyl ethyl ether; polyvinyl alcohol;
Polyvinyl alcohols such as polyvinyl formal and polyvinyl butyral; phenol resins such as novolak and resole can be used. Above all, when the conductive polymer is a sulfonated polyaniline, water-soluble or having a hydroxyl group or a carboxylic acid group from the viewpoint of good compatibility with the polyaniline and from the viewpoint of adhesion to a support made of polyester or the like. Water-dispersible copolymerized polyesters and polyvinyl alcohols are preferred.

The amount of the above-mentioned polymer compound is determined by the amount of the conductive polymer 10
The amount is preferably 0 to 1000 parts by weight, more preferably 0 to 500 parts by weight, based on 0 parts by weight. When the amount of the polymer compound exceeds 1000 parts by weight, the conductivity of the conductive layer due to the conductive polymer is not exhibited, and the original antistatic function is not exhibited.

The conductive layer coating liquid may contain various additives in addition to the above. Such additives include TiO
₂ , SiO ₂ , kaolin, CaCO ₃ , Al ₂ O ₃ , B
Inorganic particles such as aSO ₄ , ZnO, talc, mica, and composite particles; and organic particles composed of polystyrene, polyacrylate, or a crosslinked product thereof. In order to further improve the conductivity, powders of SnO ₂ and ZnO, and inorganic particles (TiO ₂ , BaSO ₄
Etc.), carbon-based conductive fillers such as carbon black, graphite, carbon fiber and the like can be added.
The content of the additive is preferably 4000 parts by weight or less based on 100 parts by weight of the conductive polymer. If the amount exceeds 4,000 parts by weight, the viscosity of the conductive layer may increase, which may cause uneven coating.

The method for forming the conductive layer on the surface of the support includes, but is not particularly limited to, a gravure roll coating method, a reverse roll coating method, a knife coater method, a dip coating method, and a spin coating method. There are an in-line coating method in which application to a film is performed simultaneously in a film-forming process and an offline coating method in which coating is independently performed after the production of a film-forming roll. However, a preferable method can be selected according to the application, and there is no particular limitation. The sulfonated polyaniline used in the present invention is unstable at a high temperature of 250 ° C. or higher,
Since the thermal stability is good for about 3 minutes at 0 ° C., heating at 200 ° C. for a short time usually does not adversely affect the conductivity, depending on the type of the coexisting polymer compound and additives.

After drying, 0.02 to 5 g of the conductive layer coating solution
/ M ² , particularly preferably 0.05 to 0.5 g / m ² . If the coating amount is too small, the conductivity may be insufficient, and if too large, the transparency may be lost.

In the present invention, the surface resistance of the conductive layer is 25 ° C. and 15% RH, preferably 10 ⁶ to 1.
It has a performance of 0 ¹² Ω / □, more preferably 10 ⁶ to 10 ¹¹ Ω / □. This surface resistance value is 10 ⁶ Ω / □
If the amount is less than the above, the amount of application increases, and thus the transparency may be lost. Conversely, if it exceeds 10 ¹² Ω / □, the antistatic effect cannot be expected because of insufficient conductivity.

(Thermosensitive Coloring Layer) The thermosensitive coloring layer in the present invention contains a coloring dye, a developer and an adhesive as main components. As the color-forming dye, a colorless or pale-color electron-donating leuco dye capable of forming a color by reacting with a developer under heating is used. Such leuco dyes include, for example, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro (phthalide-3,9'-xanthene) -2' -Ylamido] phenyl} propane, 3-diethylamino-6-methyl-7-anilinofluoran, 3-piperidino-6
Methyl-7-anilinofluoran, 3- (N-methyl-
N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-7-chloroanilinofluoran, 3- [N-ethyl-N- (p-methylphenyl) amino] -6-methyl -7-anilinofluoran, 3-diethylamino-7- (metatrifluoromethyl) anilinofluoran, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7anilinofluoran, 3- (N-ethyl-N-isopentyl) amino-6-methyl-7-anilinofluoran, 3-
(N, N-dibutyl) amino-6-methyl-7-anilinofluoran and the like.

The color developer contained in the thermosensitive coloring layer comprises an electron-accepting organic acid substance capable of reacting with a coloring dye under heating to form a color. Such a developer liquefies or vaporizes at room temperature or higher, preferably 70 ° C. or higher, and reacts with the above-described coloring dye to form a color. To maximize the color density of the developer,
Usually, 1 to 5 parts by weight, preferably 1.5 to 3 parts by weight, is mixed and used with respect to 1 part by weight of the coloring dye.

When the color-forming dye is an electron-donating leuco dye, for example, 4,4′-isopropylidene diphenol (bisphenol A),
4′-isopropylidenebis (2-chlorophenol), 4,4′-isopropylidenebis (2-methylphenol), 4,4′-isopropylidenebis (2,6
-T-butylphenol), 4,4'-sec-butylidenediphenol, 4,4'-cyclohexylidenediphenol, 4-t-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, 4,4'-
Dihydroxydiphenylsulfone, 3,3′-dihydroxydiphenylsulfone, 3,3′-diamino-4,
4′-dihydroxydiphenyl sulfone, 3,3′-diallyl-4,4′-dihydroxydiphenyl sulfone,
3,3'-dichloro-4,4'-dihydroxydiphenylsulfone, 4-hydroxydiphenylsulfone, 4-
Hydroxy-4'-isopropyloxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 2,4-dihydroxydiphenylsulfone, 2,4-dihydroxy-4'-methyldiphenylsulfone, 3,4-dihydroxyphenyl- p-Trisulfone and the like.

As the adhesive contained in the thermosensitive coloring layer, any of a water-soluble resin and a water-dispersible resin can be used. For example, polyvinyl alcohol, starch, modified starch, gum arabic, gelatin, casein, chitosan, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, polyvinylpyrrolidone, polyacrylate, polyacrylamide, polyester resin, styrene-acrylate copolymer resin Water-soluble resins such as styrene-maleic anhydride copolymer resin, methyl vinyl ether-maleic anhydride copolymer resin, isopropylene-maleic anhydride copolymer resin; vinyl acetate emulsion, acrylic ester copolymer emulsion, and methacrylic ester. Minimum film formation with emulsions such as polymerization emulsion, polyurethane emulsion, polyvinyl chloride emulsion, polyvinylidene chloride emulsion, SBR latex, MBR latex Degrees are mentioned 20 ° C. less film forming properties of good water-dispersible resin, which are used alone or in combination.

In preparing the coating solution for the thermosensitive coloring layer, it is necessary that the mixture does not develop color, aggregate, or become highly viscous when mixed with each dispersion of the coloring dye and the developer. In addition, since it is necessary that the obtained heat-sensitive heat-generating layer is tough and has no desensitizing effect, the content of the adhesive in the heat-sensitive coloring layer is preferably 8 to 20% by weight. If the content is less than 8% by weight, there is a disadvantage that the coating film strength is low, and if it exceeds 20% by weight, the color sensitivity may be reduced.

The thermosensitive coloring layer is prepared by dissolving or dispersing a coloring dye, a developer and an adhesive in a solvent to prepare a coating solution.
It is formed by applying this. The coating amount of the heat-sensitive coloring layer is generally preferably 3 to 10 g / m ² as a solid content in terms of coloring sensitivity and coloring density. As a coating method, a conventionally used method such as an air knife method, a Meyer bar method, a blade method, a reverse roll method, and a slit die method can be used. The thermosensitive coloring layer may be formed on the conductive layer, or may be formed on the surface of the support opposite to the surface on which the conductive layer is formed.

The coating solution for the thermosensitive coloring layer may further contain a crosslinking agent, a pigment and a heat-fusible substance, if necessary. The crosslinking agent is used to improve the water resistance of the heat-sensitive coloring layer by curing the above-mentioned water-soluble resin used as an adhesive and the water-dispersible resin, for example, glyoxal, dialdehyde compounds such as polyaldehyde, Polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, diglycidyl compounds such as glycerin diglycidyl ether, dimethylol urea compounds,
Aziridine compounds, blocked isocyanate compounds, and ammonium persulfate and ferric chloride, and magnesium chloride, sodium tetraborate, inorganic compounds such as potassium tetraborate or boric acid, boric acid triesters, boron-based polymers, and the like. Can be used in the range of 1 to 10% by weight based on the solid content in the thermosensitive coloring layer coating solution.

Fine pigments having a high whiteness and an average particle size of 5 μm or less are used as the pigment in order to improve the whiteness of the thermosensitive coloring layer and reduce sticks and scum. For example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomite, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated calcium carbonate and silica, etc. Inorganic pigments, and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin, and polystyrene resin are exemplified. The amount of the pigment is preferably not more than 40% by weight based on the solid content in the coating solution for the thermosensitive coloring layer so as not to lower the coloring density.

The heat-fusible substance is a substance which, when heated in contact with the thermal head, melts if its melting point is lower than that temperature and solidifies again when the temperature returns to room temperature. It plays a role in stably solidifying substances and preventing reactions with light and gas from the outside world.
For example, fatty acid amides such as stearic acid amide, stearic acid ethylene bisamide, oleic acid amide, balmitic acid amide, coco fatty acid amide, bevelic acid amide, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester Waxes such as waxes (or lubricants), dimethyl terephthalate, dibutyl terephthalate, dibenzyl terephthalate, dibutyl isophthalate, phenyl 1-hydroxynaphthoate, 1,2-di (3-methylphenoxy) ) Ethane, 1,2-diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, diphenyl carbonate, p-benzylbiphenyl, 2,2′-methylenebis (4-methyl-6-t-) Butylphenol), 4,
4-butylidenebis (6-t-butyl-3-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 2,2-methylenebis (4-ethyl Hindered phenols such as -6-t-butylphenol), 2,4-di-t-butyl-3-methylphenol, and 4,4′-thiobis (3-methyl-6-t-butylphenol); 2 '
Sensitizers such as -hydroxy-5'-methylphenyl) -benzotriazole and 2-hydroxy-4-benzyloxybenzophenone; antioxidants; and ultraviolet absorbers. These heat-fusible substances are generally blended in an amount of preferably 4 parts by weight or less based on 1 part by weight of the developer.

Further, in order to improve the wetting of the coating solution for the heat-sensitive coloring layer and to eliminate cissing, wetting agents such as acetylene glycol and dialkyl sulfosuccinate, dispersants for pigments, defoamers and fluorescent dyes are added. Can also.

The heat-sensitive recording material of the present invention can be used for output media such as various printers and plotters, and has antistatic properties even under low humidity, so that clear images can be provided without trouble in conveyance. .

[0052]

EXAMPLES Examples and comparative examples of the present invention will be described below, but the present invention is not limited to these examples. In addition, "parts" means parts by weight. The evaluation method used in the present invention is shown below.
Each evaluation was performed under the conditions of 25 ° C., 15% RH and 60% RH. 1) Surface resistance value of conductive layer Before forming the heat-sensitive coloring layer, an applied voltage of 500 V and 25 ° C. were measured with a surface resistance measuring device Hiresta HT-210 manufactured by Mitsubishi Yuka Co., Ltd.
Was measured under the following conditions. 2) Transport unevenness Commercially available thermal printer (UP-860, Sony Corporation)
The unevenness of conveyance of the recording medium when recording was performed in the following manner was evaluated as follows. (About 100 sheets) ：: There is no transport unevenness at all. X: There is one or more recording medium in which conveyance unevenness has occurred. 3) Image unevenness Commercially available thermal printer (UP-860, Sony Corporation)
Manufactured), and the resulting images were evaluated as follows. ：: A clear image was obtained without density unevenness, fading of printing, and skipping. ×: A clear image was not obtained with density unevenness, blurred printing, and skipping.

Example 1 <Formation of conductive layer> Preparation of aqueous dispersion of sulfonic acid group-containing polyester A sulfonic acid group-containing polyester was synthesized by the following method.
Further, the dispersion was prepared. First, 46 mol% of dimethyl terephthalate, 47 mol% of dimethyl isophthalate and 7 mol% of sodium 5-sulfoisophthalate are used as the dicarboxylic acid component, and 50 mol% of ethylene glycol and 50 mol% of neopentyl glycol are used as the glycol component. A transesterification reaction and a polycondensation reaction were carried out in a conventional manner. The glass transition temperature of the obtained sulfonic acid group-containing polyester was 69 ° C. The sulfonic acid group-containing polyester (300 parts) and n-butyl cellosolve (150 parts) are heated and stirred to form a viscous solution, and 550 parts of water are gradually added with stirring to obtain a uniform pale white solid having a solid content of 30% by weight. Was obtained. This dispersion was further added to a mixture of equal amounts of water and isopropanol to prepare an aqueous dispersion of a sulfonic acid group-containing polyester having a solid content of 8% by weight.

Preparation of Sulfonated Polyaniline Solution 100 mmol of 2-aminoanisole-4-sulfonic acid
Is stirred and dissolved in a 4 mol / l aqueous ammonia solution at 23 ° C., and 100 mmol of ammonium peroxodisulfate is dissolved.
Was added dropwise. After the dropwise addition, the mixture was further stirred at 23 ° C. for 10 hours, and then the reaction product was separated by filtration, washed and dried to obtain 13 g of powdery sulfonated polyaniline. The sulfonated polyaniline had a sulfonic acid group content of 100% and a volume resistivity of 12.3 Ωcm. 3 parts by weight of this sulfonated polyaniline was dissolved by stirring at room temperature in 100 parts by weight of a 0.3 mol / l sulfuric acid aqueous solution,
A sulfonated polyaniline solution was prepared.

Formation of Conductive Layer The solid content ratio of the sulfonated polyaniline to the sulfonic acid group-containing polyester is 30/70 (weight ratio) of the sulfonated polyaniline solution and the sulfonic acid group-containing polyester aqueous dispersion prepared above. And then mix
The surfactant Emulgen 810 (manufactured by Kao Corporation) was added so that the ratio to the sulfonated polyaniline was 8/100 (weight ratio) to prepare a conductive layer coating solution. A commercially available synthetic paper (Crisper, manufactured by Toyobo Co., Ltd.) is applied to the conductive layer coating solution.
Was coated by a microgravure coating method so that the coating amount after drying was 0.1 g / m ² , and dried at 160 ° C. for 1 minute to form a conductive layer.

<Formation of Thermosensitive Color-Developing Layer> Solution A (Color-forming dye dispersion) 3- (N, N-dibutyl) amino-6-methyl-7-anilinofluoran 20 parts 10% aqueous polyvinyl alcohol solution 20 parts Water 10 parts Liquid B (developer dispersion liquid) 4-hydroxy-4'-isopropyloxydiphenylsulfone 50 parts 10% aqueous polyvinyl alcohol solution 50 parts Water 25 parts

Solution A and Solution B were separately dispersed and pulverized with an Ultraviscomil, and the average particle size was 1.0 ± 0.2 μm.
It was prepared so that Liquid A 30 parts, Liquid B 90 parts, 60
% Calcium carbonate slurry 52 parts, 10% polyvinyl alcohol aqueous solution 40 parts, SBR latex (L-153
7, solid content 50%, Asahi Kasei Corporation product 28 parts, stearamide (Cellosol A-877, solid content 26.5)
%, Chukyo Yushi Co., Ltd.) (11 parts) and water (82 parts) were mixed to prepare a thermosensitive coloring layer coating solution. The coating amount after drying on a conductive layer by a microgravure coating method is 5.0 g / m ^2.
To obtain a heat-sensitive recording medium.

Example 2 In Example 1, the dicarboxylic acid component of the polyester in the aqueous dispersion of the sulfonic acid group-containing polyester was prepared by adding 47 mol% of dimethyl terephthalate and 47 mol% of dimethyl isophthalate.
Mol%, and 6 mol% of sodium 5-sulfoisophthalate, a sulfonic acid group-containing polyester aqueous dispersion was prepared in the same manner as in Example 1, and the concentration of the aqueous sulfuric acid solution of the sulfonated polyaniline solution was reduced to 0%. A sulfonated polyaniline solution was prepared in the same manner as in Example 1 except that the concentration was changed to 0.25 mol / L, and then a conductive layer and a thermosensitive coloring layer were formed in the same manner as in Example 1 to obtain a thermosensitive recording medium. Was.

Example 3 In Example 1, the solid content ratio of the sulfonated polyaniline and the sulfonic acid group-containing polyester in the sulfonated polyaniline solution and the sulfonic acid group-containing polyester aqueous dispersion was 20/80 (weight ratio). And the surfactant Emulgen 810 (manufactured by Kao Corporation) in a ratio of 40/100 (weight ratio) to the sulfonated polyaniline.
A coating solution for a conductive layer was prepared in the same manner as in Example 1 except that the addition was performed so as to be as follows. Then, a conductive layer and a thermosensitive coloring layer were formed in the same manner as in Example 1 to obtain a thermosensitive recording medium.

Example 4 In Example 1, the support was replaced with a commercially available synthetic paper (Yupo FPG).
-80, manufactured by Oji Yuka Co., Ltd.)
In the same manner as in the above, a thermosensitive recording medium was obtained.

Comparative Example 1 An anionic antistatic agent Chemistat S
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that a solution containing A-9 (manufactured by Sanyo Chemical Industries, Ltd.) was used.

Comparative Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the coating solution for the conductive layer was a solution containing a carbon-based antistatic agent.

Comparative Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that no conductive layer was provided.

The thermosensitive recording materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated for the surface resistance of the conductive layer, the presence / absence of transport unevenness of the thermal sensitive media, and the presence / absence of image unevenness. Table 1 shows the results.

[0065]

[Table 1]

As shown in Table 1, the heat-sensitive recording materials obtained in Examples 1 to 4 had a low surface resistance of the conductive layer, and showed no transport unevenness or image unevenness even at 15% RH. On the other hand, the thermal recording medium obtained in Comparative Example 1 had a high surface resistance value of the conductive layer at 15% RH, and had uneven conveyance and image unevenness. The thermal recording medium obtained in Comparative Example 2 had a low surface resistance value of the conductive layer.
Even at 5% RH, there was no transport unevenness, but the conductive layer contained carbon, so it turned black, and the heat-sensitive coloring layer looked a little dark, making it difficult to see the image under any humidity. Further, the heat-sensitive recording medium obtained in Comparative Example 3 had uneven transport and uneven image under any humidity.

[0067]

As is apparent from the above description, the heat-sensitive recording material of the present invention has antistatic properties even under low humidity, has no unevenness in conveyance and images, and exhibits excellent heat-sensitive recording properties. The thermal recording medium of the present invention is a thermal plotter that outputs a drawing created in a CAD system, and a CR for medical measurement.
It is suitable for use in a thermal printer for images that outputs a T image as a hard copy, a negative film sheet for image formation for an overhead projector (OHP) excellent in suitability for a thermal head, and a multicolor printing.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08J 9/00 C08J 9/00 A B41M 5/18 B

Claims (14)

[Claims] 1. A method comprising: a support; a thermosensitive coloring layer; and a conductive layer,
A thermosensitive recording medium, wherein the conductive layer contains a conductive polymer. 2. The thermosensitive recording medium according to claim 1, wherein the conductive layer is formed between the support and the thermosensitive coloring layer. 3. The thermosensitive recording medium according to claim 1, wherein the conductive layer is formed on a surface of the support opposite to a surface on which the thermosensitive coloring layer is formed. 4. The thermosensitive recording medium according to claim 1, wherein the thermosensitive coloring layer contains a coloring dye, a developer and an adhesive. 5. The conductive layer has a surface resistance of 25 ° C. and 15%
10 at RH⁶-10 ¹²Ω / □
The heat-sensitive recording material according to claim 1. 6. The thermosensitive recording medium according to claim 1, wherein the conductive polymer is polyaniline or a derivative thereof. 7. The thermosensitive recording material according to claim 6, wherein the polyaniline or a derivative thereof is a sulfonated polyaniline containing an alkoxy group-substituted aminobenzenesulfonic acid as a main component. 8. The thermosensitive recording medium according to claim 7, wherein the alkoxy group-substituted aminobenzenesulfonic acid is aminoanisolesulfonic acid. 9. The thermosensitive recording medium according to claim 1, wherein the conductive layer further contains a water-soluble or water-dispersible resin. 10. The heat-sensitive recording material according to claim 9, wherein the water-soluble or water-dispersible resin is a copolymerized polyester. 11. The heat-sensitive recording material according to claim 10, wherein the copolymerized polyester is a copolymerized polyester containing 5-sulfoisophthalic acid units in an amount of 2 to 10 mol%. 12. The thermosensitive recording medium according to claim 1, wherein the support is a thermoplastic film. 13. The heat-sensitive recording material according to claim 12, wherein the thermoplastic film is a polyester film. 14. The polyester film according to claim 13, wherein the polyester film is a void-containing polyester film obtained by at least uniaxially stretching a film made of a mixture of a polyester and a thermoplastic resin incompatible with the polyester. Thermal recording medium.