JPH0885730A - Antistatic film - Google Patents

Abstract

PURPOSE: To impart excellent antistatic properties, resistance to shaving, etc., to the surface of a plastic film by forming, on the surface, an antistatic layer contg. a polymer formed from an unsaid. monomer mixture contg. a specified amt. of an isoprenesulfonate. CONSTITUTION: At least one side of a plastic film (e.g. a polyester film) is coated with an antistatic compsn. comprising 3-50wt.% polymer produced from an unsatd. monomer mixture contg. 5mol% or higher isoprenesulfonate (e.g. a sodium isoprenesulfonate-ethyl acrylate copolymer) and 97-50wt.% at least one resin selected from among a polyester resin, an acrylic resin, and an acrylic modified polyester resin to form an antistatic coating layer on the side. The resultant antistatic film is suitable for producing magnetic recording materials such as telephone cards, videotapes, and floppy discs.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an antistatic film,
More specifically, magnetic recording materials such as magnetic cards (for example, telephone cards, prepaid cards), magnetic tapes (for example, audio tapes and video tapes), magnetic disks (for example, floppy disks) and electronic materials having good antistatic properties and abrasion resistance, and electronic materials The present invention relates to an antistatic film useful for graphic materials.

[0002]

2. Description of the Related Art Plastic films, particularly those made of polyester such as polyethylene terephthalate and polyethylene naphthalate, are magnetic cards,
For magnetic recording materials such as magnetic tape, packaging materials,
Widely used for general industrial materials such as photographic materials and graphic materials. However, the plastic film has a drawback that it has a large surface resistivity and is easily charged by friction or the like. When the film is charged, dust or dirt is attached to the surface of the film, which causes troubles. In addition, electric discharge occurs in the processing step, and there is a risk of ignition if an organic solvent is used.

As one of the methods for preventing such troubles due to charging, various methods for forming an antistatic coating (an antistatic coating) on the film surface have been proposed and put into practical use. As the antistatic agent to be contained in the antistatic coating film, a low molecular weight type and a high molecular weight type are known, but each has its own advantages and disadvantages. Therefore, the antistatic agent has been used properly according to its characteristics.

For example, as a low molecular type antistatic agent, a long-chain alkyl compound having a sulfonate group (Japanese Patent Laid-Open No. 4-
No. 28728) and other surfactant type anionic antistatic agents are known, and polystyrene sulfonates (Japanese Patent Laid-Open No. 5-32039) are known as high molecular type antistatic agents.
No. 0) etc. are known.

However, in the antistatic coating film using such a low molecular type antistatic agent, the antistatic agent easily moves in the coating film, accumulates at the interface, and easily migrates to the opposite surface of the film, There is a problem that the antistatic property decreases with time. On the other hand, when a polymer type antistatic agent is used, the antistatic coating film becomes too hard and lacks toughness, and thus there is a problem that it tends to be scraped.

A binder resin is generally used as a component of the antistatic coating film in order to strengthen the adhesion between the antistatic coating film and the plastic film which is the base film. Although this binder resin has a low compatibility with the antistatic agent, the obtained film has excellent antistatic property, but an antistatic coating film using such a binder resin has an antistatic property. Since the destruction occurs from the interface between the agent and the binder resin, there is a drawback that the abrasion resistance is lowered, such as the antistatic agent or the binder resin peeling off and missing. Therefore, there is a demand for the development of an antistatic film having excellent antistatic properties and excellent abrasion resistance of the antistatic coating film.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an antistatic film which is excellent in antistatic property and abrasion resistance and which is useful for magnetic recording materials, general industrial materials and the like.

[0008]

In order to achieve such an object, the present invention has the following constitution. An antistatic film in which an antistatic coating film containing a polymer made of an unsaturated monomer containing at least 5 mol% of isoprene sulfonate is provided on at least one side of a plastic film.

[Base Film] The plastic film used as the base film in the present invention is a film made of a thermoplastic resin such as a polyester film, a polyamide film, a polycarbonate film or the like. In particular, the polyester film has mechanical properties and thermal properties. It is preferable because it is excellent. The thickness of these plastic films is preferably 2 to 300 μm. A transparent film or a white film can be used as the base film depending on the use of the antistatic film. For example, a white antistatic film using the white film as the base film is used for a magnetic card or the like.

[Polyester Film] The polyester constituting the above-mentioned polyester film is a linear polyester composed of a dicarboxylic acid component and a glycol component.

Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, hexahydroterephthalic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid and dodecanedicarboxylic acid. Among them, terephthalic acid and 2,6-naphthalenedicarboxylic acid are particularly preferable.

Examples of the glycol component include ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol and 1,6-hexanediol. , Cyclohexanedimethanol, polyethylene glycol, polytetramethylene glycol and the like can be mentioned, and ethylene glycol is particularly preferable.

Preferred examples of the polyester include polyethylene terephthalate and polyethylene-2,6-naphthalate. This polyethylene terephthalate or polyethylene-2,6-naphthalate may be a polyester obtained by copolymerizing the above-mentioned dicarboxylic acid component or glycol component, and the trifunctional or higher polyvalent carboxylic acid component or polyol component is substantially linear. It may be a polyester copolymerized in a small amount within the range of polyester.

Organic or inorganic fine particles can be added to these polyesters as a lubricant in order to improve the slipperiness of the film. Specific examples of such fine particles include calcium carbonate, calcium oxide, amylnium oxide, titanium oxide, graphite, kaolin, silica, alumina, silicon oxide, zinc oxide, carbon black, silicon carbide, tin oxide, acrylic resin particles, crosslinked polystyrene resin particles. Preferable examples include melamine resin particles and silicone resin particles.

In addition to the fine particles, a colorant, an antistatic agent,
Antioxidants, organic lubricants, catalysts, optical brighteners, plasticizers, cross-linking agents, slip agents, UV absorbers, other resins and the like can be added as required.

When a transparent polyester film is used, the base film preferably has a light transmittance of 70% or more, and when a white polyester film is used, it has a light transmittance of 30% or less to which titanium oxide or the like is added. preferable.

The polyester film used in the present invention is
It can be manufactured by a conventionally known method. For example, it can be produced by melting the polyester and casting it on a cooling drum to obtain an unstretched film, and then stretching the unstretched film in the machine direction and then in the transverse direction. Further, it can be stretched again in the machine direction and / or the transverse direction. The stretching treatment is performed by the second-order transition point (T
g) It is preferable to carry out stretching at a temperature higher than 2) in each direction by a factor of 2 or more, more preferably 3 or more. At that time, the area stretching ratio is preferably 8 times or more, and more preferably 9 times or more. The upper limit of the area draw ratio depends on the use of the film, but is preferably 35 times, further preferably 30 times. The oriented crystallization can be completed by heat treatment after stretching.

[Antistatic Agent] In the present invention, the antistatic coating film contains a polymer made of an unsaturated monomer containing 5 mol% or more of isoprene sulfonate. It is preferable that the composition contains a composition containing not less than wt%. This polymer acts as an antistatic agent in antistatic coatings. Furthermore, since this polymer has appropriate flexibility, the antistatic coating film is less likely to be scraped.

As the isoprene sulfonate, sodium salt, potassium salt, lithium salt, ammonium salt,
Preferred are quaternary amine salts and tetraalkylphosphonium salts. Particularly, potassium salt and sodium salt are preferable.

The polymer of the present invention prepared from an unsaturated monomer containing 5 mol% or more of isoprene sulfonate (hereinafter sometimes referred to as "(A) isoprene sulfonate-based polymer") is isoprene sulfonic acid. It may be a homopolymer of a salt or a copolymer with another copolymerization component. In the case of a copolymer, the polymerization ratio of isoprene sulfonate needs to be 5 mol% or more, but particularly 10
It is preferably at least mol%. If the polymerization ratio is less than 5 mol%, the antistatic property may be insufficient, which is not preferable.

As the unsaturated monomer (A) used as a copolymerization component of the isoprene sulfonate polymer, ethyl acrylate, methyl acrylate, acrylic acid, butyl acrylate, sodium acrylate, ethyl methacrylate, Methyl methacrylate, methacrylic acid, butyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, acrylamide, methacrylamide, N-
Preferable examples include methoxymethyl acrylamide, N-methylol acrylamide, styrene, α-methyl styrene, sodium styrene sulfonate, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ether, sodium vinyl sulfonate and sodium methallylate.

The (A) isoprene sulfonate-based polymer is obtained by adding an unsaturated monomer used as a copolymerization component to an aqueous liquid containing isoprene sulfonate, for example, and polymerizing the same. Alternatively, it can be obtained by sulfonating an isoprene-based polymer in an aqueous liquid and then neutralizing it with an alkali. Such polymerization may be performed in an organic solvent solution. In order to reliably carry out this polymerization reaction, a polymerization initiator can be added to the above-mentioned aqueous liquid or organic solvent solution. As the polymerization initiator, usually used benzoyl peroxide, azobisisobutyronitrile, etc. can be used.

The number average molecular weight of the thus obtained (A) isoprene sulfonate polymer is not particularly limited,
1,000 to 200,000 from the viewpoint of strength of antistatic coating film
Is preferably in the range of 2,000 to 10
It is preferably in the range of 10,000.

[Binder Resin] The antistatic coating film of the present invention comprises (A) an isoprene sulfonate polymer and (B) a binder in order to make the adhesion between the coating film and the base film stronger. It is preferable to include a composition comprising a resin. The binder resin is (B-
1) polyester resin, (B-2) acrylic resin, (B
-3) Acrylic-modified polyester resins can be exemplified, and it is preferable to use one or more, and further two or more resins selected from these resins, and particularly (B-1) polyester resin and (B-2). It is preferable to use an acrylic resin.

[(B-1) Polyester Resin] The (B-1) polyester resin used as the binder resin is a linear polyester having a dicarboxylic acid component and a glycol component as constituent components.

As the dicarboxylic acid component, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 4,4 '
-Diphenyldicarboxylic acid, adipic acid, sebacic acid,
Preferable examples include dodecanedicarboxylic acid and hexahydroterephthalic acid.

As the glycol component, ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diene Preferable examples include propylene glycol, triethylene glycol, bisphenol A-alkylene oxide adduct, hydrogenated bisphenol A-alkylene oxide adduct, 1,4-cyclohexanedimethanol, polyethylene glycol, and polytetramethylene glycol.

The polyester resin (B-1) is preferably copolymerized with a component containing a sulfonate group in order to impart hydrophilicity. It is preferable to impart hydrophilicity to the polyester resin (B-1) because the dispersibility in the aqueous coating liquid becomes good. Examples of such components include 5-N
a Sulfoisophthalic acid, 5-K sulfoisophthalic acid, etc. can be mentioned.

The polyester resin (B-1) may be obtained by copolymerizing a trifunctional or higher polyvalent carboxylic acid component and a polyol component in a small amount within the range of forming a substantially linear polymer. Examples of such trifunctional or higher polycarboxylic acids and polyols include trimellitic acid, pyromellitic acid, dimethylolpropionic acid, glycerin, and trimethylolpropane.

[(B-2) Acrylic resin] The (B-2) acrylic resin used as the binder resin is, for example, ethyl acrylate, methyl acrylate, acrylic acid, butyl acrylate, sodium acrylate, ammonium acrylate, methacrylic acid. Mainly acrylic monomers represented by ethyl acidate, methyl methacrylate, methacrylic acid, butyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, acrylamide, methacrylamide, N-methoxymethyl acrylamide, N-methylol acrylamide, etc. Polymer or copolymer having styrene, α-methylstyrene, sodium styrene sulfonate, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ether, sodium vinyl sulfonate, sodium methacrylic acid, etc. as a component A.

[(B-3) Acrylic-modified polyester resin] The (B-3) acrylic-modified polyester resin used as the binder resin is ethyl acrylate, methyl acrylate, acrylic acid, in the presence of the polyester resin.
Butyl acrylate, sodium acrylate, ammonium acrylate, ethyl methacrylate, methyl methacrylate,
Made by polymerizing acrylic monomers such as methacrylic acid, butyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, acrylamide, methacrylamide, N-methoxymethyl acrylamide, and N-methylol acrylamide. Yes,
It may contain a monomer such as styrene, α-methylstyrene, sodium styrene sulfonate, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ether, sodium vinyl sulfonate, sodium methallylate as a copolymerization component.

[Other Binder Resins] Binder resins other than the above are polyurethane, epoxy resin,
Examples thereof include vinyl resins, polyethers, water-soluble resins and the like.

[Antistatic Coating] The antistatic coating in the present invention contains the above-mentioned (A) isoprene sulfonate polymer as an antistatic agent component, and further contains the above-mentioned (B) binder resin. It is preferable that the composition comprises

The proportion of the isoprene sulfonate-based polymer (A) contained in the antistatic coating film is preferably 3% by weight or more in order to improve the antistatic property, and is preferably 10% by weight.
It is more preferable that the above is satisfied. Especially when a white polyester film is used as the base film, the content is preferably 10% by weight or more. If this ratio is less than 3% by weight, the antistatic property may be insufficient. Further, when a white polyester film is used as the base film, particularly when the application is a magnetic card, the surface resistivity of the coating film required for the white antistatic film is high (for example, 1 × 10 ^12).
Therefore, if this ratio is less than 10% by weight, the antistatic property may be insufficient.

The proportion of the (A) isoprene sulfonate polymer contained in the antistatic coating film is preferably 50% by weight or less. If this ratio is more than 50% by weight, the adhesion of the antistatic coating film to the base film may be insufficient.

The proportion of the (B) binder resin contained in the antistatic coating is (B-1) polyester resin, (B)
-2) It is preferable that at least one resin selected from the group consisting of acrylic resin and (B-3) acrylic modified polyester resin is 50 to 97% by weight, and further (B-
1) Polyester resin and (B-2) acrylic resin are 5
It is preferably from 0 to 97% by weight.

Particularly when the base film is a white polyester film, the ratio of the components contained in the antistatic coating film is
If (A) isoprene sulfonate polymer is 10 to 50% by weight, (B-1) polyester resin is 10 to 80% by weight, and (B-2) acrylic resin is 10 to 80% by weight, antistatic Adhesion between the base coat and the transparent coating is good,
It is preferable because a white antistatic film having excellent antistatic properties can be obtained.

[Aqueous Coating Solution] In the present invention, an antistatic coating film is applied using an aqueous solution or an organic solvent solution containing the above-mentioned (A) isoprene sulfonate polymer. It is preferable to use an aqueous coating liquid for coating inside.

This aqueous coating liquid contains the (A) isoprene sulfonate polymer as an antistatic agent component, and further contains the (A) isoprene sulfonate polymer and the (B) binder resin. It is preferable that the composition include the composition of

As the lubricant, fine particles of polystyrene resin, acrylic resin, melamine resin, silicone resin, fluororesin, urea resin, benzoguanamine resin, polyamide resin, polyester resin and the like can be added to this aqueous coating liquid. The fine particles of these resins may be thermoplastic or thermosetting as long as they are contained in the antistatic coating in the form of fine particles. The aqueous coating solution further contains other components such as surfactants, antioxidants, other antistatic agents, colorants, pigments, optical brighteners, plasticizers, crosslinking agents, slip agents, and ultraviolet absorbers. can do.

The aqueous coating solution has a solid content concentration of 1 to 30% by weight.
Is preferable, and 2 to 20% by weight is particularly preferable. The aqueous coating liquid may contain a small amount of solvent. The aqueous coating solution in the present invention can be used in any form such as an aqueous solution, an aqueous dispersion, and an emulsion.

[Application of Antistatic Coating] The antistatic coating is preferably applied by coating the above-mentioned aqueous coating solution on at least one side of a plastic film and heating and drying. The aqueous coating solution can be applied to the plastic film by, for example, a gravure coater, a reverse roll coater, a die coater or the like. The coating amount of the aqueous coating liquid, 1~20g / m ^2, it is preferred that particularly 2~12g / m ^2.

When a polyester film is used as a base film, the antistatic coating film may be formed (coated) by coating and drying an aqueous coating film in the production process of the polyester film. Is preferable, and the adhesiveness to the base film is strong. This aqueous coating solution can be applied to an unstretched film, a uniaxially stretched film, a biaxially stretched film and the like, and particularly preferably to a uniaxially stretched film stretched in the machine direction. When an aqueous coating liquid is applied to the longitudinal uniaxially stretched film,
After the coating, it is dried and stretched in the transverse direction, and in some cases, restretched or re-stretched.

Although the thickness of the coating film thus formed can be arbitrarily selected, the thickness of the coating film after drying is 0.005 to 3 μm.
m, particularly 0.015 to 1 μm is preferable.

[Antistatic Film] Since the antistatic film of the present invention uses a polymer type antistatic agent having a specific structure as a component of the antistatic film, the antistatic film is excessively hard. It does not become a thing, and it becomes what has moderate flexibility. Therefore, it is possible to provide an antistatic film in which the antistatic coating is not easily scraped off when used. Further, since the proportion of the antistatic agent in the antistatic coating film component can be increased, the surface specific resistance value of the coating film is 1 × 10 ⁹ to 1 × 10 ¹³ Ω / □,
In particular, it is possible to provide an antistatic film having an excellent antistatic property of 1 × 10 ⁹ to 1 × 10 ¹¹ Ω / □.

[0046]

EXAMPLES The present invention will be described in more detail with reference to examples. Each characteristic value was measured by the following method.

1. Surface resistivity After leaving the sample film at 23 ° C. × 50% RH for 24 hours, the surface resistivity of the coated surface of the film is measured using an oscillating capacitance type potentiometer TR-84M (manufactured by Takeda Riken).

2. Scratch resistance of coating film [K method] Film is slit into 1 inch width and diameter is 5mm
Fixing pin (material: stainless steel, surface roughness: Ra is 0.
15m / mi with the coated surface in contact with
n. After traveling 90 m at the speed of, the amount of shavings adhering to the fixing pin is observed and the following ranking is performed. A: Almost no accumulation B: Some accumulation C: A considerable amount of accumulation

[L method] The following ranking is performed by observing the damage on the coated surface when the coated surface of a film having a width of 20 mm and the paper surface are brought into contact with each other and rubbed under a load of 100 g. A: Small damage B: Medium damage C: Large damage

3. Light transmittance Measured by a Murakami Color Research Laboratory HR-100 type haze meter according to ASTM D1003.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.62 was melted, cast on a cooling drum, and stretched 3.4 times in the machine direction. On one side of this film, terephthalic acid, isophthalic acid, 5-Nasulfoterephthalic acid, ethylene glycol, diethylene glycol and neopentyl glycol-based copolyester [b-
1] 55 wt%, Na isoprene sulfonate (82 mo
1 wt%), ethyl acrylate (18 mol%) copolymer [a-1] 33 wt%, and polyoxyethylene nonylphenyl ether 12 wt% 6 wt% aqueous solution having a composition was applied by a gravure coater. After drying, 3.
The film was stretched 8 times and heat-treated to prepare a coating film having a thickness of 45 μm. The coating thickness of this film was 0.22 μm, and the light transmittance was 82%. The characteristics of the film are shown in Table 1.

[Comparative Example 1] The same procedure as in Example 1 was carried out except that the aqueous coating solution was not applied. The properties of the obtained film are shown in Table 1.

[Examples 2 to 7 and Comparative Examples 2 to 3] The same procedure as in Example 1 was carried out except that the components, proportions and coating thickness of the coating liquid were changed. The properties of the obtained film are shown in Table 1.

Example 8 and Comparative Example 4 Titanium oxide 1
Polyethylene terephthalate having an intrinsic viscosity of 0.65 containing 1 wt% is used for the base film, and the components and proportions of the coating liquid,
Table 1 shows the characteristics of the film obtained in the same manner as in Example 1 except that the coating thickness was changed. The light transmittance of the antistatic film of Example 8 was 5%.

[0055]

[Table 1]

In the antistatic coating composition of Table 1, antistatic agents [a-1], [a-2], [a-3], [a-4] and binder resins [b-1], [b]. -2] is the following copolymer or a mixture thereof. [B-1]: Terephthalic acid, isophthalic acid, 5-Na sulfoterephthalic acid, ethylene glycol, diethylene glycol and neopentyl glycol copolymer polyester [b-2]: terephthalic acid, isophthalic acid, 5-Na sulfoterephthalic acid, Ethylene glycol, diethylene glycol and neopentyl glycol polyester (50 wt%) and ethyl acrylate, butyl acrylate, ammonium acrylate, ethyl methacrylate, methyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate and N-methoxymethyl acrylamide Mixture consisting of copolymer (50 wt%) [a-1]: Na isoprene sulfonate (82 mol)
%) And ethyl acrylate (18 mol%) copolymer [a-2]: Na isoprene sulfonate (75 mol)
%) And methyl acrylate (25 mol%) copolymer [a-3]: Na isoprene sulfonate (2 mol)
%), Ethyl acrylate (35 mol%), ethyl methacrylate (40 mol%) and ammonium acrylate (23 mol%) copolymer [a-4]: Na styrenesulfonate (95 mol%)
And an ethyl methacrylate (5 mol%) copolymer.

[0057]

INDUSTRIAL APPLICABILITY The film of the present invention is excellent in antistatic property and abrasion resistance and is useful for magnetic recording media, magnetic cards, packaging materials, photographic materials, graphic materials and the like.

Claims (6)

[Claims] 1. An antistatic film in which a plastic film is provided on at least one surface thereof with an antistatic coating film containing a polymer made of an unsaturated monomer containing 5 mol% or more of isoprene sulfonate. 2. The antistatic property according to claim 1, wherein the antistatic coating film contains a composition containing 3% by weight or more of a polymer made of an unsaturated monomer containing 5% by mole or more of isoprene sulfonate. Film. 3. The plastic film is a polyester film, and the antistatic coating film comprises 3 to 50% by weight of a polymer (A) made of an unsaturated monomer containing 5 mol% or more of isoprene sulfonate, B-1) polyester resin,
At least one selected from the group consisting of (B-2) acrylic resin and (B-3) acrylic modified polyester resin.
The antistatic film according to claim 2, comprising a composition containing 50 to 97% by weight of the seed resin. 4. The polyester film is a transparent polyester film, and the light transmittance of the antistatic film is 70.
% Or more, the antistatic film according to claim 3. 5. The polyester film is a white polyester film, and the light transmittance of the antistatic film is 30.
% Or less, the antistatic film according to claim 3. 6. The antistatic film according to claim 3 or 5, wherein the antistatic film is formed by applying an aqueous coating film in the production process of the polyester film.