JP2541637B2 - Antistatic film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an antistatic film, and more specifically,
Stable low surface resistivity value, excellent antistatic property even under low humidity condition, excellent adhesion to resin film used for base film, and water-soluble as antistatic copolymer. The present invention relates to an antistatic film which is excellent in water resistance despite using a copolymer, and is particularly useful as a material for magnetic recording media, general electronic materials, cards and the like.

<Prior Art> A resin film such as a polyester film that is heat-fixed by biaxial stretching has excellent mechanical properties, heat resistance, gas barrier property, chemical resistance, etc., but has a surface specific resistance value of 10 ¹⁴ to 10 ¹⁷ Ω / □. It is highly charged and easily charged, and as it is, it tends to cause foreign matter adsorption troubles in magnetic recording media and electronic materials.

As a method for preventing the film from being charged, conventionally, a method of applying an antistatic paint and a method of kneading an antistatic agent into a base polymer have been known. The low-molecular-weight surfactant type is best known as an antistatic agent, but it tends to exude and stick to the film surface or be easily removed by friction and lose its effect. There are also polymer types, but they are easily decomposed at 180 ° C or higher, and their ionicity is limited. Furthermore, it often cannot be used due to its rusting property. Even if it has antistatic properties, it cannot be put to practical use if it lacks in adhesion to the film.

<Object of the Invention> An object of the present invention is a film having a stable antistatic property, which has excellent resistance to high temperatures and friction solvents.
Another object is to provide an antistatic film having high adhesion.

<Structure / Effect of Invention> According to the present invention, the object and the effect of the present invention are: (a) Formula (1) is provided on at least one surface of the resin film. (Wherein R is hydrogen or an alkyl group, X is a metal element or a quaternary amino group, and n is a number from 0 to 2) 25 to 70% by weight, (b) Formula (2) An unsaturated monomer consisting of 30 to 75% by weight of a compound represented by the formula (wherein R ₁ is hydrogen or an alkyl group, R ₂ is an alkyl group), and (c) 0 to 45% by weight of another copolymerizable monomer. Antistatic property characterized by applying an aqueous coating solution containing a water-soluble copolymer having a second-order transition point (Tg) of 75 ° C or less and an average molecular weight of 5000 or more obtained by polymerization and drying. Achieved by the film.

The water-soluble copolymer exhibiting antistatic properties in the present invention has a second-order transition point (Tg) of 75 ° C. or less and an average molecular weight of 5,000.
Above, it is (a) Formula (1) (Wherein R is hydrogen or an alkyl group, X is a metal element or a quaternary amino group, and n is a number of 0 to 2) 25 to 70% by weight of a compound represented by the formula (2) (b) (Wherein R ₁ is hydrogen or an alkyl group, R ₂ is an alkyl group) 30 to 75% by weight of a compound, and (c) an unsaturated monomer consisting of 0 to 45% by weight of another copolymerization monomer It is a copolymer obtained by polymerization (addition polymerization).

In the above formula (1), methyl is used as the alkyl group of R,
Preferable examples include ethyl, and the metal element of X is N
Preferable examples are a, K, Li and the like, and preferable examples of the quaternary amino group of X are NH ₄ , HN (CH ₃ ) _{3 and the} like. Specific representative examples of the compound represented by the above formula (1) include:
Examples thereof include sodium vinyl sulfonate, ammonium allyl sulfonate, triethylamine methallyl sulfonate, and the like. The amount of the compound represented by the above formula (1) used is 25 to 70% by weight, preferably 25 to 55% by weight, based on 100% by weight of all the monomers. If this proportion is less than 25% by weight, the antistatic property will be insufficient, whereas if it exceeds 70% by weight, the water resistance will decrease, which is not preferable.

In the above formula (2), the alkyl group of R ₁ can be preferably exemplified by methyl, ethyl and the like, and the alkyl group of R ₂ can be preferably exemplified by methyl, ethyl, butyl, 2-ethylhexyl and the like. Specific examples of the compound represented by the above formula (2) include methyl methacrylate, ethyl methacrylate, ethyl acrylate and butyl acrylate. The ratio of the compound represented by the above formula (2) is 3 per 100% by weight of all the monomers.
0 to 75% by weight. If this proportion is less than 30% by weight, the adhesiveness will decrease, while if it exceeds 75% by weight, the antistatic property will decrease, which is not preferable.

Further, as the other monomer (copolymerizable monomer) copolymerizable with the compounds represented by the above formulas (1) and (2),
For example, 2-hydroxyethyl methacrylate, N, N-dieraminomethyl acrylate, cyclohexyl methacrylate, benzyl acrylate, glycidyl methacrylate, ethyleneimino group-containing ester of acrylic acid,
N-methylol acrylamide, methacrylamide, acrylic acid, methacrylic acid, ammonium acrylate, styrene, vinyl chloride, vinylidene chloride, maleic anhydride, vinyl acetate, allyl acrylate, ethyl vinyl ether, N-methoxymethyl methacrylamide, etc. may be mentioned. it can.

This usage rate is 0 to 45 per 100% by weight of all monomers.
% By weight. If this proportion exceeds 45% by weight, the adhesiveness and antistatic property will deteriorate, which is not preferable.

The water-soluble copolymer used in the present invention has a second-order transition point (Tg)
Although the temperature is 75 ° C or lower, if the second-order transition point (Tg) is higher than 75 ° C, the adhesion to the resin film is deteriorated, which is not preferable. Further, this copolymer has an average molecular weight of 5,000 or more, but if the average molecular weight is less than 5,000, the adhesiveness will be reduced, which is not preferable.

Such a copolymer can be produced by a conventional method,
For example, a bulk polymerization method, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method or the like can be freely selected. Finally, this copolymer is used as an aqueous liquid after being adjusted to an appropriate concentration.

In the present invention, the above copolymer may be used alone, or may be used in combination with at least one selected from polyurethane, acrylic resin, polyester and modified resins thereof. It is often preferable to use them together.
Specific examples thereof include a polyurethane emulsion containing a carboxylate group, an acrylic emulsion containing a hydroxyl group, and an aqueous polyester dispersion containing a sodium sulfonate group. The combined use ratio is preferably 5 to 80% by weight based on the weight of all resins.

An aqueous coating solution containing the above copolymer can be produced by a conventional method, in which case, for example, a surfactant, a filler, a pigment,
Other additives such as other antistatic agents, lubricants, stabilizers, ultraviolet absorbers, conductive materials, dispersants, etc. can be added as needed within the range not impairing the purpose of the present invention. . The resin solid content concentration in the aqueous coating liquid is 2 to 8% by weight, and further 2 to 6%.
It is preferably in the weight%.

Examples of the resin film to which the aqueous coating liquid is applied include aromatic polyester films such as polyethylene terephthalate film and polyethylene-2,6-naphthalate film, polyolefin films such as polyethylene film and polypropylene film, nylon-6 film and nylon-film. Examples thereof include polyamide film such as 66 film, polycarbonate film, polyvinyl chloride film and the like. Of these films,
Aromatic polyester films are preferred.

The resin film may be a non-stretched film or a stretched film, but in the case of a stretched film, it may be coated on an unstretched film, a uniaxially stretched film, a biaxially stretched film, etc., and stretched after coating. The coating is preferably performed by a roll coating method, a gravure coating method, or the like.

The aqueous medium of the aqueous coating liquid applied to the resin film is removed by the drying treatment to form a uniform thin film on the film. The temperature for the drying treatment is preferably 110 ° C. or higher. Although the upper limit of this temperature is determined by the physical properties of the resin film, it is preferably kept at a temperature 20 ° C. lower than the melting point of the resin. For example, in the case of polyethylene terephthalate film, it is preferable to perform the drying treatment within the temperature range of 110 to 240 ° C. Further, when the stretching treatment is performed after coating, it is preferable to perform the drying treatment in the course of the stretching treatment.

The antistatic film thus obtained has, for example, 10 ⁶ to 1
It has a characteristic that it has a surface specific resistance value of ¹³ Ω / □, and that this surface specific resistance value is not easily influenced by the atmosphere and is stable. Further, it is characterized in that the antistatic layer and the base film have excellent adhesion.

The antistatic film of the present invention is particularly preferably used as a base for magnetic recording media and cards. Apply magnetic paint to one side of the antistatic film to make a magnetic tape,
Apply magnetic paint on both sides to make a floppy disk,
You can also make a telephone card or prepaid card by applying printing ink and magnetic paint.

<Examples> Hereinafter, the present invention will be further described with reference to Examples. In addition,
The surface resistivity of the film was measured by the following method.

Aluminum is vapor-deposited on a film sample of 8 cm square, and the temperature is 20 ℃ and 50
% RH, 20 ° C, 35% RH, surface resistivity (Ω /
□) was measured.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.63 (orthochlorophenol, 35 ° C.) was melt extruded onto a rotary cooling drum maintained at 22 ° C. to obtain an unstretched film, which was stretched 3.5 times in the machine direction. Sodium methallyl sulfonate (32mol%: 42.4wt%), methylmethacrylate (33mol%: 27.6wt%), ethyl acrylate (30mol%: 25.2wt%) and ethylmethacrylate (5mol%: 4.8wt%) were added to this uniaxially stretched film. A polymer produced from
A 3% aqueous solution of a water-soluble copolymer (A) having a Tg of ° C and an average molecular weight of 85,000 was applied by a kiss coat method in an amount of 4 g / m ² (wet). Subsequently, the film was stretched in the transverse direction by 3.8 times at 104 ° C. and further heat-treated at 210 ° C. to obtain a 102 μm-thick single-side coating film (antistatic film). The surface resistivity (ρs) of the coated surface of this film is 3.7 × 10 ¹⁰ at 20 ℃ and 50% RH.
Ω / □, 9.3 × 10 ¹¹ Ω / □ at 20 ℃ and 35% RH.

Comparative Example 1 Example 1 was repeated except that the aqueous liquid was not applied. The surface resistivity (ρs) of the obtained film is 20
5.7 × 10 ¹⁵ Ω / □ at 50 ° C and 50% RH, 7 × 1 at 20 ° C and 35% RH
It was 0 ¹⁵ Ω / □.

Comparative Example 2 A polymer prepared by replacing the copolymer (A) in Example 1 with 15% by weight of potassium methallylsulfonate, 55% by weight of methyl methacrylate, 25% by weight of ethyl acrylate and 5% by weight of ethyl methacrylate. Tg of 30 ℃
And the same procedure as in Example 1 except that a water-dispersible (water-insoluble) copolymer having an average molecular weight of 96,000 was used. The surface resistivity (ρs) of the obtained film is 20 ℃, 50% RH
2.3 × 10 ¹⁴ Ω / □ under, 5 × 10 ¹⁵ Ω / □ under 20 ℃, 35% RH
Met.

Example 2 Instead of the 3% solution of the water-soluble copolymer (A) in Example 1, 80% of the 3% solution of the water-soluble copolymer (A) and 3% solution of polyurethane aqueous dispersion Implanil DLH (Bayer) 3% 20 The same procedure as in Example 1 was carried out except that a mixed solution of 10% was used. The surface resistivity (ρs) of the obtained film is 20 ℃, 50% RH
2.8 × 10 ¹¹ Ω / □, 6.7 × 10 ¹² Ω / at 20 ℃, 35% RH
It was □.

Example 3 Instead of the 3% solution of the water-soluble copolymer (A) in Example 1, 80% of the 3% solution of the water-soluble copolymer (A) and polyester aqueous dispersion WD size (Eastman Chemical) 3% Liquid 20
The same procedure as in Example 1 was carried out except that a mixed solution of 10% was used. The surface resistivity (ρs) of the obtained film is 20 ℃, 5
5.7 × 10 ¹¹ Ω / □ under 0% RH, 5.9 × 10 ¹² under 20 ° C, 35% RH
It was Ω / □.

Example 4 Instead of the 3% solution of the water-soluble copolymer (A) in Example 1, 80% of a 3% solution of the water-soluble copolymer (A) and an acrylic resin emulsion: Julimer FC30 (Nippon Pure Chemical) 3% Liquid 20
The same procedure as in Example 1 was carried out except that a mixed solution of 10% was used. The surface resistivity (ρs) of the obtained film is 20 ℃, 5
4.8 × 10 ¹¹ Ω / □ at 0% RH, 8.4 × 10 ¹² at 20 ° C, 35% RH
It was Ω / □.

Example 5 A 14 μm-thick film obtained in the same manner as in Example 1 was coated with chromium dioxide powder, polyurethane resin, on the surface opposite to the coated surface.
A magnetic layer of vinyl chloride / vinyl acetate copolymer was provided. The magnetic tape obtained had excellent antistatic properties, and thus had less foreign matter attached and had good running properties.

Example 6 Polyethylene terephthalate in Example 3 with 9 wt
% Titanium oxide was added, both sides were coated with an aqueous solution, and the film thickness was 190 μm. The magnetic card provided with a magnetic layer on one side and printed on the other side of the obtained film had very few defects due to foreign matters.

Example 7 Example 1 except that sodium sulfonate is used in place of sodium methallyl sulfonate in Example 1.
I went the same way. Surface resistivity of the obtained film (ρ
s) is 4.7 × 10 ¹⁰ Ω / □ at 20 ℃, 50% RH, 20 ℃, 35% RH
It was 9.6 × 10 ¹¹ Ω / □ below.

Comparative Example 3 Instead of the 3% solution of the water-soluble copolymer (A) in Example 1, sodium methallyl sulfonate (15 mol%), methyl methacrylate (33 mol%), ethyl acrylate (30 mol%) and ethyl were used. Same as Example 1 except using a 3% solution of a water dispersible (water insoluble) copolymer having a Tg of 31 ° C. and an average molecular weight of 74,000, which is a polymer made from methacrylate (22 mol%). Went to. The surface resistivity (ρs) of the obtained film is 8 × 10 ¹³ Ω at 20 ℃ and 50% RH.
/ □, 2.9 × 10 ¹⁴ Ω / □ at 20 ° C and 35% RH.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-52-100377 (JP, A) JP-A-61-204240 (JP, A) Special table Sho-56-501739 (JP, A)

Claims (2)

(57) [Claims] 1. A resin of formula (1) on at least one side of a resin film. (Wherein R is hydrogen or an alkyl group, X is a metal element or a quaternary amino group, and n is a number from 0 to 2) 25 to 70% by weight, (b) Formula (2) (Wherein R ₁ is hydrogen or an alkyl group, R ₂ is an alkyl group) 30 to 75% by weight of a compound, and (c) an unsaturated monomer consisting of 0 to 45% by weight of another copolymerization monomer Antistatic property characterized by applying an aqueous coating solution containing a water-soluble copolymer having a second-order transition point (Tg) of 75 ° C or less and an average molecular weight of 5000 or more obtained by polymerization and drying. Film. 2. The antistatic film according to claim 1, wherein the aqueous coating liquid contains at least one selected from polyurethane, acrylic resin, polyester and modified resins thereof together with the copolymer.