JPH0725914B2 - Antistatic polyester film - Google Patents

Description

The present invention relates to a polyester film having excellent antistatic properties.

[Problems to be solved by conventional technology and invention]

The biaxially stretched polyester film is widely used because of its excellent properties, but it has a drawback that it is easily charged.

Examples of the antistatic method include a method of kneading an anionic compound such as an organic sulfonate or an organic phosphate, a method of depositing a metal compound, a method of applying an anionic compound or a cationic compound or so-called conductive particles. is there. Although the method of kneading an anionic compound can be manufactured at low cost, it has a limit in the antistatic effect and the compound that can be used is a low molecular compound, so that the adhesion between the film and the laminated layer is deteriorated by blooming. However, there are problems such as lack of water resistance and transfer of the compound. The method of vapor-depositing a metal compound has excellent antistatic properties, and although its use is expanding as a transparent conductive film in recent years, it is high in manufacturing cost and suitable for specific applications, but as a general antistatic film. Is hard to use. The method of applying conductive carbon or conductive metal particles has an advantage that the antistatic effect is relatively good and can be manufactured at a relatively low cost, but has a drawback that the transparency of the film is deteriorated.

For this reason, a method of applying an anionic compound or a cationic compound as an antistatic agent is widely adopted as an antistatic method for biaxially stretched polyester.

As a method for producing a biaxially stretched polyester film having a coating group, there is a method called a coating stretching method (in-line coating method) in which a coating solution is coated and then the film is stretched and heat-treated. Compared with the method of forming a coating layer by coating the coating liquid on the polyester film after biaxial stretching, this method performs film formation and coating at the same time, so a wide product can be obtained at a relatively low cost. In addition, the adhesiveness between the coating layer and the polyester film of the substrate is good, and not only the coating layer can be made thin, but also the surface characteristics of the coating layer are characteristic.

However, when an antistatic polyester film is produced by coating stretching, the antistatic agent is thermally unstable, so when coating stretching is performed under normal conditions, volatilization or thermal decomposition occurs in the stretching and heat treatment steps. May occur, and the expected antistatic effect may not be exhibited.

In addition, when heat treatment conditions such as temperature and film retention time are relaxed, volatilization and decomposition of the antistatic agent are suppressed, and there is an antistatic effect, but the film is unsatisfactory in terms of mechanical strength and dimensional stability. Often you can only get it.

[Means for solving problems]

In view of the above problems, the inventors of the present invention have conducted extensive studies and found that a polymer having a specific structure has excellent antistatic properties and is stable even in the coating and stretching step, and has completed the present invention. .

That is, the gist of the present invention resides in an antistatic polyester film characterized by being formed by applying a coating solution containing a polymer having a pyrrolidinium ring in the main chain on at least one side and then stretching.

The polyester of the polyester film in the present invention is polyethylene terephthalate in which 80 mol% or more of its constituent units are ethylene terephthalate or polyethylene naphthalate in which ethylene naphthalate is used.

The polyester film of the present invention may contain inorganic particles, organic particles, an organic lubricant, an antistatic agent, a stabilizer, a dye, a pigment, and an organic polymer as a composition, if necessary. In order to impart slipperiness to the polyester film, fine particles are contained in the film composition, but the type, size, and amount of the protrusion-forming agent are selected according to the required properties such as slipperiness and transparency of the product used. Is appropriately selected.

The polymer having a pyrrolidinium ring in the main chain in the present invention is a polymer having a structure represented by the following formula (I) or (II) as a main component.

In the formula, R ₁ and R ₂ are usually an alkyl group and a phenyl group, and may be the same group, or the alkyl group and phenyl group may be substituted with the groups shown below.

Substitutable groups are, for example, hydroxy, amido, carbo lower alkoxy, lower alkoxy, phenoxy, naphthoxy, cyano, thio lower alkoxy, thiophenoxy, cycloalkyl, tree (lower alkyl) ammonium lower alkyl, and the nitro group is an alkyl group. Only on
Further, the halogen group can be substituted only on the phenyl group.

In addition, R ₁ and R ₂ may be chemically bonded, and for example, CH ₂ m (m = an integer of 2 to 5) —CH (CH ₃ ) —CH (CH ₃ ) — —CH═CH. -CH = CH -, - CH = CH-CH = N- -CH = CH-N = CH- CH 2 2 OCH 2 2, CH 2) 3 -O- (CH 2) 2 - and the like, such as. Further, only _one of R ₁ and R ₂ may be hydrogen.

Wherein X ^{- is, Cl -, Br -, ▲} 1 / 2SO 2- 4 ▼ or ▲ 1 / 3PO ^3- ₄
Inorganic acid groups of ▼, ▲ CH ₃ SO ^- ₄ ▼, ▲ C ₂ H ₅ SO ^- ₄ ▼, ClH ₂ l ₊₁
COO ⁻ (l = 1 to an integer of 6) represents an organic sulfonic acid residue or a carboxylic acid residue.

The polymer of formula (I) in the present invention is It is obtained by subjecting the compound represented by the formula (9) to cyclopolymerization using a radical polymerization catalyst. Further, the polymer of the formula (II) can be obtained by subjecting the compound of the formula (III) to cyclopolymerization in a system using sulfur diacid as a solvent. Polymerization is carried out in water or a polar solvent such as methanol, ethanol, isopropanol, formamide, dimethylformamide, dioxane, acetonitrile or sulfur dioxide as a solvent, and a polymerization initiator such as hydrogen peroxide, benzoyl peroxide or tertiary butyl peroxide. Can be carried out by a known method, but is not limited thereto.

The polymer having a pyrrolidinium ring in the main chain in the present invention may have a compound having a polymerizable carbon-carbon unsaturated bond and a compound of the formula (III) as a copolymerization component.

The molecular weight of the polymer having a pyrrolidinium ring in the main chain in the present invention is preferably 500 to 1,000,000, more preferably 1000 to 500,000. When the molecular weight of the present polymer is less than 500, although the antistatic effect is exhibited, the strength of the coating film is weak or the film is sticky and blocking is likely to occur. When the molecular weight of the present polymer is higher than 1,000,000, the viscosity of the coating solution becomes high, and the handleability and coatability tend to deteriorate.

As the polymer having a pyrrolidinium ring in the main chain in the present invention, commercially available products from Daiichi Kogyo Seiyaku Co., Ltd., Nitto Boseki Co., and Merck Co. can be used for this purpose, but the invention is not limited thereto.

The coating liquid in the present invention is preferably a polymer having a pyrrolidinium ring in the main chain dissolved or dispersed in water. The medium of the coating solution is preferably water, but alcohols, in order to improve the cohesive stability of the coating agent, the coatability of the substrate on the polyester film, the film-forming property of the coating agent, etc.
Organic solvents such as cellosolves and N-methylpyrrolidone may be added to the coating liquid.

The coating liquid in the present invention contains a urea-based, melamine-based, or guanamine-based methylol- or alkylol-based crosslinking agent for improving the adhesion (blocking property), water resistance, solvent resistance, and mechanical strength of the coating layer. , Acrylamide-based, polyamide-based compounds, epoxy compounds, aziridine compounds, blocked polyisocyanates, silane coupling agents, titanium coupling agents, zircoaluminate coupling agents, heat, peroxides, photoreactive vinyl compounds Or a photosensitive resin may be contained. In addition, silica, silica sol, alumina, alumina sol, zirconium sol, kaolin, talc, calcium carbonate, titanium oxide, barium salt, carbon black, molybdenum sulfide, antimony oxide sol, etc. are used as the inorganic fine particles for improving the sticking property and the slipping property. It may contain an antifoaming agent, a coatability improving agent, a thickener, an organic lubricant, an organic polymer particle, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, etc., if necessary. It may be contained. Further, the coating liquid of the present invention may contain a polymer other than the polymer of the present invention for improving the properties of the coating liquid or the coating layer.

As a method for applying the above-mentioned coating liquid to a polyester film, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater or other coating device shown in "Coating Method" by Yuji Harazaki, Maki Shoten, issued in 1979. Polyester unstretched film coating solution using a method of sequentially or simultaneously biaxially stretching, a method of applying to a uniaxially stretched polyester film, further stretching in a direction perpendicular to the uniaxially stretching direction, or biaxial Apply to stretched polyester film,
Further, there is a method of stretching in the transverse and / or longitudinal direction.

The above stretching step is preferably performed at 60 to 130 ° C., and the stretching ratio is at least 4 times or more, preferably 6 to 20 times in terms of area ratio. Stretched film is 150-250
Heat treated at ℃.

Further, it is preferable to relax 0.2 to 20% in the longitudinal direction and the transverse direction in the cooling zone at the maximum temperature zone of the heat treatment and / or the outlet of the heat treatment.

In particular, the coating solution is applied to a uniaxially stretched polyester film stretched 2 to 6 times by a roll stretching method at 60 to 130 ° C, and the coating solution is appropriately dried, or the polyester uniaxially stretched film is immediately dried without being dried. It is preferable to stretch the film in a direction perpendicular to the direction at a temperature of 80 to 130 ° C. by a factor of 2 to 6 and heat-treat at 150 to 250 ° C. for 1 to 600 seconds.

According to this method, the coating layer can be dried at the same time as stretching, and the thickness of the coating layer can be thinned according to the stretching ratio, so that a film suitable as a polyester film substrate can be produced at a relatively low cost. it can.

The coating liquid in the present invention may be applied to only one surface of the polyester film or may be applied to both surfaces. When coated on only one side, a coating layer other than the coating liquid of the present invention may be formed on the opposite side, if necessary, to impart other properties to the polyester film of the present invention.
In addition, in order to improve the coating property and the adhesive property of the coating agent on the film, the film may be subjected to a chemical treatment or a discharge treatment before the coating. Further, in order to improve the adhesiveness and coatability of the biaxially stretched polyester film of the present invention to the coating layer, the coating layer may be subjected to discharge treatment after forming the coating layer.

The polyester film coated with the coating liquid of the present invention obtained as described above preferably has a polyester film thickness in the range of 3 to 500 μ, and a coating layer thickness in the range of 0.01 μ to 5 μ. Is preferable, and more preferably in the range of 0.02 μ to 1 μ. If the thickness of the coating layer is less than 0.01 μ, it is difficult to obtain a uniform coating layer, so that coating unevenness is likely to occur in the product, and if it is thicker than 5 μ, the slipperiness is lowered and the handling of the film becomes difficult, which is not preferable.

〔Example〕

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

The evaluation method in the examples is based on the method described below.

(1) Charge decay property: Using a static Honest meter (trade name) manufactured by Shishido Trading Company, at a temperature of 23 ° C. and 50% RH, apply a voltage of 10 KV to the discharge electrode located 2 cm above the sample. , Charge the film and stop the discharge after the charge amount is saturated. Then, measure the charge decay of the sample with an electrometer located 2 cm above the sample, and use the half-life as a guide for evaluation.

5 seconds or less: extremely good 5 to 30 seconds: good 30 to 600 seconds: somewhat good 600 seconds or more: poor In addition, the sample charged by the above method was blown with air at 35 ° C and 100% RH for 1 second (forced humidification). Law). The forced humidification method is used to evaluate whether the electric charge remains.

(2) Surface resistivity: 16008A (trade name), which is a concentric circular electrode with an inner electrode of 50 mm diameter and an outer electrode of 70 mm diameter manufactured by Yokogawa / Hület Packard, was placed on the sample in an atmosphere of 23 ° C and 50% RH. , A voltage of 100 V was applied, and the surface resistivity of the sample was measured with the company's high resistance meter, 4329A (trade name), and the following judgment was made based on the resistivity value.

10 ⁹ Ω / mouth or less: Very good 10 ⁹ to 10 ¹¹ Ω / mouth: Good 10 ¹¹ to 10 ¹³ Ω / mouth: Slightly good 10 ¹³ Ω / mouth or more: Poor Comparative Example 1 Polyethylene terephthalate with an intrinsic viscosity of 0.65 at 280 ° C ~ 3
It was melt-extruded at a temperature of 00 ° C. and cast on a cooling drum while also using the electrostatic adhesion method to obtain an amorphous film having a thickness of 820 μ. This film was stretched 3.3 times in the machine direction at 95 ° C,
Further, it was stretched 3.3 times in the transverse direction at 110 ° C and heat-treated at 210 ° C to obtain a biaxially stretched polyester film having a thickness of 75μ.

The charge attenuating property of this film was poor, and it was also poor by the forced humidification method. The surface resistivity of this film is 10 ¹⁵ ~
It was poor at 10 ¹⁶ Ω / mouth.

Example 1 A coating solution containing the polymer represented by the formula (I), Shear Roll DC-902P (trade name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. was applied on one side after longitudinal stretching of Comparative Example 1 and before lateral stretching. , Comparative Example 1
In the same manner as above, polyester films having coating layers of various coating thicknesses were obtained. The relationship between the thickness of the coating layer of this film and the antistatic property was as follows.

That is, the polyester film of the present invention was useful as an antistatic film.

Example 2 PAS-88, a polymer represented by the formula (II), manufactured by Nitto Boseki Co., Ltd.
(Product name) is applied in the same manner as in Example 1, and the applied thickness is 0.04.
A film having a thickness of 5μ and a polyester film thickness of 75μ was obtained.

The charge attenuating property and surface resistivity of this film were extremely good.

That is, the polyester film of the present invention was useful as an antistatic film.

Example 3 A coating solution (A) containing 70 parts of the shear roll DC-902P (trade name) used in Example 1 (the same as the solid content and below), 30 parts of polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 800, and a shear roll A coating solution (B) containing 35 parts of DC-902P and 65 parts of the above-mentioned polyvinyl alcohol was applied in the same manner as in Example 1 to give a coating thickness of 0.045 µ and a polyester film of the base 75.
A film of μ was obtained.

The film using the coating solution (A) has very good charge decay properties and surface resistivity, and the coating solution (B)
Was good.

That is, the polyester film of the present invention was useful as an antistatic film.

Example 4 Polyethylene terephthalate having an intrinsic viscosity of 0.65 containing titanium oxide as additive particles was melt extruded at a temperature of 280 to 300 ° C., cast on a cooling drum while using an electrostatic contact method, and an amorphous film having a thickness of 405 μ. Got This film was stretched 3.5 times in the longitudinal direction at 95 ° C., and 55 parts of Shear Roll DC-303P (trade name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., which is a polymer represented by the formula (I), was used on both sides of the film. Apply a coating solution containing 45 parts of the used polyvinyl alcohol, then stretch it 3.5 times in the transverse direction and heat-treat at 210 ° C to obtain a coating thickness.
A film having a thickness of 0.045 μ and a substrate polyester film of 33 μ was obtained.

The charge attenuating property and surface resistivity of this film were extremely good.

That is, the polyester film of the present invention was useful as an antistatic film.

[Effects of the Invention] The coating agent containing a polymer having a pyrrolidinium ring in the main chain of the present invention, which has been described in detail above, has excellent chargeability and heat resistance, and has no problem even in the coating and stretching step, and is an antistatic polyester film easily. Can be manufactured, and its industrial value is high.

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Claims (1)

[Claims] 1. An antistatic polyester film, which is obtained by applying a coating solution containing a polymer having a pyrrolidinium ring in its main chain on at least one side and then stretching it.