JP2008214571A - Antistatic polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antistatic polyester film excellent in antistatic property, transparency and adhesive force to various optical functional layers. <P>SOLUTION: This antistatic polyester film comprising a polyester film and a coating layer disposed on at least one side of the polyester film is characterized in that the coating layer comprises 10 to 95 wt.% of an acrylic resin containing 0.1 to 25 mol% of an acrylic monomer having a ketone group in the molecule as a copolymerization component and 5 to 90 wt.% of tin oxide particles having an average primary particle diameter of 0.5 to 150 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antistatic polyester film, and more particularly to an antistatic polyester film having an antistatic coating film formed on at least one side of a polyester film.

  In recent years, polyester films have been used as optical base films. Base films for prism lens sheets for liquid crystal display devices, touch panels, backlights, etc., base films for antireflection films, electromagnetic wave shielding films for plasma displays, organic EL It is used for applications such as display base film and display explosion-proof base film. In general, a polyester film is easily charged with static electricity, and may cause problems such as poor running during processing and contamination of the film and processing steps. In addition, the optical base film is required to have excellent transparency and excellent easy adhesion to functional layers such as a prism lens layer, a hard coat layer, an adhesive layer, an antireflection layer, and a sputter layer.

  In order to solve the above problems, for example, a method of kneading an antistatic agent in a polyester film and a method of depositing a metal compound on the surface of the polyester film have been proposed and put into practical use (Japanese Patent Laid-Open No. 5-345351). No., JP-A No. 2005-162910, JP-A No. 63-255361). However, such a method has problems that the transparency of the film is lowered and the processing cost is high.

  As another method, various methods for forming a coating film having both antistatic properties and easy adhesion properties on the film surface have been proposed and put into practical use. Antistatic agents used at this time include ionic conductive antistatic agents such as long-chain alkyl compounds having sulfonate groups and polymers having ionized nitrogen atoms in the main chain, tin oxide particles, indium, antimony, etc. Electronically conductive antistatic agents such as tin oxide particles doped with these elements are mainly used (JP-A-4-28728 and JP-A-7-329250).

Ion conductive antistatic agents have advantages such as high transparency and low cost, but they are disadvantageous in that they are easily affected by the external environment and are subject to long-term stability by bleeding out.
On the other hand, the electronically conductive antistatic agent has the advantage that it is less susceptible to the influence of the external environment, but has the disadvantage that the light transmittance increases when it is stretched after coating, and the surface resistance increases when it is thinly coated. This was not suitable for applications requiring high transparency such as optical applications.

JP-A-5-345351 JP 2005-162910 A JP-A 63-255361 Japanese Patent Laid-Open No. 4-28728 JP 7-329250 A

  It is an object of the present invention to provide an antistatic polyester film that is excellent in antistatic properties and transparency and excellent in adhesive strength with various optical functional layers. To do.

  That is, the present invention is an antistatic polyester film comprising a polyester film and a coating layer provided on at least one surface thereof, wherein the coating layer has an acrylic monomer having a ketone group in the molecule as a copolymerization component in an amount of 0.1 to 25. An antistatic polyester film comprising 10 to 95% by weight of acrylic resin containing 5% by mole and 5 to 90% by weight of tin oxide particles having an average primary particle size of 0.5 to 150 nm.

  According to the present invention, it is possible to provide an antistatic polyester film that is excellent in antistatic properties and transparency and excellent in adhesive strength with various optical functional layers.

Hereinafter, the present invention will be described in detail.
[Polyester film]
In the present invention, the polyester constituting the polyester film is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Specific examples of such polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), and polyethylene-2,6-naphthalate.

  The polyester used in the polyester film may be a copolymer of these polyesters, and the polyester is the main component (for example, a component of 80 mol% or more), and other types in a small proportion (for example, 20 mol% or less). It may be blended with the above resin. Polyethylene terephthalate or polyethylene-2,6-naphthalate is particularly preferred as the polyester because of good balance between mechanical properties and optical properties.

The polyester can also contain a colorant, an antioxidant, an organic lubricant, an inorganic lubricant, a catalyst, an ultraviolet absorber, and a filler.
The thickness of the polyester film is preferably 25 to 300 [mu] m, more preferably 50 to 250 [mu] m, from the viewpoint of obtaining strength required when used as a substrate for optical films.

[Coating layer]
In the present invention, a coating layer is provided on at least one side of the polyester film. And the coating layer contains an acrylic resin as a polymer binder and contains tin oxide particles as a conductive agent.
The thickness of the coating layer is preferably 10 to 200 nm. If it is less than 10 nm, the adhesive strength is insufficient, which is not preferable, and if it exceeds 200 nm, blocking may occur or the haze value may be increased.
Hereinafter, the coating layer will be described.

[acrylic resin]
The acrylic resin itself is a polymer and an amorphous resin composed of an acrylic ester and / or a methacrylic ester. In the present invention, an acrylic resin having an acrylic monomer having a ketone group in the molecule as a copolymerization component is used. The copolymerization ratio of the acrylic monomer having the ketone group of the acrylic resin in the molecule is 0.1 to 25 mol%, preferably 1 to 25 mol%, more preferably 1 to 20 mol%, particularly preferably 2 to 10 mol%. It is. When the copolymerization ratio of the acrylic monomer having a ketone group in the molecule is less than 0.1 mol%, the antistatic performance is not exhibited. When it exceeds 25 mol%, the blocking property deteriorates.

  The acrylic resin may be copolymerized with a monomer component other than the acrylic monomer having a ketone group in the molecule. For example, alkyl acrylate, alkyl methacrylate (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, cyclohexyl, etc.); Hydroxy-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate; Epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether; acrylic acid, methacrylic acid, itaconic acid, maleic acid Monomers having a carboxy group or a salt thereof, such as fumaric acid, crotonic acid, styrenesulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Amide, methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide, N, N-dialkyl acrylamide, N, N-dialkyl methacrylate (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n -Butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.), N-alkoxyacrylamide, N-alkoxymethacrylamide, N, N-dialkoxyacrylamide, N, N-dialkoxymethacrylamide ( As the alkoxy group, methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), acryloylmorpholine, N-methylolacrylamide, N-methylolmethacrylamide, N-phenylacrylamide, N-phenylmethacrylamide Monomers having an amide group such as; monomers of acid anhydrides such as maleic anhydride and itaconic anhydride; 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl Oxazoline group-containing monomers such as 2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline; methoxydiethylene glycol methacrylate, Methoxy polyethylene glycol methacrylate, vinyl isocyanate, allyl isocyanate, styrene, α-methyl styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, Rukiruitakon acid monoester, acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene, propylene, can be exemplified vinyl chloride, vinyl acetate, butadiene.

[Tin oxide particles]
The tin oxide particles used as the conductive agent have an average primary particle size of 0.5 to 150 nm, preferably 5 to 50 nm. When the average primary particle size exceeds 150 nm, optical scattering occurs and the transparency of the coating layer deteriorates. When the average primary particle size is less than 0.5 nm, aggregation of fine particles increases, and the secondary particle size increases and optical scattering occurs. The transparency of the coating layer may deteriorate.

  As the tin oxide particles, tin oxide particles are used. Metal oxides other than tin oxide, or particles having a metal or polymer surface coated with tin oxide are also included in the category of tin oxide particles in the present invention. enter. As the tin oxide particles, it is preferable to use those in which the conductive performance is improved by doping tin oxide with an element such as indium or antimony.

  The tin oxide particles are contained in the coating layer in an amount of preferably 5 to 90% by weight, more preferably 30 to 80% by weight. When the tin oxide particles are less than 5% by weight, the surface resistance value of the coating layer does not decrease and the film cannot be used as an antistatic film. When it exceeds 90% by weight, the content of the polymer binder is relatively reduced, the cohesive force of the coating layer is lowered, and the adhesiveness is deteriorated. The tin oxide particles are preferably used as an aqueous dispersion from the viewpoint of reducing environmental burden and easy handling.

[Crosslinking agent]
The coating layer preferably contains a crosslinking agent for the purpose of improving the solvent resistance during processing. As the crosslinking agent, for example, a crosslinking agent having self-crosslinking property, a crosslinking agent having a functional group that reacts with a carboxyl group, or a metal complex having a polyvalent coordination site can be used. Among these, an isocyanate compound, a melamine compound, a urea compound, an epoxy compound, a carbodiimide compound, an oxazoline group-containing compound, a zirconium salt compound, and a silane coupling agent, particularly preferably an oxazoline group-containing compound is used.

  When a crosslinking agent is blended, the crosslinking agent blended per 100% by weight of the coating layer is, for example, 10% by weight or less, preferably 0.1 to 5% by weight. If it exceeds 10% by weight, the compatibility with the binder resin and the antistatic agent is deteriorated and the haze of the coating film is increased. If it is less than 0.1% by weight, the effect of blending the crosslinking agent cannot be expected.

[Production method]
The polyester film is obtained by melt-extruding polyester into a film and cooling and solidifying it with a casting drum to form an unstretched film. This unstretched film is once or twice or more in the longitudinal direction at Tg to (Tg + 60) ° C. Stretched to double to 6 times, and then stretched in the width direction at Tg to (Tg + 60) ° C. to a magnification of 3 to 5 times, and further heat treated at 180 to 230 ° C. for 1 to 60 seconds as necessary. It can be obtained by performing reheat treatment while shrinking 0 to 20% in the width direction at a temperature lower by 10 to 100 ° C. than the heat treatment temperature. The glass transition temperature is abbreviated as Tg.

  The polyester film may be produced by the simultaneous biaxial stretching method as follows. That is, polyester is melt-extruded into a film, cooled and solidified with a casting drum to form an unstretched film, and the unstretched film is stretched in the longitudinal direction at Tg to (Tg + 60) ° C. in the longitudinal direction at 3 to 6 times and in the width direction. Is simultaneously stretched so as to be 3 to 6 times, and further subjected to heat treatment at 180 to 230 ° C. for 1 to 60 seconds as necessary, and contracted by 0 to 20% in the width direction at a temperature 10 to 100 ° C. lower than the heat treatment temperature. However, it can be obtained by performing a reheat treatment.

  The composition of the acrylic resin and tin oxide particles constituting the coating layer is preferably applied in the form of an aqueous coating solution such as an aqueous solution, an aqueous dispersion, or an emulsion to be coated on a polyester film as a coating film. A colorant, a surfactant, an ultraviolet absorber, a wax, and a filler may be further added to the coating liquid.

  The solid content concentration of the aqueous coating liquid is usually 20% by weight or less, preferably 1 to 10% by weight. If the solid content concentration is less than 1% by weight, the wettability to the polyester film may be insufficient. On the other hand, if it exceeds 20% by weight, the stability of the coating liquid and the appearance of the coating layer may be deteriorated. It is not preferable.

  This aqueous coating liquid is preferably applied to the polyester film before orientation crystallization is completed in the course of production of the polyester film. Here, the polyester film before the crystal orientation is completed is an unstretched film, a uniaxially oriented film in which the unstretched film is oriented in either the longitudinal direction or the transverse direction, and low in both the longitudinal direction and the transverse direction. It includes a film stretched and oriented at a magnification (a biaxially stretched film before being finally re-stretched in the machine direction or the transverse direction to complete orientation crystallization).

  Among these, an unstretched film or a uniaxially stretched film oriented in one direction is preferable. That is, in a preferred production method, an aqueous coating liquid is applied to an unstretched film or a uniaxially stretched film oriented in one direction, and a coating layer is formed by performing longitudinal stretching and / or lateral stretching and heat setting as it is. .

  When applying an aqueous coating liquid to a film, as a pretreatment for improving the coating property, the film surface is subjected to physical treatment such as corona surface treatment, flame treatment, plasma treatment, etc., or chemically combined with the composition. It is preferable to use an inert surfactant in combination.

  Such a surfactant improves the function of promoting the wetting of the aqueous coating liquid onto the polyester film and the stability of the coating liquid. For example, polyoxyethylene-fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal Examples include anionic and nonionic surfactants such as soaps, alkyl sulfates, alkyl sulfonates, polyoxyethylene distyrenated phenyl ethers, polyoxylethylene derivatives, and alkyl sulfosuccinates. When using surfactant, it is preferable that 1 to 10weight% is contained in the composition which forms a coating film.

The coating liquid is applied in such an amount that the thickness of the coating layer after stretching is preferably in the range of 10 to 200 nm. The antistatic property of the antistatic polyester film of the present invention after the formation of the coating layer has a surface resistivity of, for example, less than 10 ¹³ Ω / □, preferably 10 ¹⁰ from the viewpoint of suppressing adhesion of dust, dust and the like. Less than Ω / □.

  The haze of the antistatic polyester film of the present invention after forming the coating layer is preferably less than 10%, more preferably less than 5%. If the haze exceeds 10%, it is unsuitable for use as a substrate for optical applications, which is not preferable.

As a coating method of the coating liquid for forming the coating layer, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a roll brush method, a spray coating method, an air knife coating method, an impregnation method, and a curtain coating method can be used. These can be used alone or in combination.
An application layer may be formed in the single side | surface of a polyester film, and may be formed in both surfaces.

Hereinafter, the present invention will be described in more detail with reference to examples.
Various physical properties were evaluated by the following methods.

(1) Adhesiveness 2 g of UV curable resin (trade name: Desolite) manufactured by JSR Co., Ltd. was applied onto the coating surface of the film sample using a Myer bar. The film immediately after coating was dried at 80 ° C. for 2 minutes, and the sample was further irradiated with ultraviolet rays at 20 mW / cm ² for 5 minutes to form a 5 μm thick hard coat layer.
After a hard coat layer is formed on the film-forming surface of the film sample, a cross cut is made on the grid, and a 24 mm wide cellophane tape (manufactured by Nichiban Co., Ltd.) is pasted thereon, and then suddenly at a 180 ° peeling angle. After peeling, the peeled surface was observed and evaluated according to the following criteria.
5: Peeling area is less than 10% …… Adhesion is very good 4: Peeling area is 10% or more and less than 20% …… Adhesion is good 3: Peeling area is 20% or more and less than 30% Area is 30% or more and less than 40% …… Adhesive strength failure 1: Peeling area exceeds 40% …… Adhesive strength is extremely poor

(2) Haze value According to JIS K7136, the haze value of the film was measured using a haze measuring device (NDH-2000) manufactured by Nippon Denshoku Industries Co., Ltd. The haze value of the film was evaluated according to the following criteria.
◎: Haze value ≦ 5.0% …… Extremely good haze of film ○: 5.0% <Haze value ≦ 10.0% …… Good haze of film ×: 10.0% <Haze value …… Haze of film Bad

(3) Antistatic property The antistatic property is 1 minute at an applied voltage of 500 V under the conditions of a measurement resistance of 23 ° C. and a measurement humidity of 65% using a specific resistance measuring device manufactured by Takeda Riken. The subsequent surface resistivity (Ω / □) was measured. The surface specific resistance value of the film was evaluated according to the following criteria.
A: Surface resistivity ≦ 1 × 10 ¹⁰ Ω / □
○: 1 × 10 ¹⁰ Ω / □ <surface resistivity ≦ 1 × 10 ¹³ Ω / □
×: 1 × 10 ¹³ Ω / □ <surface resistivity

(4) Glass transition temperature Approximately 10 mg of a sample is sealed in an aluminum pan for measurement and attached to a differential calorimeter (DuPont V4.OB2000 DSC), and the temperature is 25 ° C. to 300 ° C. at a rate of 20 ° C./min. The mixture was heated up to 300 ° C. for 5 minutes, then taken out, immediately transferred onto ice and rapidly cooled. The pan was again mounted on the differential calorimeter, and the glass transition temperature (Tg: ° C.) was measured by increasing the temperature from 25 ° C. to 20 ° C./min.

(5) Intrinsic viscosity Intrinsic viscosity ([η] dl / g) was measured with an o-chlorophenol solution at 25 ° C.

(6) Coating layer thickness The film is fixed with an embedding resin, the cross section is cut with a microtome, stained with 2% osmic acid at 60 ° C. for 2 hours, and coated using a transmission electron microscope (JEM2010 manufactured by JEOL Ltd.). The layer thickness was measured.

(7) Particle size The film is fixed with an embedding resin, the cross section is cut with a microtome, stained with 2% osmic acid at 60 ° C. for 2 hours, and tin oxide is used using a transmission electron microscope (JEM2010, manufactured by JEOL Ltd.). The number average primary particle diameter was calculated by measuring 50 particles arbitrarily selected at a magnification of 500,000, and this was taken as the average primary particle diameter.

[Example 1]
Molten polyethylene terephthalate ([η] = 0.63 dl / g, Tg = 78 ° C.) is extruded from a die, cooled with a cooling drum by a conventional method to form an unstretched film, and then stretched 3.4 times in the machine direction. Then, an aqueous coating solution having a concentration of 4% of a coating composition having the composition shown in Table 1 was uniformly applied on one side by a roll coater.

Next, this coated film was subsequently dried at 95 ° C., stretched 3.5 times at 120 ° C. in the transverse direction, heat-fixed by shrinking 3% in the width direction at 220 ° C., and antistatic for optical use with a thickness of 125 μm. A conductive polyester film was obtained. The evaluation results are shown in Table 2.
Each component of the coating composition is as follows.

Acrylic resin 1:
It is composed of 49.5 mol% methyl methacrylate / 49.5 mol% ethyl acrylate / 1 mol% 2- (1,3-dioxobutoxy) ethyl methacrylate (molecular weight 350,000). This acrylic resin 1 was produced as follows according to the method described in Production Examples 1 to 3 of JP-A-63-37167. That is, 304 g of ion-exchanged water was charged into a four-necked flask and the temperature was raised to 60 ° C. in a nitrogen stream, and then 0.5 g of ammonium persulfate and 0.2 g of sodium hydrogen sulfite were added as polymerization initiators. A mixture of 49.6 g of methyl methacrylate, 49.6 g of ethyl acrylate, 2.2 g of 2- (1,3-dioxobutoxy) ethyl methacrylate and 3 g of sodium lauryl sulfonate as a surfactant over 3 hours. The solution was added dropwise while adjusting the liquid temperature to 60 to 70 ° C. The reaction was continued with stirring while maintaining the same temperature range for 2 hours after the completion of the dropping, and then cooled to obtain an aqueous dispersion of acrylic resin 1 having a solid content of 25%.

Acrylic resin 2:
The monomer composition was changed to 49.1 g of methyl methacrylate, 49.1 g of ethyl acrylate, and 4.3 g of 2- (1,3-dioxobutoxy) ethyl methacrylate. An aqueous dispersion of acrylic resin 2 having a solid content of 25% was obtained (molecular weight 350,000).

Acrylic resin 3:
A method similar to that for the acrylic resin 1 except that the monomer component is changed to 47.6 g of methyl methacrylate, 47.6 g of ethyl acrylate, and 11.4 g of 1-methyl-2- (3-oxobutyryloxy) ethyl methacrylate. And an aqueous dispersion of acrylic resin 3 having a solid content of 25% was obtained (molecular weight 360000).

Acrylic resin 4:
The monomer composition was changed to 45.1 g of methyl methacrylate, 45.1 g of ethyl acrylate, and 21.5 g of 2- (1,3-dioxobutoxy) ethyl methacrylate. An aqueous dispersion of acrylic resin 4 having a solid content of 25% was obtained (molecular weight 360000).

Acrylic resin 5:
The monomer composition was changed to 40.0 g of methyl methacrylate, 40.0 g of ethyl acrylate, and 42.5 g of 2- (1,3-dioxobutoxy) ethyl methacrylate. An aqueous dispersion of acrylic resin 5 having a solid content of 25% was obtained (molecular weight 360000).

Acrylic resin 6:
The monomer composition was changed to 35.0 g of methyl methacrylate, 35.0 g of ethyl acrylate, and 64.0 g of 2- (1,3-dioxobutoxy) ethyl methacrylate, and the same production method as for acrylic resin 1 was used. An aqueous dispersion of acrylic resin 6 having a solid content of 25% was obtained (molecular weight 350,000).

Acrylic resin 7:
The monomer composition was changed to 50.0 g of methyl methacrylate and 50.0 g of ethyl acrylate, and manufactured by the same production method as acrylic resin 1 to obtain an aqueous dispersion of acrylic resin 7 having a solid content of 25% ( Molecular weight 350,000).

Polyester resin:
The acid component is composed of 90 mol% terephthalic acid / 5 mol% isophthalic acid / 5 mol% 5-sodium sulfoisophthalic acid, and the glycol component is composed of 90 mol% ethylene glycol / 10 mol% diethylene glycol (average molecular weight 13000). This polyester resin was produced as follows according to the method described in Example 1 of JP-A-06-116487. That is, 55 g of dimethyl terephthalate, 3 g of isophthalic acid, 5 g of dimethyl 5-sodium sulfoisophthalate, 35 g of ethylene glycol and 3 g of diethylene glycol were charged into a reactor, and 0.05 g of tetrabutoxytitanium was added thereto, and the temperature was increased in a nitrogen atmosphere. The mixture was heated to 230 ° C. and heated, and the produced methanol was distilled off to conduct a transesterification reaction. Next, the temperature of the reaction system was gradually raised to 255 ° C., and the inside of the system was reduced to 1 mmHg to carry out a polycondensation reaction to obtain a polyester resin. 25 g of this polyester was dissolved in 75 g of tetrahydrofuran, and 75 g of water was added dropwise to the resulting solution under high speed stirring at 10,000 rpm to obtain a milky white dispersion. The dispersion was then distilled under a reduced pressure of 20 mmHg. Tetrahydrofuran was distilled off to obtain an aqueous dispersion of a polyester resin.

Tin oxide particles 1:
Antimony-doped tin oxide fine particles (“SNW-120” manufactured by Sumitomo Osaka Cement Co., Ltd., average primary particle size: 20 nm)
Tin oxide particles 2:
Antimony-doped tin oxide fine particles (“FS-10D” manufactured by Ishihara Sangyo Co., Ltd., average primary particle size: 200 nm)
Cross-linking agent:
Oxazoline group-containing acrylic polymer ("Epocross WS-700" manufactured by Nippon Shokubai Co., Ltd.)

[Examples 2 to 10]
An antistatic polyester film for optics having a thickness of 125 μm was obtained in the same manner as in Example 1 except that the composition of the coating agent was changed as shown in Table 1. The evaluation results are shown in Table 2.

[Example 11]
Molten polyethylene terephthalate ([η] = 0.63 dl / g, Tg = 78 ° C.) is extruded from a die, cooled by a cooling drum by a conventional method to form an unstretched film, and the coating concentration shown in the table on each side is 4%. The aqueous coating solution was uniformly applied with a roll coater. Next, the coated film was dried at 95 ° C., and subsequently stretched at 120 ° C. in the longitudinal direction 3.5 times and in the transverse direction 3.5 times. Subsequently, the film was shrunk 3% in the width direction at 220 ° C. and heat-fixed to obtain an optical antistatic polyester film having a thickness of 125 μm. The evaluation results are shown in Table 2.

[Comparative Example 1]
Molten polyethylene terephthalate ([η] = 0.63 dl / g, Tg = 78 ° C.) is extruded from a die, cooled with a cooling drum by a conventional method to form an unstretched film, and then stretched 3.4 times in the machine direction. Subsequently, the film was stretched 3.5 times at 120 ° C. in the transverse direction, and 3% contracted in the width direction at 220 ° C. and heat-fixed to obtain a polyester film having a thickness of 125 μm. The evaluation results are shown in Table 2.

[Comparative Examples 2 to 7]
An antistatic polyester film for optics having a thickness of 125 μm was obtained in the same manner as in Example 1 except that the composition of the coating agent was changed as shown in Table 1. The evaluation results are shown in Table 2.

  The antistatic polyester film of the present invention is used as an optical base film, for example, a prism lens sheet of a member of a liquid crystal display device, a base film of a touch panel, a backlight, a base film of an antireflection film, an electromagnetic wave shield of a plasma display, etc. It can be suitably used for applications such as films, base films for organic EL displays, and explosion-proof base films for displays.

Claims (4)

  An antistatic polyester film comprising a polyester film and a coating layer provided on at least one surface thereof, wherein the coating layer comprises 0.1 to 25 mol% of an acrylic monomer having a ketone group in the molecule as a copolymerization component An antistatic polyester film comprising 10 to 95% by weight and 5 to 90% by weight of tin oxide particles having an average primary particle size of 0.5 to 150 nm.   The antistatic polyester film according to claim 1, wherein the antistatic polyester film is stretched in at least a uniaxial direction after application of a coating liquid for forming a coating layer.   The antistatic polyester film according to claim 1, wherein the haze value is 10% or less.   The antistatic polyester film according to claim 1, which is used as an optical base film.