KR20140078824A - Manufacturing method of anti-static polyester film and protective film for polarizing plate using polyester film manufactured thereby - Google Patents

Abstract

The present invention relates to a manufacturing method of an antistatic polyester film, and a polarizing plate protective film manufactured by the antistatic polyester film. The manufacturing method of the antistatic polyester film of the present invention prepares a polyester film by orienting the polyester film as a first shaft in a film progressing direction; forms an antistatic layer by spreading an antistatic coating composite containing a conductive polymer resin on one side or both sides of the polyester film using an in-line coating method; and orients the polyester film in which the antistatic layer is formed again as a fivefold or sextuple orientation ratio in a vertical direction of the film progressing direction and thermally processes the polyester film. The antistatic polyester film manufacture thereby prevents the deviation of antistatic properties between widths due to a characteristic of a conductive polymer which is reformed into a particle size, in which average diameter is 60 nm or smaller; minimizes an interference non-uniform phenomenon of light by optimizing the orientation ratio in the transverse orientation and controlling an orientation angle of the whole width into 10°C or lower; and executes a precise test with a cross nicol of a polarizing plate, thereby being practically used as the polarizing plate protective film.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an antistatic polyester film and a polarizing plate protective film comprising the antistatic polyester film produced therefrom. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antistatic polyester film,

The present invention relates to a method for producing an antistatic polyester film and a polarizing plate protective film comprising the antistatic polyester film produced therefrom. More particularly, the present invention relates to a polarizing plate protective film comprising an electroconductive polymer resin having an average particle diameter of 60 nm or less, It is possible to prevent the width variation of the prevention property and to optimize the stretching ratio in the transverse direction to control the alignment angle of the full width to 10 degrees or less to minimize the phenomenon of interference of light interference and to perform precise inspection by cross- And a polarizing plate protective film made of an antistatic polyester film produced from the antistatic polyester film.

In general, polymeric polymer films are excellent in mechanical properties, heat resistance, transparency, and chemical resistance while being well-elastic, so that they can be used for photographic, drafting, ouchip, electric and electronic parts, general industry and packaging materials It is widely used across all industries.

However, despite the excellent physical properties of the polymer-polymerized film as described above, there is a problem that the surface of the film is easily charged if friction is applied because the resistivity of the film surface is very large. In this case, when the polymer-polymerized film is charged, foreign matter such as dust adheres to the surface of the film due to static electricity, and electric shock is applied to the product to which the film is applied, resulting in defective products.

In addition, when a discharge is generated in a manufacturing process or a processing process of a film using a chemical substance such as an organic solvent, a fire occurs.

Examples of the known technique for suppressing the generation of static electricity in the film include an internal addition method in which an organic sulfonic acid salt or an organic phosphate is mixed in the production of a film, a metal vapor deposition method in which a metal compound is deposited on the surface, A method of applying an anionic or cationic monomolecular compound or a polymer compound to the surface, and the like. Among the above methods, the internal addition method is excellent in stability against changes over time, but has a problem that excellent physical properties inherent to the film and antistatic effect are reduced. The metal deposition method and the method of applying the conductive inorganic particles have excellent antistatic properties However, it is used only in special fields requiring high antistatic properties because the manufacturing cost is too high. On the other hand, the coating method using the anionic or cationic monomolecular compound has been widely applied to a variety of research and development, because it has a relatively good antistatic effect and is advantageous in terms of manufacturing cost.

With the recent growth of the display industry and the increasing demand for antistatic films, products using various antistatic types as described above are emerging. Among them, the cationic electrification preventing type is most commonly used as the antistatic type, and in particular, the high-grade film market using the conductive polymer is being expanded.

Conductive polymers have been widely used in off-line coatings because of their excellent transparency and antistatic properties. However, the in-line coating method has been pointed out as a problem of productivity due to lateral deviation of antistatic performance due to transverse stretching.

In addition, when the film is transversely stretched, a difference in molecular orientation in the film occurs due to a difference in stress between the center portion and the outer portion of the film. When the film having no orientation angle control is applied as a protective film, There is a problem that the quenching state is broken and the light leakage phenomenon occurs, which may cause trouble or defect in the inspection.

For example, visual inspection by the cross-Nicol method is generally used for defect inspection of a polarizing plate, and inspection by an automatic foreign substance inspection apparatus using a cross-Nicol method is also carried out for a polarizing plate etc. used for a large- . This cross-Nicol method is a method capable of inspecting defects because two polarizing plates are orthogonalized by aligning the main axis of alignment thereof, and if any foreign matter or defect is present as a luminescent spot, defect inspection can be performed. In particular, a cross- When the automatic inspection is carried out, since the polyester protective film is laminated on the surface of the polarizing plate, when the orientation angle of the polyester protective film is not controlled, the light extinction state is broken and the light leakage phenomenon occurs, So that it often happens that the test is interfered with and there is also a problem that defects occur.

According to Korean Laid-Open Patent Application No. 2012-71696 and Japanese Laid-Open Patent Application No. 2012-38840, a raw material mixed in a ratio of polyester (A) and (B) % Of the raw material is used as a b-layer to produce a three-layer laminated film of a: b: a, and the orientation angle is controlled to 3 or less or 10 or less to obtain a polarizing plate for a large- Discloses a polyester film for polarizing plate protection which can be subjected to a precise inspection in inspection and has excellent surface fouling prevention and antistatic properties. However, the manufacturing method of the present invention is pointed out to be a problem of productivity and yield deterioration due to variation in antistatic performance of the coating surface due to the difference in coating thickness between film widths due to the transverse stretching process during in-line coating.

Accordingly, the present inventors have tried to solve the problems of different coating thicknesses between the film widths due to the transverse stretching process in the conventional in-line coating process, resulting in deviation in antistatic performance of the coating surface and unevenness in productivity resulting in unevenness of light interference As a result, the conductive polymer resin having an average particle size of 60 nm or less was contained in the antistatic coating composition, so that the antistatic property of the film was excellent and the antistatic performance was not deviated in width, The present inventors have completed the present invention by confirming the manufacture of an antistatic polyester film which can control the alignment angle of 10 degrees or less to minimize the nonuniformity of interference of light and to carry out precise inspection by the Cross Ni-C for polarizing plate.

An object of the present invention is to provide a method for producing an antistatic polyester film which is excellent in antistatic property but has almost no width variation of antistatic performance and whose orientation angle of full width is controlled.

Another object of the present invention is to provide a polarizing plate protective film made of an antistatic polyester film having almost no deviation of the antistatic property at the edge portion and the central portion of the film produced from the above production method and having an angle of full width controlled to 10 degrees or less .

In order to achieve the above object, the present invention relates to an antistatic coating composition comprising: 1) uniaxially stretching a polyester film in a film advancing direction, 2) applying an antistatic coating composition containing a conductive polymer resin on one surface or the other surface of the polyester film And 3) a polyester film on which the antistatic layer is formed is re-stretched at a stretching ratio of 5 to 6 times in a direction perpendicular to the film advancing direction and then heat-treated to obtain a biaxially oriented antistatic polyester A method for producing a film is provided.

In the production method of the present invention, the conductive polymer resin having an average particle diameter of 60 nm or less is contained in the antistatic coating composition, so that the antistatic property of the film is excellent, and the antistatic performance is free from any variation in width.

The antistatic coating composition for use in the production method of the present invention may further comprise an anionic polyether polyol having at least one functional group selected from the group consisting of a hydroxyl group, an amine group, an alkyl group and a carboxyl group per 100 parts by weight of the conductive polymer resin. 100 to 1000 parts by weight of a water-dispersible polyurethane resin comprising a urethane dispersion, 100 to 1000 parts by weight of a crosslinking agent selected from the group consisting of isocyanate, carbonylimide, oxazoline, epoxy and melamine, 10 to 100 parts by weight of a resin and 0.001 to 1 part by weight of an acetylenic diol surfactant.

At this time, the solid content in the antistatic coating composition is preferably 0.5 to 10 wt%.

In the production method of the present invention, heat treatment is performed at 180 to 220 캜, thereby inducing a uniform low orientation angle in the film.

Thus, the present invention provides a polarizing plate protective film made of the biaxially stretched antistatic polyester film, which is made of the biaxial oriented antistatic polyester film, wherein the full width directional angle of the film is controlled to 10 degrees or less.

In the polarizing plate protective film of the present invention, the surface resistance value between the edge portion and the center portion of the biaxially stretched antistatic polyester film satisfies 10 ⁷ to ^{10 10} Ω / sq or less, and the deviation of the antistatic performance is 10% Respectively.

The present invention relates to an antistatic coating composition which is easy to control the coating property and which is obtained by forming an antistatic layer on one side or both sides of a polyester film by an inline coating method to form an antistatic polyester film, It is possible to provide a method for producing an antistatic polyester film free from unevenness of light interference by controlling the orientation angle of the full width within 10 degrees with almost no occurrence of the prevention property deviation.

Accordingly, the present invention provides a biaxially stretched antistatic polyester film produced from the production process, which contains a conductive polymer resin having an average particle diameter of 60 nm or less in an antistatic coating composition to prevent the width variation of antistatic property and optimize the stretch ratio in the transverse direction Thereby controlling the alignment angle of the full width at 10 degrees or less, minimizing the non-uniformity of interference of light, and enabling accurate inspection with the Cross Ni-Coulomb method of the polarizing plate, which is useful as a polarizing plate protective film.

Hereinafter, the present invention will be described in more detail.

The present invention relates to (1) a polyester film which is uniaxially stretched in a film advancing direction,

2) An antistatic coating composition containing a conductive polymer resin is coated on one side or both sides of the polyester film by an inline coating method to form an antistatic layer,

3) A method for producing a biaxially stretched antistatic polyester film, which is performed by re-stretching a polyester film having the antistatic layer formed thereon at a stretching ratio of 5 to 6 times in a direction perpendicular to the film advancing direction and heat-treating the polyester film.

Hereinafter, the steps of the production method of the present invention will be described in detail.

Step 1: One axis Stretching  Fabrication of polyester film

The polyester film used in the present invention may be any conventional resin known as a base film to which a conventional antistatic coating is applied without any particular limitation. In the present invention, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate , But it is to be understood that the present invention is not limited thereto.

The polyester film refers to a polyester obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol. The aromatic dicarboxylic acid is obtained by using terephthalic acid, 2,6-naphthalene dicarboxylic acid or the like, As the dicarboxylic acid component, there can be used isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, P-oxybenzoic acid). Examples of the aliphatic glycol include ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol, propylene glycol, butanediol, neopentyl glycol and the like. The dicarboxylic acid component and the glycol component are two kinds Or more may be used in combination.

Typical examples of the polyester film include polyethylene terephthalate (PET), polyethylene-2,6-naphthalene dicarboxylate (PEN), and copolymers containing the third component in the polyester.

The polyester resin having the above-mentioned constitution was vacuum-dried, melted by an extruder, extruded into a sheet through a T-die (DIE), adhered to the casting drum by electrostatic application (pinning) The uniaxially stretched polyester film is obtained by obtaining a polyester sheet and uniaxially stretching it at 2.5 to 4.5 times in the roll heated to a temperature not lower than the glass transition temperature of the polyester resin by the difference in the peripheral speed between the roll and the roll.

Step 2: Antistatic layer formation

In the method for producing an antistatic polyester film of the present invention, step 2 is a step of forming an antistatic layer by applying the antistatic coating composition of the present invention on one side or both sides of the uniaxially stretched polyester film in the first step. More specifically, the antistatic coating composition may be applied by a Meyer bar method, a gravure method, or the like, and a polar group may be introduced onto the surface of the film before coating to improve adhesion between the coating layer and the film Or a corona discharge treatment may be performed to improve the coating property.

At this time, the antistatic coating composition of the present invention is an anionic polyether polyurethane dispersion containing at least one functional group selected from the group consisting of a hydroxyl group, an amine group, an alkyl group and a carboxyl group per 100 parts by weight of the conductive polymer resin 100 to 1000 parts by weight of a water-dispersible polyurethane resin, 100 to 1000 parts by weight of a crosslinking agent selected from the group consisting of isocyanate, carbonylimide, oxazoline, epoxy and melamine, And 0.001 to 1 part by weight of an acetylenic diol surfactant.

Each composition of the antistatic coating composition of the present invention will be described in detail. First, the conductive polymer resin is distributed in a particle size of 60 nm or less, more preferably 20 to 50 nm, so as to exhibit stable antistatic performance do. At this time, if the average particle diameter of the conductive polymer resin exceeds 60 nm, the variation in the width of the surface resistance becomes very large, which makes the use of the product difficult.

In the two-step antistatic coating composition of the present invention, control of the coating properties is easy depending on each composition and content. In particular, by forming an antistatic layer on one side or both sides of a polyester film by an inline coating method with an antistatic coating composition containing a conductive polymer resin having an average particle diameter of 60 nm or less, it is possible to prevent electrification of the edge portion and the center portion of the antistatic polyester film It is possible to produce an antistatic polyester film having a film thickness variation of less than or equal to 10%.

The particle size of the conductive polymer resin of the present invention is a small particle size of 20% or less of that of a conventional conductive polymer resin and can be used without limitation in conventional means capable of finely dividing the particles physically. You can also use commercial products that meet.

Further, by applying the conductive polymer resin in the form of an aqueous dispersion in which fine particles having an average particle size of 60 nm or less are uniformly dispersed, it is possible to reduce the difference in coating thickness between the film widths during the production of the film by the inline coating method, The antistatic performance deviation can be minimized.

More specifically, in the production of a film by an in-line coating method, a coating process is performed immediately before the first stretching (longitudinal stretching) and the second stretching (transverse stretching), wherein the stretching stress of the center portion and the edge portion in the transverse stretching is different Therefore, a physical property deviation occurs at each position by transverse stretching.

Generally, the edge portion is higher in elongation stress than the central portion, and the coating thickness of the edge portion is thinner. The antistatic property deviation between the center portion and the edge portion of the final film is 30% or more. It is possible to obtain an antistatic polyester film having a surface resistance value of 10 ⁷ ? / Sq at the center portion of the film and a surface resistivity value of 10 ¹⁰ ? / Sq at the edge portion and having a deviation of antistatic property between the central portion and the edge portion of 30% There is a problem in productivity and yield deterioration due to difficulty in production of the product. Orientation irregularity in the lateral direction also occurs for the same reason.

Thus, in the case of the antistatic coating composition of the present invention, when a coating composition in which a conductive polymer resin having an average particle diameter of 60 nm or less is uniformly dispersed is applied, even if elongation is increased due to improvement in dispersibility, The deviation of the anti-blocking property is minimized to 10% or less so that the conventional problems can be solved. In addition, the transverse stretching conditions were optimized to uniformly attain the target orientation angle.

The conductive polymer resin contained in the antistatic coating composition of the present invention is preferably an aqueous dispersion containing a polyanion and a polythiophene or a water dispersion containing a polyanion and a polythiophene derivative use.

In the above description, the polyanion is an acidic polymer, such as a polymeric carboxylic acid or a polymeric sulfonic acid, or polyvinylsulfonic acid. Examples of the polymeric carboxylic acid include polyacrylic acid, polymethacrylic acid, and poly maleic acid, and examples of the polymeric sulfonic acid include polystyrene sulfonic acid and the like.

In the conductive polymer resin of the present invention, it is preferable that the polythiophene or the polythiophene derivative has an excessive amount of the polyanion by weight in terms of solid content, from the viewpoint of imparting conductivity. For example, when 1 wt% of the polythiophene or polythiophene derivative is used, the polyanion is preferably more than 1 wt%, and more preferably 5 wt% or less. More preferably in the range of 1 to 3% by weight. Thus, in the embodiment of the present invention, an aqueous dispersion containing 0.5% by weight of poly (3,4-ethylenedioxythiophene) and 0.8% by weight of polystyrene sulfonic acid (molecular weight Mn = 150,000) is used, but the present invention is not limited thereto.

To describe the polyurethane resin contained in the antistatic coating composition of the present invention, the polyurethane resin used in the present invention is added to the polyester film to increase the peeling force between the film surface and the tape.

Accordingly, the preferred polyurethane resin to be used in the present invention is an aqueous dispersion type resin which is composed of an anionic polyether polyurethane dispersion containing at least one functional group such as a hydroxyl group, an amine group, an alkyl group and a carboxyl group .

More specifically, the water-dispersible polyurethane resin is an anionic polyether polyurethane dispersion containing a hydroxyl group; The functional group of the repeating unit selected from the group consisting of allylamine, vinylamine, ethyleneamine, vinylpyridine, diethylaminoethyl methacrylate, diallyldimethylammonium chloride, methacryloyloxyethyltrimethylammonium sulfate, and combinations thereof An anionic polyether polyurethane dispersion containing an anion; Or anionic polyether polyurethane dispersions containing functional groups of repeating units selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, and combinations thereof.

On the other hand, the amount of the polyurethane resin to be added may be 100 to 1000 parts by weight of the polyurethane resin per 100 parts by weight of the conductive polymer resin. If the addition amount of the polyurethane resin is less than 100 parts by weight, the peeling force with the tape deteriorates and the function can not be exhibited. If the amount exceeds 1000 parts by weight, the peeling force of the tape is sufficiently secured but the antifouling performance and antistatic performance The problem of falling occurs.

The cross-linking agent used in the present invention is used to improve the solvent resistance and film performance of the antistatic layer and the polyester film by controlling the cross-linking density of the cross-linking agent contained in the antistatic coating composition of the present invention. At this time, as the preferable crosslinking agent component, any one or more resins selected from the group consisting of isocyanate-based, carbonylimide-based, oxazoline-based, epoxy-based and melamine-based resins can be used.

On the other hand, the amount of the crosslinking agent to be added may be 100 to 1000 parts by weight of the crosslinking agent resin per 100 parts by weight of the conductive polymer resin. If the amount of the cross-linking agent resin is less than 100 parts by weight, antistatic properties may not be exhibited, and the solvent resistance may be low to cause whitening. On the other hand, if it exceeds 1000 parts by weight, transparency is good, but antistatic properties may be difficult to develop.

In the antistatic coating composition, the fluororesin added to the present invention is added to the polyester film to improve the antifouling property and solvent resistance of the film.

Preferred examples of the fluororesin include tetrafluoroethylene, trifluoroethylene, fluorinated ethylene copolymer propylene, chlorotrifluoroethylene, ethyenetetrafluoroethylene copolymer, chlorotrifluoroethylene , Polytetrafluoroethylene copolymer, polyvinyl fluoride, and polyvinylidene fluoride.

At this time, the amount of the fluororesin to be added may be 10 to 100 parts by weight of the fluororesin, based on 100 parts by weight of the conductive polymer resin. If the addition amount of the fluororesin is less than 10 parts by weight, the antifouling property is lowered. On the other hand, if it exceeds 100 parts by weight, the transparency of the film, the peeling strength of the film and the antistatic performance may be deteriorated.

The antistatic coating composition of the present invention is added with a surfactant to improve the stability, wetting and leveling of the coating composition.

Therefore, by containing the acetylenic diol-based surfactant as the surfactant in the antistatic coating composition of the present invention, it is possible to maintain the main coating properties such as peeling force and antifouling property with the adhesive tape while realizing excellent wettability and coating leveling property, It is possible to provide an antistatic polyester film for optical use having a high yield.

The acetylenic diol-based surfactant used in the antistatic coating composition of the present invention is a compound represented by the following formula (1).

Formula 1

(Wherein, R _1, R ₄ is C ₃ ~ C ₁₀ alkyl group in straight or branched chain of, by halogen-substituted alkyl group, a vinyl group, an allyl group, an ethynyl group, a phenyl group, an aryl group, a halogen group, a C ₃ ~ C ₁₀ R ₂ and R ₃ are H or a C ₁ to C ₅ alkyl group, and m, n, p and q are each independently selected from the group consisting of 0 to 20 carbon atoms, It is an integer.)

Thus, in the examples of the present invention, as preferable compounds of the acetylenic diol-based surfactants, 2,5,8,11-tetramethyldodecyne-5,8-diol ethoxysilate (2,5,8,11-Tetramethyl 6 dodecyn-5,8 diol ethoxylate), but is not limited thereto.

That is, the acetylenic diol-based surfactant of the present invention may contain at least one selected from the group consisting of trifluoromethyl, methyl, vinyl, allyl, ethynyl, phenyl, aryl, halogen, An acetylenic diol surfactant containing at least one functional group selected from the group consisting of a carboxyl group can be used.

The acetylene diol surfactant is preferably added in an amount of 0.001 to 1 part by weight based on 100 parts by weight of the total antistatic coating composition. If the addition amount of the surfactant is less than 0.001 parts by weight, the wettability of the coating film is deteriorated. If the amount is more than 1 part by weight, fine bubbles in the coating composition cause coating appearance defects.

The antistatic coating composition of the present invention is preferably prepared so that the solid content is 0.5 to 10.0% by weight based on 100% by weight of the total coating composition, more preferably 1.0 to 5.0% . If the content of the solid content is less than 0.5% by weight, it is not sufficient to exhibit the coating film formation and antistatic function of the coating layer. If the content is more than 10.0% by weight, the transparency of the film is undesirably affected.

On the other hand, the solvent used in the antistatic coating composition is an aqueous coating liquid which is substantially water-based.

Further, for the purpose of improving the coatability and the transparency of the coating composition used in the present invention, it may contain an appropriate organic solvent to the extent that the effect of the present invention is not impaired. Preferred examples of the organic solvent include isopropyl alcohol , Butyl cellosolve, t-butyl cellosolve, ethyl cellosolve, acetone, ethanol, methanol and the like can be used.

However, when a large amount of an organic solvent is contained in the coating composition, there is a risk of explosion in the drying, stretching and heat treatment processes when the coating composition is applied to the in-line coating method. Therefore, the content thereof is preferably 10% by weight or less, more preferably 5% %.

That is, the above-mentioned antistatic coating composition contains a conductive polymer resin having an average particle diameter of 60 nm or less to increase the dispersibility to control the deviation of the antistatic property between the center portion and the edge portion of the film to 10% or less, And at the same time improving the solvent resistance and coating performance by controlling the crosslinking density by using a suitable crosslinking agent and improving the antifouling performance by adding the fluororesin. By controlling the composition to improve the wettability of the coating material.

Step 3: Two axes Stretching  Fabrication of polyester film

In the method for producing an antistatic polyester film of the present invention, Step 3 is a step for re-stretching a polyester film formed with an antistatic layer in Step 2 to prepare a biaxially stretched polyester film.

In this case, the stretching in the third step is performed in the direction perpendicular to the direction of film advance, which is the direction of uniaxial stretching, and the preferable stretching ratio is 5.0 to 6.0 times, whereby the full width directional alignment angle can be realized to be 10 degrees or less. At this time, if the stretching ratio is less than 5.0 times, it is difficult to realize the target orientation angle, and when it exceeds 6.0 times, the dimensional stability is deteriorated.

The biaxially stretched antistatic polyester film can be produced through heat treatment, curing and drying after the re-stretching process. The preferred heat treatment temperature for achieving a uniform low orientation angle is 180 to 220 ° C.

The thickness of the biaxially stretched antistatic polyester film produced from the production method of the present invention is 5 to 300 占 퐉, preferably 10 to 250 占 퐉, more preferably 30 to 75 占 퐉.

Accordingly, the present invention provides a polarizing plate protective film made of the biaxially stretched antistatic polyester film, which is made of a biaxially stretched antistatic polyester film having a full width directional angle of the film controlled to 10 degrees or less .

That is, from the above-described method for producing a biaxially stretched antistatic polyester film, an antistatic coating composition which can easily control a desired coating property is used, and particularly, because of the characteristics of a conductive polymer modified to a particle size of an average particle diameter of 60 nm or less, It is possible to provide an antistatic polyester film which has excellent antistatic property and has almost no width variation of antistatic property and is excellent in transparency, peelability with adhesive tape, antifouling performance and coating property, and no phenomenon of interference of light interference. At this time, the surface resistance value between the edge portion and the center portion of the biaxially stretched antistatic polyester film is within 10 ⁷ to ^{10 10} ? / Sq and the deviation of the antistatic performance is controlled to 10% or less.

Further, by controlling the orientation angle of the film full width at 10 degrees or less by optimizing the stretching ratio at the time of transverse start in the film production process, it is possible to carry out precise inspection by the Cross Ni-Coulomb method of the polarizing plate, An antistatic polyester film useful for a polarizing plate protective use can be produced. At this time, it is important that the alignment angle is controlled to 10 degrees or less. When the alignment angle exceeds 10 degrees, when the polarizing plate to which the antistatic polyester film is adhered is inspected by the Cross-Nicol method, the extinguished light is distorted, .

Such an antistatic polyester film is transparent and has a surface resistance within the range of 10 ⁷ to ^{10 10} Ω / sq in terms of characteristics of the coating surface, and can be any one selected from the group consisting of ethanol, methyl ethyl ketone, toluene and ethyl acetate The change in antistatic property before and after cleaning with a solvent is within 10 < ^{1 >} OMEGA, and since the initial surface resistance value is maintained, the antistatic agent of the antistatic layer does not drop or dissolve and has excellent solvent resistance.

In addition, the antistatic polyester film of the present invention has an excellent water repellent performance of 85 degrees or more in water contact angle, and satisfies peeling force of 230 g / 18 mm or more with a paper adhesive tape (3M # 244).

In addition, it satisfies 10 degrees or less in total width of the alignment angle, which is an important fabric characteristic that improves the visibility of the inspection by improving the non-uniformity of light interference.

The antistatic polyester film of the present invention which satisfies the above physical properties can meet a demanding level of physical properties required for high brightness and large size of an LCD screen in the future. In addition, the antistatic polyester film of the present invention can be applied to any optical display device selected from the group consisting of a liquid crystal display, a plasma display, a personal digital assistant, and a navigation device.

Hereinafter, the present invention will be described in more detail with reference to Examples.

The present invention is intended to more specifically illustrate the present invention, and the scope of the present invention is not limited to these embodiments.

< Example  1>

Step 1: One axis Stretching  Fabrication of polyester film

A polyethylene terephthalate pellet having an intrinsic viscosity of 0.625 dl / g containing 20 ppm of amorphous spherical silica particles having an average particle diameter of 2.5 μm was thoroughly dried at 160 ° C. for 7 hours by using a vacuum drier, An amorphous undrawn sheet was prepared through a die through an electrostatic application method. The amorphous undrawn sheet was heated again and stretched 2.9 times in the film advancing direction at 95 DEG C to prepare a uniaxially stretched polyester film.

Step 2: Antistatic layer formation

A conductive polymer resin having an average particle diameter distribution of 35 ± 5 nm (containing 0.5% by weight of poly 3,4-ethylenedioxythiophene and 0.8% by weight of polystyrene sulfonic acid (molecular weight Mn = 150,000) as a solid content on the surface of the film to be coated, , 200 parts by weight of a polyurethane resin (polyether polyurethane dispersion of an anion containing a hydroxy group), 200 parts by weight of an epoxy cross-linking agent (Esrix Technology Co., Ltd., CK-7B), 100 parts by weight of a fluororesin -30) and 0.1 parts by weight of 2,5,8,11-tetramethyl-6-dodecylethoxysilate as an acetylenic diol surfactant were mixed in water to prepare an antistatic coating solution. At this time, the solid content was set to be 1.5% by weight based on the total antistatic coating solution. The antistatic coating liquid was applied to the monoaxial polyester film prepared in the step 1 using a gravure roll to form an antistatic layer.

Step 3: Two axes Stretching  Fabrication of polyester film

After coating, the coating liquid applied at 105 to 140 캜 in the tenter section was dried, stretched 5.8 times in the direction perpendicular to the film advancing direction, and heat-treated at 200 캜 for 4 seconds to give a 38 탆 thick biaxially oriented antistatic polyester film .

< Example  2>

A biaxially stretched antistatic polyester film was produced in the same manner as in Example 1, except that the film was stretched 5.5 times in the direction perpendicular to the film advancing direction during biaxial stretching in Example 1 Respectively.

< Example  3>

A biaxially stretched antistatic polyester film was produced in the same manner as in Example 1, except that the film was stretched 5.2 times in the direction perpendicular to the traveling direction of the film during biaxial stretching in Example 1 Respectively.

< Comparative Example  1>

A biaxially stretched antistatic polyester film was produced in the same manner as in Example 1 except that the conductive polymer resin having an average particle diameter distribution of 100 ± 10 nm was contained.

< Comparative Example  2>

A biaxially stretched antistatic polyester film was produced in the same manner as in Example 1 except that in the step 3 of Example 1, the film was stretched 4.3 times in the direction perpendicular to the traveling direction of the film during biaxial stretching.

< Comparative Example  3>

A biaxially stretched antistatic polyester film was produced in the same manner as in Example 1, except that the film was stretched 4.0 times in the direction perpendicular to the traveling direction of the film during biaxial stretching in Example 1 above.

< Comparative Example  4>

A biaxially stretched antistatic polyester film was produced in the same manner as in Example 1, except that in the step 3 of Example 1, the film was stretched 3.7 times in the direction perpendicular to the traveling direction of the film during biaxial stretching.

< Comparative Example  5>

A biaxially stretched antistatic polyester film was produced in the same manner as in Example 1, except that in the step 3 of Example 1, the film was stretched 6.5 times in the direction perpendicular to the traveling direction of the film during biaxial stretching.

< Experimental Example  1>

The following properties of the antistatic polyester films prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were evaluated, and the results are shown in Table 1 and Table 2 .

1. Antistatic property

The samples were placed in an environment of 23 ° C and 50% RH using an antistatic meter (Mitsubishi, Model: MCP-T600), and the samples were placed on the edge and center of the film according to JIS K7194 The surface resistivity was measured.

2. Water contact angle

The water contact angle was measured by a sessile drop method using purified water obtained by distilling ion-exchange water using a contact angle meter (Kyowa Interface Science Co., Ltd., Model Dropmaster 300), and the water contact angle was measured 5 times at different positions And then an average value was taken.

3. Orientation angle

The end position in the width direction and the center position of the produced film were sampled at A4 size, and then the orientation angle was measured using MOA (molecular alignment system).

○: When the orientation angle is 10 degrees or less

?: When the orientation angle is 10 to 20 degrees

X: When the orientation angle is more than 20 degrees

4. Visual Inspection

The polarizing plate was laminated by using a pressure sensitive adhesive so that the main alignment axis of the produced film was parallel to the alignment axis of the polarizing film, and the other polarizing film beneath the polarizing film was overlapped such that the alignment axis was orthogonal to the polarizing film, Respectively. Thereafter, white light was irradiated to the lowermost portion, and 10 examinees were visually observed with each eye to evaluate visual inspection under Cross Nicol.

∘ if the testability was good, △ if the test was usable without problems at the time of actual use, and × if the testability was bad.

5. Visibility of Foreign Material

The polarizing plate was laminated by using a pressure sensitive adhesive so that the main alignment axis of the produced film was parallel to the alignment axis of the polarizing film, and the other polarizing film beneath the polarizing film was overlapped such that the alignment axis was orthogonal to the polarizing film, Respectively. Here, when the polarizing plate was manufactured, a black metal powder (foreign matter) having a size of 50 mu m was mixed between the pressure-sensitive adhesive and the polarizing film so as to have a density of 50 pieces / m &lt; ² &gt; Thereafter, white light was irradiated to the lowermost portion, and whether or not foreign substances mixed with the naked eye could be detected under cross nicol by each of 10 inspection workers was visually evaluated according to the following classification. In addition, at the time of measurement, evaluation was made using three portions of the obtained film at the center portion and both end portions. The foreign matter visibility of the film was evaluated through the result that the number of detected foreign matters was the largest.

Cross-Nicoll visibility classification criteria

&Amp; cir &amp;: The number of foreign substances detected was 40 pieces / m &lt; ^{2 &}

?: The number of detected foreign matter was 25 / m ² or more

X: The number of detected foreign matter is less than 25 / m ²

6. Ethanolicity

Ethanol was soaked in a cloth (BEMCOT, manufactured by ASAHI KASEI FIBER CO., LTD.), And the coated film surface was reciprocated 10 times under a load of 0.5 kg, and the state of the coated surface was evaluated according to the following criteria.

○: When the change of antistatic property is within the range of 10 ¹ Ω

?: The change in antistatic property was increased by 10 ¹ or more and less than 10 ¹¹ ?

X: When the change in antistatic property exceeds 10 ¹¹ Ω

7. Peel force with tape

A paper adhesive tape (3M tape No. 244, width: 18 mm) was applied to the coated surface of the film obtained above using a peel force measuring device (AR1000, manufactured by Chemical Machinery Co., Ltd.) under the atmosphere of 23 ° ± 3 and 50 ± 5% After being stuck, it is pressed once by reciprocating with a rubber roller having a load of 2 kg, left for 1 hour, and peeled 180 degrees at a peeling speed of 0.3 MPM. At this time, the obtained peel force value was measured.

As can be seen from Tables 1 and 2, when the lateral draw ratio was lower than or equal to the conventional level, it was confirmed that the orientation angle, visual inspection property, and test visibility evaluation result were all poor. In particular, it was confirmed that even in the case where the same transverse stretching magnification was used, in Comparative Example 1 in which the conductive polymer resin having a large average particle diameter was included in the antistatic coating composition, a large surface resistance variation occurred between the edge portion and the center portion.

That is, the biaxially stretched antistatic polyester films prepared in Examples 1 to 3 were prepared by adding the conductive polymer resin to the antistatic coating composition in such a manner that the average particle diameter of the conductive polymer resin was 20% smaller than the normal average particle diameter, By containing the polymer resin, even if the stretching is increased due to the improvement of the dispersibility, the deviation of the antistatic property between the center portion and the edge portion can be minimized to 10% or less. Further, when the antistatic layer was formed and transversely stretched to 5.0 to 6.0 times, the alignment angle was controlled to 10 degrees or less, and excellent results were obtained in visual inspection and inspection visibility evaluation.

As described above,

First, the present invention provides an antistatic coating composition which is easy to control the coating properties by forming an antistatic layer on one side or both sides of a polyester film by an in-line coating method, Can be obtained by controlling the orientation angle of the full width within 10 degrees with almost no occurrence of the antistatic property deviation of the antistatic polyester film. The above-mentioned method of producing an antistatic polyester film is a method of producing antistatic polyester film, which is a main cause of a decrease in productivity and yield due to a difference in coating thickness between film widths due to transverse stretching process in inline coating, Respectively.

Second, the present invention relates to a biaxially stretched antistatic polyester film produced from a production process, which contains a conductive polymer resin having an average particle diameter of 60 nm or less in an antistatic coating composition to prevent the width variation of antistatic property and optimize the stretch ratio at the transverse direction Thereby controlling the alignment angle of the full width at 10 degrees or less, minimizing the non-uniformity of interference of light, and enabling accurate inspection with the Cross Ni-Coulomb method of the polarizing plate, which is useful as a polarizing plate protective film.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. .

Claims (8)

The polyester film was uniaxially stretched in the film advancing direction,
An antistatic coating composition containing a conductive polymer resin is coated on one side or both sides of the polyester film by an inline coating method to form an antistatic layer,
Wherein the polyester film on which the antistatic layer is formed is re-stretched at a stretching ratio of 5 to 6 times in a direction perpendicular to the film advancing direction and then heat-treated to obtain a biaxially oriented antistatic polyester film. The method for producing a biaxially oriented antistatic polyester film according to claim 1, wherein the antistatic coating composition contains a conductive polymer resin having an average particle diameter of 60 nm or less. The antistatic coating composition according to claim 1, wherein the antistatic coating composition comprises an anionic polyether polyurethane having at least one functional group selected from the group consisting of a hydroxyl group, an amine group, an alkyl group, and a carboxyl group per 100 parts by weight of the conductive polymer resin 100 to 1000 parts by weight of a water-dispersible polyurethane resin comprising a dispersion, 100 to 1000 parts by weight of a crosslinking agent selected from the group consisting of isocyanate, carbonylimide, oxazoline, epoxy and melamine, 10 to 100 parts by weight and acetylene diol surfactant in an amount of 0.001 to 1 part by weight. The method for producing a biaxially oriented antistatic polyester film according to claim 1, wherein the antistatic coating composition has a solid content of 0.5 to 10 wt%. The method for producing a biaxially oriented antistatic polyester film according to claim 1, wherein the heat treatment is performed at 180 to 220 ° C. A polarizer protective film produced from the production method of any one of claims 1 to 5 and comprising a biaxially stretched antistatic polyester film having a full-width orientation angle of the film controlled to 10 degrees or less. The polarizing plate protective film according to claim 6, wherein the biaxially stretched antistatic polyester film has a surface resistance value at an edge portion and a central portion of 10 ⁷ to ^{10 10} Ω / sq. The polarizer protective film according to claim 6, wherein the deviation of the antistatic property between the edge portion and the center portion of the biaxially stretched antistatic polyester film is 10% or less.