KR101364207B1 - Polyester film for protectiing polarizing plate - Google Patents

Abstract

The present invention relates to a polyester film for protecting a polarizing plate, and more particularly, there is no interference nonuniformity of light, and a precise inspection can be carried out in the inspection by the cross nicol method of the polarizing plate, and the transparency and tape peeling force are excellent but applied voltage Regardless of the present invention, the present invention relates to a polyester film for protecting a polarizing plate having excellent surface contamination prevention and antistatic properties. To this end, the polarizing plate protective polyester film according to the present invention comprises a polyester base film and a conductive polymer resin, a sulfonate polystyrene-maleic anhydride copolymer resin, a polyurethane resin, a crosslinking agent, and a fluorine resin on at least one side of the polyester base film. It includes an antistatic layer applied with an antistatic coating liquid comprising, preferably the antistatic coating liquid 100 to 200 parts by weight of the sulfonate polystyrene-maleic anhydride copolymer resin, the polyurethane resin with respect to 100 parts by weight of the conductive polymer resin 100 to 1000 parts by weight, 100 to 2000 parts by weight of the crosslinking agent and 30 to 300 parts by weight of the fluororesin.

Description

POLYESTER FILM FOR PROTECTIING POLARIZING PLATE}

The present invention relates to a polyester film for protecting a polarizing plate, and more particularly, there is no interference nonuniformity of light, and a precise inspection can be carried out in the inspection by the cross nicol method of the polarizing plate, and the transparency and tape peeling force are excellent but applied voltage Regardless of the present invention, the present invention relates to a polyester film for protecting a polarizing plate having excellent surface contamination prevention and antistatic properties.

In recent years, with the rapid spread of mobile phones and personal computers, the demand for liquid crystal displays (LCDs), which can be lighter, thinner, lower power consumption, and higher quality than conventional CRTs, has increased significantly. The growth of the technology is spectacular. As an example of a large screen of LCD, the use of LCD is increasing rapidly for the TV use of 40 inches or more recently. In a large-sized LCD, a bright large screen LCD is realized by increasing the brightness of a backlight assembled in the LCD, assembling a film for improving brightness into the backlight unit, and the like.

In the so-called large, high luminance type LCD, the luminance of the display screen tends to be further increased to improve visibility, but the small bright spots present in the display are often a problem, and polarizers and phase shifts incorporated into the display are often a problem. In a constituent member such as a plate or a retardation polarizing plate, fine foreign matter which is not a problem in the conventional low luminance type LCD is starting to become a problem. Therefore, it is important to prevent the incorporation of foreign matters in the manufacturing process and to improve inspection accuracy, which can be reliably recognized as a defect even if foreign matters are mixed.

First, in order to prevent the incorporation of foreign substances such as dust generated in the manufacturing process, the polyester protective film being used is subjected to an antistatic coating on one side or both sides. However, when the surface resistance is measured by applying various applied voltages to the existing polyester protective film, the surface resistance rapidly increases as the applied voltage is increased, especially the antistatic property is deteriorated, especially at 500 V or higher, and the dust adhesion prevention function is actually lost. Therefore, a problem that often causes foreign material defects occurs.

In addition, the cross nicol method, which is a method of inspecting and filtering out defects such as foreign substances, is generally performed by visual inspection. However, in the polarizing plate used for large TVs of 40 inches or more in recent years, the automatic inspection using the cross nicol method is performed. Inspection by the apparatus is also performed. In this cross nicol method, two polarizing plates are quenched by orthogonal to their orientation axes and defects or defects appear as bright spots. Especially, the cross nicol method is a cross nicol method. When the automatic inspection is carried out, 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 matting state is broken and light leakage occurs, resulting in foreign matter or defects. There is a problem that a defect often becomes easy to miss.

The present invention has been made to solve the above problems, the object of the present invention is not the interference non-uniformity of light, it is possible to perform a precise inspection in the inspection by the cross nicol method of the polarizing plate, transparency and tape peeling force It is an object of the present invention to provide a polyester film for protecting a polarizing plate having excellent surface contamination prevention and antistatic properties regardless of applied voltage.

These and other objects and advantages of the present invention will become more apparent from the following description of a preferred embodiment thereof.

The object is to charge the at least one surface of the polyester base film and the polyester base film with an antistatic coating solution containing a conductive polymer resin, sulfonate polystyrene-maleic anhydride copolymer resin, polyurethane resin, crosslinking agent and fluorine resin It is achieved by the polyester film for polarizing plate protections containing the prevention layer.

Here, the antistatic coating liquid is 100 to 200 parts by weight of the sulfonate polystyrene-maleic anhydride copolymer resin, 100 to 1000 parts by weight of the polyurethane resin, 100 to 2000 parts by weight of the crosslinking agent, and 100 parts by weight of the conductive polymer resin. It characterized in that it comprises 30 to 300 parts by weight of the fluororesin.

Preferably, the conductive polymer resin is an aqueous dispersion of anionic polymer and polythiophene or an aqueous dispersion of anionic polymer and polythiophene derivative.

Preferably, the sulfonate polystyrene-maleic anhydride copolymer resin is an anionic polymer type antistatic agent represented by the following structural formula 1 having a water dispersion type and having a weight average molecular weight of 1,000 to 500,000,

(Structural formula 1)

Wherein the ratio of n: m is in the range from 2: 8 to 8: 2, and X is Na ⁺ , H ⁺ or NH ₄ ⁺ .

Preferably, the polyurethane resin is a water dispersion type, characterized in that the resin containing at least one functional group selected from hydroxyl group, amine group, carboxyl group, isocyanate group, epoxy group and oxazoline group.

Preferably, the crosslinking agent is at least one compound selected from the group consisting of isocyanate, carbonylimide, oxazoline, melamine and aziridine.

Preferably, the fluorine resin is characterized in that tetrafluoroethylene.

Preferably, the antistatic coating liquid is characterized in that the solid content of 0.5 to 10% by weight.

Preferably, the antistatic coating solution is characterized in that the coating on at least one side of the polyester base film by the in-line coating method.

Preferably, the polyester base film has an angular range of the main orientation axis in the width direction of the film within 10 degrees, a refractive index in the direction perpendicular to the main orientation axis in the film plane direction is 1.6400 or less, perpendicular to the main orientation direction The birefringence, which is the difference in refractive index in the direction, is 0.050 or more.

More preferably, the polarizing plate protective polyester film has a contact angle of water to the coating layer of 80 degrees or more, a surface resistance value of 9.9 X 10 ⁹ Ω / sq or less, and has a tape peeling force of 300 g / in or more do.

Preferably, the polarizing plate protective polyester film is characterized in that the heat shrinkage in the width direction and the longitudinal direction is 3% or less, respectively, under hot air drying conditions at 150 ° C. for 30 minutes.

Preferably, the polarizing plate protective polyester film satisfies the following equation 1,

(1)

a ≤ b * 30

Here, "b" is the luminance value measured in the state orthogonal to the two sheets of polarizing plate, "a" is the polarizing plate protective polyester film so that the main alignment axis between the two orthogonal polarizing plate and one alignment axis of the polarizing plate It is characterized in that the luminance value measured in the state.

According to the present invention, there is no interference nonuniformity of light, and precise inspection can be carried out in the inspection by the cross nicol method of the polarizing plate. It has an excellent effect.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples of the present invention. It will be apparent to those skilled in the art that these embodiments are provided by way of illustration only for the purpose of more particularly illustrating the present invention and that the scope of the present invention is not limited by these embodiments .

The polyester film for protecting a polarizing plate according to the present invention comprises a polyester base film and a conductive polymer resin, a sulfonate polystyrene-maleic anhydride copolymer resin, a polyurethane resin, a crosslinking agent, and a fluorine resin on at least one side of the polyester base film. It characterized in that it comprises an antistatic layer applied with an antistatic coating solution.

The polyester base film used was a composition polymerized with a dicarboxylic acid first component and an ethylene glycol diol component. As the dicarboxylic acid component constituting the polyester, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid and Aliphatic dicarboxylic acids and aliphatic dicarboxylic acids such as aromatic dicarboxylic acids such as orthophthalic acid, adipic acid, azaline acid and sebacic acid and decane dicarboxylic acid; and the like, and are also used in the present invention. Aliphatic diols, such as ethylene glycol, propanediol, butanediol, neophenglycol, and hexanediol, aliphatic diols, such as 1, 4- cyclohexane dimethanol, aromatic diol, etc. are mentioned as a diol component which makes polyester to become. As the composition, a polyester chip can be produced using a known technique such as TPA method or DMT method. The synthesized polyester chip may be molded into a film by the following manufacturing method, but is not limited to this manufacturing method.

First, the polyester chip synthesized in the above composition is dried using a dryer or vacuum dryer such as a hopper dryer or paddle dryer, melted at a temperature of 200 to 300 ° C, and extruded into a film form. In extrusion, conventional methods, such as a T-die method and a tubular method, are used. Rapid cooling after extrusion yields an unstretched film. The unstretched film thus obtained is at a temperature of at least Tg and less than Tg + 15 ° C., preferably at a ratio of 2.0 to 5.0 times in the longitudinal direction at a temperature of at least Tg and less than Tg + 10 ° C., preferably at a ratio of 2.5 to 4.5 times. Stretch The film stretched in the longitudinal direction is stretched at a ratio of 3.0 to 7.0 times, preferably 3.5 to 6.5, in the transverse direction. In order to impart heat shrinkage stability and thermal stability to the stretched film, a polyester film may be obtained by heat treatment at a temperature of 200 to 250 ° C.

In the polyester base film according to the present invention, it is important that the inclination (orientation angle) of the orientation major axis in the width direction is within 10 degrees. When the orientation angle exceeds 10 degrees, when the polarizing plate is inspected by the cross nicol method, light leakage may occur due to the distortion of the alignment axis of the polarizing plate and the alignment axis of the polyester film, which may cause a problem in the quality inspection of the polarizing plate.

In addition, the polyester base film according to the present invention preferably has a refractive index of 1.6400 or less in the direction perpendicular to the in-plane direction of the film with respect to the main orientation axis. When the refractive index exceeds 1.6400, the variation of the film orientation angle tends to be large, and it acts as an obstacle during cross nicol inspection of the polarizing plate. Moreover, it is preferable that birefringence (difference of the refractive index of a main orientation direction and a perpendicular direction) of the said polyester base film is 0.050 or more. If it is less than 0.050, two polarizer cross nicol test may have a high gloss, which may cause a failure of the test, so that foreign matters or defects may be omitted.

On the other hand, in order to improve the transparency of the base film, it can be composed of a laminated film of two or more layers, a method of blending particles only to the surface layer can also be preferably used. The surface layer in this case means at least one layer inside and outside, and of course, particles can be blended into both layers on the surface. That is, the base film according to the present invention may be made of a single layer or multiple layers.

In addition, the polarizing plate protective polyester film according to the present invention is coated with an antistatic coating solution containing a conductive polymer and sulfonate polystyrene-maleic anhydride copolymer resin, a polyurethane resin, a crosslinking agent and a fluorine resin on one or both sides of the polyester base film. It is composed of an antistatic layer and provides a polyester film for protecting a polarizing plate excellent in antistatic properties under transparency, solvent resistance, water repellent antifouling and various applied voltages by coating and drying the coating solution on the surface of the polyester base film.

Next, the configuration of the antistatic coating solution will be described in detail.

(A) conductive polymer

The conductive polymer resin included in the antistatic coating solution preferably uses an aqueous dispersion of anionic polymer (polyanion) and polythiophene or an aqueous dispersion of anionic polymer and polythiophene derivative to impart antistatic properties. . The anionic polymer is an acidic polymer and includes high molecular carboxylic acid or high molecular sulfonic acid, polyvinyl sulfonic acid and the like. The polymer carboxylic acid includes polyacrylic, polymethacrylic acid, polymaleic acid, and the like, and the polymer sulfonic acid includes polystyrene sulfonic acid. It is preferable to make the anionic polymer excessively present in the solid content weight ratio with respect to the polythiophene or the polythiophene derivative from the viewpoint of conductivity, and with respect to 1 weight% of the polythiophene or the polythiophene derivative, the anionic polymer is 1 weight. More than%, 5% by weight or less is preferred. More preferably, they are 1 weight% or more and 5 weight% or less. On the other hand, in the present invention, it is preferable to use an aqueous dispersion of a polymer containing 0.5% by weight of poly (3,4-ethylenedioxythiophene) and 0.8% by weight of polystyrenesulfonic acid (molecular weight Mn = 150,000).

(B) sulfonate polystyrene-maleic anhydride copolymer resin

The sulfonate polystyrene-maleic anhydride copolymer resin included in the antistatic coating solution is used to maintain the antistatic property even under high applied voltage. Preferably, the sulfonate polystyrene-maleic anhydride copolymer resin is an aqueous dispersion type. It has a weight average molecular weight of 1,000 to 500,000 and the ratio of n: m ranges from 2: 8 to 8: 2: 2, X is an anionic polymer type antistatic agent represented by the following structural formula 1 is Na ⁺ , H ⁺ or NH ₄ ⁺ .

(Structural formula 1)

On the other hand, the amount of sulfonate polystyrene-maleic anhydride copolymer resin to be added is preferably added to 100 to 200 parts by weight of sulfonate polystyrene-maleic anhydride copolymer resin with respect to 100 parts by weight of the conductive polymer resin. If the addition amount of the sulfonate polystyrene-maleic anhydride copolymer resin is less than 100 parts by weight, it is difficult to ensure sufficient antistatic performance under high applied voltage, and if it exceeds 200 parts by weight, the antistatic performance is sufficiently secured, but the water contact angle is lowered, such as foreign matters. The problem arises that it becomes easy to be exposed to pollution prevention.

(C) polyurethane resin

The polyurethane resin contained in the antistatic coating solution is used to increase the tape peeling force of the polyester film, preferably the polyurethane resin is a water dispersion type, hydroxyl group, amine group, carboxyl group, isocyanate group Resin which at least 1 type or more of functional groups, such as an epoxy group and an oxazoline group, is contained is used. On the other hand, it is preferable that the quantity of the polyurethane resin added adds 100-1000 weight part of polyurethane resins with respect to 100 weight part of said conductive polymer resins. When the amount of the polyurethane resin added is less than 100 parts by weight, the tape peeling force is lowered to express the function. When the amount of the polyurethane resin is more than 1000 parts by weight, the tape peeling force is sufficiently secured, but the antistatic performance is lowered or the water contact angle is lowered. The problem which becomes easy to be exposed to pollution prevention, etc. arises.

(D) crosslinking agent

The crosslinking agent included in the antistatic coating solution is used to improve the solvent resistance between the antistatic layer, which is an application layer, and the polyester film, which is a base film, and is preferably an isocyanate compound, a carbonylimide compound, an aziridine compound, or an oxa. At least one compound selected from the group consisting of sleepy compounds and melamine compounds is used. It is preferable to use 100-2000 weight part of crosslinking agent resin with respect to the quantity added with respect to 100 weight part of said conductive polymer resins. If less than 100 parts by weight of the solvent resistance of the coating layer may be lowered, if more than 2000 parts by weight may cause a problem of lowering the antistatic properties.

(E) Fluoropolymer

The fluorine resin contained in the antistatic coating solution is added to improve the antifouling property, water contact angle and solvent resistance of the coating layer, and may be polytetrafluoroethylene, tetrafluoroethylene, perfluoroalkyl vinyl ether copolymer, trifluoroethylene, 6 Propylene fluoride copolymers, tetrafluoroethylene copolymers, trifluoroethylene copolymers, polyvinyl fluorides, polyvinylidene fluorides, and the like, preferably tetrafluoroethylene. On the other hand, it is preferable that 30-300 weight part of fluororesins is added with respect to 100 weight part of said conductive polymer resins of the quantity of the fluororesin added. If the added amount of the fluororesin is less than 30 parts by weight, the antifouling property is lowered, and if it exceeds 300 parts by weight, the transparency of the film may be lowered and the antistatic performance may deteriorate.

In addition, the antistatic coating liquid of the polarizing plate protective polyester film according to the present invention is preferably prepared so that the content of solids is 0.5 to 10% by weight with respect to 100% by weight of the total coating liquid, more preferably the content of solids is 1.0 ~ 5.0 wt%. If the content of the solid content is less than 0.5% by weight, it is not sufficient for the film formation of the coating layer and the expression of the antistatic function. If the content is more than 10% by weight, the transparency of the film is deteriorated and coating defects are generated.

On the other hand, the solvent used in the antistatic coating liquid is preferably an aqueous coating liquid mainly composed of water. The coating liquid used for this invention may contain the suitable organic solvent in the range which does not impair the effect of this invention for the purpose of the improvement of applicability | paintability, transparency improvement, etc .. For example, isopropyl alcohol, butyl cellosolve, t-butyl cellosolve, ethyl cellosolve, acetone, ethanol, methanol and the like can be used. However, when a large amount of organic solvent is contained in the coating liquid, when applied to the in-line coating method, there is a risk of explosion in the drying, stretching and heat treatment processes, and the content thereof is 10% by weight or less in the coating liquid, preferably 5% by weight. It is as follows.

Therefore, according to the present invention, the conductive polymer resin, the sulfonate polystyrene-maleic anhydride copolymer resin, the polyurethane resin, the crosslinking agent, and the antistatic coating solution mixed with the fluororesin include 0.5 to 10.0% by weight of a polyester base film as a solid content. It is applied to one or both sides of the film and dried to provide a polarizing plate protective polyester film having an antistatic function even under water repellent antifouling properties and high applied voltage.

The polarizing plate protective polyester film according to the present invention is transparent, but the contact angle of water to the coating layer exhibits a water repellency of 80 degrees or more, and the surface resistance value is 9.9X10 ⁹ Ω / sq or less even under a 1000 V applied voltage, and 300g / in tape peeling or more. It is characterized by having a force.

In addition, the polyester film for protecting the polarizing plate according to the present invention is characterized in that the thermal shrinkage in the width direction and the longitudinal direction is 3% or less, respectively, under hot air drying conditions at 150 ° C. for 30 minutes.

In addition, the polarizing plate protective polyester film according to the present invention satisfies the following equation 1,

(1)

a ≤ b * 30

Here, "b" is the luminance value measured in the state orthogonal to the two sheets of polarizing plate, "a" is the polarizing plate protective polyester film so that the main alignment axis between the two orthogonal polarizing plate and one alignment axis of the polarizing plate It is characterized in that the luminance value measured in the state.

Hereinafter, the structure and effect of the present invention will be described in more detail with reference to examples and comparative examples. However, this embodiment is intended to explain the present invention more specifically, and the scope of the present invention is not limited to these embodiments.

[Production of Polyester (A)]

100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol were used as starting materials, and magnesium acetate salt was added as a catalyst to the reactor, the reaction starting temperature was set at 150 ° C, and the reaction temperature was gradually increased with distillation of methanol, After 3 hours, it was 230 ° C. After 4 hours, the transesterification reaction was substantially terminated. Ethyl acid phosphate was added to the reaction mixture, which was then transferred to a polycondensation tank, followed by addition of 0.04 parts by weight of antimony trioxide, followed by polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C to 280 ° C. On the other hand, the pressure gradually decreased from the normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at the point corresponding to the intrinsic viscosity of 0.625 dl / g due to the change in the stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester chip. The intrinsic viscosity of this polyester was 0.625 dl / g.

[Production of Polyester (B)]

In the production method of the polyester (A), after the addition of ethyl acid phosphate, the ethylene glycol slurry of the synthetic elastic calcium particles having an average particle size of 0.8 µm and a particle size distribution value of 1.6 is made to have a content of 1% by weight of the polyester of the particles. The polyester (B) was obtained using the method similar to the manufacturing method of polyester (A) except having added. Obtained polyester (B) was intrinsic viscosity 0.625 dl / g.

[Examples 1-3]

The raw material mixed with the said polyester (A) and (B) chip in the ratio shown in following Tables 1 and 2 is used as a raw material of a layer, and the raw material of 100% of polyester (A) chip is used as a b layer, After supplying in two extruders so that it may become a: b: a three-layer laminated film, and melt-extruding at 290 degreeC, the surface temperature was 40 using the electrostatic application adhesion method which made a layer an outer layer and b layer an inner layer. It cooled and solidified on the cooling roll set to ° C, and obtained an unstretched sheet. Then, the film was stretched in the longitudinal direction as shown in Tables 1 and 2 below, and after the corona discharge treatment on the cross section of the film, the coating solution prepared as in Tables 1 and 2 was applied using the # 5 Mayer bar. And lateral stretch temperature, the lateral stretch ratio, and heat processing temperature were implemented on the conditions similar to Table 1, 2 below, and the polyester film of width 1,000mm was obtained, respectively. The total thickness of the obtained film was 38 μm, and the thickness of the a: b: a layer was 2 μm: 34 μm: 2 μm.

[Comparative Example 1-7]

The raw material mixed with the said polyester (A) and (B) chip in the ratio as shown in following Tables 2-5 is used as a raw material of a layer, and the raw material of 100% of polyester (A) chip is b layer, After supplying in two extruders so that it may become a: b: a three-layer laminated film, and melt-extruding at 290 degreeC, the surface temperature was 40 using the electrostatic application adhesion method which made a layer an outer layer and b layer an inner layer. It cooled and solidified on the cooling roll set to ° C, and obtained an unstretched sheet. Then, the film was stretched in the longitudinal direction as shown in Tables 2 to 5 below, and after the corona discharge treatment on the cross section of the film, a coating solution prepared as in Tables 2 to 5 was applied using # 5 Meyer Bar. And lateral stretch temperature, the lateral stretch ratio, and heat processing temperature were implemented on conditions like the following Tables 2-5, and the polyester film of width 1,000mm was obtained, respectively. The total thickness of the obtained film was 38 μm, and the thickness of the a: b: a layer was 2 μm: 34 μm: 2 μm.

Meanwhile, in Tables 1 to 5, the unit of temperature is "° C".

Item Example 1 Example 2 Raw material condition a-layer raw material blending ratio (wt%) (A) :( B) = 95: 5 (A) :( B) = 90: 10 Film forming conditions Longitudinal drawing ratio 2.8 2.9 Longitudinal stretching temperature 90 90 Lateral draw ratio 5.4 5.2 Transverse stretching temperature 120 120 Heat treatment temperature 200 200 Coating solution
(Parts by weight) Conductive Polymer Resin
Bayer, Baytron P 100 100 Sulfonate polystyrene-maleic anhydride
Copolymer resin
(Alco Chemical, VERSA-TL) 100 150 Polyurethane resin
(Sytec, Daotan VTW1236) 200 400 Melamine cross-linking (Cytec, CYMEL385) 200 300 Fluorine compound (3M company, FC-4430) 100 150 Surfactants
(Ilshin Chemical Industry, EXP4051) 2 2 Results Orientation Angle (degrees) ○ ○ nβ ○ ○ △ n ○ ○ Surface resistance (Ω / sq) 10V 10 ^ 6 10 ^ 6 100 V 10 ^ 9 10 ^ 9 500 V 10 ^ 9 10 ^ 9 1000 V 10 ^ 9 10 ^ 9 Water contact angle (degrees) 101 106 Tape Peeling Force (g / in) 388 351 Visual inspection ○ ○

Item Example 3 Comparative Example 1 Raw material condition a-layer raw material blending ratio (wt%) (A) :( B) = 80: 20 (A) :( B) = 95: 5 Film forming conditions Longitudinal drawing ratio 2.9 3.1 Longitudinal stretching temperature 90 90 Lateral draw ratio 5.0 4.0 Transverse stretching temperature 120 120 Heat treatment temperature 200 240 Coating solution
(Parts by weight) Conductive Polymer Resin
Bayer, Baytron P 100 100 Sulfonate Polystyrene-Maleic Anhydride Copolymer Resin
(Alco Chemical, VERSA-TL) 200 100 Polyurethane resin
(Sytec, Daotan VTW1236) 300 200 Melamine family
(Cytec, CYMEL385) 500 200 Fluorine compound (3M company, FC-4430) 100 100 Surfactants
(Ilshin Chemical Industry, EXP4051) 2 2 Results Orientation Angle (degrees) ○ × nβ ○ × △ n ○ × Surface resistance (Ω / sq) 10V 10 ^ 6 10 ^ 6 100 V 10 ^ 9 10 ^ 9 500 V 10 ^ 9 10 ^ 9 1000 V 10 ^ 9 10 ^ 9 Water contact angle (degrees) 98 101 Tape Peeling Force (g / in) 438 388 Visual inspection ○ ×

Item Comparative Example 2 Comparative Example 3 Raw material condition a-layer raw material blending ratio (wt%) (A) :( B) = 95: 5 (A) :( B) = 95: 5 Film forming conditions Longitudinal drawing ratio 3.3 3.3 Longitudinal stretching temperature 90 90 Lateral draw ratio 3.3 3.3 Transverse stretching temperature 120 120 Heat treatment temperature 240 240 Coating solution
(Parts by weight) Conductive Polymer Resin
Bayer, Baytron P 100 100 Sulfonate polystyrene-maleic anhydride
Copolymerized resin (alcochemical company, VERSA-TL) 150 200 Polyurethane resin
(Sytec, Daotan VTW1236) 400 300 Melamine cross-linking (Cytec, CYMEL385) 300 500 Fluorine compound (3M company, FC-4430) 150 50 Surfactant (Ilshin Chemical Co., EXP4051) 2 2 Results Orientation Angle (degrees) × × nβ × × △ n × × Surface resistance (Ω / sq) 10V 10 ^ 6 10 ^ 6 100 V 10 ^ 9 10 ^ 9 500 V 10 ^ 9 10 ^ 9 1000 V 10 ^ 9 10 ^ 9 Water contact angle (degrees) 106 98 Tape Peeling Force (g / in) 351 438 Visual inspection × ×

Item Comparative Example 4 Comparative Example 5 Raw material condition a-layer raw material blending ratio (wt%) (A) :( B) = 95: 5 (A) :( B) = 90: 10 Film forming conditions Longitudinal drawing ratio 3.1 3.4 Longitudinal stretching temperature 90 90 Lateral draw ratio 3.5 3.6 Transverse stretching temperature 120 120 Heat treatment temperature 240 240 Coating solution
(Parts by weight) Conductive Polymer Resin
Bayer, Baytron P 100 100 Sulfonate polystyrene-maleic anhydride
Copolymer resin
(Alco Chemical, VERSA-TL) 0 400 Polyurethane resin
(Sytec, Daotan VTW1236) 100 100 Melamine cross-linking (Cytec, CYMEL385) 200 200 Fluorine compound (3M company, FC-4430) 100 100 Surfactants
(Ilshin Chemical Industry, EXP4051) 2 2 Results Orientation Angle (degrees) × × nβ × × △ n × × Surface resistance (Ω / sq) 10V 10 ^ 6 10 ^ 6 100 V 10 ^ 9 10 ^ 9 500 V 10 ^ 12 10 ^ 9 1000 V 10 ^ 13 10 ^ 9 Water contact angle (degrees) 93 63 Tape Peeling Force (g / in) 378 396 Visual inspection × ×

Item Comparative Example 6 Comparative Example 7 Raw material condition a-layer raw material blending ratio (wt%) (A) :( B) = 95: 5 (A) :( B) = 90: 10 Film forming conditions Longitudinal drawing ratio 2.8 2.9 Longitudinal stretching temperature 90 90 Lateral draw ratio 5.4 5.2 Transverse stretching temperature 120 120 Heat treatment temperature 200 200 Coating solution
(Parts by weight) Conductive Polymer Resin
Bayer, Baytron P 100 100 Sulfonate polystyrene-maleic anhydride
Copolymer resin
(Alco Chemical, VERSA-TL) 50 250 Polyurethane resin
(Sytec, Daotan VTW1236) 100 100 Melamine cross-linking (Cytec, CYMEL385) 200 200 Fluorine compound (3M company, FC-4430) 100 100 Surfactants
(Ilshin Chemical Industry, EXP4051) 2 2 Results Orientation Angle (degrees) ○ ○ nβ ○ ○ △ n ○ ○ Surface resistance (Ω / sq) 10V 10 ^ 6 10 ^ 6 100 V 10 ^ 9 10 ^ 9 500 V 10 ^ 11 10 ^ 9 1000 V 10 ^ 12 10 ^ 9 Water contact angle (degrees) 93 75 Tape Peeling Force (g / in) 375 395 Visual inspection ○ ○

Hereinafter, the characteristic evaluation method of the polyester film for polarizing plate protection which concerns on an Example and a comparative example is demonstrated in detail. The results of the characteristic evaluation by the following characteristic evaluation method are described in Tables 1 to 4 above.

(1) Intrinsic viscosity measurement of polyester

After precisely weighing 1 g of polyester, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added to dissolve and measured at 30 ° C.

(2) Orientation angle

After sampling the end position and center position of the width direction of the produced film to A4 size, the orientation angle was measured using MOA (molecular orientation).

(Circle): Orientation angle is 10 degrees or less

Ⅹ: orientation angle is greater than 10 degrees

(3) perpendicular refractive index of the film main alignment axis (nβ)

After sampling the end position and center position in the width direction of the manufactured film in A4 size, using an Abbe refractometer manufactured by Atago Optical Co., Ltd., the refractive index in the direction perpendicular to the main alignment axis in the film plane was measured to obtain an average value. It was.

○: nβ is 1.6400 or less

Ⅹ: nβ is greater than 1.6400

(4) birefringence

After sampling the end position and the center position in the width direction of the produced film in A4 size, using the Abbe refractometer manufactured by Atago Optical Co., Ltd., the refractive index (nx) in the film width direction by the visible light (λ = 589 nm) and its right angle direction It is an absolute value obtained by the following formula by the difference of refractive index ny of the following.

Δn = l (nx)-(ny) l

○: Δn is 0.050 or more

Ⅹ: Δn is less than 0.050

(5) water contact angle

On the coated surface of the produced film, using a contact angle measuring instrument (manufactured by Kyowa Interface Science), the ion-exchanged water was measured by distillation with purified water obtained by distillation, and the average value was taken after a total of five measurements. .

(6) surface resistance

On the coated surface of the produced film, using a surface resistance measuring instrument (manufactured by Mitsubishi Corporation), the sample was installed in an environment of a temperature of 23 ° C. and a relative humidity of 45%, and then in accordance with JIS K7149 under an applied voltage of 10 V, 100 V, 500 V, and 1000 V. The surface resistance was measured, and averaged after 5 measurements in total.

(7) tape peeling force

Using a peel force measuring instrument AR1000 (manufactured by Chem Instruments), Nitto Denko's tape NO.31B (thickness 25 µm, width 25 mm) was applied on the coated surface of the film under a temperature of 23 ° C. and a relative humidity of 45%. Then, after reciprocating and crimping with a rubber roller of 2 kg load once, it peels 180 degrees at a peeling speed of 0.3mpm. The peeling force value obtained at this time was measured.

(8) visual inspection

The sampled film was sampled in a size of 10 cm in width and then sandwiched between two polarizing plates having an orthogonal alignment axis. With the longitudinal direction of the biaxially stretched polyester film coinciding with the alignment axis of any one polarizer, the luminance was measured at nine intervals within a sample using a CA2000 luminance meter manufactured by Konica Minolta Co., Ltd., and the average value (a) was obtained. It was. Visual inspection property was evaluated as follows based on the brightness average value (b) measured in the state which orthogonally crossed two polarizing plates.

○: a≤b * 30

Ⅹ: a> 60

As described above, according to the polyester film for protecting a polarizing plate according to the present invention, there is no interference irregularity of light, and it is possible to perform precise inspection in the inspection by the cross nicol method of the polarizing plate, and to prevent surface contamination and charging regardless of applied voltage. It can be confirmed that there are effects such as excellent prevention characteristics.

As mentioned above, although this invention was demonstrated about embodiment considered to be the most preferable at this time, this invention is not limited to embodiment disclosed in this specification, and is contrary to the summary or idea of the invention grasped | ascertained from the Claim and the whole specification. Changes may be made without departing from the scope of the present invention, and they should be understood as being the technical scope of the present invention.

 The present invention enables a precise inspection in the cross nicol inspection of a polarizing plate for a large LCD TV of 40 inches or more, and provides a polyester film for protecting a polarizing plate having excellent antistatic properties even under surface contamination prevention and high applied voltage. It can be seen that the industrial value of the present invention is very high.

Claims (13)

In the polyester film for polarizing plate protection,
A polyester base film,
At least one surface of the polyester base film includes a conductive polymer resin, sulfonate polystyrene-maleic anhydride copolymer resin, an antistatic layer coated with an antistatic coating liquid containing a polyurethane resin, a crosslinking agent and a fluorine resin,
The antistatic coating solution is 100 to 200 parts by weight of the sulfonate polystyrene-maleic anhydride copolymer resin, 100 to 1000 parts by weight of the polyurethane resin, 100 to 2000 parts by weight of the crosslinking agent and the fluorine resin based on 100 parts by weight of the conductive polymer resin. It contains 30-300 weight part, The polyester film for polarizing plate protections. delete The method of claim 1,
The conductive polymer resin is an aqueous dispersion of an anionic polymer and polythiophene or an aqueous dispersion of anionic polymer and polythiophene derivative, polarizing plate protective polyester film. The method of claim 1,
The sulfonate polystyrene-maleic anhydride copolymer resin is an aqueous dispersion type, an anionic polymer type antistatic agent represented by the following structural formula 1 having a weight average molecular weight of 1,000 to 500,000,
(Formula 1)

Wherein the ratio of n: m is in the range of 2: 8 to 8: 2, and X is Na ⁺ , H ⁺ or NH ₄ ⁺ . The method of claim 1,
The polyurethane resin is a water dispersion type, characterized in that the resin containing at least one functional group selected from hydroxyl group, amine group, carboxyl group, isocyanate group, epoxy group and oxazoline group, polarizing plate protective polyester film. The method of claim 1,
The crosslinking agent is at least one compound selected from the group consisting of isocyanate, carbonylimide, oxazoline, melamine and aziridine, polyester film for polarizing plate protection. The method of claim 1,
The said fluororesin is tetrafluoroethylene, The polyester film for polarizing plate protections characterized by the above-mentioned. The method of claim 1,
The antistatic coating solution is characterized in that the solid content of 0.5 to 10% by weight, polarizing plate protective polyester film. The method of claim 1,
The antistatic coating liquid is coated on at least one side of the polyester base film by in-line coating method, polarizing plate protective polyester film. The method of claim 1,
The polyester base film has an angular range of the main orientation axis in the width direction of the film within 10 degrees, a refractive index in the direction perpendicular to the main orientation axis in the film plane direction is 1.6400 or less, and the refractive index in the direction perpendicular to the main orientation direction The birefringence which is a difference is 0.050 or more, The polyester film for polarizing plate protections characterized by the above-mentioned. 11. The method according to any one of claims 1 to 10,
The polarizing plate protective polyester film is a polarizing plate protective poly, characterized in that the contact angle of water to the coating layer is 80 degrees or more, the surface resistance value is 9.9 X 10 ⁹ Ω / sq or less, and has a tape peeling force of 300 g / in or more. Ester film. 11. The method according to any one of claims 1 to 10,
The polyester film for protecting the polarizing plate is a polyester film for protecting the polarizing plate, characterized in that the heat shrinkage in the width direction and the longitudinal direction is 3% or less, respectively, under hot air drying conditions at 150 ° C. for 30 minutes. 11. The method according to any one of claims 1 to 10,
The polarizing plate protective polyester film satisfies the following equation 1,
(1)
a ≤ b * 30
Here, "b" is the luminance value measured in the state orthogonal to the two sheets of polarizing plate, "a" is the polarizing plate protective polyester film so that the main alignment axis between the two orthogonal polarizing plate and one alignment axis of the polarizing plate It is a luminance value measured in the state which put it, The polyester film for polarizing plate protections characterized by the above-mentioned.