WO2014035185A1

WO2014035185A1 - Polyester film

Info

Publication number: WO2014035185A1
Application number: PCT/KR2013/007823
Authority: WO
Inventors: Mi-So Lim; Eun Hye Cho; Sang-Hyun Baek; Si Min Kim
Original assignee: Kolon Industries, Inc.
Priority date: 2012-08-31
Filing date: 2013-08-30
Publication date: 2014-03-06
Also published as: CN104603185B; TWI505934B; JP2015527460A; CN104603185A; JP6006419B2; TW201418024A

Abstract

Provided is a polyester film for shielding an oligomer through a primer layer, and more particularly, an oligomer blocking polyester film capable of blocking the oligomer from migrating and having a low haze changing rate to thereby be used as an optical use.

Description

Title of Invention: POLYESTER FILM Technical Field

[1] The present invention relates to a polyester film for shielding an oligomer through a primer layer, and more particularly, to an oligomer blocking polyester film capable of blocking the oligomer from migrating and having a low haze changing rate to thereby be used as an optical use.

Background Art

[2] An optical film, which is a film used as an optical member for a display, is used as an optical material of a liquid crystal display (LCD) back light unit (BLU) or used as an optical member for protecting surfaces of various displays such an LCD, a plasma display panel (PDP), a touch panel, or the like.

[3] In this optical film, excellent transparency and visibility are required, and a bi-axially stretched polyester film having excellent mechanical and electrical properties is used as a base film.

[4] In this bi-axially stretched polyester film, since surface hardness is low and abrasion resistance or scratch resistance is insufficient, surface damage may easily occur due to friction or contact with an object when the film is used as an optical member for various displays. Therefore, in order to prevent this damage, a hard coating layer is laminated on a film surface, and a primer coating layer is formed as an interlayer in order to improve close adhesion between the polyester film, that is, the base film and the hard coating layer.

[5] In this polyester film for a display, a quality problem associated with an oligomer has been generated. As an example of this quality problem, when heat is applied during a curing process after prism coating or diffusion coating in a post processing process of the polyester film, the oligomer is migrated in the polyester film, which causes a whitening phenomenon that a surface is changed to be white as shown in FIG. 1. In addition, as shown in FIG. 2, a diamond mark phenomenon that a diamond shaped pattern is formed by pressure of a diamond pattern roll used in a slitting process after manufacturing the polyester film may be generated.

[6] In the case in which the whitening phenomenon and diamond mark phenomenon as described above are generated, a film roll may be contaminated by the process, and optical properties of a final product may be deteriorated.

[7] In order to prevent the oligomer of the polyester film from migrating, an attempt to decrease an oligomer content at the time of polymerizing the polyester film has been conducted, but it was difficult to completely block the oligomer. [8] Further, in order to form a laminate film on a polyester film to control leakage of an oligomer, a laminate polyester film in which an average size of oligomer particles precipitated on the laminate film corresponds to ΙΟμνι² or less in terms of area and the number of oligomer particles is 100 or less within a visual field of lOO/ m lOOjwn, after heating the film to 150°C for 60 minutes, has been disclosed in Japanese Patent Laid- Open Publication No. 2007-253511 (December 4, 2007) as a polyester film having the laminate film on at least one surface thereof. The invention as described above was to control the leakage of the oligomer, but the leakage of the oligomer was not completely blocked.

Disclosure of Invention

Technical Problem

[9] An object of the present invention is to provide a polyester film capable of

completely blocking leakage of an oligomer.

[10] Another object of the present invention is to provide a polyester film capable of suppressing a haze from being increased due to surface leakage of an oligomer at the time of performing a heating-processing process, and having a haze change rate of 0.1% or less.

Solution to Problem

[11] In order to achieve the objects, the present inventors conducted studies and found that leakage of an oligomer may be blocked by using a specific water dispersion resin composition having an oligomer blocking property as a composition for forming a primer layer, and accordingly, a polyester film having a haze changing rate after heating was significantly low as compared to the related art may be manufactured, thereby completing the present invention.

[12] In addition, a cross-linking agent having a specific structure was used in the water dispersion resin composition, such that the oligomer blocking property may be further improved, and coating strength may be increased, thereby improving scratch resistance and solvent resistance. Therefore, appearance defects to be generated at the time of performing a post-processing process may be reduced. At the same time, the present inventors found that since a reaction rate may be further increased by using the cross- linking agent having a specific structure, a low reaction conversion rate of the cross- linking agent that may be generated due to characteristics of a film forming process may be increased, deterioration in the properties and a haze increase of the primer layer due to the unreacted and remaining cross-linking agent in the primer layer may be overcome, and the polyester film having a more improved oligomer blocking property due to a cross-linking degree increase, thereby completing the present invention. [13] In one general aspect, a polyester film includes a polyester base film and a primer layer formed by applying a water dispersion resin composition having an oligomer blocking property onto one surface or both surfaces of the polyester base film, wherein after it is maintained at 150°C for 60 minutes, a haze change rate (ΔΗ) according to the following Equation 1 is 0.1% or less.

[14] [Equation 1]

[16] (In Equation 1, H_f is a haze(%) of the film after being maintained at 150°C for 60 minutes, and H_: is a haze of the film before heating.)

[17] The primer layer may have a T_g of 60°C or more, a swelling ratio of 30% or less, a gel fraction of 95% or more, and a density of 1.3 to 1.4.

[18] After the polyester film is heated at 150°C for 60 minutes, the number of oligomer particles precipitated on a surface of the film may be 10 or less per 10000/zm² and an average size thereof may be 20 m² or less per 10000/mi².

[19] The water dispersion resin composition may include an acrylic resin in which a

glycidyl group containing radically polymerizable unsaturated monomer is

copolymerized and a water dispersion polyester-based resin as binder resins.

[20] In the water dispersion resin composition, a solid content weight ratio (A:B) of the acrylic resin in which the glycidyl group containing radically polymerizable unsaturated monomer is copolymerized to the water dispersion polyester-based resin may be 20-80: 80-20 weight%.

[21] The water dispersion resin composition may include the binder resin and water to have a solid content of 0.5 to 10 weight%.

[22] The water dispersion resin composition may further include 0.1 to 0.5 weight% of a silicone-based wetting agent.

[23] The water dispersion polyester-based resin may be a copolymer of a dicarboxylic acid component including a sulfonic acid alkali metal salt.

[24] The water dispersion polyester-based resin may contain diethylene glycol at a content of 20 to 80 mole% based on the total glycol component.

[25] The water dispersion polyester-based resin may contain the sulfonic acid alkali metal salt compound at a content of 6 to 20 mole% based on the total acid component.

[26] The acrylic resin may contain the glycidyl group containing radically polymerizable unsaturated monomer as a copolymerization monomer at a content of 20 to 80 mole% based on the total monomer component.

[27] The water dispersion resin composition may further include any one of the

compounds represented by Chemical Formulas 1 and 2 or a mixture thereof.

[28] [Chemical Formula 1]

[30] (In Chemical Formula 1, A, to A₃ are each independently chemical bonds or selected from (C1-C10) alkylene, and R, to R₃ are each independently selected from hydrogen and (Cl-ClO)alkyl.)

[31] [Chemical Formula 2]

(In Chemical Formula 2, A, to A₃ are each independently (Cl-ClO)alkylene, and B is a blocking agent.)

A content of any one of compounds represented by Chemical Formulas 1 and 2 or a mixture thereof may be 0.1 to 10 weight%.

The compound of Chemical Formula 1 may be the following compound.

The polyester base film may be a polyethylene terephthalate film.

The polyester base film may have a thickness of 25 to 250/ m.

The primer layer may have a dried coating thickness of 20 to 200nm.

The water dispersion resin composition may be applied by an in-line application method during a manufacturing process of the polyester film.

The polyester film as described above may be a film for a display. Advantageous Effects of Invention

[42] The polyester film according to the present invention may have optical properties suitable for an optical film, block an oligomer from being leaked, and prevent a haze from being increased.

Brief Description of Drawings

[43] FIG. 1 is a photograph showing a whitening phenomenon of a polyester film in

which an oligomer is leaked.

[44] FIG. 2 is a photograph showing a diamond mark phenomenon of a polyester film in which an oligomer is leaked.

[45] FIG. 3 shows a cross-section of a polyester film according to a first aspect of the present invention.

[46] FIG. 4 shows a cross-section of a polyester film according to a second aspect of the present invention.

[47] [Detailed Description of Main Elements]

[48] 10: Polyester base film

[49] 20: First primer layer

[50] 30: Second primer layer

Mode for the Invention

[51] Hereinafter, configurations of the present invention will be described in detail.

[52] A first aspect of the present invention relates to a polyester film including a polyester base film 10 and a primer layer 20 on one surface thereof as shown in FIG. 3, wherein after it is maintained at 150°C for 60 minutes, a haze change rate (ΔΗ) according to the following Equation 1 is 0.1 % or less.

[53] [Equation 1]

[55] (In Equation 1, H_f is a haze(%) of the film after being maintained at 150°C for 60 minutes, and H is a haze of the film before heating.)

[56] A second aspect of the present invention relates to a polyester film including a

polyester base film 10 and first and second primer layers 20 and 30 on both surfaces thereof, wherein after it is maintained at 150°C for 60 minutes, a haze change rate

(ΔΗ) according to the following Equation 1 is 0.1% or less.

[57] [Equation I]

[58] ΔΗ(%) = Η_Γ¾

[59] (In Equation 1, H_fis a haze(%) of the film after being maintained at 150°C for 60 minutes, and His a haze of the film before heating.)

[60] In the polyester film according to the present invention, the primer layer is formed by applying a water dispersion resin composition having an oligomer blocking property. The present invention was completed by finding that the oligomer blocking property may be significantly improved by using a specific resin as the water dispersion resin composition having the oligomer blocking property, such that the haze changing rate after heating is significantly improved to be 0.1% or less, more specifically, 0 to 0.1%, thereby completing the present invention. In addition, the present invention was completed by finding that in the case in which any one of the compounds represented by Chemical Formulas 1 and 2 or a mixture according to the present invention is further included in the water dispersion resin composition, the haze changing rate is further improved to be 0.05% or less, more specifically, 0 to 0.05%.

Further in the first and second aspects of the present invention, the primer layer may have a T_gof 60°C or more, a swelling ratio of 30% or less, a gel fraction of 95% or more, and a density of 1.3 to 1.4.

Furthermore, in the first and second aspects of the present invention, the polyester film may satisfy the following physical properties. After heating 150°C for 60 minutes, the number of oligomer particles precipitated on the surface of the film is 30 per lOOOOjUm² and an average size of the oligomer particle may be 20//m² per lOOOO^m². It may be confirmed that in the case of a film in which a migration degree of the oligomer is within the above-mentioned ranges, a diamond mark phenomenon and a whitening phenomenon are not shown.

That is, in the range in which the primer layer satisfies the following physical properties: T_gis 60°C or more, the swelling ratio is 30% or less, the gel fraction is 95% or more, and the density is 1.3 or more, after heating 150°C for 60 minutes, the number of oligomer particles precipitated on the surface of the film may be 10 or less per

10000/zm² and the average size of the oligomer particles may be 20 zm² or less per lOOOOjum².

In detail, it may be confirmed that in the range in which the primer layer satisfies the following physical properties: T_gis 60°C or more, more specifically, 60 or more and the upper limit is not limited, the swelling ratio is 30% or less, more specifically 0 to 30%, the gel fraction is 95% or more, more specifically, 95 to 100%, and the density is 1.3 or more, more specifically, 1.3 to 1.4, after heating 150°C for 60 minutes, structural compactness of a coating layer and mobility of the primer layer are decreased, such that the oligomer present in the polyester film is not migrated to the surface even though heat and pressure are applied.

In the polyester film according to the present invention, the primer layer is formed by applying a water dispersion resin composition having the oligomer blocking property.

In one general aspect, as the water dispersion resin composition for forming the primer layer, a water dispersion resin composition including an acrylic resin in which the glycidyl group containing radically polymerizable unsaturated monomer is copolymerized and a water dispersion polyester-based rein may be used.

[68] In one general aspect, in the water dispersion resin composition, a solid content weight ratio (A:B) of the acrylic resin A in which the glycidyl group containing radically polymerizable unsaturated monomer is copolymerized to the water dispersion polyester-based resin B may be 20-80: 80-20 weight%. More preferably, the weight ratio may be 40-60:60-40 weight . In the case in which the solid content of the water dispersion polyester-based resin B is less than 20 weight% and the solid content of the acrylic resin A in which the glycidyl group containing radically polymerizable unsaturated monomer is copolymerized is more than 80 weight , as a particle size of emulsion increases, a stain may be generated at the time of in-line coating, and adhesion with the polyester base film and transparency may be deteriorated. Further, in the case in which the solid content of the water dispersion polyester-based resin B is more than 80 weight% and the solid content of the acrylic resin A in which the glycidyl group containing radically polymerizable unsaturated monomer is

copolymerized is less than 20 weight , it may be difficult to sufficiently implement an oligomer blocking effect.

[69] The water dispersion resin composition according to the present invention may be prepared by mixing an aqueous dispersion of the water dispersion polyester-based resin B and an emulsion of the acrylic resin A in which the glycidyl group containing radically polymerizable unsaturated monomer is copolymerized with each other and may be prepared by polymerizing the glycidyl group containing radically polymerizable unsaturated monomer alone in the aqueous dispersion of the water dispersion polyester-based resin B or copolymerizing a radically polymerizable unsaturated monomer copolymerizable with the glycidyl group containing radically polymerizable unsaturated monomer. In this case, a surfactant and a polymerization initiator may be used. Any surfactant and any polymerization initiator may be used without limitation as long as they are generally used in emulsion polymerization. As a specific example of the surfactant, an anionic surfactant, a non-ionic surfactant, or a non-reactive surfactant may be used, and these surfactants may be used together with each other. As the polymerization initiator, which is a radical polymerization initiator, a peroxide-based initiator, or a nitrogen compound such as azobisisobutyronitrile, or the like, may be used.

[70] The water dispersion resin composition according to the present invention may

further include an antifoaming agent, a wetting agent, a surfactant, a thickening agent, a plasticizer, an anti-oxidant, a UV absorber, a preservative, or the like, as needed.

[71] More preferably, any one selected from compounds represented by the following Chemical Formula 1 or 2, or a mixture thereof is included as a cross-linking agent, such that a reaction rate may be further increased, and the primer layer may be formed at a low temperature, thereby making it possible to completely block the oligomer that may be leaked by heating after forming the primer layer.

[Chemical Formula 1]

[74] (In Chemical Formula 1, A] to A₃ are each independently chemical bonds or selected from (C l-ClO)alkylene, and R_v to R₃are each independently selected from hydrogen and (Cl-ClO)alkyl.)

[75] [Chemical Formula 2]

[77] (In Chemical Formula 2, A, to A₃ are each independently (Cl-ClO)alkylene, and B is a blocking agent.)

[78] The compound of Chemical Formula 1 has a reaction temperature of 120 to 140°C, more specifically about 130°C while increasing the reaction rate, such that at the time of performing a film forming process of the polyester film, the reaction starts in a preheating zone. Therefore, the compound reacts with the glycidyl group of the acrylic resin A in which the glycidyl group containing radically polymerizable unsaturated monomer is copolymerized, thereby forming a primer coating layer having a more compact structure.

[79] Therefore, in the case of using the compound of Chemical Formula 1, at the time of performing the film forming process, since application may be performed in an in-line applying process and thus a separate process for applying the primer layer after forming the film is not required, the process may become simple. In addition, since a thickness of the coating layer may be uniformly formed by being stretched after application by the in-line application process, a polyester film having excellent optical properties may be manufactured.

[80] As a more specific example of the compound of Chemical Formula 1 , a compound represented by Chemical Formula 3 may be used.

[81] [Chemical Formula 3]

[82]

[83] As the compound of Chemical Formula 2 is present in a water dispersion state, after being applied onto the film, the compound reacts with water in the preheating zone to thereby be converted into amine, and this amine reacts with isocyanate to conduct a self-reaction or reacts with the glycidyl group of the acrylic resin A in which the glycidyl group containing radically polymerizable unsaturated monomer is copolymerized, thereby making it possible to form the primer layer having a more compact structure.

[84] In detail, in Chemical Formula 2, A| to A₃ may be each independently

(C4-C5)alkylene, and B may be a pyrazol-based blocking agent, more specifically, 3,5-dimethylpyrazol.

[85] As a more specific example of the compound of Chemical Formula 2, there may be a compound represented by Chemical Formula 4.

[86] [Chemical Formula 4]

[88] Contents of the compounds of Chemical Formulas 1 and 2 may be preferably 0.1 to 10 weight%, more preferably 0.5 to 2 weight% in the water dispersion resin composition. In the case in which the content is less than 0.1 weight%, the effect of the compound is insignificant, and in the case in which the content is more than 10 weight , the coating layer may be excessively brittle, such that a crack may be generated in a surface of the primer layer at the time of manufacturing the polyester film.

[89] In the case of further including the compounds of Chemical Formulas 1 and 2, a polyester film of which the haze changing rate (ΔΗ) after being maintained at 150°C for 60 minutes is 0.05% or less, more specifically, 0 to 0.05%, and the scratch resistance and solvent resistance are further improved may be provided.

[90] In the water dispersion resin composition of the present invention, the water

dispersion polyester-based resin B may be a copolymer of a dicarboxylic acid component including a sulfonic acid alkali metal salt compound and a glycol component including diethylene glycol.

[91] In more detail, as the dicarboxylic acid component, aromatic dicarboxylic acid and the sulfonic acid alkali metal salt compound may be used, wherein the sulfonic acid alkali metal salt compound may be contained at a content of 6 to 20 mole% based on the total acid component.

[92] As the dicarboxylic acid component, aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, dimethyl terephthalic acid, isophthalic acid, dimethyl isophthalic acid, 2,5-dimethyl terephthalic acid, 2,6-naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, or the like; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, or the like; or alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid, or the like, may be used.

[93] As a specific example of the sulfonic acid alkali metal salt compound, alkali metal salts of sulfoterephthalic acid, 5-sulfo isophthalic acid, 4-sulfo isophthalic acid, 4-sulfo naphthalic acid, 2,7-dicarboxylic acid, or the like, may be used, and a content thereof may be preferably 6 to 20 mole%. In the case in which the content is less than 6 mole%, a dispersion time of the resin in water may be increased, and dispensability may be decreased, and the content is more than 20 mole%, water resistance may be deteriorated.

[94] As the glycol component, diethylene glycol, aliphatic glycol having 2 to 8 carbon atoms, or alicyclic glycol having 6 to 12 carbon atoms, or the like, may be used. As a specific example, ethylene glycol, 1,3-propanediol, 1,2-propylene glycol, neopentyl glycol, 1,4-butanediol, 1 ,4-cyclohexane dimethanol, 1,3-cyclohexane dimethanol, 1,2-cyclohexane dimethanol, 1,6-hexanediol, P-xylene glycol, triethylene glycol, or the like, may be used. In this case, it is preferable that at a content of diethylene glycol is 20 to 80 mole% based on the total glycol component.

[95] The water dispersion polyester-based resin B may have a number average molecular weight of 1000 to 50000, more preferably 2000 to 30000. In the case in which the number average molecular weight is less than 1000, the oligomer blocking effect may be insignificant, and the number average molecular weight is more than 50000, dispersion of the water dispersion polyester-based resin B may be difficult.

[96] As the water dispersion polyester-based resin B, a water dispersion material prepared by uniformly dispersing the polyester-based resin in water or water containing an aqueous solvent while heating to 50 to 90°C is used. In the water dispersion material prepared as described above, a solid content thereof may be preferably 30 weight%, more preferably 10 to 30 weight%. As the aqueous solvent, alcohols such as methanol, ethanol, propanol, or the like, or polyols such as ethylene glycol, propylene glycol, di- ethylene glycol, dipropylene glycol, glycerin, or the like, may be used.

[97] Next, the acrylic resin A in which the glycidyl group containing radically polymerizable unsaturated monomer is copolymerized will be described.

[98] The acrylic resin A in which the glycidyl group containing radically polymerizable unsaturated monomer is copolymerized is a homopolymer of the glycidyl group containing radically polymerizable unsaturated monomer or a copolymer of the glycidyl group containing radically polymerizable unsaturated monomer and another radically polymerizable unsaturated monomer copolymerizable with the glycidyl group containing radically polymerizable unsaturated monomer.

[99] . The acrylic resin may contain the glycidyl group containing radically polymerizable unsaturated monomer as a copolymerization monomer at a content of 20 to 80 mole% based on the total monomer component. Since the glycidyl group containing radically polymerizable unsaturated monomer may improve coating strength of the primer layer by cross-linking reactions and increase cross-linking density, leakage of the oligomer may be blocked. As a specific example, glycidyl acrylate, glycidyl methacrylate, glycidyl ether such as allyl glycidyl ether, or the like, may be used.

[100] Examples of the radically polymerizable unsaturated monomer copolymerizable with the glycidyl group containing radically polymerizable unsaturated monomer may include vinyl ester, unsaturated carboxylic acid ester, unsaturated carboxylic acid amide, unsaturated nitrile, unsaturated carboxylic acid, allyl compounds, nitrogen- containing vinyl monomers, hydrocarbon vinyl monomers vinyl silane compounds, or the like. As the vinyl ester, vinyl propionate, vinyl stearate, vinyl chloride, or the like, may be used. As the unsaturated carboxylic acid ester, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, butyl methacrylate, butyl maleate, octyl maleate, butyl fumarate, octyl fumarate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, or the like, may be used. As the unsaturated carboxylic acid amid, acrylamide, methacrylamide, methylol acrylamide, butoxymethylol acrylamide, or the like, may be used. As the unsaturated nitrile, acrylonitrile, or the like, may be used. As the unsaturated carboxylic acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic acid ester, fumaric acid ester, itaconic acid ester, or the like, may be used. As the allyl compound, allyl acetate, allyl methacrylate, allyl acrylate, allyl itaconate, diallyl itaconate, or the like, may be used. As the nitrogen containing vinyl monomer, vinyl pyridine, vinyl imidazole, or the like, may be used. As the hydrocarbon vinyl monomer, ethylene, propylene, hexane, octene, styrene, vinyl toluene, butadiene, or the like, may be used. As the vinyl silane compound, dimethyl vinyl methoxy silane, dimethyl vinyl ethoxy silane, methyl vinyl dimethoxy silane, methyl vinyl diethoxy silane, gamma-methacryloxy propyl trimethoxy silane, gamma-methacryloxy propyl dimethoxy silane, or the like, may be used.

[101] The water dispersion resin composition of the present invention may be a water dispersion or water soluble composition having the entire solid content of 0.5 to 10 weight , and in the water dispersion resin composition, the acrylic resin in which the glycidyl group containing radical polymerizable unsaturated monomer is

copolymerized and the water dispersion polyester-based resin may be contained at a solid content of 0.5 to 10 weight , the wetting agent may be contained at a content of 0.1 to 0.5 weight%, and silica having an average particle size of 100 to 200nm may be contained at a content of 0.1 to 1.0 weight%. In view of adjusting a coating thickness, it is preferable that the solid content is in the range of 0.5 to 10 weight .

[102] The wetting agent is used to improve a coating property. As a specific example, a modified silicone-based wetting agent such as Q2-5212 (Dow Corning), TEGO WET 250 (ENBODIC), BYK 348 (BYK CHEMIE), or the like may be used, but the present invention is not limited thereto. It is preferable that the wetting agent is used at a content of 0.1 to 0.5 weight%. In this range, the desired improvement of the coating property may be achieved.

[103] The silica having an average particle size of 50 to 1 OOOnm is used to improve a film winding property, and ACESOL Series (Acehitech), NYACOL Series (Nano Technologies), Spherical slurry series (JGC C&C), or the like, may be used, but the present invention is not limited thereto. A content of the silica may be preferably 0.1 to 1.0 weight%.

[104]

[105] In one aspect of the present invention, the polyester base film may be polyethylene terephthalate film. The polyester base film may have a thickness of 25 to 250jwn.

[106] In the present invention, the primer layer may have a dried coating thickness of 20 to 200nm. In the case in which the dried coating thickness is less than 20nm, the oligomer blocking property may not be sufficiently implemented, and in the case in which the dried coating thickness is more than 200nm, coating stains may occur, and it is highly likely to generate a blocking phenomenon that the primer layers stick to each other after winding the film.

[107] In the present invention, the water dispersion resin composition may be applied by the in-line application method during a manufacturing process of the polyester film. That is, at the time of manufacturing the polyester base film, the water dispersion resin composition may be applied by the in-line application method before a stretching process or between primary and secondary stretching processes, and water is vaporized by heating during stretching and heat-setting processes, thereby making it possible to form the primer layer. The application method is not limited as long as the method is known in the art.

[108] An upper portion of the polyester film according to the present invention may be provided with a hard coating layer, an adhesive layer, a light-diffusion layer, an indium tin oxide (ITO) layer, or the like, and even in the case of heating after forming these functional coating layer, the leakage of the oligomer may be block, such that the optical properties may be maintained. Therefore, the polyester film according to the present invention may be suitable for being used as an optical film.

[109] Hereinafter, Examples will be provided in order to describe the present invention in more detail. However, the present invention is not limited to the following Examples.

[1 10] Hereinafter, physical properties are measured by the following measuring methods.

[I l l] 1) Dried coating thickness of primer layer

[112] In the whole piece of the film coated with a coating composition, five points were designated at an interval of 1 m in a direction (TD) vertical to a machine direction, and cross-sections thereof were measured using scanning electron microscopy (SEM, Hitachi S-4300). In addition, the designated section was enlarged at a magnification of 50000x, thicknesses were measured at 30 points in the section, and an average value thereof was calculated.

[113]

[114] 2) Haze changing rate (ΔΗζ)

[115] After forming the primer layer,

[116] (1 ) At the time of forming double-sided primer layer

[117] A haze of the film before heating and a haze of the film after being maintained at 150^CC for 60 minutes were measured, and the changing rate was calculated by the following Equation 1.

[118] (2) At the time of forming single-sided primer layer

[119] Corona treatment was performed on a surface opposite to a primer layer formed surface, and a hard coating solution (AIKA Corp., Z-711) was applied using a Mayer Bar #4 and dried at 80°C for 2 minutes, followed by UV irradiation 200mj/cm²

),thereby forming a hard coating layer on the surface.

[120] A haze of the film before heating and a haze of the film after being maintained at

150°C for 60 minutes were measured, and the changing rate was calculated by the following Equation 1.

[121] [Equation 1]

[123] (In Equation 1, H_fis a haze(%) of the film after being maintained at 150°C for 60 minutes, and Hi is a haze of the film before heating.)

[124]

[125] 3) Average area of oligomer particles after heating

[126] After a polyester film was cut at a size of 100mm x 100mm and aged in an oven set at 150°C for 60 minutes, at the time of observing the aged polyester film using a reflective mode of a microscope (Leica, DM 2500M) at a magnification of 500x, the observed area of the oligomer particle was 27000^m². Surface observation was performed 10 times on the area as described above, and the shortest length and longest length of the oligomer particle surface-observed 10 times were recorded, thereby calculating an average area of the migrated oligomer in an area of 10000/ΛΠ².

[127] Area of one oligomer = (the shortest length of the oligomer particle xthe longest length of the oligomer particle)

[128] Area of oligomer per unit area (lOOOO^m²) = sum of areas of the migrated oligomer/ 2.7

[129] Average value of the areas of the oligomer observed 10 times

[130]

[131] 4) The number of oligomer particles after heating

[132] After a polyester film was cut at a size of 100mm xlOOmm and aged in an oven set at 150°C for 60 minutes, at the time of observing the aged polyester film using a reflective mode of a microscope (Leica, DM 2500M) at a magnification of 500x, the observed area of the oligomer particle was 27000/im². Surface observation was performed 10 times on the area as described above, and an average of the numbers of oligomer particles obtained by performing the surface observation 10 times was calculated.

[133] The number of oligomer per unit area (10000//m²) = (the number of oligomer

observed one time/2.7)

[134] Average value of the numbers of oligomer observed 10 times

[135]

[136] 5) Swelling ratio, gel fraction, and glass transition temperature (T_g) measurement [137] 15g of water dispersion resin compositions prepared in Examples and Comparative Examples were put into a round container having a diameter of 80mm and a height of 15mm and dried at 80°C for 24 hours and at 120°C for 3 hours, followed by aging at 180°C for 1 hour, lg of dried coating layer was collected from the resultant, and then T g as measured. In addition, the dried coating layer was immersed in 50g of distilled water and left at 70°C for 24 hours. The left coating layer was picked out and a swelling ratio thereof was measured. The left coating layer was dried at 120°C for 3 hours, and then a weight thereof was measured, thereby calculating a gel fraction.

[138] Swelling Ratio:

[139] After the dried coating layer (about lg) was immersed in distilled water (50g) and left at 70°C for 24 hours, the left coating layer was picked out and a swelling ratio thereof was recorded.

[140] Swelling ratio = (weight after being left initial weight)/initial weight)/initial weight x 100

[141]

[142] Gel Fraction:

[143] The left coating layer was dried at 120°C for 3 hours, and then a weight thereof was recorded.

[144] Gel Fraction = (weight after drying initial weight) xl 00

[145]

[146] T_g measurement

[147] The T_g was measured using a differential scanningcalorimetry (DSC, PerkinElmer

DSC 7) with the second run mode. The T_g measurement was performed on 10 to 11 mg of the dried coating layer using PerkinElmer DSC7 under the following condition.

[ 148] 1st Run = A temperature was raised from 0 to 200 °C at a rate of 200°C/min,

[149] the temperature was maintained at 200 °C for a holding time (3min),

[150] the temperature was lowered from 200°C to -40°C at a rate of 200°C/min,

[151] and then the temperature was maintained at -40°C for a holding time (5min).

[152] 2nd Run = T_g measurement was performed under the condition at which the temperature was raised from -40°C to 200°C at a rate of 20°C/min.

[153]

[154] [Example 1]

[155] 1) Preparation of water dispersion resin composition 1

[156] 16 weight% of KLX-007 binder (TAKAMATSU Corp., Japan, water dispersion resin composition having a solid content of 25%), 0.3 weight% of a silicone based wetting agent (Dow Corning Corp., polyester-siloxane copolymer, Q2-5212), and 0.3 weight% of a colloidal silica particle having an average particle size of 140nm were added to water and stirred for 2 hours, thereby obtaining a water dispersion resin composition 1 having the entire solid content of 4.6 weight%. [157] In the KLX-007 binder, a solid content weight ratio (A:B) of an acrylic resin A in which a glycidyl group containing radically polymerizable unsaturated monomer is copolymerized to a water dispersion polyester-based resin B is 50:50,

[158] the acrylic resin contains the glycidyl group containing radically polymerizable unsaturated monomer as a copolymerization monomer at a content of 50 mole% based on the total monomer component, and

[159] the water dispersion polyester-based resin contains diethylene glycol at a content of 50 mole% based on the total glycol component and a sulfonic acid alkali metal salt compound at a content of 10 mole based on the total acid component.

[160]

[161] 2) Manufacturing oligomer blocking polyester film

[162] After a dehydrated polyethylene terephthalate chip was put into an extruder and melt extruded, the temperature was rapidly cooled and hardened using a casting drum having a surface temperature of 20°C, thereby manufacturing a polyethylene terephthalate sheet having a thickness of 2000/ . The manufactured polyethylene terephthalate sheet was stretched 3.5 times in a machine direction (MD) at 80°C and cooled to room temperature. Next, the prepared water dispersion resin composition 1 was coated on both sides of the sheet by a bar coating method, the temperature was raised to 110 to 150°C at a rate of l°C/sec, and the coated sheet was stretched 3.5 times in a transverse direction (TD) through preheating and drying. Then, thermal treatment was performed in a 5-stage tenter at 235°C, the thermal treated film was relaxed by 10% in the machine and transverse directions to be heat-set at 200°C, thereby manufacturing a bi-axially stretched film coated on both sides thereof and having a thickness of 188/ffli.

[163] A dried coating thickness of the primer layer made of the composition was 80nm.

Physical properties of the polyester film obtained as described above were shown in the following Table 1.

[164]

[165] [Example 2]

[ 166] 1 ) Preparation of water dispersion resin composition 2

[167] 16 weight% of KLX-007 binder (TAKAMATSU Corp., Japan, water dispersion resin composition having a solid content of 25%), 0.4 weight% (10 parts by weight based on the solid content of the binder) of a compound of the following Chemical Formula 3, 0.3 weight% of a silicone based wetting agent (Dow Corning Corp., polyester-siloxane copolymer, Q2-5212), and 0.3 weight% of a colloidal silica particle having an average particle size of 140nm were added to water and stirred for 2 hours, thereby obtaining a water dispersion resin composition 2 having the entire solid content of 4.6 weight%.

[168] [Chemical Formula 3] [169]

ΗΝ-χ

o—

[170] 2) Manufacturing oligomer blocking polyester film

[171] After a dehydrated polyethylene terephthalate chip was put into an extruder and melt extruded, the temperature was rapidly cooled and hardened using a casting drum having a surface temperature of 20°C, thereby manufacturing a polyethylene terephthalate sheet having a thickness of 2000#m. The manufactured polyethylene terephthalate sheet was stretched 3.5 times in a machine direction (MD) at 80°C and cooled to room temperature. Next, the prepared water dispersion resin composition 2 was coated on both surfaces of the sheet by a bar coating method, the temperature was raised to 110 to 150°C at a rate of l°C/sec, and the coated sheet was stretched 3.5 times in a transverse direction (TD) through preheating and drying. Then, thermal treatment was performed in a 5-stage tenter at 235°C, the thermal treated film was relaxed by 10% in the machine and transverse directions to be heat-set at 200°C, thereby manufacturing a bi-axially stretched film coated on both sides thereof and having a thickness of 188jfln.

[172] A dried coating thickness of the primer layer made of the composition was 86nm.

[173]

[174] [Examples 3 to 6]

[175] A film was manufactured by the same method as in Example 1 except that a kind and a content of a binder resin and a content of a cross-linking agent were changed as shown in the following Table 1.

[176] In a KLX-008 binder (TAKAMATSU Corp., Japan), a solid content weight ratio (A:B) of an acrylic resin A in which a glycidyl group containing radically poly- merizable unsaturated monomer is copolymerized to a water dispersion polyester- based resin B is 50:50,

[177] the acrylic resin contains the glycidyl group containing radically polymerizable unsaturated monomer as a copolymerization monomer at a content of 40 mole% based on the total monomer component, and

[178] the water dispersion polyester-based resin contains diethylene glycol at a content of 50 mole% based on the total glycol component and a sulfonic acid alkali metal salt compound at a content of 10 mole% based on the total acid component. [179]

[180] In a KLX-030 binder (TAKAMATSU Corp., Japan), a solid content weight ratio (A:B) of an acrylic resin A in which a glycidyl group containing radically poly- merizable unsaturated monomer is copolymerized to a water dispersion polyester- based resin B is 50:50,

[181] the acrylic resin contains the glycidyl group containing radically polymerizable unsaturated monomer as a copolymerization monomer at a content of 50 mole% based on the total monomer component, and

[182] the water dispersion polyester-based resin contains diethylene glycol at a content of 40 mole% based on the total glycol component and a sulfonic acid alkali metal salt compound at a content of 15 mole% based on the total acid component.

[183]

[184] [Comparative example 1]

[185] 9.1 weight% of P-3208 binder (water dispersion resin composition having a solid content of 44%), 0.3 weight% of a silicone based wetting agent (Dow Corning Corp., polyester-siloxane copolymer, Q2-5212), and 0.3 weight% of a colloidal silica particle having an average particle size of 140nm were added to water and stirred for 2 hours, thereby obtaining a water dispersion resin composition having the entire solid content of 4.6 weight%.

[186] The P3208 binder, which is a product prepared by Rohm & Haas Company, is a binder containing 40 weight% of methylmethacrylate, 40 weight% of ethylacrylate, and 20 weight% of melamine.

[187]

[188] [Comparative example 2]

[189] 20 weight% of H-3 Binder 20 (water dispersion resin composition having a solid content of 20%), 0.3 weight% of a silicone based wetting agent (Dow Corning Corp., polyester-siloxane copolymer, Q2-5212), and 0.3 weight% of a colloidal silica particle having an average particle size of 140nm were added to water and stirred for 2 hours, thereby obtaining a water dispersion resin composition having the entire solid content of 4.6 weight%.

[190] The H-3 binder, which is a product prepared by Daichi ogyo Seiyaku Company, is an aqueous polyurethane binder prepared by reacting 9 weight% of polyester-based polyol (polyethylene adipatediol having a weight average molecular weight of 1000), 10 weight% of hexamethylene diisocyanate, 1 weight% of a reactive emulsifier having an ionic group (Asahi Denka, Adecaria Soap that is sulfonic acid ester of polyoxy ethylene allyl glycidyl nonyl phenyl ether (SETM)), and 80 weight% of water with one another and having a solid content of 20 weight%. [192] [Comparative example 3]

[193] 16 weight% of Z-561 Binder (water dispersion resin composition having a solid content of 25%), 0.4 weight% (10 parts by weight based on the solid content of the binder) of a compound of the following Chemical Formula 2, 0.3 weight% of a silicone based wetting agent (Dow Corning Corp., polyester-siloxane copolymer, Q2-5212), and 0.3 weight% of a colloidal silica particle having an average particle size of 140nm were added to water and stirred for 2 hours, thereby obtaining a water dispersion resin composition having the entire solid content of 4.6 weight .

[194] The Z-561 binder, which is a product prepared by Goo Chemical Company, was an aqueous polyester binder having a solid content of 25 weight% and prepared by performing a copolymerization reaction using 6-naphtalene dicarboxylic acid 40 mol (26 mole%), sodium 2,5-dicarboxy benzene sulfonate 5 mol (3.3 mole%), dimethyl- terephthalic acid 5 mol (3.3 mole%), and a mixture 100 mol (66.66 mole%) obtained by mixing ethylene glycol and 1,4 butylene glycol at a ratio of 1: 1.

[195]

[196] [Table I]

[197] Cross- linkin Area of

Binder The Coati g oligomer

Kinds conten number of ng agent particle

of t ΔΗζ oligoitiers thick conten s

Binder (weigh (per ness t (per

t%) 10000/fln²) (nm)

(weigh 10000an²)

t%)

Example

KXX007 16 0 0.07 3 4 80 1

Example

KLX007 16 0.4 0.05 2.3 3 86 2

Exam le

KLX007 16 1 0.03 1.8 2 97 3

Example

KLX008 16 0 0.09 3.2 6 79 4

Exam le

KLX008 16 1 0.05 2 4 97 5

Example

KLX030 16 0 0.10 2.3 5 77 6

Compara

tive

P3208 9.1 0 0.81 9 57 88 Example

1

Compara

tive

H-3 20 0 2.01 14 145 67 Example

2

Compara

tive

Z-561 16 0 1.22 108 72 Example

3

Compara

tive

Z-561 16 1 1.01 11 87 91 Example

4

[198] As shown in Table 1, it may be appreciated that in Examples 1 to 6 according to the present invention, the haze changing rate was significantly low (0.1% or less), and it was confirmed that as the cross-linking agent was used, the haze changing rate was further decreased and the area and the number of oligomer were significantly decreased.

[199]

[200] [Example 7]

[201] 1) Preparation of water dispersion resin composition 3

[202] As a binder, a binder in which a solid content weight ratio (A:B) of an acrylic resin A in which a glycidyl group containing radically polymerizable unsaturated monomer is copolymerized to a water dispersion polyester-based resin B is 40:60 was used. [203] The acrylic resin A prepared by copolymerizing 60 mole% of glycidyl acrylate and 40 mole% of vinyl propionate and having a weight average molecular weight of 35000 was used.

[204] The water dispersion polyester-based resin B, which was a resin polymerized using acid components of sulfoterephthalic acid (15 mole ) and terephthalic acid (85 mole%) at a content of 50 mole based on 50 mole% of the glycol components of di- ethylene glycol (50 mole%) and ethylene glycol (50mole%), having a weight average molecular weight of 14000 was used.

[205]

[206] 0.5 weight% (as a solid content) of the binder and 0.3 weight of a silicon based wetting agent (BYK 348, BYK CHEMIE Corp.) were added to water and stirred for 2 hours, thereby preparing a water dispersion resin composition 3 having the entire solid content of 0.8 weight%.

[207] The above-mentioned swelling ratio, gel fraction and T_g were measured using the prepared water dispersion resin composition, and the results were shown in the following Table2.

[208]

[209] 2) Manufacturing oligomer blocking polyester film

[210] After a dehydrated polyethylene terephthalate chip was put into an extruder and melt extruded, the temperature was rapidly cooled and hardened using a casting drum having a surface temperature of 20°C, thereby manufacturing a polyethylene terephthalate sheet having a thickness of 2000//m. The manufactured polyethylene terephthalate sheet was stretched 3.5 times in a machine direction (MD) at 75°C and cooled to room temperature. Next, the prepared water dispersion resin composition 3 was coated on both surfaces of the sheet by a bar coating method, the temperature was raised to 110 to 150°C at a rate of l°C/sec, and the coated sheet was stretched 3.5 times in a transverse direction (TD) through preheating and drying. Then, thermal treatment was performed in a 5-stage tenter at 230°C, the thermal treated film was relaxed by 10% in the machine and transverse directions to be heat-set at 200°C, thereby manufacturing a bi-axially stretched film coated on both sides thereof and having a thickness of 188μπι.

[211] A dried coating thickness of the primer layer made of the composition was 20nm.

Physical properties of the polyester film obtained as described above were shown in the following Table 3.

[212]

[213] [Example 8]

[214] The same binder resin as that in Example 7 was used, and 2 weight% (as a solid content) of the binder, 0.3 weight% of a silicon based wetting agent (BYK 348, BYK CHEMIE Corp.), and 0.4 weight% of an isocyanate-based hardening agent of Chemical Formula 4 were added to water and stirred for 2 hours, thereby preparing a water dispersion resin composition 4 having the entire solid content of 2.7 weight%. The above-mentioned swelling ratio, gel fraction and Tg were measured using the prepared water dispersion resin composition, and the results were shown in the following Table 2.

[215] A bi-axially stretched film coated on both sides thereof and having a thickness of

188jUm was manufactured using the prepared water dispersion resin composition 4 by the same method as in Example 7. A dried coating thickness of the primer layer made of the composition was 50nm. Physical properties of the polyester film obtained as described above were shown in the following Table 3.

[216] [Chemical Formula 4]

[218] [Example 9]

[219] The same binder resin as that in Example 7 was used, and 2 weight% (as a solid content) of the binder, 0.3 weight% of a silicon based wetting agent (BYK 348, BYK CHEMIE Corp.), and 1 weight of an isocyanate-based hardening agent of Chemical Formula 4 were added to water and stirred for 2 hours, thereby preparing a water dispersion resin composition 5 having the entire solid content of 3.3 weight%. The above-mentioned swelling ratio, gel fraction and Tg were measured using the prepared water dispersion resin composition, and the results were shown in the following Table 2.

[220] A bi-axially stretched film coated on both sides thereof and having a thickness of 188#m was manufactured using the prepared water dispersion resin composition 5 by the same method as in Example 7. A dried coating thickness of the primer layer made of the composition was 80nm. Physical properties of the polyester film obtained as described above were shown in the following Table 3.

[221]

[222] [Example 10]

[223] 1) Preparation of water dispersion resin composition 6

[224] As a binder, a binder in which a solid content weight ratio (A:B) of an acrylic resin A in which a glycidyl group containing radically polymerizable unsaturated monomer is copolymerized to a water dispersion polyester-based resin B is 70:30 was used.

[225] The acrylic resin A prepared by copolymerizing 60 mole% of glycidyl acrylate and 40 mole of vinyl propionate and having a weight average molecular weight of 30000 was used.

[226] The water dispersion polyester-based resin B, which was a resin polymerized using acid components of sulfoterephthalic acid (15 mole ) and terephthalic acid (85 mole%) at a content of 50 mole% based on 50 mole% of the glycol components of di- ethylene glycol (50 mole%) and ethylene glycol (50mole ), having a weight average molecular weight of 12000 was used.

[227] 5 weight% (as a solid content) of the binder and 0.3 weight of a silicon based wetting agent (BYK 348, BYK CHEMIE Corp.) were added to water and stirred for 2 hours, thereby preparing a water dispersion resin composition 6 having the entire solid content of 5.3 weight%. The above-mentioned swelling ratio, gel fraction and T_gwere measured using the prepared water dispersion resin composition, and the results were shown in the following Table2.

[228] A bi-axially stretched film coated on both sides thereof and having a thickness of 188/im was manufactured using the prepared water dispersion resin composition 6 by the same method as in Example 7. A dried coating thickness of the primer layer made of the composition was 1 lOnm. Physical properties of the polyester film obtained as described above were shown in the following Table 3.

[229]

[230] [Example 11]

[231] The same binder resin as that in Example 10 was used, and 5 weigh t% (as a solid content) of the binder, 0.3 weight% of a silicon based wetting agent (BYK 348, BYK CHEMIE Corp.), and 0.5 weight% of an isocyanate-based hardening agent of Chemical Formula 4 were added to water and stirred for 2 hours, thereby preparing a water dispersion resin composition 7 having the entire solid content of 5.8 weight%. The above-mentioned swelling ratio, gel fraction and Tg were measured using the prepared water dispersion resin composition, and the results were shown in the following Table 2.;

[232] A bi-axially stretched film coated on both sides thereof and having a thickness of 188#m was manufactured using the prepared water dispersion resin composition 7 by the same method as in Example 7. A dried coating thickness of the primer layer made of the composition was 105nm. Physical properties of the polyester film obtained as described above were shown in the following Table 3.

[233]

[234] [Example 12]

[235] The same binder resin as that in Example 7 was used, and 2 weight% (as a solid

content) of the binder, 0.3 weight% of a silicon based wetting agent (BYK 348, BYK CHEMIE Corp.), and 0.5 weight% of a compound of Chemical Formula 3 were added to water and stirred for 2 hours, thereby preparing a water dispersion resin composition 8 having the entire solid content of 2.8 weight%. The above-mentioned swelling ratio, gel fraction and T_g were easured using the prepared water dispersion resin composition, and the results were shown in the following Table2.

[236] [Chemical Formula 3]

[238] A bi-axially stretched film coated on both sides thereof and having a thickness of

188/ was manufactured using the prepared water dispersion resin composition 8 by the same method as in Example 7. A dried coating thickness of the primer layer made of the composition was 80nm. Physical properties of the polyester film obtained as described above were shown in the following Table 3.

[239]

[240] [Comparative example 5]

[241 ] As the binder, a binder (P3208, Rohm & Haas Company) containing 40 weight% of methylmethacrylate, 40 weight% of ethylacrylate, and 20 weight% of melamine was used.

[242] 2 weight% (as a solid content) of the binder and 0.3 weight of a silicon based

wetting agent (BYK 348, BYK CHEMIE Corp.) were added to water and stirred for 2 hours, thereby preparing a water dispersion resin composition 9 having the entire solid^' content of 2.3 weight%. The above-mentioned swelling ratio, gel fraction and T_gwere easured using the prepared water dispersion resin composition, and the results were shown in the following Table2.

[243] A bi-axially stretched film coated on both sides thereof and having a thickness of 188 zm was manufactured using the prepared water dispersion resin composition 9 by the same method as in Example 1. A dried coating thickness of the primer layer made of the composition was 80nm. Physical properties of the polyester film obtained as described above were shown in the following Table 3.

[244]

[245] [Comparative example 6]

[246] An aqueous polyurethane binder having a solid content of 20 weight% was prepared by reacting 9 weight% of polyester-based polyol (polyethylene adipatediol having a weight average molecular weight of 1000), 10 weight% of hexamethylene di- isocyanate, 1 weight% of a reactive emulsifier having an ionic group (Asahi Denka, Adecaria Soap that is sulfonic acid ester of polyoxy ethylene allyl glycidyl nonyl phenyl ether (SETM)), and 80 weight% of water with one another.

[247] 4 weight% (as a solid content) of the binder and 0.3 weight% of a silicon based

wetting agent (BYK 348, BYK CHEMIE Corp.) were added to water and stirred for 2 hours, thereby preparing a water dispersion resin composition 10 having the entire solid content of 4.3 weight%. The above-mentioned swelling ratio, gel fraction and Tg were measured using the prepared water dispersion resin composition, and the results were shown in the following Table 2.

[248] A bi-axially stretched film coated on both sides thereof and having a thickness of

188 m was manufactured using the prepared water dispersion resin composition 10 by the same method as in Example 7. A dried coating thickness of the primer layer made of the composition was 80nm. Physical properties of the polyester film obtained as described above were shown in the following Table 3.

[249]

[250] [Comparative example 7]

[251] 2,6-naphtalene dicarboxylic acid 40 mol (26 mole%), sodium 2,5-dicarboxy benzene sulfonate 5 mol (3.3 mole%), dimethylterephthalic acid 5 mol (3.3 mole ), and a mixture 100 mol (66.66 mole%) obtained by mixing ethylene glycol and 1,4 butylene glycol at a ratio of 1 : 1 were mixed with each other under a solvent-free condition and put into a reactor, and an estenfication reaction was conducted by raising a temperature from 170 to 250°C at a rate of l°C/min while removing water or methanol, which is a by-product. Next, a polycondensation reaction was conducted while recovering diol, which is a by-product, by reducing pressure to lmmHg in the reactor simultaneously with raising the temperature to 260°C, thereby preparing a polyester resin having an intrinsic viscosity of 0.4.

[252] 75 weight% of water was added to 25 weight% of the prepared polyester resin and emulsified, thereby preparing an aqueous polyester binder having a solid content of 25 weight%.

[253] 4 weight% (as a solid content) of the binder and 0.3 weight% of a silicon based

wetting agent (BYK 348, BYK CHEMIE Corp.) were added to water and stirred for 2 hours, thereby preparing a water dispersion resin composition 11 having the entire solid content of 4.3 weight%. The above-mentioned swelling ratio, gel fraction and T_g were easured using the prepared water dispersion resin composition, and the results were shown in the following Table2.

[254] A bi-axially stretched film coated on both sides thereof and having a thickness of

188 /m was manufactured using the prepared water dispersion resin composition 11 by the same method as in Example 7. A dried coating thickness of the primer layer made of the composition was 70nm. Physical properties of the polyester film obtained as described above were shown in the following Table 3.

[255]

[256] [Table 2]

[257]

[258] [Table 3] [259] h e

Ar of

Polyester Primer number of

ol i gome r

base film l aye ol gomer

part cle ΔΗζ thi ckness thickne particles

(per 10000

(/an) ss (tm) (per 10000

2)

Example 7 188 20/20 3 4 0.09

Example 8 188 50/50 2.3 3 0.07

Example 9 188 80/80 1.8 2 0.03

Exam l e

188 110/110 2.3 5 0.06 10

E ampl e

188 105/105 1.9 3 0.05 11

E m l e

188 80/80 1.5 2 0.04

Comparative

188 80/80 9 59 0.84 Example 5

Comparative

188 80/80 14 146 2.1 Example 6

Comparative

188 70/70 12 110 1.24 Example 7

[260] As shown in Tables 2 and 3, it may be appreciated that when Tg of the primer layer was 60°C or more, the swelling ratio was 30% or less, the gel fraction was 95% or more, and the density was 1.3 to 1.4, the number of oligomer particles was 10 or less per 10000/m² and the average size thereof was 20 m² or less per ΙΟΟΟΟ ιτι².

[261] Further, it may be appreciated that the haze changing rate was 0.1% or less.

Claims

A polyester film comprising:

a polyester base film; and

a primer layer formed by applying a water dispersion resin composition having an oligomer blocking property onto one surface or both surfaces of the polyester base film, wherein after it is maintained at 150°C for 60 minutes, a haze change rate (ΔΗ) according to the following Equation 1 is 0.1% or less.

[Equation 1 ]

(In Equation 1, H_fis a haze(%) of the film after being maintained at 150°C for 60 minutes, and Hi is a haze of the film before heating.) The polyester film of claim 1, wherein the primer layer has a T_g of 60°C or more, a swelling ratio of 30% or less, a gel fraction of 95% or more, and a density of 1.3 to 1.4.

The polyester film of claim 1, wherein after it is heated at 150°C for 60 minutes, the number of oligomer particles precipitated on a surface of the film is 10 or less per lOOOOjum² and an average size thereof is 20[M² or less per 10000#m².

The polyester film of claim 1, wherein the water dispersion resin composition includes an acrylic resin in which a glycidyl group containing radically polymerizable unsaturated monomer is copolymerized and a water dispersion polyester-based resin as binder resins.

The polyester film of claim 4, wherein in the water dispersion resin composition, a solid content weight ratio (A:B) of the acrylic resin A in which the glycidyl group containing radically polymerizable unsaturated monomer is copolymerized to the water dispersion polyester- based resin B may be 20-80: 80-20 weight%.

The polyester film of claim 4, wherein the water dispersion resin composition includes the binder resin and water to have a solid content of 0.5 to 10 weight%.

The polyester film of claim 4, wherein the water dispersion resin composition further includes 0.1 to 0.5 weight% of a silicone-based wetting agent.

The polyester film of claim 4, wherein the water dispersion polyester- based resin is a copolymer of a dicarboxylic acid component including a sulfonic acid alkali metal salt compound and a glycol component including diethylene glycol.

The polyester film of claim 4, wherein the water dispersion polyester- based resin contains diethylene glycol at a content of 20 to 80 mole% based on the total glycol component.

The polyester film of claim 4, wherein the water dispersion polyester- based rein the water dispersion polyester-based resin contains the sulfonic acid alkali metal salt compound at a content of 6 to 20 mole% based on the total acid component.

The polyester film of claim 4, wherein the acrylic resin contains the glycidyl group containing radically polymerizable unsaturated monomer as a copolymerization monomer at a content of 20 to 80 mole based on the total monomer component.

The polyester film of claim 4, wherein the water dispersion resin composition further includes any one of the compounds represented by Chemical Formulas 1 and 2 or a mixture thereof.

[Chemical Formula 1 ]

(In Chemical Formula 1, A, to A₃ are each independently chemical bonds or selected from (Cl-ClO)alkylene, and R, to R₃ are each independently selected from hydrogen and (Cl-ClO)alkyl.)

[Chemical Formula 2]

[Claim 13] The polyester film of claim 12, wherein a content of any one of

compounds represented by Chemical Formulas 1 and 2 or a mixture thereof is 0.1 to 10 weight%.

[Claim 14] The polyester film of claim 12, wherein the compound of Chemical

Formula 1 is the following compound.

[Claim 15] The polyester film of claim 1, wherein the polyester base film is a polyethylene terephthalate film.

[Claim 16] The polyester film of claim 1, wherein the polyester base film has a thickness of 25 to 250 πι.

[Claim 17] The polyester film of claim 1, wherein the primer layer has a dried coating thickness of 20 to 200nm.

[Claim 18] The polyester film of claim 1 , wherein the water dispersion resin composition is applied by an in-line application method during a manufacturing process of the polyester film.

[Claim 19] The polyester film of any one of claims 1 to 18, wherein it is a film for a display.