CN118284658A - Polyester release film and method for producing same - Google Patents

Abstract

The invention relates to a polyester release film and a manufacturing method thereof. The polyester release film may have excellent peeling property and coating processability, excellent antistatic property, and remarkably low frictional static voltage of less than 50V, may prevent static electricity from being generated during film operation and winding, and may remarkably reduce the amount of air or foreign matter introduced due to the static electricity.

Description

Polyester release film and method for producing the same

Technical Field

The following disclosure relates to a polyester release film and a method for making the same.

Background technique

As displays become larger and thinner, there is an increasing demand for thinner polarizing plates in image display devices.

One way to thin the polarizing plate is to thin a conventional polarizer protective material such as polyethylene terephthalate (PET) or triacetyl cellulose (TAC). Another way to thin the polarizing plate is to replace the polarizer protective material with a coating (hereinafter, referred to as a "barrier coating").

The barrier coating layer is formed by uniformly applying a composition for forming a barrier coating layer to an arbitrary substrate, curing the composition, and peeling off the cured barrier coating layer.

To obtain a high quality barrier coating, the barrier coating should be evenly applied to the substrate and the cured barrier coating should release well from the substrate.

When a silicone-based release film is used as a substrate, it is difficult to form a barrier coating layer with a uniform thickness because the silicone-based release film has a low surface energy, and static electricity problems caused by silicone may occur.

Summary of the invention

technical problem

One embodiment of the present invention is to provide a polyester release film having excellent peeling performance, coating processability and antistatic performance and low tribostatic voltage.

Another embodiment of the present invention is directed to providing a polyester release film capable of preventing static electricity from being generated during film running and winding and significantly reducing the amount of air or foreign matter introduced due to static electricity.

Another embodiment of the present invention is to provide a method for manufacturing a polyester release film.

Technical solutions

In a general aspect, a polyester release film comprises:

Polyester base film;

a release layer formed on one surface of the base film; and

an antistatic layer formed on the other surface of the base film,

Wherein, the release layer comprises an aqueous coating composition containing polyester resin, acrylic resin and polyolefin wax,

The antistatic layer comprises a water-dispersible antistatic composition containing a conductive polymer.

In another general aspect, a method of making a polyester release film comprises:

The first step is to prepare a polyester base film;

A second step of forming a release layer by applying an aqueous coating composition comprising a polyester resin, an acrylic resin and a polyolefin wax to one surface of the base film;

A third step of forming an antistatic layer by applying a water-dispersible antistatic composition including a conductive polymer to the other surface of the base film; and

In a fourth step, while stretching the laminate including the base film and the release layer and the antistatic layer formed on the base film, the laminate is heat-treated.

Other features and aspects will be apparent from the following detailed description, and from the claims.

Beneficial Effects

The polyester release film according to the exemplary embodiment of the present invention has excellent peeling property and coating processability, excellent antistatic property, and a significantly low tribostatic voltage of less than 50V.

Furthermore, the polyester release film according to the exemplary embodiment of the present invention can prevent static electricity from being generated during film running and winding and significantly reduce the amount of air or foreign matter introduced due to static electricity.

Furthermore, the polyester release film according to the exemplary embodiment of the present invention can solve problems such as reduction in yield due to unreacted substances and adsorption of foreign matter due to static electricity, which occur when forming a coating using the polyester release film.

Detailed ways

Hereinafter, the present invention will be described in detail.

Meanwhile, the exemplary embodiments of the present invention may be modified in many different forms, and the scope of the present invention is not limited to the exemplary embodiments described herein.

Furthermore, exemplary embodiments of the present invention are provided so that those skilled in the art can more completely understand the present invention.

Furthermore, as used in this specification and the appended claims, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

In addition, throughout the specification, unless explicitly described otherwise, “comprising” any components will be understood as implying the inclusion of other components rather than excluding any other components.

A polyester release film according to an exemplary embodiment of the present invention includes:

a polyester base film; a release layer formed on one surface of the base film; and an antistatic layer formed on the other surface of the base film.

In an exemplary embodiment, the release layer may include an aqueous coating composition including a polyester resin, an acrylic resin, and a polyolefin wax.

Furthermore, in an exemplary embodiment, the antistatic layer may include a water-dispersible antistatic composition including a conductive polymer.

Furthermore, in an exemplary embodiment, the polyester release film may have a tribostatic voltage of less than 50V.

The present inventors have continuously studied release films used as substrates in the production of optical films such as thin film polarizing plates.

As a result, the present inventors have found that, when an aqueous coating composition comprising a polyester resin, an acrylic resin and a polyolefin wax is applied to a base film by an in-line coating method to form a release layer, and an antistatic layer is formed by applying a water-dispersible antistatic composition comprising a conductive polymer to the other surface of the base film on which the release layer is not formed, a polyester release film having excellent coating processability and stripping performance as well as excellent antistatic performance and low tribostatic voltage can be provided, thereby completing the present invention.

The polyester release film can have excellent coating processability and peeling performance in post-processing using the same (eg, a process of forming a barrier coating on the release film, etc.), and can prevent contamination due to static electricity because it has a low friction static voltage of less than 50V.

The polyester release film includes: a polyester base film; a release layer formed on one surface of the base film; and an antistatic layer formed on a surface of the base film on which the release layer is not formed (hereinafter referred to as the other surface).

The polyester base film may be formed of polyester resin, and a conventional polyester base film in the art to which the present invention pertains may be used without particular limitation. For example, the polyester base film may be formed of polyethylene terephthalate, polyethylene naphthalate, and the like.

As a non-limiting example, a base film formed of polyethylene terephthalate having an intrinsic viscosity of 0.6 to 0.8 dl/g may be advantageous in terms of ensuring weather resistance and hydrolysis resistance.

The release layer may include an aqueous coating composition including a polyester resin, an acrylic resin, and a polyolefin wax.

Polyester resin is a resin obtained by polycondensation of an acid component containing dicarboxylic acid as a main component and a diol component containing alkylene glycol as a main component. As the acid component, terephthalic acid or its alkyl ester or phenyl ester can be mainly used, and some of them can be replaced by isophthalic acid, oxyethoxybenzoic acid, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, sulfoterephthalic acid, etc. As the diol component, ethylene glycol, diethylene glycol, etc. can be mainly used, and some of them can be replaced by propylene glycol, trimethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,4-bisoxyethoxybenzene (1,4-bisoxyethoxybenzene), bisphenol, polyoxyethylene glycol, etc.

As a non-limiting example, the polyester resin may be obtained by polycondensation of 50 mol % of a diol component comprising diethylene glycol and ethylene glycol in a molar ratio of 5:5 and 50 mol % of an acid component comprising terephthalic acid and sulfoterephthalic acid in a molar ratio of 8.5:1.5.

When the polyester resin has a weight average molecular weight of 2,000 to 25,000 g/mol, it may be advantageous for the release layer to have suitable solvent resistance. Preferably, the weight average molecular weight of the polyester resin may be 2,000 to 25,000 g/mol, 2,000 to 20,000 g/mol, 3,000 to 20,000 g/mol, or 3,000 to 15,000 g/mol.

In this specification, weight average molecular weight refers to the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC). In the measurement method of the weight average molecular weight in terms of polystyrene measured by the GPC method, commonly known analytical devices, detectors such as differential refractometer detectors (refractive index detectors), and analytical columns can be used, and commonly used temperature conditions, solvents, and flow rates can be applied.

The acrylic resin may contain 20 to 80 mol % of a glycidyl group-containing free radical polymerizable unsaturated monomer as a copolymerizable monomer relative to the total monomer components. The glycidyl group-containing free radical polymerizable unsaturated monomer is preferred because it can improve the strength of the release layer through a cross-linking reaction and prevent the outflow of oligomers. Examples of the glycidyl group-containing free radical polymerizable unsaturated monomer include glycidyl acrylate, glycidyl methacrylate, and aryl glycidyl ether.

Examples of free radical polymerizable unsaturated monomers copolymerizable with free radical polymerizable unsaturated monomers containing glycidyl groups include vinyl esters, unsaturated carboxylates, unsaturated carboxylic acid amides, unsaturated nitrile, unsaturated carboxylic acids, allyl compounds, nitrogen-containing vinyl monomers, hydrocarbon vinyl monomers and vinyl silane compounds. As vinyl esters, vinyl propionate, vinyl stearate, vinyl chloride, etc. can be used. As unsaturated carboxylates, 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, etc. can be used. As unsaturated carboxylic acid amides, acrylamide, methacrylamide, hydroxymethyl acrylamide, butoxy hydroxymethyl acrylamide, etc. can be used. As unsaturated nitrile, acrylonitrile, etc. can be used. As unsaturated carboxylic acids, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic acid esters, fumaric acid esters, itaconates, etc. can be used. As allyl compounds, allyl acetate, allyl methacrylate, allyl acrylate, allyl itaconate, diallyl itaconate, etc. can be used. As nitrogen-containing vinyl monomers, vinyl pyridine, vinyl imidazole, etc. can be used. As hydrocarbon vinyl monomers, ethylene, propylene, hexene, octene, styrene, vinyl toluene, butadiene, etc. can be used. As vinyl silane compounds, dimethylvinyl methoxysilane, dimethylvinyl ethoxysilane, methylvinyl dimethoxysilane, methylvinyl diethoxysilane, γ-methacryloxypropyl trimethoxysilane, γ-methacryloxypropyl dimethoxysilane, etc. can be used.

As a non-limiting example, the acrylic resin may be obtained by copolymerizing 40 mol % to 60 mol % of glycidyl acrylate and 40 mol % to 60 mol % of vinyl propionate.

Preferably, the acrylic resin has a weight average molecular weight of 20,000 g/mol to 70,000 g/mol. More preferably, the weight average molecular weight of the acrylic resin may be 20,000 g/mol to 60,000 g/mol, 30,000 g/mol to 60,000 g/mol, 40,000 g/mol to 60,000 g/mol, or 45,000 g/mol to 55,000 g/mol.

In an exemplary embodiment, the weight ratio of the polyester resin to the solids of the acrylic resin may be 1: 0.1 to 1: 1.5, and more specifically, may be 1: 0.2 to 1: 1. When the release layer is manufactured using the aqueous coating composition satisfying the above range, the polyester release film may have excellent peeling properties and the effect of further improving coating processability.

The release layer may include polyolefin wax, and may be dispersed in polyester resin and acrylic resin.

There is no particular limitation on the specific type of the polyolefin wax, but at least one selected from polyethylene wax and polypropylene wax may be preferably used.

The polyolefin wax may be contained in an amount of 20 to 50 parts by weight or 30 to 40 parts by weight relative to 100 parts by weight of the polyester resin. In order for the release layer to exhibit an appropriate peeling force, preferably, the polyolefin wax is contained in an amount of 20 parts by weight or more relative to 100 parts by weight of the polyester resin. However, when an excessive amount of polyolefin wax is added to the release layer, back-side transfer problems and deterioration of coating processability may be caused. Therefore, preferably, the polyolefin wax is contained in an amount of 50 parts by weight or less relative to 100 parts by weight of the polyester resin.

For example, the polyolefin wax may be contained in an amount of 20 parts by weight or more, 25 parts by weight or more, or 30 parts by weight or more, and 50 parts by weight or less, 45 parts by weight or less, or 40 parts by weight or less, relative to 100 parts by weight of the polyester resin. Specifically, the polyolefin wax may be contained in an amount of 20 to 50 parts by weight, 25 to 50 parts by weight, 25 to 45 parts by weight, 30 to 45 parts by weight, or 30 to 40 parts by weight, relative to 100 parts by weight of the polyester resin.

The total content of the polyester resin, acrylic resin and polyolefin wax contained in the aqueous coating composition is preferably 1 to 10 wt %, 2 to 9 wt %, 4 to 8 wt %, or 5 to 6 wt % based on the solid content.

When the total content of the polyester resin, acrylic resin, and polyolefin wax contained in the aqueous coating composition satisfies the above range based on solid content, the manufactured polyester release film can have excellent transfer performance and peeling performance and a significantly low tribostatic voltage of less than 50 V. In addition, the polyester release film manufactured by satisfying the above range can prevent the generation of fine pinholes, thereby improving coating processability.

In an exemplary embodiment of the present invention, the aqueous coating composition applied to the release layer may further include additives such as silicone wetting agents, fluorine wetting agents, curing agents, acid catalysts, slip agents, defoamers, wetting agents, surfactants, thickeners, plasticizers, antioxidants, ultraviolet absorbers, preservatives and crosslinking agents as needed. Additives may be selectively used within the limit of not damaging the physical properties of the release layer.

The antistatic layer may include a water-dispersible antistatic composition including a conductive polymer.

According to an exemplary embodiment of the present invention, the polyester release film includes a release layer and an antistatic layer formed of a non-silicone material, so that the polyester release film can have excellent coating processability and peeling performance, excellent antistatic performance, and a significantly low tribostatic voltage of less than 50V.

The conductive polymer may be a nano-sized structure having conductivity and polarity. The conductive polymer may include, for example, one or more selected from polythiophene-based polymers, polypyrrole-based polymers, and polyaniline-based polymers.

In addition, as an exemplary embodiment, a resin composition including a conductive polymer may also be included in the category of the conductive polymer. The resin may be, for example, a water-based resin, and may include an ionomer.

The ionic polymer is a polymer having a group including a cationic group or an anionic group, and may be an ionic polymer such as polystyrene sulfonate or polystyrene ammonium salt, but is not limited thereto. In the case of using the ionic polymer, there is no particular limitation on its content as long as the purpose of the present invention is achieved, and for example, the ionic polymer may be used at a weight ratio of 0.01 to 2 relative to the conductive polymer.

As an exemplary embodiment, preferably, the conductive polymer may be a polythiophene-based conductive polymer or polyethylene dioxythiophene: polystyrene sulfonate (PEDOT:PSS). In the case of using PEDOT:PSS as the conductive polymer, due to its excellent water dispersibility, it is suitable for use in an online coating process, and even when a stretching process is performed after the online coating process, the transparency is not deteriorated, and a surface resistance of 10 ¹⁰ Ω/□ or less can be exhibited, which is more preferred.

The water-dispersible antistatic composition may further include an aqueous polyurethane resin. The aqueous polyurethane resin is used by mixing with a conductive polymer, so that an antistatic layer having excellent miscibility, improved surface resistance, excellent adhesion to a polyester base film, small changes in physical properties under high temperature and high humidity conditions, and reduced yellowing can be formed. By using a polyurethane adhesive obtained by reacting a polycarbonate polyol with a diisocyanate, the aqueous polyurethane resin can achieve small changes in physical properties such as excellent heat resistance and surface resistance. As a specific example of diisocyanate, hexamethylene diisocyanate is more preferably used to improve heat resistance, which is preferred from the viewpoint of forming a coating film with reduced yellowing, but the present invention is not limited thereto.

In an exemplary embodiment, the conductive polymer and the aqueous polyurethane resin may be included in an amount of 1% to 30% by weight and 70% to 99% by weight, respectively, relative to 100% by weight of the solid content of the water-dispersible antistatic composition. More specifically, the conductive polymer and the polyurethane adhesive may be included in an amount of 5% to 25% by weight and 75% to 95% by weight, respectively. Still more specifically, the conductive polymer and the polyurethane adhesive may be included in an amount of 5% to 20% by weight and 80% to 95% by weight, respectively.

More specifically, the antistatic layer may be formed by applying a water-dispersible antistatic composition including a conductive polymer solution, an aqueous polyurethane resin solution, an organic solvent, and water.

More specifically, the water-dispersible antistatic composition may include, for example, 40 to 90 wt % of a conductive polymer solution having a solid content of 1 to 3 wt %, 5 to 50 wt % of an aqueous polyurethane resin solution having a solid content of 30 to 40 wt %, 3 to 50 wt % of an organic solvent, and the balance of water.

The conductive polymer may be used as a conductive polymer solution mixed with a solvent so as to exhibit optimal dispersibility. Specifically, for example, in the case of using PEDOT:PSS, PEDOT:PSS may be used by mixing with water, alcohol, a solvent having a high dielectric constant, or the like.

The content of the conductive polymer solution in the water-dispersible antistatic composition may be 40 to 90 wt %, and more preferably 50 to 70 wt %, which is sufficient to achieve the purpose of the present invention, but is not limited thereto.

In addition, the aqueous polyurethane resin may be dispersed in a solvent, the solvent is not limited, and one or a mixed solvent of two or more selected from amide organic solvents and aprotic high dipole (AHD) organic solvents may be used.

The content of the aqueous polyurethane resin in the water-dispersible antistatic composition may be 5 wt % to 50 wt %, and more preferably 10 wt % to 30 wt %, but is not limited thereto.

There is no particular limitation on the organic solvent, and one or a mixed solvent of two or more selected from alcohol organic solvents and aprotic high-dipole organic solvents can be used, but the invention is not limited thereto.

The content of the organic solvent in the water-dispersible antistatic composition may be 50 wt % or less, 40 wt % or less, 30 wt % or less, 20 wt % or less, or 10 wt % or less, and its lower limit may be 1 wt % or 2 wt % or more. When the content is within the above range, it is suitable for improving the dispersibility of the conductive polymer and the aqueous polyurethane resin, but the present invention is not limited thereto.

There is no limitation on the alcohol organic solvent, and as specific examples, there can be used methanol, ethanol, propanol, isopropanol, butanol, 2-amino-2-methyl-1-propanol, etc. These alcohol organic solvents may be used alone or as a mixture of two or more thereof.

There is no limitation on the aprotic high dipole organic solvent, and as specific examples, dimethyl sulfoxide, propylene carbonate, etc. can be used. These aprotic high dipole organic solvents can be used alone or as a mixture of two or more thereof. The use of an aprotic high dipole organic solvent makes it possible to further improve the conductivity of the conductive polymer.

The water-dispersible antistatic composition includes the respective materials within the above content range, so that the polyester release film according to the exemplary embodiment of the present invention has a significantly low tribostatic voltage of less than 50 V. Therefore, the antistatic performance can be excellent, static electricity can be prevented from being generated during film operation and winding, and the amount of air or foreign matter introduced due to static electricity can be significantly reduced.

In addition, the water-dispersible antistatic composition satisfies the above content range, so that the polyester release film according to the exemplary embodiment of the present invention can solve problems such as reduced yield due to unreacted substances and foreign matter adsorption due to static electricity that occur when forming a coating using the polyester release film.

In an exemplary embodiment of the present invention, the surface resistance of the antistatic layer may be 10 ¹⁰ Ω/□ or less, and more specifically, may be 10 ⁹ Ω/□ or less.

In an exemplary embodiment of the present invention, the water-dispersible antistatic composition may further include a silicone-based wetting agent, a fluorine-based wetting agent, a slip agent, a defoaming agent, a wetting agent, a surfactant, a thickener, a plasticizer, an antioxidant, an ultraviolet absorber, a preservative, and a crosslinking agent as needed.

The thickness of each of the base film, the release layer and the antistatic layer is not particularly limited and may be adjusted according to the specific application field of the polyester release film.

For example, the base film may have a thickness of 10 μm to 300 μm, and the release layer and the antistatic layer may each have a thickness of 10 nm to 200 nm, but the present invention is not limited thereto.

The thickness of the release layer and the antistatic layer may be the same or different from each other. Specifically, the thickness of the base film may be 10 μm to 200 μm, 10 μm to 100 μm, or 10 μm to 50 μm, the thickness of the release layer may be 10 nm to 100 nm, and more specifically, 50 nm to 100 nm, and the thickness of the antistatic layer may be 10 nm to 100 nm, and more specifically, 20 nm to 80 nm.

In the polyester release film, the base film is not particularly limited and may be uniaxially stretched in the machine direction (MD) or the transverse direction (TD), or biaxially stretched in the machine direction (MD) or the transverse direction (TD), and the release layer and the antistatic layer may be uniaxially stretched or biaxially stretched, but in the case where the release layer and the antistatic layer are uniaxially stretched in the transverse direction (TD), the performance of the present invention can be further provided, which is preferred.

As the polyester release film satisfies the above-mentioned properties, the polyester release film may have excellent peeling properties and low friction electrostatic voltage, so that the polyester release film may have excellent antistatic properties.

For example, the polyester release film may have a peel force of 350 gf/inch to 700 gf/inch, 400 gf/inch to 650 gf/inch, or 400 gf/inch to 600 gf/inch. The polyester release film having a peel force within the above range may have excellent coating processability and peeling performance in post-processing (e.g., a process of forming a barrier coating on the release film, etc.).

In this specification, the peel force is measured according to the standard test method of ASTM D 3330. Specifically, the peel force can be measured by the following method: an acrylic adhesive tape (NITTO #31B, tape width: 25 mm, manufactured by NittoDenko Corporation) is cut into a size of 5 mm×180 mm and the cut tape is laminated on a release layer of a polyester release film, a load of 70 g/cm ² is applied, the tape is allowed to stand at room temperature for 30 minutes, and then the tape is peeled off using a peel tester at 180 degrees and a peel rate of 300 mm/min.

Furthermore, the polyester release film may have a significantly low tribostatic voltage of less than 50 V, less than 40 V, less than 30 V, less than 20 V, or less than 10 V. The lower limit of the tribostatic voltage is not particularly limited, and may be, for example, 1 V or more, 3 V or more, or 5 V or more.

In this specification, the tribostatic voltage is measured according to the standard test method of KS K 0555. Specifically, the tribostatic voltage can be measured by a method of measuring the tribostatic of a polyester release film using a conventional rotary static tester. In this case, the amount of static electricity generated by rubbing surface A (the surface of the release layer in the polyester release film) and surface B (the surface of the antistatic layer in the polyester release film) at a rotation speed of 300 rpm for 180 seconds is measured.

In addition, the polyester release film may have a low haze value and excellent coating processability.

For example, the polyester release film may have a haze of 3.90% or less. Preferably, the polyester release film may have a haze of 3.50% to 3.90%, 3.60% to 3.90%, or 3.70% to 3.86%.

In addition, the polyester release film may have excellent coating processability satisfying the following Equation 1:

[Equation 1]

_NH ＝0

In Equation 1, _NH is the number of pinholes formed per unit area (m ² ) when a UV resin is applied to a release layer of a polyester release film to a thickness of 10 μm and the UV resin is cured.

That is, in any manufacturing process using the polyester release film as a substrate, when any resin layer is formed on the release layer, substantially no pinholes are formed on the release layer, so that excellent coating processability can be exhibited.

In addition, the polyester release film may have a total transmittance of 90% to 95%, a water contact angle of 85° to 90°, a diiodomethane contact angle of 50° to 60°, and a surface energy of 30 mN/m to 35 mN/m.

In addition, the polyester release film according to an exemplary embodiment of the present invention may be a polyester release film for a thin film polarizing plate, but is not limited thereto, and may be applied to various fields requiring antistatic properties, coating processing properties, and peeling properties. For example, in addition to being used for a thin film polarizing plate, the polyester release film according to an exemplary embodiment of the present invention may also be applied to: a cover tape for a multilayer ceramic capacitor (MLCC) carrier; and for flexible printed circuit board (FPCB) process protection, optically clear adhesive (OCA) and OCA protection, and optical components of displays (for protecting various display surfaces).

In the polyester release film, in particular, the release layer and the antistatic layer can be formed by online coating on the polyester base film. The release layer can be formed by applying an aqueous coating composition containing polyester resin, acrylic resin and polyolefin wax to one surface of the polyester base film by an online coating method.

The antistatic layer may be formed by applying a water-dispersible antistatic composition including a conductive polymer to the other surface of the base film by an in-line coating method.

The release layer and the antistatic layer are formed by an in-line coating method, so that even if the coating thickness is thin, the adhesion with the polyester base film can be excellent and excellent moisture resistance and solvent resistance can also be exhibited.

The polyester release film has excellent coating processability and peeling property and low tribostatic voltage, so that the polyester release film can be suitably used as a release base film when manufacturing a thin film polarizing plate.

As a non-limiting example, when manufacturing a thin film polarizing plate, a laminate can be formed on a base film of a polyester release film by sequentially laminating a barrier coating; a polyvinyl alcohol resin layer; an adhesive layer; and a resin layer, such as a polyethylene terephthalate (PET) layer, a triacetyl cellulose (TAC) layer, or a polymethyl methacrylate (PMMA) layer.

Furthermore, the polyester release film may be removed from the laminate.

Hereinafter, a method of manufacturing a polyester release film will be described in detail.

A method for manufacturing a polyester release film according to an exemplary embodiment of the present invention may include:

The first step is to prepare a polyester base film;

The second step is to form a release layer by applying an aqueous coating composition comprising a polyester resin, an acrylic resin and a polyolefin wax onto one surface of the base film;

A third step of forming an antistatic layer by applying a water-dispersible antistatic composition including a conductive polymer to the other surface of the base film; and

In a fourth step, while stretching the laminate including the base film and the release layer and the antistatic layer formed on the base film, the laminate is heat-treated.

The first step is a step of preparing a polyester base film, and the polyester base film is formed of a polyester resin.

Conventional polyester base films in the art to which the present invention belongs can be used without particular limitation. The polyester base film can be prepared to be stretched in the machine direction (MD) (or longitudinal direction), but is not limited thereto. Preferably, the polyester base film can be stretched to 2 to 5 times the initial length in the machine direction (MD). The polyester base film preferably has a thickness of 10 μm to 300 μm, but is not limited thereto within the limit of achieving the purpose of the present invention.

The second step is a step of forming a release layer by applying an aqueous coating composition including a polyester resin, an acrylic resin, and a polyolefin wax to one surface of the base film, and the aqueous coating composition is used to form a release layer on the polyester base film.

The aqueous coating composition may include a polyester resin, an acrylic resin, and a polyolefin wax, and specific details regarding the resins and waxes may apply as described above.

The aqueous coating composition may be prepared by uniformly mixing the above components with water. The solid content of the aqueous coating composition is preferably 20 to 60 wt % to ensure the efficiency of the coating process.

The release layer can be formed on one surface of the polyester base film by an online coating method using an aqueous coating composition. The release layer is formed by the online coating method so that even if the coating thickness is thin, the adhesion to the polyester base film can be excellent and excellent moisture resistance and solvent resistance can also be exhibited.

The in-line coating process can be carried out using conventional equipment.

When in-line coating is performed, the aqueous coating composition may be applied to a thickness of 20 nm to 200 nm after final stretching and drying of the release layer. Specific details regarding the thickness and other properties of the release layer may apply as described above.

The aqueous coating composition is applied to the polyester base film, and then the aqueous coating composition is cured to remove moisture, so that a release layer may be formed.

The third step is a step of forming an antistatic layer by applying a water-dispersible antistatic composition containing a conductive polymer to the other surface of the base film. The water-dispersible antistatic composition may further contain an aqueous polyurethane resin, and specific details about the conductive polymer, aqueous polyurethane resin, etc. may be applied as described above.

The water-dispersible antistatic composition may be prepared by uniformly mixing the above components with water. The solid content of the water-dispersible antistatic composition is preferably 5 to 50 wt % to ensure the efficiency of the coating process.

The water-dispersible antistatic composition may further include an organic solvent, and specific details thereon may apply as described above.

The antistatic layer may be formed on the other surface of the polyester base film by an in-line coating method using the water-dispersible antistatic composition, and specific details about the in-line coating method may be applied as described in the release layer.

The fourth step is a step of heat-treating the laminate including the base film and the release layer and the antistatic layer formed on the base film while stretching the laminate in the machine direction (MD) or the transverse direction (TD).

In one exemplary embodiment, although not limited thereto, when the laminate is stretched 2 to 5 times the original length in the transverse direction (TD), the exemplary embodiment of the present invention is suitable for achieving desired physical properties, which is preferred.

For example, a release layer and an antistatic layer may be formed on a polyester base film uniaxially stretched in a machine direction (MD), and then the polyester base film on which the release layer and the antistatic layer are formed may be stretched in a transverse direction (TD). Through this stretching process, the polyester base film may be biaxially stretched in the machine direction and the transverse direction, and the release layer and the antistatic layer may be uniaxially stretched in the transverse direction.

The fourth step can be performed using a conventional heat treatment device such as a tenter. In the fourth step, the laminate can be continuously passed through the tenter.

The laminate may be preheated while passing through the front portion of the tenter, the laminate may be stretched in the transverse direction (TD) while passing through the middle portion of the tenter, and the laminate may be heat treated while passing through the rear portion of the tenter. The heat treatment may be performed while maintaining the tension applied to the laminate during stretching in the transverse direction.

Preferably, the fourth step can be performed while the laminate passes through a heat treatment device in which the total calorific value of air supplied to the passing area is 222,000 kcal/min to 229,000 kcal/min. The laminate passing through the heat treatment device is stretched and heat-treated while being exposed within the total calorific value range.

Specifically, the fourth step can be carried out while passing the laminate through a heat treatment device, in which the total calorific value of the air supplied to the entire pass-through area is 222,000 kcal/min to 229,000 kcal/min, 225,000 kcal/min to 229,000 kcal/min, 226,000 kcal/min to 229,000 kcal/min, 226,000 kcal/min to 228,000 kcal/min, or 226,000 kcal/min to 227,000 kcal/min.

The total calorific value (kcal) of the air supplied to the entire passing area through which the laminate passes in the fourth step can be calculated from data such as the temperature (°C) of the area, the mass (kg/min) of the air supplied to the heat treatment device, and the specific heat (kcal/kg°C) of the air. The mass (kg/min) of the air can be obtained from the volume flow rate ( ^Nm3 /min) of the air and the density (kg/ ^Nm3 ) of the air.

For example, when the density of air supplied to a specific area in the heat treatment device is 1.286 kg/Nm ³ , the specific heat of the air is 0.24 kcal/kg°C, the volume flow rate of the air is 380 Nm ³ /min, the initial temperature of the air is 20°C, and the set temperature of the area is 220°C, the total calorific value (kcal) of the air supplied to the area can be obtained by the following equations 1 and 2, which is 23,456.64 kg/min.

[Equation 1]

Air mass (kg/min) = air volume flow (Nm ³ /min) × air density (kg/Nm ³ )

[Equation 2]

Calorific value of air (kcal/min) = mass of air (kg/min) × specific heat of air (kcal/kg℃) × temperature change (℃)

Furthermore, when the passing length of the zone is 3 m and the laminate passes through the zone at a speed of 100 m/min, the heat value to which the laminate is exposed in the zone can be obtained by the following Equation 3 as 7,037 kcal/zone.

[Equation 3]

Heat value of laminate exposure (kcal/area) = Heat value of air (kcal/min) × Passing length of area (m/area) × Speed of laminate (m/min)

According to an exemplary embodiment of the present invention, the fourth step can be performed in the following manner: preheating the laminate while passing the laminate through a region supplied with a calorific value of 44,000 kcal/min to 46,000 kcal/min; stretching the preheated laminate in the machine direction (MD) or the transverse direction (TD) while passing the preheated laminate through a region supplied with a calorific value of 62,000 kcal/min to 64,000 kcal/min; and heat treating the stretched laminate while passing the stretched laminate through a region supplied with a calorific value of 114,000 kcal/min to 120,000 kcal/min.

Preferably, the preheating process may be performed while passing the laminate through a zone supplied with a heat value of 45,000 kcal/min to 46,000 kcal/min.

Preferably, the stretching process may be performed while passing the preheated laminate through a zone supplied with a heat value of 63,000 kcal/min to 64,000 kcal/min.

In addition, preferably, the heat treatment may be performed while passing the stretched laminate through a region supplied with a calorific value of 115,000 kcal/min to 120,000 kcal/min, 115,000 kcal/min to 119,000 kcal/min, 116,000 kcal/min to 119,000 kcal/min, 117,000 kcal/min to 118,500 kcal/min, or 118,000 kcal/min to 118,500 kcal/min.

In the fourth step (particularly, the heat treatment area after stretching), when the total calorific value of the air supplied to the passing area is too low, the peeling performance and transfer performance of the polyester release film are deteriorated and the friction electrostatic voltage increases. In addition, in the fourth step (particularly, the heat treatment area after stretching in the transverse direction), when the total calorific value of the air supplied to the passing area is too high, the surface energy of the polyester release film is reduced, and therefore, the coating processability is deteriorated.

Furthermore, in the fourth step, the laminate preferably passes through the heat treatment device at a speed of 80 m/min to 120 m/min, 90 m/min to 110 m/min, or 90 m/min to 100 m/min.

In performing the fourth step, in order to expose the laminate to an appropriate heat value in each region and to sufficiently perform stretching and heat treatment in the transverse direction, the laminate preferably passes through a heat treatment device within the above-mentioned speed range.

The fourth step may be performed at 120° C. to 245° C. For example, the fourth step may be performed by preheating the laminate at 120° C. to 150° C.; stretching the preheated laminate in the transverse direction at 130° C. to 150° C.; and heat-treating the stretched laminate at 215° C. to 245° C.

Specifically, the heat treatment of the stretched laminate may be performed at 215°C or more, 220°C or more, 225°C or more, or 230°C or more, and 245°C or less or 240°C or less. Specifically, the heat treatment of the stretched laminate may be performed at 215°C to 245°C, 220°C to 245°C, 220°C to 240°C, 225°C to 240°C, or 230°C to 240°C.

When the temperature of the heat treatment of the stretched laminate satisfies the above range, the peeling property of the polyester release film can be excellent, the friction electrostatic voltage can be reduced, and fine pinholes are not formed during the manufacture of the polyester release film, thereby improving the coating processability.

After performing the fourth step, a process of relaxing the laminate by 2% to 10% in each of the machine direction and the transverse direction at 150° C. to 200° C. may be performed.

The final thickness of the polyester release film obtained by the above process may be 20 μm to 100 μm, 30 μm to 80 μm, or 30 μm to 50 μm.

Hereinafter, the preparation examples, embodiments and experimental examples of the present invention will be described in detail below. However, the embodiments and experimental examples described below are only illustrations of a part of the present invention, and the present invention is not limited thereto.

<Preparation Example 1> Preparation of the first aqueous coating composition

(1) Preparation of the first resin composition

The first polyester resin (weight average molecular weight: 10,000 g/mol) was obtained by polycondensation of 50 mol % of a diol component including diethylene glycol and ethylene glycol in a molar ratio of 5:5 and 50 mol % of an acid component including terephthalic acid and sulfoterephthalic acid in a molar ratio of 8.5:1.5.

100 parts by weight of the first polyester resin and 25 parts by weight of polyethylene wax (Wax No. 1, TAKAMATSU OIL & FAT CO., LTD., Japan) were added to distilled water, and the mixture was stirred for 30 minutes to prepare a first resin composition (solid content: 20 wt%).

(2) Preparation of the Second Resin Composition

The second polyester resin (weight average molecular weight: 3,000 g/mol) was obtained by polycondensation of 50 mol % of a diol component comprising diethylene glycol and ethylene glycol in a molar ratio of 5:5 and 50 mol % of an acid component comprising terephthalic acid and sulfoterephthalic acid in a molar ratio of 8.5:1.5.

An acrylic resin (weight average molecular weight: 50,000 g/mol) was obtained by copolymerizing 60 mol % of glycidyl acrylate and 40 mol % of vinyl propionate.

50 parts by weight of the second polyester resin, 50 parts by weight of an acrylic resin, and 25 parts by weight of a polyethylene wax were added to distilled water, and the mixture was stirred for 30 minutes, thereby preparing a second resin composition (solid content: 20 wt %).

(3) Preparation of water-based coating composition

14.3 wt % of the first resin composition (solid content: 20 wt %), 14.3 wt % of the second resin composition (solid content: 20 wt %), 0.2 wt % of a silicone-based wetting agent (Q2-5212, solid content: 90 wt %, Dow Corning Corporation), 0.2 wt % of a fluorine-based wetting agent (FS-31, solid content: 25 wt %, DuPont de Nemours, Inc.), and the remainder of water are mixed to prepare a first aqueous coating composition.

<Preparation Example 2> Preparation of the Second Aqueous Coating Composition

A second aqueous coating composition was prepared in the same manner as in Preparation Example 1, except that the first resin composition prepared in Preparation Example 1 was not used, and the second resin composition was further used in the same content as the first resin composition. That is, the second aqueous coating composition according to Preparation Example 2 contained 28.6 wt % of the second resin composition.

<Preparation Example 3> Preparation of the first antistatic coating composition

60 wt % of an aqueous conductive polymer dispersion (Clevios P, solid content: 1.3 wt %, Heraeus), 6 wt % of water and 5 wt % of isopropyl alcohol (IPA) were added to a mixing container, the mixture was stirred for 1 hour, 2 wt % of 2-amino-2-methyl-1-propanol (95%, Alfa aesar) was further added to the mixing container, the mixture was stirred for another 1 hour, 20 wt % of an aqueous polyurethane resin (Neo rez R-960, solid content: 31 wt %, NeoResins) was added to the mixing container, the mixture was stirred again for 30 minutes, 5 wt % of dimethyl sulfoxide and 2 wt % of a silicone-based wetting agent (BYK 348) were added to the mixing container, and the mixture was stirred for another 1 hour, thereby preparing a first water-dispersible antistatic composition (solid content: 6.98 wt %). In addition, a second dilution of the first water-dispersible antistatic composition was prepared. At this time, 30 wt % of the first water-dispersible antistatic composition, 69.6 wt % of water, 0.2 wt % of a silicone-based wetting agent (Q2-5212, solid content: 90 wt %, Dow Corning Corporation), and 0.2 wt % of a fluorine-based wetting agent (FS-31, solid content: 25 wt %, DuPont de Nemours, Inc.) were mixed to prepare a first antistatic coating composition.

<Comparative Preparation Example 1> Preparation of the Third Aqueous Coating Composition

20 wt % of a silicone release body material (400E, solid content: 55 wt %, Wacker Chemie AG), 1.1 wt % of a curing agent (V-72, solid content: 40 wt %, Wacker Chemie AG), 0.18 wt % of a silicone wetting agent (Q2-5212, solid content: 90 wt %, Dow Corning Corporation), 5 wt % of isopropyl alcohol (IPA) and the remainder of water were mixed to prepare a third aqueous coating composition.

<Comparative Preparation Example 2> Preparation of the Fourth Aqueous Coating Composition

A fourth aqueous coating composition was prepared in the same manner as in Preparation Example 1, except that the second resin composition prepared in Preparation Example 1 was not used, and the first resin composition was further used in the same amount as the second resin composition. That is, the fourth aqueous coating composition according to Comparative Example 1 included 28.6 wt % of the first resin composition.

<Comparative Preparation Example 3> Preparation of the Second Antistatic Coating Composition

5.1 wt % of an acrylic aqueous dispersion (ATX-014, solid content: 40 wt %, TAKAMATSUOIL & FAT CO., LTD., Japan), 9 wt % of an anionic polymer antistatic agent (ICP-323, molecular weight: 100,000 g/mol or more, solid content: 25.5 wt %, JINBO Co., Ltd.), 2 wt % of a silicone wetting agent (BYK 384) and the remainder of water were mixed to prepare a second antistatic coating composition.

<Example 1>

(1) PET chips from which moisture was removed to 100 ppm or less were injected into a melt extruder and melted, and then, while the melted PET chips were extruded through a T-die, they were rapidly cooled and solidified using a casting drum having a surface temperature of 20° C., thereby preparing a PET sheet. The prepared PET sheet was stretched in a machine direction at 110° C. to 3.5 times the initial length, and then the stretched PET sheet was cooled to room temperature, thereby obtaining a PET base film.

(2) Using a gravure coater, the first aqueous coating composition according to Preparation Example 1 was applied to one surface of the PET base film so that the thickness after final drying was 70 nm to form a release layer, and the first antistatic coating composition according to Preparation Example 3 was applied to the other surface of the PET base film so that the thickness after final drying was 50 nm to form an antistatic layer.

(3) Subsequently, in a tenter divided into a preheating zone, a stretching zone, and a heat treatment zone, the laminate having the release layer and the antistatic layer formed therein was heat treated while being stretched in the transverse direction (TD) to 4 times the original length.

Heat treatment was performed while the laminate (initial width: 5.12 m, initial thickness: 152 μm) was passed through a tenter having a total length of 33 m and including a preheating zone, a stretching zone, and a heat treatment zone in sequence at a moving speed of 100 m/min.

The heat treatment was performed while the laminate was passed through a tenter in which the total calorific value of air supplied to the passing area was 226,400 kcal/min.

It was confirmed that the density of the air supplied to the tenter was 1.286 kg/nm ³ , the specific heat of the air was 0.24 kcal/kg° C., and the volume flow rate of the air was adjusted within the range of 270 nm ³ /min to 680 nm ³ /min.

Specifically, the laminate was passed through a preheating zone (passing length: 7.5 m) supplied with a heat value of 45,000 kcal/min at a temperature of about 120° C. to 130° C. Subsequently, the preheated laminate was stretched to 4 times the initial length in the transverse direction while passing through a stretching zone (passing length: 10.5 m) supplied with a heat value of 63,200 kcal/min at a temperature of about 130° C. to 140° C. Subsequently, the stretched laminate was heat-treated while passing through a heat treatment zone (passing length: 15 m) supplied with a heat value of 118,200 kcal/min at a temperature of 230° C. to 235° C.

(4) After the heat treatment, the laminate was relaxed by 10% in each of the machine direction and the transverse direction at 200° C., thereby preparing a polyester release film having a total thickness of 38 μm.

<Example 2>

In Example 2, a polyester release film having a total thickness of 38 μm was prepared in the same manner as in Example 1, except that the second aqueous coating composition according to Preparation Example 2 was applied to form the release layer of Example 1.

<Comparative Example 1>

In Comparative Example 1, a polyester release film having a total thickness of 38 μm was prepared in the same manner as in Example 1, except that the antistatic layer of Example 1 was not formed.

<Comparative Example 2>

In Comparative Example 2, a polyester release film having a total thickness of 38 μm was prepared in the same manner as in Example 1, except that the third aqueous coating composition of Comparative Preparation Example 1 was applied to form the release layer of Example 1.

<Comparative Example 3>

In Comparative Example 3, a polyester release film having a total thickness of 38 μm was prepared in the same manner as in Comparative Example 2, except that the antistatic layer of Comparative Example 2 was not formed.

<Comparative Example 4>

In Comparative Example 4, a polyester release film having a total thickness of 38 μm was prepared in the same manner as in Example 1, except that the second antistatic coating composition of Comparative Preparation Example 3 was applied to form the antistatic layer of Example 1.

<Comparative Example 5>

In Comparative Example 5, a polyester release film having a total thickness of 38 μm was prepared in the same manner as in Example 1, except that the fourth aqueous coating composition of Comparative Preparation Example 2 was applied to form the release layer of Example 1.

<Evaluation Items>

Table 1 shows the measured values of the following properties of Examples and Comparative Examples.

1. Optical performance

The haze and total transmittance (TT) of the film of each of Examples and Comparative Examples were measured using a haze meter (NDH 5000, Nippon Denshoku Industries Co., Ltd.).

2. Transfer performance (transfer test)

An untreated PET base film was laminated on the release layer of the polyester release film, a load of 50 gf/inch was applied, and the laminate was allowed to stand in an oven at 45° C. for 24 hours. When the difference in the water contact angle was Δ2° or more, it was marked as "transfer", and when there was no difference in the water contact angle, it was marked as "no transfer".

The same transfer test was performed on the antistatic layer of the polyester release film and the presence or absence of transfer was marked.

3. Water contact angle

The water contact angle of the release layer of the film was measured using a contact angle measuring instrument (DSA 100, KRUSS Scientific Instruments, Inc.). 3 μl of pure water (S1, volume mode) was dropped on the film sample, and the average water contact angle for 15 seconds was measured. The water contact angle was measured 5 times, and the average value thereof is shown.

4. Diiodomethane contact angle

The diiodomethane contact angle of the release layer of the film was measured using a contact angle measuring instrument (DSA 100, KRUSS Scientific Instruments, Inc.). 1 μl of diiodomethane (S1, volume mode) was dropped on the film sample, and the average diiodomethane contact angle was measured for 15 seconds. The diiodomethane contact angle was measured 5 times, and the average value is shown.

5. Surface energy

The surface energy of the release layer of the film was calculated from the measurement results of the water contact angle and the diiodomethane contact angle using the Owens-Wendt method.

6. Coating processing performance

A UV resin (MIRAMER M1130, Miwon Specialty Chemical Co., Ltd.) was applied to the release layer of the film to a thickness of 10 μm to prepare a UV-cured sample. The coating processability of the sample was evaluated according to the following criteria.

*Grade 1 - No pinholes per unit area (m ² )

*Level 2 - less than 2 pinholes per unit area (m ² )

*Level 3 - less than 5 pinholes per unit area ( ^m2)

*Level 4 - less than 10 pinholes per unit area (m ² )

*Level 5 - more than 10 pinholes per unit area (m ² )

7. Peel force

The peel force was measured by a method comprising the following steps: preparing a first sample obtained by adhering an acrylic adhesive tape (NITTO #31B tape, width: 25 mm, manufactured by Nitto Denko Corporation) to a release layer of a polyester release film; preparing a second sample by cutting the first sample into a size of 5 mm x 180 mm; and applying a load of 70 g/cm ² to the second sample, allowing the second sample to stand at room temperature for 30 minutes, and then peeling the tape at 180° and a peeling speed of 300 mm/min using a peel tester.

8. Tribostatic voltage

The friction static electricity on the polyester release film was measured using a rotation static electricity tester (RST-300a, Daiei Kagaku Seiki MFG CO., LTD.). At this time, the amount of static electricity generated by rubbing the surface A (the surface of the release layer in the polyester release film) and the surface B (the surface of the antistatic layer in the polyester release film) at a rotation speed of 300 rpm for 180 seconds was measured.

9. Surface resistance

The surface resistance of the antistatic layer of the film prepared in each of Examples and Comparative Examples was evaluated. The surface resistance was measured under the conditions of 25° C., 50% RH and 10 V for 10 seconds using Hiresta-Up MCP-HP450 manufactured by Mitsubishi Chemical Corporation.

[Table 1]

Referring to Table 1, it can be confirmed that the polyester release film according to the embodiment has excellent transfer performance, peeling performance and coating processability as well as excellent antistatic performance, and has a significantly low friction static voltage of less than 50V compared with the polyester release film according to the comparative example.

Therefore, the polyester release film of the present invention includes a release layer comprising an aqueous coating composition (containing a polyester resin, an acrylic resin and a polyolefin wax) and an antistatic layer comprising a water-dispersible antistatic composition (containing a conductive polymer), so that the polyester release film has excellent stripping performance and coating processability, excellent antistatic performance and a significantly low tribostatic voltage of less than 50 V. Therefore, the polyester release film can prevent static electricity from being generated during film operation and winding, and can significantly reduce the amount of air or foreign matter introduced due to static electricity.

In addition, the polyester release film of the present invention can solve problems such as reduced yield due to unreacted substances and foreign matter adsorption due to static electricity that occur when using the polyester release film to form a coating, and is therefore suitable for use as a substrate when manufacturing an optical film such as a thin film polarizing plate.

Claims (17)

1. A polyester release film, comprising: Polyester base film; a release layer formed on one surface of the base film; and an antistatic layer formed on the other surface of the base film, Wherein, the release layer comprises an aqueous coating composition containing polyester resin, acrylic resin and polyolefin wax, The antistatic layer comprises a water-dispersible antistatic composition containing a conductive polymer. 2 . The polyester release film according to claim 1 , wherein the polyester release film has a tribostatic voltage of less than 50V. 3 . The polyester release film according to claim 1 , wherein a weight ratio of the polyester resin to the acrylic resin in solid form is 1:0.1 to 1:1.5. 4 . The polyester release film according to claim 1 , wherein the polyolefin wax is contained in the release layer in an amount of 20 to 50 parts by weight relative to 100 parts by weight of the polyester resin. The polyester release film according to claim 1 , wherein the polyolefin wax is one or more waxes selected from polyethylene wax and polypropylene wax. 6 . The polyester release film according to claim 1 , wherein the conductive polymer comprises one or more selected from the group consisting of polythiophene polymers, polypyrrole polymers and polyaniline polymers. 7 . The polyester release film according to claim 1 , wherein the water-dispersible antistatic composition further comprises an aqueous polyurethane resin. 8 . The polyester release film according to claim 7 , wherein the solid of the water-dispersible antistatic composition comprises 1 to 30 wt % of the conductive polymer and 70 to 99 wt % of the aqueous polyurethane resin. 9 . The polyester release film according to claim 1 , wherein the surface resistance of the antistatic layer is 10 ¹⁰ Ω/□ or less. 10. The polyester release film according to claim 1, wherein the polyester release film has a haze of 3.90% or less and a coating processability satisfying the following equation 1: [Equation 1] _NH ＝0 In Equation 1, _NH is the number of pinholes formed per unit area (m ² ) when a UV resin is applied to a release layer of a polyester release film to a thickness of 10 μm and the UV resin is cured. 11. The polyester release film according to claim 1, wherein the release layer is formed by coating the aqueous coating composition in-line, The antistatic layer is formed by in-line coating of the water-dispersible antistatic composition. 12 . The polyester release film according to claim 1 , wherein the base film is biaxially stretched, and the release layer and the antistatic layer are uniaxially stretched in a transverse direction (TD). 13 . The polyester release film according to claim 1 , wherein the base film has a thickness of 10 μm to 300 μm, and the release layer and the antistatic layer have a thickness of 10 nm to 200 nm respectively. The polyester release film according to claim 1 , wherein the polyester release film is used to protect a polarizing plate. 15. A method for manufacturing a polyester release film, the method comprising: The first step is to prepare a polyester base film; A second step of forming a release layer by applying an aqueous coating composition comprising a polyester resin, an acrylic resin and a polyolefin wax to one surface of the base film; A third step of forming an antistatic layer by applying a water-dispersible antistatic composition including a conductive polymer to the other surface of the base film; and In a fourth step, while stretching the laminate including the base film, the release layer and the antistatic layer formed on the base film, the laminate is heat-treated. 16. The method according to claim 15, wherein, in the fourth step, the stretching and the heat treatment are performed while passing the laminate through a heat treatment device in which a total calorific value of air supplied to a passing area is 222,000 kcal/min to 229,000 kcal/min. 17. The method according to claim 15, wherein the fourth step is performed by: preheating the laminate while passing the laminate through a zone supplied with a calorific value of 44,000 kcal/min to 46,000 kcal/min; stretching the preheated laminate in a transverse direction (TD) while passing the preheated laminate through a zone supplied with a heating value of 62,000 kcal/min to 64,000 kcal/min; and The heat treatment is performed on the stretched laminate while passing the stretched laminate through a zone supplied with a heat value of 114,000 kcal/min to 120,000 kcal/min.