KR20010045562A - Polyester film formed primer layer and producing method therefor - Google Patents

Abstract

PURPOSE: Provided is a polyester film having a primer layer, which is excellent in adhesive strength to an aqueous resin such as an ink aqueous layer of an inkjet film and a subbing layer of a photo film. CONSTITUTION: The polyester film comprises: a polyester base film layer; the primer layer comprising a polyester of which the both ends are blocked by isocyanate groups and a multifunctional aziridine hardener in the weight ratio of 50:1-1:1, which is formed on one or both sides of the base film layer, wherein the thickness of the primer layer is 0.001-1 micrometer. Additionally, the primer layer contains 4-18wt. (based on the total weight of the primer layer) of colloidal silica having a particle size of 50-200nm and 0.4-18wt. (based on the total weight of the primer layer) of an anionic surfactant.

Description

Polyester film formed primer layer and producing method therefor}

The present invention relates to a polyester film and a method for manufacturing the same, and more particularly, a polyester film having a primer layer having excellent adhesion to water-soluble resins such as a subbing layer of a photographic film and an ink receiving layer of an inkjet film. And to a method for producing the same.

Polyester film represented by polyethylene terephthalic acid film has excellent mechanical properties and has the advantage of imparting transparent optical properties, but crystallization and molecular orientation shows high surface cohesion. Therefore, when the polyester film is not surface-treated, the adhesive force to water-soluble resin is low.

For example, the photopolymer film consists of a polyester film, a photosensitive layer adhered thereon, and a serving layer for bonding a hydrophobic polyester film and a hydrophilic photosensitive layer. The serving layer is mainly formed using a water-soluble resin such as cellulose acetate phthalate, cellulose acetate maleate or vinyl copolymer polymer with maleic anhydride.

As described above, a problem occurs in that a serving layer made of a polyester film and a water-soluble resin is separated or peeled off during various handling processes such as development, fixation, and washing.

Various methods have been used to improve adhesion to the water-soluble resin. For example, a method of removing crystallinity of a film using an organic solvent such as chlorophenol or cresol has been used. However, this method has disadvantages of environmental pollution caused by the toxicity of the organic solvent and the generated vapor, and deteriorates the transparency of the film.

In addition, another method of improving the adhesive strength is a method of coating a primer layer using an organic solvent type resin on a biaxially stretched polyester film. However, this method also causes the risk of fire and contamination of the working environment due to the evaporation of the solvent used in the coating liquid, and the dust present in the working environment during coating clings to the surface of the primer-treated film and causes surface defects. Will occur.

Efforts have been made to form a primer layer by coating various water-soluble resins during the film manufacturing process in order to eliminate disadvantages such as explosion caused by solvents or environmental pollution caused by the use of organic solvent type resins. For example, in US Pat. No. 3,615,556, a water-soluble coating solution containing butadiene styrene copolymer, US Pat. No. 2,627,088 and US Pat. No. 2,698,240, a water-soluble coating solution containing vinylidene copolymer, US Pat. No. 4,229,523 are glycy A water-soluble coating liquid containing a copolymer of dill methacrylate and a coating liquid containing a water-soluble poly epoxy resin were used in US Pat. No. 4,988,572.

However, even when the above-mentioned water-soluble coating solution is applied, it does not have a satisfactory adhesive strength to the water-soluble resin or the adhesive strength is reduced by the change of the inclination, and thus there is a problem that a long time cannot be used after the film production.

Accordingly, the technical problem to be achieved by the present invention is to provide a polyester film in which the water-soluble resin and the adhesive strength are improved, and hardly the adhesive force decreases due to change over time.

Another technical problem to be achieved in the present invention is to provide a method for producing the polyester film.

In order to achieve the above technical problem, a base film layer made of polyester: and both ends having a weight ratio of 50: 1 to 1: 1 is made of a polyester blocked with an isocyanate group and a polyfunctional aziridine-based curing agent, the base film layer It provides a polyester film comprising a primer layer formed on one or both sides of.

In the present invention, the primer layer may further comprise 4 to 18 weight of the colloidal silica having a particle diameter of 50 to 200nm relative to the total weight of the primer layer.

In the present invention, the primer layer may further comprise 0.4 to 18% by weight based on the total weight of the primer layer anionic surfactant.

In the present invention, the polyester of the primer is at least one saturated or unsaturated dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, sebacic acid, phthalic acid and maleic acid; And at least one alkyl glycol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentyl glycol, and hexanediol.

In the present invention, the polyfunctional aziridine-based curing agent is trimetholol propane-tris (B (N- aziridyl) propionate, pentaerythritol-tris (B (N- aziridyl) propionate, 1- aziri Dinpropanoic acid, 2-methyl-2,3-(2-methyl) -1-aziridinyl-1-oxy propoxy-1,3-propanediyl ester and 2-ethyl-2,3-(2 -Methyl) -1-aziridinyl-1-oxy propoxy-1,3-propanediyl ester is preferably any one or more selected from the group consisting of.

In this invention, it is preferable that the thickness of the said primer layer is 0.001-1 micrometer.

In order to achieve the above another technical problem, the present invention

(a) preparing a polyester film;

(b) reacting the polyester and the polyisocyanate compound to prepare a polyester having both ends of the isocyanate group;

(c) mixing the product of step (b) with water and reacting with bisulfite to prepare a composition comprising a polyester having a structure in which isocyanate groups at both ends are blocked with bisulfite;

(d) adding a multifunctional aziridine-based curing agent to the composition to prepare a composition for forming a primer layer; And

(e) applying the composition for forming the primer layer on one or both surfaces of the polyester film of step (a), and heat-treating at 80 to 150 ° C. to dissociate the bisulfite and regenerate an isocyanate group to form a primer layer. It provides a method for producing a polyester film comprising a.

In the manufacturing method according to the present invention, the method may further include adding colloidal silica having a particle size of 50 to 200 nm to the primer-forming composition.

In the manufacturing method according to the present invention, the method may further include adding an anionic surfactant to the composition for forming the primer layer.

In the manufacturing method according to the invention, it may further comprise the step of stretching the polyester film.

In the production method according to the present invention, the polyisocyanate compound is selected from toluene diisocyanate, xylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate and trimethyl. It is preferably at least one selected from the group consisting of hexamethylene diisocyanate.

In the production method according to the present invention, the bisulfite is preferably at least one selected from the group consisting of sodium bisulfite, potassium bisulfite and ammonium bisulfite.

Polyester film according to the present invention is a base film layer made of polyester; And it is a polyester film composed of a polyester and a polyfunctional aziridine-based curing agent blocked at both ends of the weight ratio of 50: 1 to 1: 1, and formed on one side or both sides of the base film layer.

In addition, the polyester film according to the present invention, the primer layer is colloidal silica having a particle size of 50 to 200nm 4 to 18% by weight based on the total weight of the primer layer and / or anionic surfactant 0.4 to 18% by weight of the primer layer Weight further includes.

Such a polyester film according to the present invention is a polyester film having strong adhesion to a water-soluble resin such as a serving layer of a photographic film or an ink receiving layer of an inkjet film, and hardly changing with time.

Hereinafter, the present invention will be described in detail by explaining a method for producing a polyester film according to the present invention.

First, a polyester and a polyisocyanate compound are reacted to prepare a polyester having both ends of an isocyanate group.

The polyester may be saturated or unsaturated dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, sebacic acid, phthalic acid and maleic acid; And ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentylglycol, and hexanediol, and alkyl glycol selected from the group consisting of condensation polymerization, more preferably phthalic acid or adipic acid and ethylene glycol are condensation polymerization. It is done.

The polyisocyanate compound is also a group consisting of toluene diisocyanate, xylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate and trimethylhexamethylene diisocyanate It is preferable that it is any one selected from.

Next, the both ends of the polyester of isocyanate are diluted in water in a small amount to react with addition of an aqueous solution in which a predetermined amount of bisulfite such as sodium bisulfite, potassium bisulfite or ammonium bisulfite is added and reacted. An aqueous solution or an aqueous dispersion of polyester in which an isocyanate group is blocked with bisulfite is obtained.

Here, since the isocyanate group is more reactive with bisulfite materials than water, it is possible to obtain a water-soluble or water-dispersible polyester having a structure in which isocyanate groups at both ends are blocked with bisulfite.

Next, a polyfunctional aziridine-based curing agent is added to the aqueous solution or the aqueous dispersion to obtain a composition for forming a primer layer.

Colloidal silica and / or anionic surfactant having a particle size of 50 to 200 nm may be further added to the composition for forming a primer layer.

In addition, the composition for forming the primer layer is a polyester having a structure in which isocyanate groups at both ends are blocked with bisulfite is transformed into a polyester in which both ends are blocked with isocyanate in a subsequent process, and both ends are blocked with an isocyanate group. 4 to 18% by weight and / or the anionic interface based on the total weight of the composition comprising a weight ratio of the polyester and the polyfunctional aziridine-based curing agent is 50: 1 to 1: 1, or the primer layer formed by drying the colloidal silica The activator is adjusted to a composition comprising 0.4 to 018 weights further.

The polyfunctional aziridine-based curing agent is trimetholpropane-tris (B (N- aziridyl) propionate, pentaerythritol-tris (B (N- aziridyl) propionate, 1- aziridine propanoic acid, 2 -Methyl-2,3-(2-methyl) -1-aziridinyl-1-oxy propoxy-1,3-propanediyl ester and 2-ethyl-2,3-(2-methyl) -1 -At least one selected from the group consisting of aziridinyl-1-oxy propoxy-1,3-propanediyl ester, more preferably 1-aziridinepropanoic acid, 2-methyl-2,3- -(2-methyl) -1-aziridinyl-1-oxy propoxy-1,3-propanediyl ester and 2-ethyl-2,3-(2-methyl) -1-aziridinyl-1- At least one selected from the group consisting of oxy propoxy-1,3-propanediyl ester.

The anionic surfactant is not particularly limited as long as it is known in the art to which the present invention pertains. For example, keryl benzene sulfonate, polypropylene benzene sulfonate, sulfuric acid ester of stearic acid or sulfuric acid ester of recinolic acid, etc. Can be.

In addition, the composition for forming a primer may contain additives well known in the art to which the present invention pertains, for example, antistatic agents, wetting agents, pH adjusting agents, dyes or pigments in a range that does not reduce the adhesion with the water-soluble resin layer. It is possible.

Subsequently, the composition for forming the primer layer is applied to one or both surfaces of the polyester film and heat treated at 80 to 150 ° C. The bisulfite is dissociated by the heat treatment, whereby the cyanate group is regenerated so that both ends are blocked with an isocyanate group, and the primer layer or the cyanate group consisting of an aziridine-based curing agent is regenerated and both ends are blocked with isocyanate groups. And a primer layer containing aziridine-based curing agent as a main component and further adding colloidal silica and / or anionic surfactant.

The polyester film may be any of unstretched, uniaxially stretched or biaxially stretched, and, in the case of the stretched polyester film, further stretching the manufacturing method according to the present invention.

The coating time of the composition for forming the primer layer may be before or after the stretching step when the polyester film is a uniaxially stretched film, and in the case of a biaxially stretched film, before stretching in the longitudinal direction, and laterally after longitudinal stretching. It may be before or after lateral stretching.

In addition, the coating method of the composition for forming the primer layer is not particularly limited as long as it is a common method widely known in the art, for example, a coating method using a roll such as gravure roll, reverse gravure roll, The coating method using the Mayer bar etc. and the coating method of an air knife system are mentioned.

And, it is preferable to adjust the thickness of the primer layer to 0.001 to 1㎛, if the layer thickness is less than 0.001㎛ it is difficult to form a primer layer, if the layer thickness exceeds 1㎛ may be low adhesion to the water-soluble resin Not desirable Moreover, it is preferable that the application amount of the said composition for primer layer formation is 0.01-0.5 g / m <^2> on a polyester film.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. It is obvious that the present invention is not limited to the following examples.

<Production of Composition for Primer Formation>

0.3 mole part of adipic acid and 0.6 mole part of ethylene glycol were condensation-polymerized to prepare polyester having a weight average molecular weight of 2000. The polyester was reacted with hexamethylene isocyanate to prepare 50 g of polyester having both ends composed of isocyanate groups.

Next, the two ends of the polyester isocyanate group is diluted in 2000g of water, and then, 56 g of sodium bisulfite aqueous solution is added thereto, and the mixture is stirred with stirring at 35 ° C. for 60 minutes, thereby forming a polyisocyanate group at both ends blocked with bisulfite. An aqueous ester solution was prepared.

Subsequently, 30 g of Xama-7, a polyfunctional aziridine-based curing agent manufactured by Cordoba Chemical Company, was added thereto to prepare a composition for forming a primer layer.

<Example 1>

By mixing water and a composition for forming a primer layer prepared as described above, the polyester having a structure in which isocyanate groups at both ends blocked with bisulfite is transformed into a polyester in which both ends are blocked with isocyanate in a subsequent process. Both ends were adjusted to 10 weights of polyester blocked with isocyanate groups, 1 weight of Xama-7 and 89 weights of water.

Next, the primer layer forming composition adjusted as described above on one side of a polyethylene terephthalate film having a thickness of 100 μm, which can be purchased under the trade name SH31 from SKC Co., Ltd., Korea, was applied to the Mayer 3 coating method. Coated on one surface of the amorphous polyester sheet by a coating rate of 3 m / sec, and then heat-treated at 180 ° C. for 2 minutes to dissociate bisulfite and regenerate an isocyanate group, and both ends of the polyester and Xama-7 blocked at the isocyanate group. A primer layer was formed. The coating amount of the composition for primer formation was adjusted so that the thickness of the primer layer was 0.1 μm after drying.

Subsequently, the film was stretched 3.5 times at 90 ° C. in the longitudinal direction, 3.5 times at 140 ° C. in the lateral direction and heat-set at 210 ° C. for 3 seconds to prepare a polyester having a thickness of 10 μm.

According to the method described below for the polyester film prepared as described above, the adhesive strength of the serving layer of the photographic film and the ink receiving layer of the inkjet film to the water-soluble resin was evaluated and the results are shown in Table 1, Also evaluated and the results are shown in Table 2.

<Example 2>

A polyester film having a primer layer formed in the same manner as in Example 1 except that the composition for forming the primer layer was adjusted so that both ends of the polyester blocked with an isocyanate group were 10 wt%, 2 wt% Xama-7, and 88 wt% water. Prepared.

According to the method described below, the adhesive force of the serving layer of the photographic film and the ink-receiving layer of the inkjet film to the water-soluble resin was evaluated, and the results are shown in Table 1. Is shown in Table 2.

<Example 3>

A polyester film having a primer layer formed in the same manner as in Example 1, except that the composition for forming the primer layer was adjusted so that both ends of the polyester blocked with an isocyanate group were 10 wt%, 0.5 wt% Xama-7, and 89.5 wt% water. Prepared.

According to the method described below, the adhesive force of the serving layer of the photographic film and the ink-receiving layer of the inkjet film to the water-soluble resin was evaluated, and the results are shown in Table 1. Is shown in Table 2.

<Example 4>

A polyester film having a primer layer formed in the same manner as in Example 1 except that the composition for forming the primer layer was adjusted so that both ends of the polyester blocked with an isocyanate group were 5 weight, 0.5 weight of Xama-7, and 94.5 weight of water. Prepared.

According to the method described below, the adhesive force of the serving layer of the photographic film and the ink-receiving layer of the inkjet film to the water-soluble resin was evaluated, and the results are shown in Table 1. Is shown in Table 2.

<Comparative Example 1>

Except that Xama-7 was not added to prepare a composition for forming a primer layer by the same method as described above.

The primer layer was prepared in the same manner as in Example 1 except that the primer layer forming composition was mixed with water to adjust the composition for forming the primer layer so that both ends thereof were blocked with isocyanate groups to 10 weights and 90 weight water. The formed polyester film was prepared.

According to the method described below, the adhesive force of the serving layer of the photographic film and the ink-receiving layer of the inkjet film to the water-soluble resin was evaluated, and the results are shown in Table 1. Is shown in Table 2.

<Comparative Example 2>

A primer layer-forming composition was prepared in the same manner as described above, except that Cymel 303, a melamine formaldehyde-based curing agent manufactured by American Cyanamide, was added instead of Xama-7.

Except for adjusting the composition for forming a primer layer so that the primer layer-forming composition and water were mixed so that both ends of the polyester blocked with an isocyanate group to 10 weight, Cymel 303 1 weight and 89 weight of water. In the same manner, a polyester film having a primer layer formed thereon was prepared.

According to the method described below, the adhesive force of the serving layer of the photographic film and the ink-receiving layer of the inkjet film to the water-soluble resin was evaluated, and the results are shown in Table 1. Is shown in Table 2.

<Comparative Example 3>

A polyester film was prepared in the same manner as in Example 1 except that the primer layer was not formed.

According to the method described below, the adhesive force of the serving layer of the photographic film and the ink-receiving layer of the inkjet film to the water-soluble resin was evaluated, and the results are shown in Table 1. Is shown in Table 2.

<Comparative Example 4>

A polyester film was prepared in the same manner as in Example 1, except that the primer layer was formed using AC503, an acrylic emulsion manufactured and sold by Rohm and Haas, instead of the composition for forming a primer layer as described above. It was.

According to the method described below, the adhesive force of the serving layer of the photographic film and the ink-receiving layer of the inkjet film to the water-soluble resin was evaluated, and the results are shown in Table 1. Is shown in Table 2.

<Adhesive evaluation method>

1. Evaluation of Serving Layer and Adhesion of Photographic Film

1) Manufacture of photographic film

The serving layer was formed by applying a composition having the following composition on the primer layer of the polyester film prepared according to the above Examples and Comparative Examples.

-------------------------------------------------- ------------

Gelatin (1.2 weight aqueous solution) 84 weight

Formaldehyde 0.3 weight

15 weights of methanol

-------------------------------------------------- ------------

Type A gelatin of Kind & Knox Inc. was used as the gelatin used in the composition. The gelatin serving layer was completed by drying at 140 ° C. for 2 minutes by coating on a primer layer in a Meyer No. 6 method.

After coating the composition for evaluation photosensitive layer (SPSE Handbook of Photographic Science and engineering, John Wiley $ Sons, Woodlief Thomas.,: 515-519) which is generally used on the serving layer formed film as described above 20 times It dried for 1 hour at 35 ℃ to form a photosensitive layer to complete the photographic film.

2) Dry adhesive evaluation method

Dry adhesiveness was investigated by examining whether the serving layer was peeled off and the degree of peeling when the photo film manufactured by the above method was made in the method set forth in ASTM D3359, attached to the cellophane tape, and then peeled off suddenly. It was evaluated by five grades.

At this time, the case where peeling of a serving layer did not occur at all was made into 5 grades, and the case where most peeled was made into 1 grade.

(2) wet adhesiveness

The photographic film prepared by the above method was immersed in a photographic developing solution (Reprolith 200, Anitec Image Corporation) for 2.5 minutes and washed with water for 30 seconds. Subsequently, it was immersed in a fixed solution (Reprolith 160, Anitec Image Corporation) for 1.5 minutes and washed with water for 3 minutes. The photographic film treated as described above was scratched at regular intervals in parallel with an experimental knife, and rubbed the rubber 30 times with a pressure of 2 kg to investigate whether the serving layer was peeled off and the degree of peeling. Evaluated.

At this time, the case where peeling of a serving layer did not occur at all was made into 5 grades, and the case where most peeled was made into 1 grade.

2. Evaluation of adhesive force of inkjet film with ink receiving layer

1) Preparation of Inkjet Film

On the primer layer of the polyester film prepared according to the above Examples and Comparative Examples, the composition having the following composition was applied in the compound No. 40 method and dried at 140 ° C. for 5 minutes to prepare an inkjet film having an ink receiving layer. .

-------------------------------------------------- ------------

Polyvinyl alcohol (10 weight aqueous solution) 58.4 weight

Polyvinylpyrrolidone (10 weight aqueous solution) 8.3 weight

Methanol 33.3 Weight

-------------------------------------------------- -------------

2) Adhesion Evaluation

The inkjet film prepared by the above method was made by cross-sectional area by using the method suggested by ASTM D3359, and then adhered to the cellophane tape. Rating was made.

At this time, the case where peeling of a serving layer did not occur at all was made into 5 grades, and the case where most peeled was made into 1 grade.

3. Evaluation of Changes in Adhesion Over Time

1) Evaluation of changes over time of adhesion to the serving layer of photographic film

The polyester films prepared in Examples and Comparative Examples were formed in the same manner as described above to form a serving layer and a photosensitive layer to prepare a photographic film, which was then left in the air for 30 days.

With this photographic film, dry adhesion and wet adhesion were evaluated in the same manner as described above.

2) Evaluation of the change over time of the adhesive force of the inkjet film to the ink receiving layer

The polyester films prepared in Examples and Comparative Examples were formed in the same manner as described above to form an ink receiving layer to prepare an inkjet film, which was then left in the air for 30 days.

With this inkjet film, the adhesive force was evaluated in the same manner as the above-described method.

Adhesion to Inkjet Receptive Layer Adhesion to the Serving Layer of Photographic Films Dry adhesion Wet adhesion Example One 5 5 5 2 4 4 5 3 4 4 4 4 4 4 4 Comparative example One 4 4 3 2 3 4 3 3 One One One 4 One One One

Adhesion to Inkjet Receptive Layer Adhesion to the Serving Layer of Photographic Films Dry adhesion Wet adhesion Example One 5 5 4 2 4 4 4 3 4 5 4 4 4 4 4 Comparative example One 4 4 One 2 3 4 One 3 One One One 4 One One One

As can be seen from the results of Table 1, in the case of the photographic film and the inkjet film using a polyester film formed of a primer layer by the method of the example of the serving layer and the inkjet film of the photographic film compared to the comparative example It can be confirmed that the adhesive force with the ink receiving layer is generally good.

In addition, it can be seen from the results of Table 2 that the photographic film and the inkjet film using the polyester film prepared according to the example have no or little change over time in the adhesive force.

As described above, the polyester film according to the present invention has excellent adhesion to water-soluble resins, such as a serving layer of a photographic film and an ink receiving layer of an inkjet film, and has little change with time. Therefore, the polyester film according to the present invention can be used as an image base film for various uses.

Although the present invention has been described with reference to the embodiments, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent implementations are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (14)

A base film layer made of polyester: and Polyester having a weight ratio of 50: 1 to 1: 1 at both ends is made of a polyester blocked with an isocyanate group and a polyfunctional aziridine-based curing agent, and comprises a primer layer formed on one or both sides of the base film layer. film. The polyester film of claim 1, wherein the primer layer further comprises 4 to 18 weights of colloidal silica having a particle size of 50 to 200 nm based on the total weight of the primer layer. The polyester film according to claim 1 or 2, wherein the primer layer further contains 0.4 to 18 weights of the anionic surfactant based on the total weight of the primer layer. The method of claim 1, wherein the polyester of the primer is at least one saturated or unsaturated dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, sebacic acid, phthalic acid and maleic acid; And at least one alkyl glycol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentyl glycol, and hexanediol is condensation-polymerized. The polyfunctional aziridine-based curing agent according to claim 1, wherein the polyfunctional aziridine-based curing agent is trimethyrolpropane-tris (B (N-aziridyl) propionate, pentaerythritol-tris (B (N-aziridyl) propionate, 1- Aziridinepropanoic acid, 2-methyl-2,3-(2-methyl) -1-aziridinyl-1-oxy propoxy-1,3-propanediyl ester and 2-ethyl-2,3-( A polyester film, characterized in that any one or more selected from the group consisting of 2-methyl) -1-aziridinyl-1-oxy propoxy-1,3-propanediyl ester. The polyester film according to claim 1, wherein the primer layer has a thickness of 0.001 to 1 µm. (a) preparing a polyester film; (b) reacting the polyester and the polyisocyanate compound to prepare a polyester having both ends of the isocyanate group; (c) mixing the product of step (b) with water and reacting with bisulfite to prepare a composition comprising a polyester having a structure in which isocyanate groups at both ends are blocked with bisulfite; (d) adding a multifunctional aziridine-based curing agent to the composition to prepare a composition for forming a primer layer; And (e) applying the composition for forming the primer layer on one or both surfaces of the polyester film of step (a), and heat-treating at 80 to 150 ° C. to dissociate the bisulfite and regenerate an isocyanate group to form a primer layer. Method for producing a polyester film comprising a. The method of claim 7, further comprising adding colloidal silica having a particle size of 50 to 200 nm to the composition for forming a primer. The method of claim 7 or 8, further comprising adding an anionic surfactant to the composition for forming the primer layer. The method of claim 7, further comprising the step of stretching the polyester film. The method of claim 7, wherein the polyester of step (b) is at least one saturated or unsaturated dicarboxylic acid and ethylene glycol, diethylene glycol, selected from the group consisting of succinic acid, adipic acid, sebacic acid, phthalic acid and maleic acid Method for producing a polyester film characterized in that the condensation polymerization of at least one alkyl glycol selected from the group consisting of propylene glycol, butanediol, neopentyl glycol and hexanediol. 8. The polyfunctional aziridine-based curing agent according to claim 7, wherein the trifunctional aziridine-based curing agent is trimetholpropane-tris (B (N-aziridyl) propionate, pentaerythritol-tris (B (N-aziridyl) propionate, 1- Aziridinepropanoic acid, 2-methyl-2,3-(2-methyl) -1-aziridinyl-1-oxy propoxy-1,3-propanediyl ester and 2-ethyl-2,3-( A polyester film, characterized in that any one or more selected from the group consisting of 2-methyl) -1-aziridinyl-1-oxy propoxy-1,3-propanediyl ester. The method of claim 7, wherein the polyisocyanate compound is selected from toluene diisocyanate, xylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate and trimethylhexamethylene diisocyanate. Method for producing a polyester film, characterized in that any one or more selected from the group consisting of isocyanates. 8. The method according to claim 7, wherein the bisulfite is at least one selected from the group consisting of sodium bisulfite, potassium bisulfite and ammonium bisulfite.