KR20170091971A - Polyester film with reduced rainbow - Google Patents

Abstract

The present invention relates to a polyester film comprising a polyester base film and a primer layer coated on at least one side of the base film, wherein the primer layer is a coating film comprising a polyethylene naphthalate (PEN) polyester aqueous dispersion The present invention provides a rainbow-improved polyester film which is formed by applying a liquid to a film. According to the above-described invention, it is possible to provide a polyester film which has high adhesiveness to a top coating, has a high refractive index, generates less rainbow, has excellent heat resistance and water resistance, prevents blocking and can recycle the film.

Description

[0001] The present invention relates to a polyester film with reduced rainbow,

The present invention relates to a polyester film having a primer layer comprising a polyethylene naphthalate (PEN) polyester aqueous dispersion.

Conventional optical and industrial polyester films are formed by coating urethane or acrylic resin on the primer layer on the polyester base film. Polyurethane based polymer resins have relatively high dimensional stability, but generate severe rainbow, and yellowing occurs in a high temperature environment. In addition, when the acrylic resin is coated, the adhesion to the hard coating on the primer is not excellent.

The present invention uses a polyester resin having excellent heat resistance and water resistance to produce a polyester film having improved rainbow and yellowing while maintaining this adhesiveness.

Korean Patent Publication No. 10-2013-0035904

An object of the present invention is to provide a polyester film having a primer layer containing a polyethylene naphthalate (PEN) polyester aqueous dispersion.

A polyester film comprising a polyester base film and a primer layer coated on at least one side of the base film, wherein the primer layer is made of polyethylene naphthalate polyester water Wherein the polyester film is formed by coating with a coating liquid containing an acid.

 Further, the coating liquid for forming the primer layer comprises a water-based dispersion of polyethylene naphthalate-based polyester resin comprising 70 to 80% by weight of water and 20 to 30% by weight of polyethylene naphthalate-based polyester resin A rainbow-modified polyester film is provided.

Further, the polyethylene naphthalate-based polyester resin constituting the polyethylene naphthalate-based polyester water dispersion has a molecular weight of 25000 to 27000 and a refractive index of 1.56 to 1.60.

The present invention uses a polyethylene naphthalate-based polyester resin having excellent heat resistance and water resistance to prevent the occurrence of rainbow due to high refractive index while maintaining the adhesiveness, preventing blocking easily caused by urethane resin due to excellent heat resistance and water resistance, To produce a recyclable polyester film.

Hereinafter, the present invention will be described.

The present invention relates to a polyester film comprising a polyester base film and a primer layer coated on at least one side of the base film, wherein the primer layer is coated with a coating liquid containing a polyethylene naphthalate polyester aqueous dispersion And the polyester film is formed.

The primer layer is characterized in that the primer layer is applied with a coating liquid comprising a polyethylene naphthalate-based polyester resin, a melanin-based or epoxy-based curing agent, an anionic surfactant and inorganic particles.

Wherein the coating liquid for forming the primer layer comprises a water-based dispersion of polyethylene naphthalate-based polyester resin comprising 70 to 80% by weight of water and 20 to 30% by weight of polyethylene naphthalate-based polyester resin.

The present invention overcomes the rainbow phenomenon and the yellowing phenomenon of the conventional urethane resin and the low adhesiveness of the acrylic resin, and the primer layer includes a polyethylene naphthalate-based polyester resin.

The polyethylene naphthalate-based polyester resin contains two benzene rings and an aliphatic polymer in a molecular structure at the same time, thereby improving heat resistance and water resistance. The polyethylene naphthalate-based polyester resin is preferably soluble or dispersible in water. The polyethylene naphthalate-based polyester has a molecular weight of 25,000 to 27,000, preferably 26,000, and a refractive index of 1.56 to 1.60, preferably 1.59.

When the refractive index exceeds 1.6, transparency is lowered.

If the molecular weight is out of the above range, it is not suitable for use as a primer.

The polyethylene naphthalate-based polyester has a sulfonic acid and an OH group in its molecular structure and forms a hydrogen bond with the polyester film.

The coating liquid for forming the primer layer may contain 10 to 90 wt% of a mixed liquid composed of 70 to 80 wt% of water and 20 to 30 wt% of water-dispersed polyethylene naphthalate-based polyester resin, , Preferably 15 wt% to 50 wt%, and more preferably 15 wt% to 40 wt%. If it is out of the range of 10 wt% to 90 wt%, it is not suitable for film coating. By changing the mixing ratio of the water and the water-dispersed polyethylene naphthalate-based polyester resin, it is possible to find optimum conditions for adhesion and lowering of yellowing. More details of this will be understood with reference to the following embodiments.

The coating liquid may further contain a curing agent, a surfactant, silica, and the like used in the related art.

Hereinafter, the present invention will be described concretely with reference to Examples. However, the following Examples are merely illustrative of one embodiment of the present invention, and the scope of the present invention is not limited by the following Examples.

Example

Example  1 to 3

For the production of the polyester film constituting the primer layer of the present invention, the non-stretched polyester film is used as the base film and the coating liquid for forming the primer layer is water and a polyethylene naphthalate-based polyester resin having a molecular weight of 26000, 20% by weight of water dispersion and 5% by weight of a curing agent aqueous dispersion composed of 70% by weight of water and 30% by weight of melamine curing agent, and 63.9% by weight of water were mixed and mixed with 90% by weight of water and 10% by weight of anionic surfactant , 5 wt% of an inorganic particle water dispersion composed of 30 wt% of water and 70 wt% of silica particles, and the remaining amount of water to prepare a coating liquid. Then, the non-drawn To a polyisocyanate-based film to prepare a polyester film. The application of the coating liquid was applied using a # 3 wire bar.

division Polyethylene naphthalate-based polyester resin (% by weight) Solid content (%) Water (% by weight) Viscosity (CPS) Example 1 20 10 80 1.43 Example 2 25 10 75 1.65 Example 3 30 10 70 1.78

Comparative Example

20.0% by weight of an aqueous dispersion comprising a binder resin composed of 70% by weight of water and 30% by weight of a polyurethane resin (see Table 2), and 30% by weight of a curing agent aqueous dispersion composed of 70% by weight of water and a melamine curing agent 5% by weight of water and 63.9% by weight of water, 1.0% by weight of a surfactant water dispersion consisting of 90% by weight of water and 10% by weight of anionic surfactant, and 30% by weight of water and 70% The coating liquid was prepared using 5 wt% of the particle water dispersion and the remaining amount of water, and then applied to the unstretched polyester base film of the above example having a thickness of 100 mu m to prepare an optical polyester film. The application of the coating liquid was applied using a # 3 wire bar.

division Main ingredient Solid content (%) Viscosity (CPS) Comparative Example Polyurethane 10 1.53

Experimental Example

Physical properties of the polyester films according to Examples 1 to 3 and Comparative Examples were measured through the following experimental examples, and the results are shown in Table 3 below.

1. Measurement of coating layer thickness

The thicknesses of the coating layers of the polyester films prepared in Examples 1 to 3 and Comparative Examples were measured using a pressure-sensitive meter (Mitsutoyo, Model: ID-Ff125) using a micrometer, (Μm) of the transparent base film was subtracted from the value obtained by subtracting the thickness (μm) of the transparent base film.

2. Measurement of refractive index

Since the refractive index of the coating layer of the polyester films prepared in Examples 1 to 3 and Comparative Examples was difficult to measure on the polyester film, the coating liquid was coated on a Si wafer and the refractive index was measured using Ellipsometry.

3. Confirmation of adhesion (adhesion)

The adhesion between the base material and the primer layer of the polyester film produced in Examples 1 to 3 and Comparative Examples was measured. Using a # 20 wire bar, an acrylic UV curable resin was applied to the surface to which the primer layer was adhered, and a cut line was formed on the film coated with the primer layer with a cutter, and 2 mm x 2 mm squares were arranged in a matrix of 10 x 10 mm. A cellophane tape (No. 205, made by NICHIBAN, width: 24 mm) was attached to the cut line film, and the tape was rubbed on the polyester film using a velvet tape, and then the tape was vertically peeled off. The area of the primer layer remained in the adhesion was visually observed, and the adhesive force was calculated by the following equation (1).

Equation 1

Also, an adhesion test for evaluation of moisture resistance after 96 hours at 60 占 폚 and 90% humidity was carried out in the same manner as described above.

4. Check coating property

In Examples 1 to 3 and Comparative Examples, the coating properties between the primer layer coating liquid and the substrate were measured. The primer layer was applied to the substrate using 0 # to 6 # wire bar to confirm whether the primer layer was coated on the entire surface of the substrate. It was evaluated that the coatability was excellent when there were two or less portions of the small untreated portions (1 square: 1 x 1 mm) of the uncoated portion like the island.

5. Confirm Haze / light transmittance

The coating solutions prepared in Examples 1 to 3 and Comparative Examples were applied to a polyester film of 188 μm and thermally cured, and haze and transmittance were measured using a haze meter manufactured by NIPPON DENSHOKU.

division Coating layer thickness
(μm) Refractive index Adhesion (%) Humidity Adhesion (%) Coating property Haze (%)
/ Light transmittance (%) Example 1 0.1 1.58 100 95 O 0.23 / 88.2 Example 2 0.1 1.59 100 96 O 0.26 / 87.4 Example 3 0.1 1.59 100 100 O 0.28 / 89.3 Comparative Example 0.1 1.42 100 80 O 0.3 / 87.3

(O: good,?: Normal, X: poor)

As shown in Table 3, instead of the primer layer containing a polyurethane resin, a primer layer comprising a polyethylene naphthalate-based polyester resin was constituted to have a low refractive index and a low rainbow appearance, It was confirmed that it is possible to produce a film having improved adhesion.

Claims (3)

A polyester film comprising a polyester base film and a primer layer coated on at least one side of the base film, wherein the primer layer is coated with a coating liquid containing a polyethylene naphthalate base (PEN base) polyester aqueous dispersion The rainbow-improved polyester film
The coating liquid for forming the primer layer according to claim 1, wherein the coating liquid comprises a polyethylene naphthalate-based polyester resin aqueous dispersion comprising 70 to 80% by weight of water and 20 to 30% by weight of a polyethylene naphthalate-based polyester resin ≪ RTI ID = 0.0 >
The polyethylene naphthalate-based polyester resin as set forth in claim 1 or 2, wherein the polyethylene naphthalate-based polyester resin constituting the polyethylene naphthalate-based polyester water dispersion has a molecular weight of 25000 to 27000 and a refractive index of 1.56 to 1.60. Polyester film