KR101623075B1 - Polyester film for optical use - Google Patents

Abstract

More specifically, the present invention relates to a polyester film for optical use, and more particularly, to a polyester film for optical use, which comprises a base layer made of a primer layer containing nanoparticles having a specific functional group and having a surface modified to have uniform adhesion with an ultraviolet curable resin, Transmittance, and adhesiveness, thereby securing the productivity of the product and reducing the percentage of defects.

Description

POLYESTER FILM FOR OPTICAL USE

The present invention relates to an optical polyester film, and more particularly, to a polyester film for optical applications applied to a touch panel, a liquid crystal display (LCD), a plasma display panel (PDP) (A post-processing layer) such as a prism, a lens or a hard coating, and has a uniform adhesion, and accordingly, the productivity of a product And a reduction in the defective ratio, and the like.

The polyester film is excellent in dimensional stability, thickness uniformity and optical transparency, and is widely used for various industrial materials as well as display devices.

Among them, plastic films used for optical use are widely used as components of display devices, for example, PDP (Plasma Display) and LCD (liquid crystal display). When optical transparency is required, a polyester film is used And polyimide films are mainly used when durability and heat resistance are required. In particular, biaxially stretched polyester films are excellent in dimensional stability, thickness uniformity and optical transparency, and are used in various industries as base films.

The optical polyester film is used as a base film for various purposes by applying various resins through a post-treatment, and ultraviolet (UV) curable resins are generally used as the resins used in post-processing. Therefore, in order to uniformly adhere the UV-curable resin coating layer and the optical polyester film applied through the post-processing, a method of locating the primer coating layer on the surface of the polyester base material is generally used industrially.

In general, in the case of an optical polyester film subjected to a primer processing treatment, a copolymerized polyester resin (binder) having excellent adhesion to a polyester base material has often been used as a primer layer. However, The adhesiveness to the base film is sufficient, but the heat resistance and the adhesion of the moisture absorption are poor. When the post processing is performed together with the prism processing layer, the lens processing layer, the antireflection layer, or the hard coating layer which is another substrate, the adhesiveness is very poor.

In recent years, acrylic or polyurethane-based binders have been added to solve the above problems, so that they are excellent in heat resistance and moisture resistance. They have excellent adhesion to various functional UV curable resins used in post-processing and have excellent refractive index Development of an acrylic or polyurethane-based binder has progressed much. Particularly, in the case of the polyurethane-based binder, since the functional group is generally diol (OH-R-OH), it is known as a substance which can be applied in various industrial applications by changing physical properties and controlling it easily by substituting with other polymer.

However, in the case of an acrylic or polyurethane-based binder, even when the binder has excellent heat resistance and adhesion to a UV-curing resin in post-processing, it also has insufficient adhesion with various polyester substrates, There is a problem that the layer is separated from the polyester substrate.

Therefore, the optical polyester film is required to have a post-processing characteristic, in particular, a uniform adhesion force with a resin used in a post-processing, and a technique of maintaining a uniform adhesion force is essential for reducing the defect rate of the product, As a matter of fact, development of an optical polyester film having such properties is urgently required.

Japanese Patent Application Laid-Open No. 2014-065887 Korean Patent Publication No. 10-2010-0067286 Korean Patent Publication No. 10-2005-0016381

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to improve the adhesion of an optical polyester film and a UV curable resin coating layer such as a prism, a lens or a hard coating, And it is intended to provide an optical polyester film capable of achieving reduction in defect rate, life span, and high quality of a product by maintaining uniform adhesion even when evaluating the wettability.

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

The above object is achieved by a polyester film comprising at least a base film formed of polyester and at least monoaxially stretched, and a primer layer applied on at least one surface of the base film, wherein the primer layer comprises at least one of a polymer binder resin, a curing agent and an ultraviolet curable functional group Or more of the nanoparticles comprise nanoparticles.

Here, the polymer binder resin may be a polymeric binder resin selected from the group consisting of a polyester-based polymer, a polyurethane-based polymer, and a polyacrylic polymer, or a combination of two or more thereof.

Preferably, the curing agent may be at least one of an epoxy curing agent and a melanin curing agent.

Preferably, the ultraviolet curable functional group may include at least one functional group selected from the group consisting of an acrylate group, a thiol group, a vinyl ether group and an epoxy group.

Preferably, the thickness of the primer layer may be 0.04 to 0.4 mu m.

Preferably, the average particle diameter of the nanoparticles may be 2.0 to 3.0 times the thickness of the primer layer.

Preferably, the primer layer comprises 48 to 90% by weight of a binder resin aqueous dispersion comprising 70% by weight of water and 30% by weight of a binder resin, 8 to 50% by weight of a curing agent aqueous dispersion composed of 70% And 0.1 to 2.0% by weight of a nanoparticle water dispersion composed of 10% by weight of water and 90% by weight of water and nanoparticles.

Preferably, the ultraviolet curable resin coating layer may be further coated on the surface of the primer layer.

Preferably, the ultraviolet-curable resin coating layer is made of an acrylic resin and may have a thickness of 0.5 to 8 탆.

Preferably, the adhesion between the primer layer and the ultraviolet-curable resin coating layer may be 95% or more when tested in a moisture resistance test at 85 ° C and 85% humidity for 240 hours.

According to the present invention, the ultraviolet curable resin coating layer including the substrate, prism, lens, hard coating or the like including surface-modified nanoparticles in the primer layer has uniform adhesion even after the post-processing, It is possible not only to prevent the cured resin coating layer from falling off, but also to secure the productivity of the product and reduce the defective rate by having excellent transparency, transmittance and adhesiveness.

However, the effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a cross-sectional view of an optical polyester film according to one aspect of the present invention.
2 is a cross-sectional view of an optical polyester film according to another aspect of the present invention.

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

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. Also, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

FIG. 1 is a cross-sectional view of an optical polyester film according to an aspect of the present invention. The optical polyester film after primary processing according to an aspect of the present invention comprises at least a monoaxially stretched base film 1) and a primer layer (2) applied on at least one side of the base film, wherein the primer layer (2) comprises nanoparticles having at least one polymer binder resin, a curing agent and an ultraviolet curable functional group.

There is no limitation on the type of the polyester base film, but conventionally known ones known as base films for optical polyester films can be used. In this specification, polyethylene terephthalate (PET) will be mainly described, but the present invention is not limited thereto.

The polymeric binder resin may be a binder resin selected from the group consisting of a polyester resin, a polyacrylic resin and a polyurethane resin, or a combination of two or more thereof.

In order to form a primer layer using a polyester resin, a coating liquid containing a dicarboxylic acid component and a branched glycol component is usually used.

In order to form a primer layer by using a polyacrylic resin, a coating liquid containing at least one selected from the group consisting of methyl tetraacrylate, methacrylate, butyl acrylate and acrylic acid is generally used. The binder component used in the coating liquid preferably has a glass transition temperature (Tg) of 20 to 100 캜.

In order to form a primer layer using a polyurethane resin, an ester or carbonate type is generally used as the polyol, an aliphatic isocyanate is used as the isocyanate, and a diol or diamine as the chain extender is used as the coating liquid.

As the curing agent, an epoxy curing agent, a melamine curing agent, or a curing agent obtained by mixing them may be used, but the present invention is not limited thereto.

The nanoparticles are used for effects such as running property, scratch prevention, and blocking resistance of a film, forming roughness on the surface of the primer layer, silica as the inorganic particles, poly (methyl methacrylate (PMMA) is generally used because the affinity of the reactor located on the particle surface with the ultraviolet curable resin used in post-processing is generally low. Therefore, in order to secure the physical properties of the adhesion force, I have been.

However, in the present invention, nanoparticles contain an ultraviolet reactive functional group structure in a specific functional group, thereby participating in a UV curing reaction such as an ultraviolet curable resin that is placed on a base film at the time of post-processing to further improve adhesion with existing ultraviolet curable resins .

That is, unlike the conventional polyester film for optical use, the polyester film according to one aspect of the present invention includes nanoparticles added to the primer layer and having nanoparticles having at least one functional group capable of ultraviolet curing.

The ultraviolet curable functional group includes at least one ultraviolet reactive functional group selected from the group consisting of an acrylate group, a thiol group, a vinyl ether group and an epoxy group, and the inorganic particles may be modified and used so as to include such a functional group.

By containing such nanoparticles, the nanoparticles can be cured by passing through a primary thermosetting system, followed by a second ultraviolet curable resin located on the primer layer and a UV curing system of 200 to 400 nm, and the nanoparticles can be cured with the ultraviolet curable resin coating layer When cured together, the adhesion between the polyester base film and the ultraviolet curable resin coating layer is improved and sufficient adhesion can be maintained, and uniform and excellent adhesion can be obtained even when evaluating the moisture resistance of high temperature and humidity.

The thickness of the primer layer is preferably 0.04 to 0.4 mu m, and the nanoparticles have a spherical shape. The average particle diameter is preferably 2.0 to 3.0 times the thickness of the primer layer. When the thickness of the primer layer is less than 2.0 times the thickness of the primer layer, There is a disadvantage that the take-up property is weakened, and when it exceeds 3.0 times, there is a disadvantage that nanoparticles are dropped from the coating layer.

The primer layer contained 48 to 90% by weight of a binder resin water dispersion consisting of 70% by weight of water and 30% by weight of a binder resin, 8 to 50% by weight of a curing agent aqueous dispersion composed of 70% by weight of water and 30% % Of water and 0.1 to 2.0% by weight of a nanoparticle water dispersion composed of 10% by weight of nanoparticles.

2 is a cross-sectional view of an optical polyester film according to another aspect of the present invention. In the optical polyester film according to another aspect of the present invention, an ultraviolet-curing resin coating layer 3 is further provided on the surface of the primer layer 2 . That is, a functional coating layer after the secondary processing of the optical polyester film.

The ultraviolet curable resin coating layer is a functional optical resin subjected to a post-treatment such as a prism, a lens, or a hard coating, and generally acrylic resin is used, but not limited thereto. The thickness of the ultraviolet-curable resin coating layer is preferably 0.5 to 8 占 퐉.

The primer layer and the ultraviolet curable resin coating layer can be cured by an ultraviolet curing system of 200 to 400 nm. Conventionally, the adhesive force is improved by changing the ratio of the binder resin and using two or more kinds of curing agents. However, the present invention is characterized in that the nanoparticles of the primer layer contain an ultraviolet reactive functional group and are thus cured together with the ultraviolet- .

The optical polyester film produced as described above had a total light transmittance of 80% or more, a haze value of 0.4 to 2.4%, and an adhesion force between the primer layer and the ultraviolet curable resin coating layer at 240 deg. C And has an excellent effect of showing 95% or more in the moisture resistance test.

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

[Example 1-9]

Production of polyester base film

The polyethylene terephthalate resin pellets were dried at 135 DEG C for 6 hours under reduced pressure (1.3 hPa), and then extruded by an extruder. The extruded pellets were melt extruded at about 280 DEG C onto a sheet, To obtain a casting film having a thickness of 1024 mu m. Next, this casting film was heated to 100 DEG C in a heated roll group and an infrared heater, and then stretched at a 3.2-fold stretching ratio in the longitudinal direction by a roll group having a peripheral speed to obtain a uniaxially oriented PET film, Respectively. Subsequently, the film was gripped at the end with a clip, introduced into a hot air region, and dried. Thereafter, stretching was carried out at 130 占 폚 in the transverse direction at 3.2 times the stretching ratio, followed by heat setting at 240 占 폚, and then lateral relaxation at 3 占 폚 at 200 占 폚. Thus, a biaxially oriented polyester base film having a thickness of 100 탆 was produced.

Preparation of Primer Layer Coating Liquid

As shown in the following Table 1, 65% by weight of a binder resin water dispersion consisting of 70% by weight of water and 30% by weight of a polyurethane resin as a binder resin, a curing agent aqueous dispersion 34 of 70% by weight of water and 30% by weight of a melanin- To 34.9% by weight and 90% by weight of water and 0.1% by weight to 1.0% by weight of a nanoparticle water dispersion comprising 10% by weight of silica inorganic particles having a vinyl ether group as a vinyl functional group on the surface. This was prepared by adding 70% by weight of water and 30% by weight of silica sol as a starting material to an alkoxysilane such as vinyltrimethoxysilane and stirring at room temperature for 12 hours.

Production of optical polyester film

The coating liquid for forming the primer layer after the step of stretching at 3.2 times the stretching ratio in the machine direction in the longitudinal direction of the polyester base film was applied on one side of the uniaxially oriented polyester base film by the reverse roll method so that the solid weight was 0.08 g / Was further inserted to prepare a biaxially oriented optical polyester film.

As shown in Table 1 below, the ratio of the size and content of the surface-modified nanoparticles in the primer layer coating solution was adjusted so that the total molecular weight was 15,000 g / mol or less, and the biaxially oriented polyester films for optical applications Example 1-9.

division Binder resin water dispersion
Weight ratio (%) Hardener
Aqueous dispersion
Weight ratio (%) Nanoparticle water dispersion Solids
(%) Particle size (nm) Weight ratio (%) Example 1 65 34.9 100 0.1 4.21 Example 2 65 34.9 200 0.1 4.21 Example 3 65 34.9 300 0.1 4.21 Example 4 65 34.5 100 0.5 4.21 Example 5 65 34.5 200 0.5 4.21 Example 6 65 34.5 300 0.5 4.21 Example 7 65 34 100 1.0 4.21 Example 8 65 34 200 1.0 4.21 Example 9 65 34 300 1.0 4.21

[Comparative Example 1]

Comparative Example 1 was the same as that of Example 1 except that a biaxially oriented polyester film for optical use having no primer layer was prepared.

[Comparative Example 2-10]

Comparative Example 2-10 was the same as that of Example 1 except that a biaxially oriented polyester film for optical use having a primer layer containing nanoparticles having no vinyl ether group in the primer layer coating liquid was prepared as in Table 2 below And the total molecular weight was adjusted to 15,000 g / mol or less by adjusting the size and content ratio of the nanoparticles as shown in Table 2. The biaxially oriented polyester films for optical applications coated with the nanoparticles were designated as Comparative Examples 2-10.

Preparation of Primer Layer Coating Liquid

65% by weight of a binder resin water dispersion comprising 70% by weight of water and 30% by weight of a polyurethane resin, 34 to 34.9% by weight of a curing agent aqueous dispersion comprising 70% by weight of water and 30% by weight of melanin- 0.1 to 1.0% by weight of a nanoparticle aqueous dispersion comprising 10% by weight of water and 10% by weight of general silica inorganic particles not containing a vinyl ether group on the surface thereof.

division Binder resin
Aqueous dispersion
Weight ratio (%) Hardener
Aqueous dispersion
Weight ratio (%) General Nanoparticle Water Dispersion Solid content (%) Particle Size (nm) Weight ratio (%) Comparative Example 1 0 0 - 0 0 Comparative Example 2 65 34.9 100 0.1 4.21 Comparative Example 3 65 34.9 200 0.1 4.21 Comparative Example 4 65 34.9 300 0.1 4.21 Comparative Example 5 65 34.5 100 0.5 4.21 Comparative Example 6 65 34.5 200 0.5 4.21 Comparative Example 7 65 34.5 300 0.5 4.21 Comparative Example 8 65 34 100 1.0 4.21 Comparative Example 9 65 34 200 1.0 4.21 Comparative Example 10 65 34 300 1.0 4.21

The properties of the optical polyester films according to Examples 1 to 9 and Comparative Examples 1 to 10 were measured through the following experimental examples, and the results are shown in Table 1 below.

[Experimental Example 1]

Haze / Determination of light transmittance

After thermally curing the optical polyester film (the polyester base was made to have a thickness of 100 μm) prepared in Examples and Comparative Examples, haze and light were measured using a haze meter manufactured by NIPPON DENSHOKU Co., The transmittance was measured.

[Experimental Example 2]

Confirm adhesion

The adhesion between the substrate and the primer layer of the optical polyester film prepared in Examples 1 to 9 and Comparative Examples 1 to 10 was measured under normal temperature and humidity conditions. A UV-curable resin was applied to the surface of the base material to which the primer layer was adhered by using a # 20 wire bar, and then a cut line was formed on the film coated with the primer layer by a cutter, Place 2 mm squares. Attach cellophane tape (No. 405, made by NICHIBAN; width: 24 mm) to the film with cutting line and rub the tape using velvet and attach it strongly to the film, then remove the tape vertically. The area of the primer layer remaining on the coating layer was visually observed, and the adhesive force was calculated by the following equation (1).

&Quot; (1) "

Also, the adhesion test for evaluating the moisture resistance after 240 hours at 85 캜 and 85% humidity was also conducted in the same manner as described above.

[Experimental Example 3]

Measure the thickness of the primer layer

The thicknesses of the primer layers of the optical polyester films prepared in Examples 1 to 9 and Comparative Examples 1 to 10 were measured using a pressure-sensitive meter (MITUTOYO Corporation, Model: ID-Ff125) Was calculated as the average of the remaining values obtained by subtracting the thickness of the transparent substrate from the thickness measurement values of the sheet in the sheet.

[Experimental Example 4]

Check coatability

The coating properties between the primer layer and the substrate of the optical polyester films prepared in Examples 1 to 9 and Comparative Examples 1 to 10 were evaluated. The primer layer was applied to the substrate using # 0 to # 6 wire bar to confirm that the primer layer was coated on the entire surface of the substrate. (O: excellent, Δ: moderate, X: not good) when the coatings were not visually observed in the presence of two or less of 100 small square reference points (square: 1 × 1 mm) .

division Optical property Adhesion Coating property Light transmittance
(%) Haze
(%) Room temperature
(%) High temperature intrusion
(%) Coating layer thickness (nm) Coating property
(O /? / X) Example 1 92.2 0.31 100 82 0.1 O Example 2 92.8 0.51 100 88 0.1 O Example 3 92.0 0.69 100 92 0.1 O Example 4 91.9 0.45 100 92 0.1 O Example 5 92.4 0.68 100 93 0.1 O Example 6 92.2 0.78 100 95 0.1 O Example 7 92.6 0.89 100 100 0.1 O Example 8 93.4 1.09 100 99 0.1 O Example 9 93.1 1.15 100 100 0.1 O Comparative Example 1 88.4 0.19 - - - - Comparative Example 2 92.2 0.36 97 60 0.1 O Comparative Example 3 92.8 0.59 98 62 0.1 O Comparative Example 4 91.0 0.72 98 62 0.1 O Comparative Example 5 91.9 0.39 94 55 0.1 O Comparative Example 6 92.4 0.71 92 51 0.1 O Comparative Example 7 92.2 0.88 92 49 0.1 O Comparative Example 8 92.6 0.92 90 46 0.1 O Comparative Example 9 92.4 1.02 90 47 0.1 O Comparative Example 10 92.1 1.10 91 45 0.1 O

As can be seen from the above Table 3, the optical polyester films prepared in Examples 1-9 and Comparative Examples 1-10 were compared with each other in the same manner as in Example 1 except that the primer layer contained nanoparticles having a vinyl ether group It can be confirmed that the optical polyester films 1-9 are superior to the optical polyester films of the comparative examples in terms of the adhesion at room temperature and the adhesion to humidity.

In addition, the effects of nanoparticle size and addition weight ratio were different. Although there is no significant difference in the coating properties, if the amount of the nanoparticles is excessively large, the haze of the optical properties is lowered, and it can be confirmed that the optimum amount should be applied.

As described above, the optical polyester film according to the present invention can be applied to various fields in accordance with a desired use, but is not limited thereto.

It is to be understood that the present invention is not limited to the above embodiments and various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.

1: Polyester base film
2: Primer layer
3: UV curable resin coating layer (secondary ultraviolet finishing)

Claims (10)

A substrate film made of polyester and at least monoaxially stretched;
And a primer layer applied on at least one side of the base film,
Wherein the primer layer comprises nanoparticles having at least one polymer binder resin, a curing agent, and an ultraviolet curable functional group,
Wherein the ultraviolet curable functional group is a vinyl ether group. The method according to claim 1,
Wherein the polymeric binder resin is a polymeric binder resin selected from the group consisting of a polyester-based polymer, a polyurethane-based polymer, and a polyacrylic polymer, or a combination of two or more thereof. The method according to claim 1,
Wherein the curing agent is at least one of an epoxy curing agent and a melanin curing agent. delete The method according to claim 1,
Wherein the primer layer has a thickness of 0.04 to 0.4 占 퐉. The method according to claim 1,
Wherein the nanoparticles have an average particle diameter of 2.0 to 3.0 times the thickness of the primer layer. The method according to claim 1,
The primer layer contains 8 to 50% by weight of a curing agent aqueous dispersion composed of 70% by weight of water and 48% to 90% by weight of a binder resin water dispersion consisting of 30% by weight of a binder resin, 70% And 0.1 to 2.0% by weight of a nanoparticle water dispersion comprising 10% by weight of water and 10% by weight of nanoparticles. The method according to any one of claims 1 to 3 and 5 to 7,
And a UV-curable resin coating layer applied to the surface of the primer layer. 9. The method of claim 8,
Wherein the ultraviolet curable resin coating layer is made of an acrylic resin and has a thickness of 0.5 to 8 占 퐉. 9. The method of claim 8,
Wherein the adhesive force between the primer layer and the ultraviolet-curable resin coating layer is 95% or more when tested in a humidity resistance test at 85 ° C and 85% humidity for 240 hours.

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