KR101493517B1 - Optical polyester film - Google Patents

Abstract

The present invention relates to an optical polyester film having a primer layer having a high refractive index, and more particularly, to a polyester film for optical use having a primer layer having a high refractive index, A high refractive index resin layer can be added to minimize interference phenomenon due to a high refractive index and a high refractive index primer layer having excellent adhesion with moisture-hardened resin and moisture-resistant adhesion and excellent optical properties due to the production of a transparent film To an optical polyester film for optical use. To this end, the optical polyester film having a primer layer having a high refractive index according to the present invention is characterized in that a coating layer is formed by mixing two kinds of binder resins and two kinds of curing agents.

Description

[0001] OPTICAL POLYESTER FILM [0002]

The present invention relates to an optical polyester film having a primer layer having a high refractive index, and more particularly, to a polyester film for optical use having a primer layer having a high refractive index, A high refractive index resin layer can be added to minimize interference phenomenon due to a high refractive index and a high refractive index primer layer having excellent adhesion with moisture-hardened resin and moisture-resistant adhesion and excellent optical properties due to the production of a transparent film To an optical polyester film for optical use.

In general, the polyester film is excellent in dimensional stability, thickness uniformity, and optical transparency, and is widely used as a material for various industrial materials as well as display devices. Particularly, as interest in liquid crystal display devices, organic light emitting display devices, and electronic paper has increased recently, researches for replacing substrates of these display devices with polyester films instead of glass substrates have been actively conducted. This is because replacing a glass substrate with a polyester film can reduce the overall weight of the display device, provide flexibility in design, be strong against impact, and can be manufactured in a continuous process, resulting in higher productivity than a glass substrate .

Development for such applications requires high glass transition temperature, high light transmittance, surface scratch resistance, adhesion to substrate and post-coating liquid, which can withstand the deposition temperature of the transparent electrode.

In addition, in the case of such a polyester film, a process of coating a hard coat layer on the surface is often carried out. The problem with the production of such a polyester film is that the polyester film is deformed by a difference in the coefficient of linear expansion between the polyester film and the hard coat layer Cracks and peeling may occur, and the interference of light due to the difference in refractive index may cause interference scattering phenomenon. In addition to hard coatings typified by a touch panel (TSP), hard coatings for electrodes and electrodes have recently been increasingly used, and hard coating resins are also different depending on applications. In order to control interference phenomenon, The control of the physical properties of the primer layer of the polyester film used becomes more important than ever. In addition, due to use in portable devices, reliability (wet adhesion) has also been required to be high.

Therefore, it is very important to design a suitable structure that minimizes the stress at the interface of each layer, the adhesion between the coating layers, and the coating thickness according to the refractive index of the primer layer.

Such a primer layer is often composed of a composition of an acrylic resin, a polyester copolymer or a polyurethane resin (Korean Patent Laid-Open Publication No. 2010-0081568).

On the other hand, there is an attempt to solve the conventional low refractive index primer layer by controlling the refraction of the primer layer because interference is generated after the hard coating process.

In addition, there is an attempt to increase the surface hardness through the improvement of hardenability, but the polymer material itself has a limitation, and when a display device is constituted, a highly transparent substrate film is required in order to improve brightness. However, There are many problems such that the transparency is lowered due to the refractive index and turbidity of the particles put in order to impart the running property.

Korean Patent Laid-Open Publication No. 2010-0081568

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a primer layer having high running property and a primer layer having sufficient adhesion with a base material, A resin can be added to minimize interference phenomenon due to a high refractive index, and an optical film having a high refractive index primer layer having excellent adhesion with a hard-coated processed resin and having a moisture- And to provide a polyester film.

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

The object is achieved by a polyester film comprising at least a monoaxially stretched transparent polyester base film having a thickness of 50 to 500 占 퐉 and a polymer applied on at least one side of the base film comprising a primer layer of an adhesive layer, A binder resin composed of a copolymer resin and a polyurethane resin, and at least two curing agents and inorganic particles, wherein the adhesive force between the base film and the primer layer and the moisture-resistant adhesion force are 95% to 100% Of a primer layer for optical use.

Here, the polyester base film is characterized by being a polyester base film having no particles.

Preferably, the curing agent is a mixture of an oxazoline curing agent and an epoxy curing agent, and the coating thickness of the primer layer is 0.05 to 5 占 퐉.

Preferably, the refractive index of the primer layer is 1.57 to 1.60.

Preferably, the inorganic particles are at least one of silica particles or a silica-organic composite, and have an average particle diameter of 10 to 300 nm and a refractive index of 1.5 or more.

Preferably, the base film on which the primer layer is formed has a total light transmittance of 90 to 100% and a haze value of 1.5% or less.

Preferably, the refractive index of the primer layer is 1.57 to 1.60.

More preferably, the adhesive force between the base film and the primer layer is 95 to 100% after a 100-hour moisture resistance test at 85 캜 and 85% humidity.

More preferably, the adhesive force between the primer layer and the processing layer is 95 to 100% after a 100-hour moisture resistance test at 85 캜 and 85% humidity.

Industrial Applicability According to the present invention, it is possible to minimize the occurrence of interference and minimize the occurrence of interference phenomenon, thereby improving productivity at the time of post-processing, having excellent adhesion with moisture-hardened resin and moisture-resistant adhesive force, and excellent optical properties due to the production of a transparent film.

1 is a cross-sectional view of an optical polyester film having a primer layer of high refractive index according to an embodiment 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 .

Fig. 1 is a cross-sectional view of an optical polyester film having a primer layer of high refractive index according to an embodiment of the present invention, which comprises a uniaxially stretched polyester film 2 and a primer layer 1 coated on one side of the film, And the back layer 3 is formed on the other surface.

The optical polyester film having a primer layer having a high refractive index according to the present invention minimizes interference phenomenon after a post-process such as a prism, a lens or a hard coating, and is excellent in an adhesive force even in a room temperature, high temperature, To a polyester film for high optical transparency having a primer layer. That is, unlike the conventional polyester film for optical use which can control the refractive index, the optical polyester film having the primer layer of high refractive index according to the present invention uses a substrate film without particles in the film to impart transparency to the film A binder for forming the primer layer is mixed with a resin having a high refractive index and a resin for adhesive force to increase the refractive index of the film as a whole to increase the refractive index of the base film And is also a polyester film excellent in adhesion under high temperature and high humidity.

To this end, the optical polyester film with a primer layer of high refractive index according to the present invention comprises at least a monoaxially stretched transparent polyester base film having a thickness of 50 to 500 μm and a polymer coated on at least one side of the base film And a primer layer of an adhesive layer, wherein the primer layer comprises a binder resin composed of a water-dispersed polyester copolymer resin and a polyurethane resin, and at least two curing agents and inorganic particles, and the adhesion between the base film and the primer layer And the moisture-proof adhesion force is 95% to 100%.

The optical polyester film having a primer layer having a high refractive index according to the present invention is characterized in that the polyester base film is a polyester base film having no particle to achieve high transparency. That is, a monoaxially stretched transparent polyester base film having a thickness of 50 to 500 占 퐉 without adding particles into the base film.

The primer layer of the adhesive layer of the polymer is composed of a binder resin in which a water-dispersible polyester copolymer resin and a polyurethane resin are mixed with a binder resin and contains inorganic particles for securing the running property. Is in the range of 95% to 100%

Further, the primer layer can be provided with adhesiveness and moisture-proof adhesion by mixing an oxazoline-based curing agent and an epoxy-based curing agent with a curing agent resin. In particular, the oxazoline-based curing agent plays a role of preventing the occurrence of blocking by suppressing or reacting moisture permeable to the film. That is, the oxazoline-based curing agent is responsible for adhesion between the film and the primer layer, and the epoxy-based curing agent is responsible for adhesion between the primer layer and the hard-coating processing resin (processing layer).

The coating thickness of the primer layer is preferably 0.05 to 5 탆, more preferably 0.05 to 3 탆. When the thickness of the coating is less than 0.05 탆, the transparency is good, but the adhesiveness is decreased during the post-processing. If it is thicker than 5 탆, the adhesive property is excellent but transparency and coating property are deteriorated.

The polyester copolymer resin or the polyurethane resin is preferably soluble or dispersible in water, and in particular, the polyurethane resin can be obtained by substitution polymerization, preferably copolymerization, of an acrylic polymer of diol.

In addition, the primer layer may contain an anionic surfactant as an additive. The surfactant is for use in the aqueous coating solution of the polyester film according to the present invention, and it is preferable to use a known amount of a known anionic or nonionic surfactant to increase the wettability of the base film and uniformly apply the coating solution.

In the present invention, an additive may be added to the coating liquid for improving the coating property and the function, and such additives may be organic particles, inorganic particles, defoaming agents, and the like. According to the present invention, inorganic particles are contained in the primer layer to ensure running properties. However, when the average particle size exceeds 500 nm, there arises a problem that the haze increases. Accordingly, the size of the inorganic particles used in the present invention preferably has a particle size (average particle size) in the range of 10 to 300 nm. The inorganic particles are preferably at least one of silica particles or a silica-organic composite, and the refractive index is 1.5 or more.

Further, the optical polyester film having the primer layer of high refractive index according to the present invention has a total light transmittance of 90% or more and a haze of 1.5% or less, and the substrate film after high temperature and high humidity conditions of 100 hours at 85 캜 and 85% And the adhesion between the primer layers is 95 to 100%. Further, the adhesive force between the primer layer and the processing layer is 95 to 100% after a 100-hour moisture resistance test at 85 캜 and 85% humidity.

The optical polyester film having a primer layer having a high refractive index according to the present invention is characterized in that the refractive index of the primer layer is 1.57 to 1.60.

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.

[Examples 1 to 3]

To obtain a high transparency film, a uniaxially stretched polyester film having a thickness of 100 占 퐉 and having no particles added thereto was used as a base film, and a coating liquid for forming a primer layer was prepared by mixing 70% by weight of water with 30% by weight of a polyurethane resin as a binder resin, , 20.0% by weight of a binder resin aqueous dispersion which was prepared by mixing 70% by weight of water and 30% by weight of a binder resin of a polyester-based copolymer resin (mixing ratio is shown in Table 1) 5 parts by weight of a curing agent aqueous dispersion in which a curing agent composed of 40% by weight of a hexoxazoline-based curing agent and 60% by weight of water and two curing agents consisting of 70% by weight of an epoxy curing agent and 30% % Of water-dispersed particles composed of 1.0% by weight of a surfactant aqueous dispersion composed of 90% by weight of water and 10% by weight of an anionic surfactant, 70% by weight of silica particles and 30% A coating liquid was prepared using 0.5% by weight of a foamy solution and a residual amount of water (see Table 1), and then applied in-line to the uniaxially stretched polyester base film to prepare an optical polyester film having a primer layer having a high refractive index . The coating was applied using a # 4 wire bar. The solid content was adjusted to be constant, but the refractive index was controlled by varying the mixing ratio as in the following examples. The crude liquid used in this example is shown in Table 1 below.

division Polyurethane resin: Polyester resin
(Weight ratio) Solids
(%) Viscosity
(CPS) Example 1 2: 1 7.18 1.18 Example 2 1: 1 7.18 1.23 Example 3 1: 2 7.18 1.5

[Comparative Examples 1 to 4]

The same polyester film as the above-mentioned example was used as the base film, and as shown in the following Table 2, the binder resin for forming the primer layer of Example 2 was coated with only one curing agent (curing agent water dispersion 5% by weight) As Examples 1 and 2, the mixing ratios of the polyurethane resin and the polyester-based copolymer resin were differently applied to obtain Comparative Examples 3 and 4.

division Composition of liquid Solids
(%) Viscosity
(CPS) Comparative Example 1 Use only oxazoline curing agent 7.18 1.25 Comparative Example 2 Use only epoxy-based curing agent 7.18 1.28 Comparative Example 3 Polyurethane resin: Polyester resin
= 3: 1 (weight ratio) 7.18 1.20 Comparative Example 4 Polyurethane resin: Polyester resin
= 1: 3 (weight ratio) 7.18 1.56

Physical properties were measured by the following experimental examples using the optical polyester films according to Examples 1 to 3 and Comparative Examples 1 to 4, and the results are shown in Table 3 below.

[Experimental Example]

1. Measurement of thickness of primer layer (coating layer)

The thicknesses of the primer layers (coating layers) of the optical polyester films prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were measured using a pressure-sensitive meter (MITSUTOYO, model: ID-Ff125) , And the average of remaining values obtained by subtracting the thickness (탆) of the transparent base film from the thickness measurement values of 10 sheets in total was calculated.

2. Measurement of refractive index

Since the refractive index of the primer layer of the optical polyester film prepared in Examples 1 to 3 and Comparative Examples 1 to 4 is difficult to measure on the optical film, the coating liquid is coated on a Si wafer and refractive index is measured using Ellipsometry Respectively.

3. Confirm adhesion and adhesion

The adhesion between the substrate and the primer layer of the optical polyester film prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was measured. For the adhesion, cut lines are made on a film coated with a primer layer with a cutter, and 2 mm x 2 mm squares are placed in a 10 x 10 matrix. Attach a cellophane tape (No. 405, made by NICHIBAN: 24 mm) to the film with the cut line, rub the tape with a velvet, attach it strongly to the film, and remove the tape vertically. The area of the primer layer remaining on the adhesive layer was visually observed, and the adhesion was calculated by the following equation (1). Further, the adhesive strength was measured by the same method as that of the adhesion test after preparing a working layer by applying an acrylic UV curable resin to the surface to which the primer layer was adhered using a # 20 wire bar.

(1)

4. Evaluation of adhesion of moisture and moisture

Adhesion and adhesion tests for moisture resistance evaluation after 100 hours at 85 ° C and 85% humidity were also carried out in the same manner as described above.

5. Check coating property

In Examples 1 to 3 and Comparative Examples 1 to 4, the coating properties between the coating liquid as the primer layer and the substrate were measured. Use a # 0 to # 6 wire bar to coat the primer layer on the substrate to see if the primer layer is coated on the entire surface of the substrate. It was evaluated that the coatings were excellent when there were no more than 2 parts in 100 small square reference (1 square: 1 x 1 mm), where no coating solution was observed like an island.

6. Confirm Haze / Light Transmittance

The coating solution prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was coated on a PET film of 188 탆 and thermally cured. The haze and transmittance were measured using a haze meter (NDH 4000) manufactured by NIPPON DENSHOKU Respectively.

division Coating layer
Thickness (㎛) Refractive index Adhesion
(%) inroad
Adhesion (%) Coating property Haze / light transmittance Example 1 0.15 1.57 100 100 0 0.28 / 92.9 Example 2 0.15 1.58 100 100 O 0.32 / 91.4 Example 3 0.15 1.60 100 100 O 0.48 / 91.0 Comparative Example 1 0.15 1.58 100 60 O 0.54 / 90.9 Comparative Example 2 0.15 1.59 100 80 0 0.68 / 90.1 Comparative Example 3 0.15 1.54 100 100 0 1.1 / 88.4 Comparative Example 4 0.15 1.61 80 40 0 0.38 / 89.2

(O: good, Δ: normal, X: poor)

As shown in Table 3, when a coating layer is formed by mixing two kinds of binder resins and two kinds of curing agents to produce an optical film, it is possible to obtain a high transparency optical polyester film It can be seen that the production is possible.

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.

The polyester film for high optical quality having a high refractive index primer layer according to the present invention can minimize the occurrence of interference unevenness after hard coating processing to improve productivity in post-processing, and also has excellent optical properties, And can also be widely used as a protective film for liquid crystal displays and the like.

1: primer layer 2: substrate film
3: backside layer

Claims (9)

In the optical polyester film,
A transparent polyester base film (2) at least monoaxially stretched having a thickness of 50 to 500 占 퐉; and a primer layer (1) of an adhesive layer of a polymer applied on at least one side of the base film (2)
The primer layer (1) comprises a binder resin composed of a water-dispersed polyester copolymer resin and a polyurethane resin, two kinds of curing agents and inorganic particles,
The curing agent is prepared by mixing a curing agent composed of 40 wt% of an oxazoline curing agent and 60 wt% of water, a curing agent composed of 70 wt% of an epoxy curing agent and 30 wt% of water in a weight ratio of 1: 1,
Wherein the adhesive force between the base film (2) and the primer layer (1) and the moisture-resistant adhesion force is 95% to 100%. The method according to claim 1,
Wherein the polyester base film (2) is a polyester base film (2) having no particles. The method according to claim 1,
Wherein the coating thickness of the primer layer (1) is 0.05 to 5 占 퐉. The method according to claim 1,
Wherein the refractive index of the primer layer (1) is 1.57 to 1.60. The method according to claim 1,
Wherein the inorganic particles are at least one of silica particles or a silica-organic composite, and the average particle diameter is 10 to 300 nm and the refractive index is 1.5 or more. The method according to claim 1,
Wherein the base film (2) on which the primer layer (1) is formed has a total light transmittance of 90 to 100% and a haze value of 1.5% or less. delete 7. The method according to any one of claims 1 to 6,
Wherein the adhesive force between the base film (2) and the primer layer (1) is 95 to 100% after a wet test in 100 hours at 85 캜 under a humidity of 85%. delete

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