KR20140026812A - Optical polyester film with easily controllable refraction ratio using polymer blend - Google Patents

Abstract

The present invention relates to an optical polyester film capable of adjusting a refractive index easily using a polymer blend and, more specifically, to an optical polyester film capable of adjusting a refractive index easily using a polymer blend which can suppress non-uniformity of a refractive index, which can occur in a deposition step, can improve adhesion with a base film and a post processing layer by using blending of a thermo setting resin and a thermo plastic resin on a primer layer used in a polyester film, and has excellent optical property by improving the refractive index by adding particles. For this, an optical polyester film capable of adjusting a refractive index easily using a polymer blend according to the present invention uses a polyester film of 50-500 micrometers thickness as a base film, and forms a primer layer on at least one side of the base film as a polymer readily-adhesive layer. The polymer primer layer includes at least one particle among a barium sulphate, a titanium dioxide, a titanium-organic matter composite and an organic tin compound and a polyurethane based resin and a blend resin of a polyehtylene naphthalate (PEN). [Reference numerals] (AA) Particle-free refractive index; (BB) Particle added refractive index

Description

Optical polyester film with easy refractive index control using polymer blends {OPTICAL POLYESTER FILM WITH EASILY CONTROLLABLE REFRACTION RATIO USING POLYMER BLEND}

The present invention relates to an optical polyester film that is easy to control the refractive index using a polymer blend, and more particularly, the refractive index that may occur in the coating step by using a blend of thermosetting / thermoplastic resin in the primer layer used for the polyester film The present invention relates to an optical polyester film that can easily control the refractive index using a polymer blend which can suppress the nonuniformity as much as possible and improve the adhesion to the substrate and the post-processing layer, and also improve the refractive index by adding particles. .

In general, polyester films are excellent in dimensional stability, thickness uniformity, and optical transparency, so that they are widely used in various industrial materials as well as display devices. Among them, PDP and LCD, which occupy most of the display industry, use plastic film as a component of the device. Among them, if optical transparency is required, polyester film is used, and durability and heat resistance are required. In this case, a polyimide film is mainly used. In particular, the biaxially stretched polyester film is excellent in dimensional stability, thickness uniformity, and optical transparency, and has been used in various industries as mentioned above.

In the case of the functional polyester base material, the primer layer has often used a copolyester-based resin (binder) having excellent adhesion with the polyester base material. Although the adhesiveness of is sufficient, heat resistance and moisture resistance adhesiveness is inferior, and it is very inadequate at the time of post-processing, such as a prism processing layer, a lens processing layer, an antireflection layer, or a hard coating layer which is another base material. In addition, when the biaxial stretching is performed, the light transmittance is as low as 90% or less. In order to improve the running property, the particles contained in the film lower the light transmittance, raise the haze, and cause optical defects due to particle agglomeration have.

Recently, in order to solve the above problems, acrylic or polyurethane-based binders are additionally introduced to provide excellent heat and moisture resistance, and excellent UV curing resins and welding properties used for post-processing. Or a lot of polyurethane-based binders are being developed. In particular, in the case of a polyurethane-based binder (see FIG. 1), since the functional group is di-ol (OH-R-OH), when the polymer is substituted with another polymer, physical properties can be easily changed and controlled. Known.

However, in the case of the above-mentioned acrylic or polyurethane-based binder, even if the binder has excellent heat resistance and adhesion to UV cured resin in post-processing, adhesion to various polyester laminated films as substrate layers There is a problem that the primer layer is separated from the polyester base layer. In addition, it is very difficult to attain the proper refractive index used in the industry, which causes many problems in the use of the film for optical use.

In addition, since the adhesive force in the prior art consists of only the adhesion by the dispersing force, there is an attempt to solve this problem by using a primer such as a reactor. For example, in Korean Patent Publication No. 2010-0081568, "A thermosetting resin having a function of moisture resistance and improvement of hardenability, and has a hydroxyl group, an acetate group, an alkoxy group, a carbodiimide group or an epoxy, oxetane, aziridine in a polymer chain. "An optical biaxially oriented polyester adhesive film for forming a primer layer using a thermally reactive resin including a nucleophilic reactor such as" is disclosed. Despite these attempts, however, it is very difficult to give adhesion to resins in extreme environments of high temperature and high humidity.

Therefore, in order to solve the above problems, while maintaining the adhesion with the base layer together with the aqueous solvent of the primer crude solution, to adjust the refractive index of the coating layer by using a blending according to the mole ratio of the copolymer polymer to obtain a higher refractive index It is an object to manufacture the high transparency optical polyester film which is excellent in an optical characteristic by adding inorganic particle with a relatively high refractive index. In addition, since the inorganic particles also play a role of suppressing blocking occurrence depending on the amount added, the inorganic particles have better stability in the processing process.

Korean Patent Laid-Open Publication No. 2010-0081568

In order to solve the above problems and meet the conventional requirements, the present invention utilizes a blend of a thermosetting / thermoplastic resin in a primer layer used in a polyester film to minimize the refractive index nonuniformity that may occur in the coating step as much as possible. And it is to provide an optical polyester film that is easy to control the refractive index using a polymer blend that can improve the easily adhesiveness with the post-processing layer and also improve the refractive index by adding particles.

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 an optical film having a polyester film having a thickness of 50 to 500 µm as a substrate, and having a primer layer formed on at least one surface of the substrate as a polymer adhesive layer, wherein the polymer primer layer comprises a polyurethane-based resin and polyethylene To the optical polyester film with easy refractive index control using a polymer blend comprising a blend resin of naphthalate (PEN) and at least one particle of barium sulfate, titanium oxide, titanium-organic composite, organic tin compound Is achieved.

Here, the particles are characterized in that the size is 10 ~ 300nm and the refractive index is 1.6 or more.

Preferably, the refractive index of the primer layer is characterized in that 1.50 or more.

Preferably, the surface of the base film on which the primer layer is formed is characterized in that the total light transmittance is 85% or more and the haze value is 0.3 to 2%.

Preferably, the adhesion between the base film and the primer layer is characterized in that 100% after a 96 hours moisture resistance test at 65 ℃, 95% humidity.

According to the present invention, since the water dispersion coating liquid is applied to at least one axially stretched transparent polyester base film, the desired refractive index can be adjusted with a simple crude liquid composition in the raw material state.

In addition, since the average refractive index is achieved and maintained at the same time as drying, there is no change in physical properties, and the processing processes such as post-aging and post-treatment are reduced, thereby increasing productivity.

In addition, since the coating strength is improved, it is possible to prevent the coating layer from falling off due to the scratch during post-processing, and to prevent the blocking phenomenon between the primer layers due to the particles, thereby improving workability in the machining process. Has

1 is a graph showing the change in refractive index according to the mole fraction of polyethylene naphthalate (PEN) and the particle addition amount.
2 is a schematic diagram schematically showing a reaction degree for polymerizing a polyurethane resin.

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 .

The optical polyester film with easy refractive index adjustment using the polymer blend according to the present invention is based on a polyester film having a thickness of 50 to 500 µm, and a primer layer is formed on at least one side of the substrate as a polymer adhesive layer. An optical film, wherein the polymer primer layer comprises a blend resin of polyurethane-based resin and polyethylene naphthalate (PEN) and at least one particle of barium sulfate, titanium oxide, titanium-organic composite, or organic tin compound. .

The polyester film according to the present invention can see the effect of improving the (vertical) luminance value after the post-processing process such as prism, lens or hard coating than conventional.

That is, the polyester film according to the present invention, unlike the conventional polyester film for optics, by blending the binder constituting the primer layer rather than using the synthesis of the copolymer polymer, thereby increasing the luminance increase effect through the refractive index gradient and all other It is characterized by being a polyester film which maintains an optical characteristic or exhibits the outstanding characteristic. That is, the optical polyester film according to the present invention is characterized by using a polymer blend, and not using a copolymer polymer in a raw material preparation step, but using a blend of a crude liquid composition step after raw material preparation.

The copolymer resin forming the polyester film according to the present invention is a blend of a polyurethane-based resin and liethylene naphthalate (PEN), and is preferably soluble or dispersible in water. Such a polyurethane-based resin may be prepared by the polymerization method of FIG. 2. You can get it.

In addition, by introducing a functional group capable of photoreaction to such a urethane resin, it increases the adhesion to the UV-curable resin coating on the primer layer when processing radicals or ring-opening reaction using a photoinitiator, and also improves durability due to network formation do.

A surfactant is used for use in the aqueous coating solution of the polyester film according to the present invention and a known amount of anionic or nonionic surfactant is applied to the base film in order to increase the wettability of the base film and uniformly apply the coating solution .

The primer layer according to the present invention is formed by coating with a resin binder or the like on the film after uniaxial stretching of a polyester film. At this time, the thickness of the resin-coated layer is preferably 0.01 to 5.00 µm, more preferably 0.05 to 3.00 µm. If the thickness of the coating is thinner than 0.05㎛ the transparency is good but the adhesive strength during post-processing, if thicker than 3㎛ because the adhesive properties are excellent, but the transparency and coating properties are not preferred because it is not preferred.

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, the particles included in the water-soluble polymer primer layer are at least one of titanium oxide, titanium-organic composite, and organic tin compound, and have a size of 10 to 300 nm and a refractive index of 1.6 or more. If the inorganic particles have an average particle diameter of more than 300 nm, there is a problem that hazes the haze. Of course, since the refractive index is high, it may have a good effect on the optical properties, but it is preferable to use particles in the range of 10 to 300 nm because it may appear cloudy.

In addition, in the optical polyester film having an easy refractive index control using the polymer blend according to the present invention, the primer layer forms a binder using a blend of a polyurethane-based resin and polyethylene naphthalate (PEN), such as melamine or epoxy. The use of a curing agent improves durability, and includes nanoparticles, wherein the weight ratio of the dispersed binder is 10 to 90% by weight, the crosslinking agent is 1 to 50% by weight, and the particles are preferably 0.1 to 40% by weight.

In the present invention, the surface of the base film on which the primer layer is formed has an adhesive strength of 95% or more, a total light transmittance of 85% or more, a haze of 0.3 to 2.0%, and an adhesive force between the base film and the primer layer is 65 ° C. It is characterized in that 100% after a 96 hours humidity resistance test under 95% humidity.

Hereinafter, the present invention will be described in more detail by way of examples. This embodiment is intended to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.

[Example 1-10]

Polyurethane-based resin and polyethylene naphthalate (PEN) blending resin to form a primer layer is 70% by weight of water and 30% by weight of the copolymer copolymer block copolymer containing 30.0% by weight, melamine-based curing agent to improve the moisture resistance 70 5% by weight of aqueous dispersion containing 30% by weight of water and 30% by weight of melamine curing agent, 63.9% by weight of water, anionic surfactant is 90% by weight of water and 10% by weight of anionic surfactant 1.0 wt%, the colloidal silica particles were prepared by using a water dispersion of 0.1% by weight containing 30% by weight of water and 70% by weight of colloidal silica particles.

At this time, the blending resin was adjusted to the mole fraction, to prepare a crude liquid adjusted so that the total molecular weight does not exceed 15k (15,000 / mol) was set to Examples 1 to 5 as shown in Table 1 below. In addition, by adjusting the amount of the inorganic particles used, the same amount of nano-titanium oxide particles were added (0.1 wt% aqueous dispersion) to the crude liquid of Examples 1 to 5 to obtain Examples 6 to 10. In the case of the crude liquid containing titanium particles, the amount of water was reduced by the amount of particles.

In the crude liquid prepared by the above method, a film was prepared through inline coating using a wire bar when forming an inline film.

division PEN: PU mole fraction Solid content (%) Viscosity (CPS) Example 1 9: 1 2.95 1.1 Example 2 7: 3 2.95 1.11 Example 3 5: 5 2.95 1.2 Example 4 3: 7 2.95 1.12 Example 5 1: 9 2.95 1.1 Example 6 Example 1 + titanium oxide 5% by weight 3.4 1.6 Example 7 Example 2 + 5% by weight of titanium oxide 3.4 1.62 Example 8 Example 3 + 5 wt% titanium oxide 3.4 1.6 Example 9 Example 4 + 5 wt% titanium oxide 3.4 1.61 Example 10 Example 5 + 5 wt% titanium oxide 3.4 1.63

Comparative Example 1-4

Coated with the same resin as in Example, except that Comparative Example 1 used only the polyurethane binder crude liquid, and Comparative Example 2 used only the polyethylene naphthalate (PEN) binder crude liquid as in Table 2 below. Was prepared. In Comparative Example 3, titanium oxide particles were added to Comparative Example 1, and in Comparative Example 4, titanium oxide particles were added to Comparative Example 2 to prepare a crude liquid.

In the crude liquid prepared by the above method, a film was prepared through inline coating using a wire bar when forming an inline film.

division Binder component Solid content (%) Viscosity (CPS) Comparative Example 1 Polyurethane 2.95 1.1 Comparative Example 2 PEN 2.95 1.15 Comparative Example 3 Comparative Example 1 + titanium oxide 5% by weight 3.4 1.5 Comparative Example 4 Comparative Example 2 + 5% by weight of titanium oxide 3.4 1.45

Using the film according to Examples 1 to 10 and Comparative Examples 1 to 4 to measure the physical properties through the following experimental example and the results are shown in Table 3 and FIG.

[Experimental Example]

1. Measurement of thickness of coating layer

The coating layer thicknesses of the optical polyester film with easy refractive index control prepared in Examples 1 to 10 and Comparative Examples 1 to 4 were calculated using the solid content of the crude liquid * the wetting thickness of the wire bar.

Theoretical Wetting Thickness: Wire Bar # 3: 8.7㎛, # 4: 10.2㎛

2. Measurement of refractive index

Since the refractive index of the coating layers prepared in Examples 1 to 10 and Comparative Examples 1 to 4 was difficult to measure on the optical film, the coating solution was coated on a Si wafer and the refractive index was measured by using Ellipsometry.

3. Confirmation of adhesion

The adhesion between the substrate and the primer layer of the film prepared in Examples 1 to 10 and Comparative Examples 1 to 4 was measured. Apply acrylic UV curable resin to the surface to which the primer layer is bonded using a # 20 wire bar, and then use a cutter to make a cutting line on the film coated with the primer layer, and then cut a 2 mm 2 mm into a 10 × 10 matrix. Place the squares. The cellophane tape (No. 405, product of NICHIBAN; width: 24 mm) is attached to the film with a cutting line, and it is rubbed with a tape using a velvet, and it adheres strongly to a film, and a tape is removed vertically. The area of the primer layer remaining in the adhesive layer was visually observed, and the adhesive force was calculated by the following equation.

(1)

In addition, the adhesion test for evaluation of moisture resistance after 96 hours at 65 ° C. and 90% humidity was also performed in the same manner as above.

4. Coating Check

In Examples 1 to 10 and Comparative Examples 1 to 4, the coating property between the coating solution, which is a primer layer, and the substrate was 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. Visually, it was evaluated that coating property was excellent when there were less than two parts on 100 small squares ((1 square: 1 x 1mm)) such as islands.

5. Haze / light transmittance check

Haze and transmittance were measured using a HAZE meter manufactured by NIPPON DENSHOKU after applying a 188 ㎛ PET film with a coating solution prepared in Examples 1 to 10 and Comparative Examples 1 to 4 and thermosetting.

6. Coating strength measurement

Using a rubbing tester KPD-301 manufactured by Gibae Inc, the dropping phenomenon of the coating layer was observed when reciprocating with a load of 200 g and the following criteria were evaluated.

○: no change more than 70 times (good)

△: 30 to 70 times (normal)

X: Less than 30 times (bad)

Experimental results of the above Examples 1 to 10 and Comparative Examples 1 to 4 are shown in Table 3 and Graph 1 below.

division Coating layer
Thickness (um) Refractive index Adhesion
(%) Invasion
Attack Strength (%) Coating property Haze /
Light transmittance Coat
burglar Example 1 0.1 1.55 80 60 Δ 1.71 / 90.9 △ Example 2 0.1 1.52 80 100 O 1.68 / 90.1 △ Example 3 0.1 1.51 100 100 O 1.41 / 91.2 ○ Example 4 0.1 1.50 100 100 O 1.55 / 90.7 ○ Example 5 0.1 1.50 80 65 Δ 1.56 / 90.1 ○ Example 6 0.1 1.64 90 70 Δ 1.79 / 90.9 ○ Example 7 0.1 1.60 90 100 O 1.72 / 90.1 ○ Example 8 0.1 1.59 100 100 O 1.62 / 91.2 ○ Example 9 0.1 1.59 100 80 O 1.5 / 90.7 ○ Example 10 0.1 1.57 100 90 Δ 1.45 / 90.1 ○ Comparative Example 1 0.1 1.61 90 80 Δ 1.4 / 89.2 △ Comparative Example 2 0.1 1.51 70 30 X 1.6 / 88.4 △ Comparative Example 3 0.1 1.63 100 80 Δ 1.56 / 89.2 ○ Comparative Example 4 0.1 1.53 70 40 X 1.82 / 88.4 ○

As shown in Table 3 and FIG. 1 showing the change in refractive index according to the mole fraction of polyethylene naphthalate (PEN) and the particle addition amount, when applied to a film using blending, the desired refractive index can be easily adjusted and there is no problem in adhesive strength. It can be seen that the production of an optical polyester film is possible. In addition, the addition of inorganic particles having a high refractive index increases hertz (Hz), but it can be seen that the refractive index can be increased without affecting the adhesion or other optical properties.

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.

Claims (5)

In the optical polyester film with easy refractive index control using a polymer blend,
As an optical film which used the polyester film of 50-500 micrometers in thickness as a base material, and formed the primer layer in at least one surface of the said base material as a polymer adhesive layer,
The polymer primer layer comprises a blend resin of polyurethane-based resin and polyethylene naphthalate (PEN) and at least one particle of barium sulphate, titanium oxide, titanium-organic composite, or organic tin compound. Optical polyester film with easy refractive index adjustment. The method of claim 1,
The particles have a size of 10 ~ 300nm and the refractive index is 1.6 or more, the optical polyester film easy to control the refractive index using the polymer blend. The method of claim 1,
Refractive index of the primer layer is characterized in that 1.50 or more, the optical polyester film easy to control the refractive index using the polymer blend. The method of claim 1,
The surface of the base film on which the primer layer is formed has a total light transmittance of 85% or more and a haze value of 0.3 to 2%. 5. The method according to any one of claims 1 to 4,
The adhesive force between the base film and the primer layer is 100% after a 96 hour humidity resistance test at 65 ° C. and 95% humidity.

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