KR101218148B1

KR101218148B1 - Optical polyester film with easily controllable refraction ratio

Info

Publication number: KR101218148B1
Application number: KR1020100071915A
Authority: KR
Inventors: 김황용; 김상필; 황창익; 서상원
Original assignee: 도레이첨단소재 주식회사
Priority date: 2010-07-26
Filing date: 2010-07-26
Publication date: 2013-01-03
Also published as: KR20120010403A

Abstract

The present invention relates to an optical polyester film that is easy to control the refractive index, and more particularly, using a copolymer of acrylic and polyethylene naphthalate (PEN) as a resin to form a primer layer, to prepare a coating liquid in the form of an aqueous dispersion. Therefore, it is related with the polyester film for optics which is easy to adjust refractive index which can make refractive index adjustment of a required level easy. To this end, the optical polyester film having an easy refractive index control according to the present invention is a transparent polyester base film drawn in at least one axis with a thickness of 50 to 500 μm, and a polymer adhesive layer on at least one side of the base film, a primer The optical film having a layer formed thereon, wherein the primer layer comprises a polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer resin, characterized in that the refractive index is adjusted according to the mole fraction.

Description

Optical polyester film with easy refractive index control {OPTICAL POLYESTER FILM WITH EASILY CONTROLLABLE REFRACTION RATIO}

The present invention relates to an optical polyester film that is easy to control the refractive index, and more particularly, using a copolymer of acrylic and polyethylene naphthalate (PEN) as a resin to form a primer layer, to prepare a coating liquid in the form of an aqueous dispersion. Therefore, it is related with the polyester film for optics which is easy to adjust refractive index which can make refractive index adjustment of a required level easy.

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 adhesiveness of is sufficient, heat resistance and moisture-resistant adhesion are inferior, and when it is post-processing like another prism processing layer, a lens processing layer, an antireflection layer, or a hard coating layer, it is very poor in adhesiveness. In addition, when the biaxial stretching is performed, the light transmittance is lower than 90%, and the particles contained in the film decrease the light transmittance, increase the haze, and exhibit optical defects due to particle aggregation. have.

Recently, in order to solve the above problems, acrylic or polyurethane-based binders are additionally introduced to provide excellent heat resistance and moisture resistance, and excellent adhesion to various UV curable resins used in post-processing. The development of polyurethane-based binders is progressing a lot. Particularly, in the case of a polyurethane-based binder, since the functional group is a diol (OH-R-OH) as shown in FIG. 1, when it is replaced with another polymer, it is known as a material that can be easily changed and controlled in various industrial fields. .

However, in the case of the acrylic or polyurethane-based binder, even if the heat-resistance and easy adhesion to the UV curable resin during the post-processing has excellent properties, when the adhesion test is conducted, the adhesion to various polyester laminated films as the substrate layer The problem that the primer layer falls out from a polyester base material layer is found lacking. 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.

According to US Patent Publication No. US2009 / 0076185 for solving this problem, a technique for achieving the optical properties required in the optical film using a blending technology of thermoplastic / thermosetting resin is being developed. However, when such a blending technique is used, there is a problem that the refractive index is changed in the thickness direction. This is a phenomenon that appears because of the inferior uniformity when applying the primer layer, which may not be preferable in terms of controlling physical properties. In addition, when the coating liquid is prepared by blending, it is disadvantageous in terms of time and cost.

Therefore, in order to solve the problem, the present invention maintains the adhesion with the base layer together with the aqueous solvent of the primer crude liquid, while controlling the refractive index of the coating layer using the synthesis according to the mole ratio of the copolymer polymer and satisfying the desired optical properties. It is to provide a functional polyester film.

United States Patent Publication US2009 / 0076185

The present invention has been made to solve the above problems and to meet the conventional requirements, the object of the present invention is to suppress the refractive index nonuniformity that may occur in the application step using a copolymer polymer in the primer layer to maximize the substrate and By providing a structure that can improve the adhesiveness with the post-processing layer to provide a polyester film for optics that enhances the adhesiveness after the post-processing, such as substrate and prism, lens, or hard coating, and easy to control the refractive index and excellent optical properties I would like to.

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 in which a primer layer is formed as a transparent polyester base film stretched in at least one axis having a thickness of 50 to 500 μm and a polymer easily adhesive layer applied to at least one side of the base film. The layer comprises a polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer resin, the refractive index is adjusted according to the mole fraction is achieved by an optical polyester film easy to control the refractive index.

Here, the polyurethane-based acrylic-polyethylene naphthalate copolymer resin is a random copolymer or a structure of a diblock (Di-block) or tri-block (Tri-Bolck) according to the polymerization method, it is characterized in that the resin capable of water dispersion It is done.

Preferably, the primer layer is coated with a coating liquid containing a polyurethane-acryl-polyethylene naphthalate copolymer resin, a melanin or epoxy curing agent, anionic surfactant and inorganic particles as a binder resin.

Preferably, the size of the inorganic particles is characterized in that 10 ~ 200nm.

Preferably, the coating liquid is a polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer resin aqueous dispersion containing 70% by weight of water and 30% by weight of the polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer resin 10 To 90% by weight, 70% by weight of water and melamine-based curing agent containing 30% by weight of the melamine-based curing agent 1 to 50% by weight, 90% by weight of water and 10% by weight of the anionic surfactant 1.0 to 10% by weight of the aqueous surfactant dispersion, 30% by weight of water and the inorganic particles aqueous dispersion containing 0.1% to 40% by weight and 70% by weight of the inorganic particles and a residual amount of water.

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, haze value is 0.3 ~ 2% or less.

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 aqueous dispersion coating liquid of the copolymer polymer 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 processing processes such as post-aging and post-treatment can be reduced, thereby increasing productivity. In addition, since the film strength is improved, it is possible to prevent the coating layer from falling off due to scratches during post-processing.

1 is a schematic diagram showing a method of synthesizing a polyurethane-based resin into a copolymer polymer.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. These examples are only presented by way of example only to more specifically describe the present invention, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples. .

The polyester film according to the present invention relates to an optical polyester film having an easy refractive index adjustment, in which the (vertical) luminance value is improved after the post-processing process such as a prism, a lens, or a hard coating. That is, the polyester film according to the present invention, unlike the conventional optical polyester film, by using the synthesis of the copolymer polymer in the binder constituting the primer layer, to maintain the brightness increase effect through the refractive index gradient and all other optical properties Or a polyester film exhibiting more excellent properties.

An optical polyester film having an easy refractive index control according to the present invention includes a transparent polyester base film stretched on at least one axis having a thickness of 50 to 500 μm, and a polymer easily adhesive layer applied to at least one side of the base film. The optical film having a layer formed thereon, wherein the primer layer comprises a polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer resin, characterized in that the refractive index is adjusted according to the mole fraction.

The copolymer resin forming the polyester film according to the present invention is a copolymer of an acrylic polymer and polyethylene naphthalate (PEN), preferably soluble or dispersible in water, and such a block copolymer resin is shown in FIG. Can be synthesized together. In FIG. 1, R1 and R2 represent polymers of acryl and PEN series, respectively. The polyurethane-based acrylic-polyethylene naphthalate copolymer resin is a random copolymer or a di-block (Di-block) or a tri-block (Tri-Bolck) structure according to the polymerization method, it is characterized in that the resin capable of water dispersion. .

In addition, by introducing a functional group capable of photoreaction to the urethane resin in the synthesis of the polyurethane-based copolymer resin, when increasing the adhesion to the UV-curable resin coated on the primer layer when processing radicals or ring-opening reaction using a photoinitiator, network formation Due to the durability also plays a role.

In addition, a surfactant is used for use in the water-soluble coating solution of the polyester film according to the present invention, and in order to increase the wettability of the base film and to uniformly apply the coating solution, a known amount of anionic or nonionic surfactant is used to the base film. It is preferable to apply.

Moreover, the primer layer which concerns on this invention is formed by apply | coating with a resin binder etc. 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. When the thickness of the coating is thinner than 0.05 μm, the transparency becomes good, but the adhesive strength decreases during post-processing.

In addition, in the present invention, an additive may be used in the coating liquid to improve coating properties and functionality, and organic additives, inorganic particles, and antifoaming agents may be used as such additives. According to the present invention, the water-soluble polymer primer layer may include inorganic particles having a relatively small difference in refractive index with the resin, thereby ensuring runability. However, when the average particle diameter exceeds 500 nm, a problem occurs that affects the haze. . Therefore, the size of the silica inorganic particles used in the present invention preferably has a particle size in the range of 10 ~ 200nm.

The coating solution of the optical polyester film for easy refractive index adjustment according to the present invention is polyurethane-based acrylic-polyethylene containing 70% by weight of water and the polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer resin 30% by weight Naphthalate (PEN) copolymer resin water dispersion 10 to 90% by weight, 70% by weight of water and 1 to 50% by weight of the melamine-based curing agent aqueous dispersion containing 30% by weight of the melamine-based curing agent, and 90% by weight of water 1.0 to 10% by weight of an aqueous dispersion of anionic surfactant containing 10% by weight of anionic surfactant, 30% by weight of water, and 0.1 to 40% by weight of an aqueous dispersion of inorganic particles containing 70% by weight of the inorganic particles and a residual amount of water. Characterized in that made.

In addition, the refractive index of the optical polyester film according to the present invention is easy to adjust the surface of the base film on which the primer layer is formed, the adhesion is 95% or more, the light transmittance is 85% or more, haze is 0.3% to 2%, The adhesion between the base film and the primer layer after a high temperature and high humidity condition of 96 hours at 65 ° C. and 95% humidity is 100%.

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 -5]

Polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer polymer resin forming the primer layer is 30.0% by weight of an aqueous dispersion containing 70% by weight of water and 30% by weight of a block copolymer resin, melamine-based to improve moisture resistance 30 wt% of the curing agent is mixed with 5 wt% of the aqueous dispersion containing 70 wt% of water and 63.9 wt% of the water, and the anionic surfactant is 1.0 wt% containing 90 wt% of water and 10 wt% of the anionic surfactant. By weight%, colloidal silica particles were prepared by using an aqueous dispersion containing 0.1% by weight of 30% by weight of water and 70% by weight of colloidal silica particles, and then uniaxially stretched polyester base film having a thickness of 100 μm. It applied to to prepare an optical polyester film easy to control the refractive index.

Examples 1 to 5, as shown in Table 1, to adjust the mole fraction of the copolymer-based polyurethane-acryl-polyethylene naphthalate resin, the total molecular weight was adjusted not to exceed 15k (15,000 / mol).

division Acrylic: PEN mole fraction Solid content (%) Viscosity (CPS) Example 1 9: 1 7.13 1.1 Example 2 7: 3 7.13 1.11 Example 3 5: 5 7.13 1.2 Example 4 3: 7 7.13 1.12 Example 5 1: 9 7.13 1.1

[ Comparative example ]

The coating was performed with the same resin as in Example, but as shown in Table 2, Comparative Example 1 formed a coating layer using only an acrylic binder crude solution, and Comparative Example 2 using only a PEN binder crude solution.

division Binder components Solid content (%) Viscosity (CPS) Comparative Example 1 acryl 7.13 1.1 Comparative Example 2 PEN 7.13 1.15

Physical properties were measured through the following Experimental Examples using the polyester film for optical refractive index control according to Examples 1 to 5 and Comparative Examples 1 and 2, and the results are shown in Table 3 below.

[ Experimental Example ]

1. Measurement of thickness of coating layer

The thickness of the coating layer of the polyester film for easy refractive index control prepared in Examples 1 to 5 and Comparative Examples 1 and 2 was measured using a micrometer using a pressure gauge [Mitsutoyo Co., Model: ID-Ff125]. It was measured, and was calculated as the average of the remaining values minus the thickness of the transparent base film from the thickness measurement value of a total of 10 sheets.

2. Refractive index Measure

Since the refractive index of the coating layers prepared in Examples 1 to 5 and Comparative Examples 1 and 2 was difficult to measure on the optical film, the coating solution was coated on a Si wafer to measure the refractive index by using Ellipsometry.

3. Confirmation of adhesion

The adhesion between the substrate and the primer layer of the films prepared in Examples 1 to 5 and Comparative Examples 1 and 2 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 apply a cut line to a matrix of 10 × 10 by 2 mm × 2 mm. 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 Confirm

In Examples 1 to 5 and Comparative Examples 1 and 2, the coating property between the coating liquid and the base material as the primer layer was measured. A primer layer is applied to the substrate using # 0 to # 6 wire bars to confirm that 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 Of Light transmittance Confirm

After coating and thermosetting the 188 ㎛ PET film with the coating solution prepared in the experimental example, the haze and transmittance were measured using a HAZE meter manufactured by NIPPON DENSHOKU.

6. Coating strength Measure

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 Examples 1 to 5 and Comparative Examples 1 and 2 are shown in Table 3 and Graph 1 below.

division Coating layer
Thickness (㎛) Refractive index Adhesion (%) inroad
Adhesion (%) Coating Haze /
Light transmittance Coating strength Example 1 0.1 1.63 80 60 Δ 1.71 /
90.9 △ Example 2 0.1 1.60 80 100 O 1.68 /
90.1 △ Example 3 0.1 1.58 100 100 O 1.41 /
91.2 ○ Example 4 0.1 1.52 100 100 O 1.55 /
90.7 ○ Example 5 0.1 1.52 80 65 Δ 1.56 /
90.1 ○ Comparative Example 1 0.1 1.63 90 80 Δ 1.4 /
89.2 △ Comparative Example 2 0.1 1.51 70 30 X 1.6 /
88.4 ○

(O: Good, Δ: Normal, X: Poor)

[Graph 1]

As shown in Table 3 and Graph 1, when applied to the film using a copolymer polymer, it is possible to prepare a polyester film for optics easy to control the refractive index, easy to control the refractive index without problems in the adhesion. .

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

In the optical polyester film which is easy to adjust refractive index,
As an optical film in which the primer layer was formed, As a transparent polyester base film extended | stretched at least uniaxially with a thickness of 50-500 micrometers, and the polymer easily bonding layer apply | coated to at least one surface of the said base film,
The primer layer comprises a polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer resin, the mole fraction of the acrylic component and polyethylene naphthalate (PEN) component contained in the polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer resin According to the refractive index is adjusted, the mole fraction is 3: 7 to 5: 5, the refractive index is easy to control the optical polyester film.

The method of claim 1,
The polyurethane-acryl-polyethylene naphthalate copolymer resin has a random copolymer or a structure of di-block or tri-block according to the polymerization method, and is a resin capable of water dispersion. Optical polyester film with easy refractive index adjustment.

The method of claim 1,
The primer layer is coated with a coating liquid containing a polyurethane-based acrylic-polyethylene naphthalate copolymer resin, a melanin or epoxy curing agent, anionic surfactant and inorganic particles as a binder resin, easy to control the refractive index Optical polyester film.

The method of claim 3,
The size of the inorganic particles is characterized in that 10 to 200nm, the polyester film for optics easy to control the refractive index.

The method according to claim 3 or 4,
The coating liquid is a polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer resin aqueous dispersion 10 to 90% by weight containing 70% by weight of water and 30% by weight of the polyurethane-based acrylic-polyethylene naphthalate (PEN) copolymer resin , 1 to 50% by weight of an aqueous dispersion of melamine-based curing agent containing 70% by weight of water and 30% by weight of the melamine-based curing agent, the number of anionic surfactants containing 90% by weight of water and 10% by weight of the anionic surfactant Dispersion 1.0 to 10% by weight, 30% by weight of water and the inorganic particles aqueous dispersion containing 0.1% to 40% by weight of the inorganic particles containing 70% by weight and the remaining amount of water, the refractive index easy to control optical polyester film.