KR101218147B1 - Optical polyester film with easily controllable refraction ratio - Google Patents

Abstract

The present invention relates to an optical polyester film that is easy to control the refractive index, and more particularly, in order to correspond to an optical film having a different refractive index depending on the application used for the polyester film, Blending is used to adjust the desired refractive index and to create a structure that can improve the adhesion between the substrate and the post-processing layer to increase the adhesion after post-processing such as the substrate and prism, lens, or hard coating, and also has excellent optical properties. The present invention relates to an optical polyester film with easy refractive index adjustment. To this end, the 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 adhesive layer applied to at least one side of the base film. , An optical film having a primer layer formed thereon, wherein the primer layer comprises a water-dispersed polyurethane-based resin as a binder, wherein the polyurethane-based resin is polymerized and blended with an acrylic polymer and polyethylene naphthalate (PEN). It is characterized in that the refractive index is adjusted according to the mole fraction of polyethylene naphthalate (PEN).

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, in order to correspond to an optical film having a different refractive index depending on the application used for the polyester film, Blending is used to adjust the desired refractive index and to create a structure that can improve the adhesion between the substrate and the post-processing layer to increase the adhesion after post-processing such as the substrate and prism, lens, or hard coating, and also has excellent optical properties. The present invention relates to an optical polyester film with easy refractive index adjustment.

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.

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 resistance are inferior, and when performing 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, there exists a problem that the adhesiveness is very lacking.

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 in post-processing. A lot of development of the binder of an acryl or polyurethane type is progressing. In particular, in the case of a polyurethane-based binder, as shown in FIG. 1, since the functional group is a diol (OH-R-OH), when it is replaced with another polymer, it is known as a material that can be easily changed and controlled in various industrial fields. have.

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.

Therefore, the present invention is to provide a high-functional film that allows the refractive index to be adjusted to a desired level by using a blending technique of two polymers having different refractive indices while maintaining adhesion with the base layer together with the aqueous solvent of the primer crude solution. .

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 provide a primer layer to cope with the optical film is required to vary the refractive index according to the use used in the polyester film By blending polymers with different refractive indices, the desired refractive index is adjusted, and the structure can be improved to improve adhesion to the substrate and the post-processing layer. Thus, the adhesiveness after post-processing such as the substrate and prism, lens, or hard coating is It is an object of the present invention to provide an optical polyester film that is easy to elevate and has excellent refractive index control.

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 water-dispersed polyurethane resin as a binder, the polyurethane resin is polymerized and blended with the acrylic polymer and polyethylene naphthalate (PEN), the refractive index is depending on the mole fraction of the acrylic polymer and polyethylene naphthalate (PEN) It is achieved by the optical polyester film which is easy to adjust refractive index characterized by being adjusted.

Here, the primer layer is characterized in that the binder resin is applied with a coating liquid containing a polyurethane-based resin, a melanin- or epoxy-based curing agent, an anionic surfactant and inorganic particles.

Preferably, the inorganic particles are characterized in that the size of 10 ~ 300nm.

Preferably, the coating solution contains 10 to 95% by weight of a water-based polyurethane resin dispersion containing 70% by weight of water and 30% by weight of the polyurethane-based resin, 70% by weight of water and the melamine-based curing agent 30% by weight. 1 to 50% by weight of the aqueous melamine-based curing agent, 90% by weight of water and 10% by weight of the anionic surfactant 1.0 to 10% by weight, 30% by weight of water and the inorganic particles It is characterized in that consisting of 0.1 to 40% by weight of the aqueous dispersion of inorganic particles containing 70% by weight and the remaining amount of water.

According to the present invention, by applying a blended polymer resin to at least one uniaxially stretched transparent polyester base film, it is possible to form a primer layer that can easily control the refractive index.

1 is a schematic diagram schematically showing a reaction for substituting other functional groups in polyurethane-based resin polymerization.

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 polyester film for easy refractive index control, using a blending technology of two polymers incompatible with the binder constituting the primer layer, the brightness through the refractive index gradient It is characterized by a polyester film that retains synergistic effects and all other optical properties or exhibits better 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. A layer-forming optical film, wherein the primer layer comprises a water-based polyurethane resin as a binder, wherein the polyurethane-based polymer is polymerized and blended with an acrylic polymer and polyethylene naphthalate (PEN), wherein the acrylic polymer and polyethylene or It is characterized in that the refractive index is adjusted according to the mole fraction of phthalate (PEN).

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

Polyurethane-based resin for forming an optical polyester film that is easy to control the refractive index according to the present invention is preferably soluble or dispersible in water, such a polyurethane-based resin is a substitution polymerization of an acrylic polymer of diol (di-ol), Preferably, it can obtain by copolymerization.

In addition, the polyurethane-based resin for blending according to the present invention is preferably soluble or dispersible in water, and such a polyurethane-based resin may be obtained by polymerizing and preferably copolymerizing polyethylene naphthalate (PEN) polymer.

In addition, the adhesive layer (primer layer) according to the present invention increases the adhesion to the UV-curable resin coated on the primer layer when processing a radical or ring-opening reaction using a photoinitiator to a urethane resin containing a functional group capable of dispersed photoreaction. Also, due to network formation, 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 ~ 300nm.

10 to 95% by weight of the aqueous dispersion of the polyurethane-based resin containing 70% by weight of water and 30% by weight of the polyurethane-based resin is 70% by weight of the coating liquid of the optical polyester film easy to control the refractive index according to the present invention 1 to 50% by weight of a water-soluble melamine-based curing agent containing water and 30% by weight of the melamine-based curing agent, 1.0 to 10% by weight of an anionic surfactant containing 10% by weight of water and the anionic surfactant %, 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, characterized in that consisting of the remaining amount of water.

In addition, in the optical polyester film having an easy refractive index control according to 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 light transmittance of 85% or more, and a haze of 0.3% to 2%, 65 The adhesion between the base film and the primer layer after 96 hours of high temperature and high humidity at 95 ° C. and 95% humidity is characterized by 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]

The polyurethane resin forming the primer layer is 70% by weight of water and 20.0% by weight of an aqueous dispersion containing 30% by weight of polyurethane resin, and 30% by weight of melamine-based curing agent to improve moisture resistance in 70% by weight of water. 5% by weight of aqueous dispersion and 63.9% by weight of water are mixed, 1.0% by weight of an aqueous dispersion containing 90% by weight of water and 10% by weight of anionic surfactant, and 30% by weight of colloidal silica particles. An optical polyester that is easy to control the refractive index by preparing a coating solution using 0.1 wt% of an aqueous dispersion containing 70 wt% of water and colloidal silica particles and then applying it to a uniaxially stretched polyester base film having a thickness of 100 μm. A film was prepared.

At this time, the polyurethane resin is blended with an acrylic polyurethane resin polymerized acrylic polymer on one side and a PEN-based polyurethane resin polymerized polyethylene naphthalate (PEN) on one side according to the molar ratio of acrylic: PEN as shown in Table 1 A coating liquid was prepared. Application was applied using # 0 meyer bar.

division Acrylic: PEN mole fraction Solid content (%) Viscosity (CPS) Example 1 9: 1 7.13 1.13 Example 2 7: 3 7.13 1.1 Example 3 5: 5 7.13 1.2 Example 4 3: 7 7.13 1.19 Example 5 1: 9 7.13 1.24

[ 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 a polyurethane crude liquid polymerized with acrylic, and Comparative Example 2 using only a polyurethane crude liquid polymerized only with PEN.

division Acrylic: PEN mole fraction Solid content (%) Viscosity (CPS) Comparative Example 1 1: 0 7.13 1.08 Comparative Example 2 0: 1 7.13 1.25

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 indices of the coating layers prepared in Examples 1 to 5 and Comparative Examples 1 and 2 were difficult to measure on the optical film, the coating liquid was coated on a Si wafer, and the refractive index was measured 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 to the 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.

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
(%) Moisture Adhesion
(%) Coating Haze /
Light transmittance Example 1 0.15 1.63 80 50 Δ 1.75 /
90.9 Example 2 0.15 1.62 100 100 O 1.84
/90.4 Example 3 0.15 1.58 100 100 O 1.9 /
89.7 Example 4 0.15 1.52 100 100 O 1.8 /
91.2 Example 5 0.15 1.5 80 70 Δ 1.6 /
90.1 Comparative Example 1 0.15 1.65 90 80 Δ 1.8 /
89.2 Comparative Example 2 0.15 1.5 70 30 Δ 1.4 /
91.1

(O: Good, Δ: Normal, X: Poor)

 [Graph 1]

As shown in Table 3 and Graph 1, when the optical film is prepared using a blend between incompatible polymers, the desired refractive index can be easily adjusted, and the refractive index can be easily adjusted without any problem in the adhesive force. Production of the film was 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.

Claims (4)

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 includes a water-dispersed polyurethane resin as a binder, the polyurethane resin is an acrylic polyurethane resin polymerized acrylic polymer on one side and a polyethylene naphthalate polyurethane resin polymerized on polyethylene naphthalate (PEN) on one side The refractive index is blended with the acrylic component and the refractive index is adjusted according to the mole fraction of the polyethylene naphthalate (PEN) component contained in the polyethylene naphthalate-based resin, the mole fraction is 3: 7 to 7 : 3, the 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 resin, a melanin- or epoxy-based curing agent, an anionic surfactant, and inorganic particles as a binder resin, the refractive index control easy optical polyester film. The method of claim 2,
The size of the inorganic particles, characterized in that 10 to 300nm, the polyester film for optics easy to control the refractive index. The method according to claim 2 or 3,
The coating liquid is a water-based polyurethane resin dispersion 10 to 95% by weight, 70% by weight of water and 30% by weight of the polyurethane-based resin, 70% by weight of the melamine-based curing agent containing 30% by weight of the melamine-based curing agent Aqueous dispersion 1 to 50% by weight, 90% by weight of water and 10% by weight of the anionic surfactant 1.0 to 10% by weight aqueous dispersion containing water, 30% by weight of water and the inorganic particles 70% by weight The inorganic polyester aqueous dispersion contained 0.1 to 40% by weight and the remaining amount of water, characterized in that the refractive index is easy to control the optical polyester film.

Images