KR102108629B1 - Optical Polyester Film - Google Patents

Abstract

The present invention applies a mixed resin of a urethane resin and an acrylic resin to the coating layer (primer layer), and adjusts the refractive index by adding specific inorganic particles to the refractive index loss caused by acrylic, thereby providing excellent transparency required in an optical film (oligomeric block It relates to an optical polyester film capable of reducing the adhesion and the rainbow phenomenon.

Description

Optical polyester film {Optical Polyester Film}

The present invention relates to an optical polyester film, and more particularly, to an optical polyester film capable of reducing a rainbow phenomenon and simultaneously preventing oligomer precipitation.

In recent years, the evaluation level of the appearance in the process of processing an optical sheet has become increasingly strict. In particular, in the case of a liquid crystal protective film or a film for preventing scattering, which should be located on the most surface, the defect rate due to rainbow (interference stain), foreign matter, etc. is gradually increasing. Due to the properties of the material, an oligomer having a low degree of polymerization precipitates on the surface, causing turbidity of the film itself, or causing many problems such as deterioration of electrical properties due to the oligomer.

Among the problems of the polyester film, a method of adjusting the refractive index of the primer layer to improve the rainbow phenomenon (Korea Patent Publication No. 2014-0146717) and a method of modifying the primer layer to prevent precipitation of the oligomer as much as possible (Korea Patent Publication) 2014-0042352).

However, these methods are difficult to achieve the properties of reducing rainbow and oligomer block at the same time, and in particular, due to the acrylic resin used in the oligomer block, the refractive index of the primer layer is adjusted to improve the rainbow phenomenon.

Thus, the present inventors have induced the adhesion of the oligomer block and the resin to be further processed with a combined polymer blend resin selected from the group consisting of polyurethane-based polymers and acrylic-based polymers, and inorganic particles with high refractive index to improve rainbow The present invention was completed by manufacturing a polyester film by including in a coating layer.

Korean Patent Publication No. 2014-0146717 Korea Patent Publication No. 2014-0042352

The present invention has been devised to solve the above problems, and an object of the present invention is to provide a polyester film for optics that can reduce the rainbow phenomenon, prevent oligomer precipitation at the same time, and have excellent optical properties.

The above and other objects and advantages of the present invention will become more apparent from the following description of the preferred embodiment.

The objective is to include at least one axially stretched transparent polyester base film having a thickness of 50 to 500 μm, and a coating layer on at least one surface of the polyester base film, wherein the coating layer is mixed with a polyurethane polymer and an acrylic polymer. It is formed by coating with a coating solution containing a polymer mixed resin, a crosslinking agent, a surfactant, and inorganic particles having a refractive index of 1.8 or higher, and the total refractive index of the coating layer is achieved by an optical polyester film, characterized in that it is 1.56 to 1.62. .

Here, the inorganic particles are characterized in that the zirconia particles or tin oxide particles have an average particle diameter of 100 nm or less.

Preferably, the coating liquid is characterized in that it comprises 0.03% by weight to 0.1% by weight of the total weight of the coating liquid, the dispersed inorganic particle water dispersion of 30% solids.

Preferably, the inorganic particle dispersion is characterized in that it comprises 0.05% to 0.07% by weight relative to the total weight of the coating solution.

Preferably, the crosslinking agent is characterized in that at least one member selected from the group consisting of oxazoline-based, carbodiimide-based, epoxy-based and melamine-based.

Preferably, the optical polyester film is characterized in that the total light transmittance is 90 ~ 100%, haze value is 1.5% or less.

Preferably, the optical polyester film is characterized in that the haze change rate before and after the heat treatment by performing heat treatment at 150 ° C. for 1 hour is within 1%.

Preferably, the polyester film for optics is characterized in that the adhesion at room temperature and the moisture resistance at 65 ° C. and 95% RH for 120 hours are tested for humidity for at least 95%.

According to the present invention, by preventing the oligomer precipitation of the polyester film, there is an effect such as having a small change in light properties during post-processing, less foreign matter generation, and can have excellent adhesion and moisture adhesion to the post-processing resin.

Furthermore, the present invention has the effect of being transparent and having excellent optical properties since no rainbow phenomenon occurs.

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

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

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

Unless defined otherwise, 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.

1 to 2 are schematic cross-sectional views of an optical polyester film according to a preferred embodiment of the present invention.

1, the optical polyester film according to an embodiment of the present invention includes a base film 20 and a coating layer 10 on one surface of the base film. That is, the coating layer 10 may be configured on both sides of the base film 20 as shown in FIG. 2.

The base film 20 may be a single layer as a transparent base film, a laminate of two or more layers, and may be employed in any suitable material depending on the application, for example, selected from the group consisting of plastic, paper, metal film, and non-woven fabric. It is any one, and it is preferable to use plastic among them.

In addition, the base film may be composed of one kind of material, or may be composed of two or more kinds of materials, but more preferably, two or more kinds of plastics.

Examples of such plastics may be selected from polyester-based resins, polyamide-based resins, polyolefin-based resins, etc., and polyester-based resins are selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate. You can use one.

In the present invention, as a base film, a transparent polyester base film that is at least uniaxially stretched having a thickness of 50 to 500 μm is used as an example, but is not limited thereto.

The coating layer 10 is formed by coating with a coating solution containing a polymer mixed resin, a crosslinking agent, a surfactant mixed with a polyurethane polymer and an acrylic polymer, and inorganic particles having a refractive index of 1.8 or higher, and the total refractive index of the coating layer is 1.56 to 1.62. It is preferred.

In one embodiment, the binder resin used in the coating layer is a mixed form in the group consisting of a water-dispersible urethane resin and an acrylic resin comprising at least one functional group selected from the group consisting of hydroxyl group, carboxyl group, and N-methylol group. Contains resin. More preferably, it is preferable to be soluble or dispersible in water, and particularly, the polyurethane resin can be obtained by substitution polymerization of diol acrylic polymer, preferably copolymerization.

In one embodiment, the crosslinking agent may impart at room temperature and moisture adhesion by including at least one crosslinking agent resin selected from the group consisting of oxazoline-based, carbodiimide-based, epoxy-based, and melamine-based. In particular, the carbodiimide-based curing agent and the oxazoline-based curing agent serve to prevent blocking by inhibiting or reacting to moisture permeating the film, and the melamine-based curing agent preferentially reacts with an acrylic resin for suppressing oligomer precipitation. , And oligomer blocking properties.

In one embodiment, the coating solution includes a nonionic, anionic surfactant. The surfactant is for use in a water-soluble coating solution, and it is preferable to apply a known amount of anionic or nonionic surfactant to the substrate film in order to increase the wettability of the substrate film and apply the coating solution uniformly.

In one embodiment, additives may be used in the coating solution to improve coating properties and functionality, and inorganic particles, organic particles, antifoaming agents, and the like may be used as such additives.

Preferably, the inorganic particles are contained in the coating layer to reduce the rainbow and ensure runability, but when the average particle diameter exceeds 100 nm, haze increases. Therefore, it is preferable that the average particle diameter of the inorganic particles used in the present invention has a particle size of 100 nm or less. The inorganic particles may be at least one of silica particles, silica-organic composites, zirconia, tin oxide, and titanium oxide, and zirconia particles or tin oxide particles are preferred.

The refractive index of the inorganic particles is preferably 1.8 or more, more preferably 2.0 or more. It can be used for optics by introducing high-refractive-index high-refractive inorganic particles with a decrease in refractive index due to acrylic polymers, and can form a coating layer (primer layer) that reduces rainbow phenomena, adhesion between the base film and the coating layer, and excellent This is because it has reliability.

In addition, the inorganic particles having a high refractive index have a refractive index of 1.8 or more and are present in the form of water dispersion, and it is preferable to include 0.03% to 0.1% by weight of the total weight of the dispersed inorganic particle water dispersion of 30% of the solid content, More preferably, by containing 0.05% by weight to 0.07% by weight relative to the total weight of the coating solution, it is possible to reduce the rainbow while maintaining transparency.

In one embodiment, the coating thickness of the coating layer is preferably 0.05 to 5㎛, more preferably 0.05 to 3㎛. If the coating thickness is thinner than 0.05 µm, the transparency becomes good, but the adhesion is poor during post-processing, and when it is thicker than 5 µm, the adhesion characteristics are excellent, but the transparency and coating properties are lowered, which is not preferable.

The optical polyester film according to the present invention has a total light transmittance of 90 to 100% and a haze value of 1.5% or less.

In addition, the optical polyester film according to the present invention is subjected to heat treatment at 150 ° C for 1 hour, so that the haze change rate before and after heat treatment is within 1%.

In addition, the polyester film for optics according to the present invention has an adhesion at room temperature and a moisture resistance at 65 ° C. and 95% RH, which has been tested for 120 hours, and has an adhesion of at least 95%. That is, the optical polyester film according to the present invention has high reliability even after high temperature and high humidity conditions, and has high adhesion between the base film and the coating layer.

As described above, the optical polyester film according to the present invention applies a mixed resin of a urethane resin and an acrylic resin to the coating layer (primer layer), and adjusts the refractive index by adding specific inorganic particles to the refractive index loss caused by acrylic , It is possible to reduce the excellent transparency (oligomeric block property), adhesion and rainbow phenomenon required in the optical film.

Therefore, the present invention can block the oligomer generated in the polyester film from being precipitated on the surface, even if a UV- or heat-curable resin is applied on the coating layer formed on the polyester film, and in particular, the heat-curing resin is not precipitated on the surface. Therefore, it is possible to provide an optical polyester film having excellent optical properties and reliability even after being processed into a product for display optical members.

Hereinafter, the configuration of the present invention and its effects will be described in more detail through examples and comparative examples. However, this example is intended to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.

[Example]

The components used in this example are as follows.

Urethane resin: H-15 (Japan, Cheil Industries)

Carbodiimide resin: SV-02 (Nishinbo company, Japan)

Acrylic resin: RX-7013ED (Japan, Japan Carbide)

Zirconia water dispersion: DT-ZRO-30DI (Korea, Dito Technology)

[Examples 1 to 4]

The components and contents shown in Table 1 below (contents are all by weight), 90% by weight of water, and an aqueous surfactant dispersion composed of 10% by weight of anionic surfactant (10% by weight of solid content) 0.75% by weight and residual water After the coating solution was prepared using the coating, the polyester film for optics was prepared by applying inline to a uniaxially stretched polyester base film having a thickness of 100 µm. The application was performed using a # 4 Wire bar.

Urethane resin
(20% solids) Carbodiimide resin
(40% solids) Acrylic resin
(25% solids) Zirconia water dispersion
(30% solids) Example 1 1.95% 0.21% 0.85% 0.03% Example 2 1.95% 0.21% 0.85% 0.05% Example 3 1.95% 0.21% 0.85% 0.07% Example 4 1.95% 0.21% 0.85% 0.1%

[Comparative Examples 1 to 5]

An optical polyester film was prepared in the same manner as in Example 1, except for the components and contents shown in Table 2 below.

Urethane resin
(20% solids) Carbodiimide resin
(40% solids) Acrylic resin
(25% solids) Zirconia water dispersion
(30% solids) Comparative Example 1 1.95% 0.21% 0.85% - Comparative Example 2 1.95% 0.21% 0.85% 0.3% Comparative Example 3 1.95% 0.21% 0.85% 0.5% Comparative Example 4 1.95% 0.21% - 0.1% Comparative Example 5 - 0.21% 0.85% 0.1%

Using the polyester films for optics according to Examples 1 to 4 and Comparative Examples 1 to 5, physical properties were measured through the following experimental examples and the results are shown in Table 3 below.

[Experimental Example]

1. Evaluation of adhesion (adhesive power)

After applying the # 20 wire bar to the coating layers of the films prepared in Examples 1 to 4 and Comparative Examples 1 to 5, the acrylic UV cured resin was applied, and then the adhesion between the coating layer and the UV resin was measured. The adhesion is made by cutting lines on the film coated with the cutter, and placing 2 mm X 2 mm squares in a 10 X 10 matrix. Cellophane tape (No. 405, width: 24 mm, manufactured by NICHIBAN) was attached to the film with a cutting line, and the tape was rubbed and strongly attached to the film using velvet, and then the tape was removed vertically. The area of the UV resin remaining on the coating layer was visually observed, and adhesion was calculated by the following equation (1).

(Equation 1)

Adhesion (%) = (1-defective area / evaluation area) * 100

2. Moisture adhesion evaluation

The adhesion after 65 hours at 65 ° C and 95% RH was carried out in the same manner as in Experimental Example 1 above.

3. Check coating properties

In Examples 1 to 4 and Comparative Examples 1 to 5, the coating properties between the coating liquid as the coating layer and the substrate were measured. The coating layer was applied to the substrate using # 0 to # 6 wire bars to confirm whether the coating layer was coated on the entire surface of the substrate. It was evaluated that the coating properties were excellent when the portions without the coating solution, such as islands, with the naked eye existed in two or less on 100 small square standards (1 square: 1 X 1 mm).

4. Rainbow observation

The coating layer of the films prepared in Examples 1 to 4 and Comparative Examples 1 to 5 was coated with a UV resin for hard coating, and a black tape was attached to the back side, and it was confirmed whether rainbow light was observed. When no rainbow was observed with the naked eye, it was evaluated as excellent.

5. Haze / light transmittance measurement

Haze and transmittance were measured using a HAZE measuring device (NDH 4000) manufactured by NIPPON DENSHOKU, after coating and heat-curing on a 100 μm PET film with the coating solutions prepared in Examples 1 to 4 and Comparative Examples 1 to 5. .

6. Haze change rate (△ Haze) measurement

The coating liquids prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were applied to a 100 μm PET film to heat-cure, and then subjected to heat treatment at 150 ° C. for 1 hour to change the Haze value before and after the heat treatment. It was measured using a HAZE meter (NDH 4000) manufactured by NIPPON DENSHOKU.

7. Measurement of refractive index

After applying the coating solution prepared in Examples 1 to 4 and Comparative Examples 1 to 5 to a PET film having a thickness of 100 µm and heat-curing it, pasting a black insulating tape on the back side of the coating, ellipso manufactured by Ellipso Technology Co., Ltd. The refractive index of the coating layer was measured with a meter (Elli-SE).

division Adhesion (%) Coating properties Rainbow Hayes /
Light transmittance
(%) Haze change rate
(△ Haze) Application layer
Refractive index Room temperature inroad Example 1 100 95 Great Great 1.06 /
90.07 0.21 1.56 Example 2 100 96 Great Great 1.28 /
90.78 0.25 1.57 Example 3 100 95 Great Great 1.34 /
91.08 0.26 1.60 Example 4 100 95 Great Great 1.45 /
90.72 0.22 1.62 Comparative Example 1 100 98 Great Bad 1.02 /
90.58 0.12 1.53 Comparative Example 2 100 90 Great Great 5.73 /
88.96 0.31 1.74 Comparative Example 3 100 92 Great Great 17.2 /
88.96 0.28 1.76 Comparative Example 4 100 98 Great Great 1.41 /
90.12 10 1.64 Comparative Example 5 25 0 Great Bad 1.38
/91.4 0.11 1.51

As can be seen from Table 3, it can be confirmed that the optical polyester film according to the embodiment of the present invention has excellent adhesion (adhesiveness) and oligomer blocking property, and also has excellent optical properties and no rainbow phenomenon.

In this specification, only a few examples of the various embodiments performed by the present inventors are described, but the technical spirit of the present invention is not limited to or limited thereto, and can be variously implemented by a person skilled in the art.

10: coating layer
20: base film

Claims (8)

At least uniaxially stretched transparent polyester base film having a thickness of 50 to 500㎛,
A coating layer is included on at least one surface of the polyester base film,
The coating layer is formed by coating with a coating solution containing a polymer mixed resin, a crosslinking agent, a surfactant mixed with a polyurethane-based polymer and an acrylic-based polymer, and inorganic particles having a refractive index of 1.8 or more,
The total refractive index of the coating layer is characterized in that 1.56 ~ 1.62, optical polyester film. According to claim 1,
The inorganic particles are zirconia particles or tin oxide particles, characterized in that the average particle diameter of 100nm or less, optical polyester film. According to claim 1,
The coating liquid is characterized in that it comprises an aqueous dispersion of inorganic particles having a solid content of 30%, 0.03% by weight to 0.1% by weight relative to the total weight of the coating solution, optical polyester film. According to claim 3,
The inorganic particle aqueous dispersion is characterized in that it comprises 0.05% by weight to 0.07% by weight relative to the total weight of the coating solution, the optical polyester film. According to claim 1,
The crosslinking agent is characterized in that at least one member selected from the group consisting of oxazoline-based, carbodiimide-based, epoxy-based and melamine-based, optical polyester film. According to claim 1,
The optical polyester film is characterized in that the total light transmittance is 90 to 100%, haze value is 1.5% or less, the optical polyester film. According to claim 1,
The optical polyester film is 150 ℃, heat treatment for 1 hour, characterized in that the haze change rate before and after the heat treatment is within 1%, the optical polyester film. The method according to any one of claims 1 to 7,
The optical polyester film is characterized in that the adhesion at room temperature and 65 ° C, 95% RH under 120 hours moisture resistance test, characterized in that the moisture resistance is at least 95%.

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