KR20200003491A - Optical Polyester Film - Google Patents

Abstract

The present invention relates to an optical polyester film capable of providing excellent transparency (oligomer blocking properties) and adhesiveness required for an optical film, and reducing a rainbow phenomenon by applying a mixed resin of a urethane resin and an acrylic resin to a coating layer (primer layer), and adding specific inorganic particles and adjusting a refractive index to overcome refractive index loss due to acryl.

Description

Optical polyester film {Optical Polyester Film}

TECHNICAL FIELD The present invention relates to an optical polyester film, and more particularly, to an optical polyester film capable of reducing a rainbow phenomenon and at the same time preventing oligomer precipitation.

In recent years, the evaluation level of the appearance in the optical sheet processing process has become increasingly strict. In particular, in the case of a liquid crystal protective film or a scattering prevention film that must be located on the most surface, the defect rate due to rainbow (interference stain), foreign matters, etc. is gradually increasing, and when the heat is applied to the base film according to the processing conditions, the polyester film is Due to the properties of the material, oligomers having a low degree of polymerization precipitate on the surface, causing turbidity of the film itself to be severely changed, or causing many problems such as deterioration of electrical properties by 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 (Korean Patent Publication No. 2014-0146717) and a method of modifying the primer layer to prevent the precipitation of the oligomer (Max. 2014-0042352).

However, these methods are difficult to achieve the properties of the rainbow reduction and oligomer block at the same time, in particular, due to the acrylic resin used in the oligomer block has a problem that the rainbow phenomenon is not improved by adjusting the refractive index of the primer layer.

Accordingly, the inventors of the present invention induced a polymer mixed resin selected from the group consisting of a polyurethane-based polymer and an acrylic-based polymer to maintain the adhesion between the oligomer block and the additionally processed resin, and inorganic particles having a high refractive index for rainbow improvement. The present invention was completed by preparing a polyester film by including in a coating layer.

Korean Unexamined Patent Publication No. 2014-0146717 Korean Laid-Open Patent Publication No. 2014-0042352

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

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

The object includes at least one uniaxially 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 liquid containing a polymer mixed resin, a crosslinking agent, a surfactant, and inorganic particles having a refractive index of 1.8 or more, and the total refractive index of the coating layer is achieved by an optical polyester film, characterized in that 1.56 to 1.62. .

Herein, the inorganic particles are zirconia particles or tin oxide particles, and the average particle diameter is 100 nm or less.

Preferably, the coating liquid is characterized in that it comprises 0.03% to 0.1% by weight of the aqueous dispersion of the inorganic particles dispersed in the solid content 30% of the total weight of the coating liquid.

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

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 to 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 a heat treatment for 150 ℃, 1 hour is within 1%.

Preferably, the optical polyester film is characterized in that the room temperature adhesion and moisture resistance adhesion after the test for 120 hours at 65 ℃, 95% RH moisture resistance adhesion is 95% or more.

According to the present invention, it is possible to prevent the oligomer precipitation of the polyester film, so that there is little change in the optical properties during post-processing, less foreign substances are generated, and can have excellent adhesion to the post-processing resin and moisture-resistant adhesion.

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

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.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of the polyester film for optics which concerns on one Embodiment of this invention.
It is a cross-sectional schematic diagram of the polyester film for optics which concerns on other embodiment of this invention.

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. .

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 cross-sectional schematic diagrams of an optical polyester film according to a preferred embodiment of the present invention.

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

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

Moreover, the base film may be comprised from 1 type of material, and may be comprised from 2 or more types of materials, More preferably, it is comprised from 2 or more types of plastics.

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

In the present invention, as the base film, at least uniaxially stretched transparent polyester base film 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 liquid containing a polymer mixed resin, a crosslinking agent, a surfactant, and an inorganic particle having a refractive index of 1.8 or more mixed with a polyurethane-based polymer and an acrylic polymer, and the total refractive index of the coating layer is 1.56 to 1.62. Is preferably.

In one embodiment, the binder resin used in the coating layer is a mixed form in the group consisting of water-dispersible urethane resin and acrylic resin containing at least one functional group selected from the group consisting of hydroxyl group, carboxyl group, N- methylol group. Resin. More preferably, it is preferable to be 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 (di-ol).

In one embodiment, the crosslinking agent may be imparted to room temperature and moisture resistance, including at least one crosslinker 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 serves to prevent the occurrence of blocking by inhibiting or reacting the moisture permeated into the film, the melamine-based curing agent preferentially reacts with the acrylic resin for suppressing oligomer precipitation , Oligomer blockability can be imparted.

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

In one embodiment, an additive may be used in the coating liquid to improve the coating property and functionality, and such additives may be inorganic particles, organic particles, antifoaming agents, and the like.

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

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 and transparent inorganic particles, which can be used for optics, and can make a coating layer (primer layer) which reduces rainbow phenomenon, and has excellent adhesion between base film and coating layer. This is because it becomes reliable.

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

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

The optical polyester film which concerns on this invention is 90-100% of the total light transmittance, and haze value is 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, and the haze change rate before and after the heat treatment is within 1%.

In addition, the optical polyester film according to the present invention is at least 95% at room temperature adhesion and moisture resistance adhesion test after 65 hours, 95% RH moisture resistance test. That is, the optical polyester film according to the present invention has high adhesiveness between the base film and the coating layer even after high temperature and high humidity conditions and has reliability.

As described above, in the optical polyester film according to the present invention, a mixed resin of a urethane resin and an acrylic resin is applied to an application layer (primer layer), and by adjusting the refractive index by adding specific inorganic particles to the refractive index loss due to acryl It is possible to reduce the excellent transparency (oligomer blockability), adhesion, and rainbow phenomenon required for an optical film.

Therefore, the present invention has a low rainbow phenomenon even when the curable resin is coated with ultraviolet rays or heat on the coating layer formed on the polyester film. Particularly, in the case of curing by heat, the oligomer generated in the polyester film may be prevented from being deposited on the surface. Therefore, even after being processed into a product for display optical members, it is possible to provide an optical polyester film having excellent optical characteristics and reliability.

Hereinafter, the configuration and effects of the present invention will be described in more detail with reference to Examples and Comparative Examples. However, 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

The components used in this example are as follows.

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

Carbodiimide Resin: SV-02 (Nishinbosa, Japan)

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

Zirconia Aqueous Dispersion: DT-ZRO-30DI (Korea, Dito Technology)

[Examples 1 to 4]

To Table 1, the components and contents (contents are all in weight%), 0.75% by weight of a surfactant aqueous dispersion (solid content 10% coating liquid) consisting of 90% by weight of water and 10% by weight of anionic surfactant and the remaining amount of water After the coating liquid was prepared, the optical polyester film was prepared by applying in-line to a uniaxially stretched polyester base film having a thickness of 100 μm. Application was applied using a # 4 wire bar.

Urethane resin
(20% solids) Carbodiimide resin
(40% solids) Acrylic resin
(25% solids) Zirconia Aqueous Solution
(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]

Except for the components and contents shown in Table 2 in the same manner as in Example 1 to prepare an optical polyester film.

Urethane resin
(20% solids) Carbodiimide resin
(40% solids) Acrylic resin
(25% solids) Zirconia Aqueous Solution
(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%

Physical properties of the optical polyester films according to Examples 1 to 4 and Comparative Examples 1 to 5 were measured through the following experimental examples, and the results are shown in Table 3 below.

Experimental Example

1. Evaluation of adhesion

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

(Equation 1)

% Adhesion = (1-Defective Area / Evaluation Area) * 100

2. Moisture resistance adhesion evaluation

The adhesion after 120 hours at 65 ° C. and 95% RH was carried out in the same manner as in Experimental Example 1.

3. Check coatability

In Examples 1-4 and Comparative Examples 1-5, the coating property between the coating liquid which is a coating layer, and a base material was 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. Visually, it was evaluated that the coating property was excellent when there were less than two parts on the basis of 100 small squares (one square: 1 × 1mm) like the islands.

4. Rainbow Observation

Coating the UV resin for the hard coating on the coating layer of the film prepared in Examples 1 to 4 and Comparative Examples 1 to 5, the black tape was attached to the back, and it was confirmed whether the rainbow light is observed. When no rainbow was observed visually, it evaluated as excellent.

5. Haze / Light Transmittance Measurement

Haze and transmittance were measured using a HAZE measuring instrument (NDH 4000) manufactured by NIPPON DENSHOKU company after thermal curing by applying to the PET film of 100㎛ with the coating solution prepared in Examples 1-4 and Comparative Examples 1-5. .

6. Haze change rate (△ Haze) measurement

After applying to a 100 μm PET film with a coating solution prepared in Examples 1 to 4 and Comparative Examples 1 to 5 and thermosetting, the heat treatment was performed again at 150 ° C. for 1 hour to change the Haze value before and after heat treatment. Measurement was performed using a HAZE meter (NDH 4000) manufactured by NIPPON DENSHOKU.

7. Refractive Index Measurement

After the thermosetting by coating the PET film of 100㎛ with the coating liquid prepared in Examples 1 to 4 and Comparative Examples 1 to 5, and then attaching a black insulating tape on the back of the coating, Ellipso technology manufactured by Ellipso Technology Co., Ltd. The refractive index of the coating layer was measured with a meter (Elli-SE).

division Adhesion (%) Coating Rainbow Haze /
Light transmittance
(%) Haze rate of change
(△ Haze) Coating 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, the optical polyester film according to the embodiment of the present invention has excellent adhesion (adhesive force) and oligomer block property, it can be confirmed that the optical properties are excellent and there is no rainbow phenomenon.

In the present specification, only a few examples of various embodiments performed by the present inventors are described, but the technical idea of the present invention is not limited thereto, but may be variously modified and implemented by those 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 μm,
Including at least one surface of the polyester base film coating layer,
The coating layer is formed by coating with a coating liquid containing a polymer mixed resin, a crosslinking agent, a surfactant and an inorganic particle having a refractive index of 1.8 or more mixed with a polyurethane-based polymer and an acrylic-based polymer,
The total refractive index of the said coating layer is 1.56-1.62, The optical polyester film characterized by the above-mentioned. The method of claim 1,
The inorganic particles are zirconia particles or tin oxide particles, the average particle diameter of 100nm or less, optical polyester film, characterized in that. The method of claim 1,
The coating liquid is an optical polyester film, characterized in that it comprises 0.03% to 0.1% by weight of the aqueous dispersion of the inorganic particles dispersed in the solid content of 30% of the total weight of the coating liquid. The method of claim 3,
The inorganic particles aqueous dispersion is characterized in that it comprises 0.05% to 0.07% by weight relative to the total weight of the coating liquid, the optical polyester film. The method of claim 1,
The crosslinking agent is at least one member selected from the group consisting of oxazoline-based, carbodiimide-based, epoxy-based and melamine-based, the optical polyester film. The method of claim 1,
The said optical polyester film is 90-100% of total light transmittance, and haze value is 1.5% or less, The optical polyester film characterized by the above-mentioned. The method of claim 1,
The said optical polyester film is heat-processed at 150 degreeC for 1 hour, and the haze change rate before and after heat processing is 1% or less, The optical polyester film characterized by the above-mentioned. The method according to any one of claims 1 to 7,
The optical polyester film is an optical polyester film, characterized in that the adhesion at room temperature and moisture resistance adhesion after a test for 120 hours at 65 ℃, 95% RH moisture resistance is more than 95%.

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