KR20130068931A - Polyester film for optical use - Google Patents

Abstract

PURPOSE: An optical polyester film is provided to improve adhesive force between resin and base film even in the environment of high temperature and high humidity and prevent drop-out of a coating layer generated during the post processing by forming a primer layer blended with water soluble acryl polymer resin and polyurethane resin to elongate transparent polyester substrate film at least one shaft. CONSTITUTION: An optical polyester film comprises a polyester substrate film(1) and a primer layer(2) coated on at least one side of the base film. The primer layer coated with coating solution composed of polyacrylo-nitrile resin in a blended form has urethane type polymer resin as main material. The surface of the base film formed the primer layer has 90~100% of light transmittance and 0.2~0.7% of haze values. The adhesive force between the base film and the primer layer is 95~100% under is 65°C, and 95% of humidity after 96 hours of an excess water tolerance test. The acrylic polymer resin is a resin given water-soluble by controlling molecular weight and through copolymer with hydrophilic group which is at least one among methylmethacrylate, ethylmethacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methylmethacrylate, acrylic acid, methacrylic acid, etc.

Description

POLYESTER FILM FOR OPTICAL USE

The present invention relates to an optical polyester film, and more specifically, to a primer layer mainly containing a urethane-based polymer resin having relatively high dimensional stability, blending an acrylic polymer resin for imparting adhesion force with a processing resin to a primer layer. By the micro phase separation of the two polymers, which are incompatible with each other, the urethane-based polymer resin is responsible for the adhesive force to the base film and the acrylic polymer resin is responsible for the adhesive force to the processing resin. It is related with the polyester film for optics which can improve the adhesive force between films, and can prevent the fall of the coating layer which may arise at the time of post-processing.

In general, polyester films are excellent in dimensional stability, thickness uniformity, and optical transparency, so that they are widely used not only for display devices but also for various industrial materials. In particular, as the interest in liquid crystal displays, organic light emitting displays, and electronic papers has recently increased, studies are being actively conducted to replace the substrates of these display devices with polyester films instead of glass substrates. The reason for this is that replacing the glass substrate with a polyester film makes the overall weight of the display device lighter, gives design flexibility, and is more resistant to impact and can be manufactured in a continuous process. .

The development for such applications requires high glass transition temperature, high light transmittance and surface scratch resistance, and adhesion to the substrate and the post-coating liquid, which can withstand the deposition temperature of the transparent electrode. 1 is a cross-sectional view of a conventional polyester film for optics is composed of a polyester base film (1) and a primer layer (2) formed on the base film, the primer layer (2) is composed of a single resin.

In addition, such a polyester film is often subjected to a process of coating a hard coating layer on the surface, the problem when manufacturing such a structure is the deformation of the polyester film due to the large difference in coefficient of linear expansion between the polyester film and the hard coating layer Cracking and peeling may occur, and in order to prevent this phenomenon, adhesion between the substrate and the processing resin is required even in a high temperature and high humidity environment.

Therefore, the proper structure design to minimize the stress at the interface of each layer and the adhesion between the coating layer is evaluated as a very important physical property, and to solve the adhesion force, the primer layer is composed of the same components as the composition of the processing resin do. The primer layer is composed of a composition of an acrylic crude liquid and a polyester copolymer or a polyurethane resin (Korean Patent Publication No. 2010-0081568).

On the other hand, since the adhesive force in the prior art consists of only the adhesion by the dispersing force, there are attempts to solve this problem by using a primer with a reactor, etc. It was very difficult to give.

Korean Patent Publication No. 2010-0081568

The present invention has been made to solve the above problems, the object of the present invention is to improve the adhesion between the resin and the base film even in a high temperature, high humidity environment, which can prevent the coating layer from falling off during processing It is to provide an optical polyester film.

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

The object is a film comprising a polyester base film and a primer layer primer-coated on at least one side of the base film, the primer layer is mainly composed of a urethane-based polymer resin and the acrylic polymer resin is composed of a blend form It is achieved by the optical polyester film characterized by being apply | coated and formed with the coating liquid.

Here, the coating liquid to form the primer layer is 10 to 90% by weight of an aqueous dispersion of a binder resin composed of 70% by weight of water, 30% by weight of polyurethane resin and 40% by weight of a water-soluble acrylic polymer resin, Surfactant aqueous dispersion consisting of 1 to 50% by weight of a curing agent aqueous dispersion composed of 70% by weight of water and 30% by weight of melanin or epoxy curing agent, and 90% by weight of water and 10% by weight of anionic surfactant. 10 wt%, 30 wt% of water and 70 wt% of inorganic particles composed of inorganic particles, characterized in that consisting of 0.1 to 40 wt% and the balance of water.

Preferably, the water-soluble acrylic polymer resin in the total composition of the binder resin and the water-soluble acrylic polymer resin is characterized in that 1 to 10% by weight.

Preferably, the surface of the base film on which the primer layer is formed is characterized in that the light transmittance is 90 to 100% and haze value is 0.2 to 0.7%.

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

Preferably, the acrylic polymer resin is at least one of acrylic polymers such as methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid It is characterized in that the resin to adjust the molecular weight and to impart water solubility through a copolymer with a hydrophilic group.

Preferably, the primer layer is characterized in that the urethane-based polymer resin is predominantly formed on the base film side after drying, the acrylic polymer resin is predominantly formed on the surface side.

According to the present invention, a primer layer in which a water-soluble acrylic polymer resin is blended with a polyurethane resin is formed on at least one uniaxially stretched transparent polyester base film, thereby improving adhesion between the resin and the base film even in a high temperature and high humidity environment, and post-processing. It is possible to prevent the falling off of the coating layer that may occur at the time.

1 is a cross-sectional view of a conventional polyester film for optics.
2 is a cross-sectional view of an optical polyester film according to the present invention.

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 .

Optical polyester film according to the present invention is a film comprising a polyester base film and a primer layer primer-coated on at least one side of the base film, the primer layer is based on the urethane-based polymer resin and acrylic polymer resin is Characterized in that the coating is formed with a coating liquid consisting of a blend form. That is, the main component of the coating liquid constituting the primer layer of the optical polyester film according to the present invention is based on a polyurethane-based resin, more preferably in a form in which an acrylic polymer resin is blended with the polyurethane-based resin.

As shown in FIG. 2, the optical polyester film according to the present invention comprises a polyester base film 1 and a primer layer 3 formed on the base film, wherein the primer layer 3 is a urethane-based polymer. It is applied with a coating liquid consisting of a resin and an acrylic polymer resin. In addition, it is preferable that the primer layer 3 has a fine phase separation between the composition after drying, the urethane-based polymer resin is predominant on the base film side, the acrylic polymer resin is predominantly formed on the surface side. Through the microphase separation of two incompatible polymers as described above, the adhesion force with the base film is in charge of the urethane-based polymer resin and the acrylic polymer resin is in charge with the processing resin. By improving the adhesion of the liver, it is possible to prevent the falling off of the coating layer that can occur during post-processing.

In addition, as the acrylic polymer resin blended with the polyurethane resin, specifically, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, meta It is at least one of acrylic polymers, such as acrylic acid, it is characterized in that the resin is adjusted to the molecular weight and given water solubility through a copolymer with a hydrophilic group.

In addition, the coating liquid for forming the primer layer of the optical polyester film according to the present invention is a binder resin composed of 70% by weight of water and 30% by weight of polyurethane resin and 40% by weight of water-soluble acrylic polymer resin Curing agent 1-50% by weight of aqueous dispersion 10-90% by weight, 70% by weight of water and 30% by weight of melanin- or epoxy curing agent, 90% by weight of water and 10% by weight of anionic surfactant Surfactant aqueous dispersion consisting of 0.1 to 10% by weight and 30% by weight of water and 70% by weight of inorganic particles consisting of inorganic particles, characterized in that consisting of 0.1 to 40% by weight and the balance of water.

In addition, the water-soluble acrylic polymer resin of the total composition of the binder resin and the water-soluble acrylic polymer resin is characterized in that 1 to 10% by weight. If it is less than 1% by weight, it is difficult to commercialize the film due to poor process runability. In other words, since the film is manufactured in the in-line process and the coating is applied to impart the functionality, when the particle is less than 1% by weight in the coating layer, it is difficult to commercialize itself. This is because the transmittance is lowered, and therefore, the luminance may be lowered, which makes it impossible to use the optical film.

In addition, the coating thickness of the primer layer according to the present invention is preferably 0.05 ~ 5㎛.

In addition, it is preferable that the base film of the optical polyester film according to the present invention is a transparent polyester film, based on stretching at least one axis or more for strength of the film, and the base film has a thickness of 50 to 300 μm. It is desirable to have.

In addition, the optical polyester film according to the present invention proceeds from the inline to the primer layer coating process using the base film to enable the production of finished products at once.

In addition, the optical polyester film according to the present invention is characterized in that the surface of the base film on which the primer layer is formed has a light transmittance of 90 to 100% and a haze value of 0.2 to 0.7%, and the base film and the primer The adhesion between the layers is characterized in that 95 to 100% after a 96 hours humidity resistance test at 65 ℃, 95% humidity.

Hereinafter, the structure and effect of the present invention will be described in more detail with reference to examples and comparative examples. However, this embodiment is intended to explain the present invention more specifically, and the scope of the present invention is not limited to these embodiments.

[Examples 1 to 5]

In order to manufacture the optical polyester film which comprises the primer layer of this invention, the uniaxially-stretched polyester film is used as a base film, and the coating liquid which forms a primer layer is 70 weight% water and 30 weight% polyurethane resin. 5% by weight of aqueous dispersion of water and 63.9% by weight of aqueous dispersion of 40% by weight of water-soluble acrylic polymer resin blended in the binder resin as shown in Table 1, 70% by weight of water and 30% by weight of melamine curing agent. 5% by weight of an inorganic particle dispersion consisting of 1.0% by weight of a water-based surfactant dispersion composed of 90% by weight of water and 10% by weight of anionic surfactant, 30% by weight of water, and 70% by weight of titanium oxide particles. And after using the remaining amount of water to prepare a coating liquid was applied to the uniaxially stretched polyester base film having a thickness of 100㎛ to prepare an optical polyester film. The coating solution was applied using a # 4 wire bar.

"Aqueous acrylic resin addition amount" of Table 1 below is the weight% of the water-soluble acrylic polymer resin in the total composition of the binder resin and the water-soluble acrylic polymer resin.

division Water-soluble acrylic resin addition amount (% by weight) Solid content (%) Viscosity (CPS) Example 1 One 7.18 1.18 Example 2 3 7.18 1.23 Example 3 5 7.18 1.5 Example 4 7 7.18 1.84 Example 5 10 7.18 1.92

[Comparative Example]

20.0 wt% of an aqueous dispersion composed of 70 wt% water and 30 wt% polyurethane resin as binder resin, 5 wt% of an aqueous dispersion of hardener composed of 70 wt% of water and 30 wt% of melamine curing agent, and 63.9 wt% of water. 1.0% by weight of a surfactant aqueous dispersion consisting of 90% by weight of water and 10% by weight of anionic surfactant, and silica particles of 30% by weight of water and an inorganic particle aqueous dispersion consisting of 70% by weight of titanium oxide particles. After preparing the coating solution using the weight% and the remaining water (see Table 2), the optical polyester film was prepared by applying to the monoaxially stretched polyester base film of the above example having a thickness of 100 μm. The coating solution was applied using a # 4 wire bar.

division Host ingredient Solid content (%) Viscosity (CPS) Comparative example Polyurethane 7.18 1.1

Using the film according to Examples 1 to 5 and Comparative Examples to measure the physical properties through the following experimental example and the results are shown in Table 3 below.

[Experimental Example]

1. Measurement of thickness of coating layer

The coating layer thicknesses of the films prepared in Examples 1 to 5 and Comparative Examples were measured using a micrometer-based sedimentation measuring instrument (Mitsutoyo Co., Model: ID-Ff125). The average value of the remaining values minus the thickness (μm) of the transparent base film was calculated.

2. Refractive index measurement

Since the coating layer refractive index of the films prepared in Examples 1 to 5 and Comparative Examples is 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. Check the adhesion

The adhesion between the substrate and the primer layer of the films prepared in Examples 1 to 5 and Comparative Examples was measured. Apply acrylic UV curable resin on the surface to which the primer layer is attached using a # 20 wire bar, and then use a cutter to make a cutting line on the film coated with the primer layer, and apply a 2 mm × 2 mm square to a 10 × 10 matrix. To place. The cellophane tape (No. 405, width of NICHIBAN: 24 mm) is affixed to the film with a cutting line, and the tape is rubbed strongly with the film using velvet, and then the 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 5 and Comparative Examples, the coating property between the coating solution, which is a primer layer, and the substrate were measured. The primer layer was applied to the substrate using # 0 to # 6 wire bars to confirm whether the primer 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 x 1 mm) such as islands.

5. Haze / light transmittance check

The coating liquids prepared in Examples 1 to 5 and Comparative Examples were applied to a 188 μm PET film and thermally cured, and then haze and transmittance were measured using a HAZE meter manufactured by NIPPON DENSHOKU.

division Coating layer thickness (㎛) Refractive index Adhesion (%) Moisture Adhesion (%) Coating property Haze / light transmittance Example 1 0.15 1.58 100 95 0 0.28 / 92.9 Example 2 0.15 1.57 100 100 O 0.32 / 91.4 Example 3 0.15 1.57 100 100 O 0.48 / 91.0 Example 4 0.15 1.55 100 100 O 0.54 / 90.9 Example 5 0.15 1.51 100 98 0 0.68 / 90.1 Comparative example 0.15 1.59 100 83 0 0.4 / 88.4

(O: Good, Δ: Normal, X: Poor)

As shown in Table 3, it can be confirmed that the addition of the acrylic resin can be produced in the optical film with improved moisture resistance adhesion with the resin.

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.

1: polyester base film 2: primer layer
3: urethane + acrylic primer layer 3-1: acrylic polymer resin
3-2: Urethane Polymer Resin

Claims (7)

In the optical polyester film,
A film comprising a polyester base film and a primer layer coated on at least one side of the base film,
The primer layer is a polyester film for optics, characterized in that the urethane-based polymer resin as a main material and the acrylic polymer resin is applied by a coating liquid consisting of a blend form. The method of claim 1,
The coating liquid for forming the primer layer is 10 to 90% by weight and 70% by weight of an aqueous dispersion of a binder resin composed of 70% by weight of water, 30% by weight of polyurethane resin and 40% by weight of water-soluble acrylic polymer resin. Surfactant aqueous dispersion consisting of 1 to 50% by weight of aqueous dispersion of hardener composed of% water and 30% by weight of melanin or epoxy curing agent, and 90% by weight of water and 10% by weight of anionic surfactant. An optical polyester film, characterized in that consisting of 0.1 to 40% by weight of the aqueous dispersion of inorganic particles composed of%, 30% by weight of water and 70% by weight of inorganic particles, and the remaining amount of water. The method of claim 2,
The polyester film for optics, characterized in that the water-soluble acrylic polymer resin is 1 to 10% by weight in the total composition of the binder resin and the water-soluble acrylic polymer resin. The method of claim 1,
The surface of the base film on which the primer layer is formed has a light transmittance of 90 to 100% and a haze value of 0.2 to 0.7%, the polyester film for optics. The method of claim 1,
Adhesive force between the base film and the primer layer is characterized in that 95 to 100% after a moisture resistance test for 96 hours at 65 ℃, 95% humidity, optical polyester film. The method of claim 1,
The acrylic polymer resin is at least one of acrylic polymers such as methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid and methacrylic acid It is resin which adjusted and provided water solubility through the copolymer with a hydrophilic group, The optical polyester film characterized by the above-mentioned. 7. The method according to any one of claims 1 to 6,
The primer layer is an optical polyester film, characterized in that the layer is predominantly composed of the urethane-based polymer resin on the substrate film side, the acrylic polymer resin on the surface side after drying.

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