KR102226138B1 - Cpi film for flexible displays comprising low-reflection coating layer - Google Patents

Abstract

CPI film in the present specification; A hard coating layer formed on the CPI film; And a low-reflection coating layer formed on the hard coating layer, wherein a refractive index of the low-reflection coating layer is lower than that of the hard coating layer, and a low-reflection CPI film is provided.

Description

CPI film for flexible display including a low-reflective coating layer {CPI FILM FOR FLEXIBLE DISPLAYS COMPRISING LOW-REFLECTION COATING LAYER}

As a CPI film for a flexible display, the present specification discloses a CPI film having a low-reflective function surface-treated.

In recent years, as the product's bendable and flexible functions are emphasized in the display field, many studies are being conducted to use CPI in the display field.

In particular, the flexible display device can be applied to various electronic display products, and accordingly, demands for total light transmittance, low reflection characteristics, and physical characteristics are continuously increasing.

Unexamined Patent Publication No. 10-2006-0069326

Embodiments of the present invention are a CPI film that can be applied as a substitute for a cover glass of a flexible display, and is to provide a flexible film having a low reflectivity.

In addition, embodiments of the present invention are intended to provide a film having a predetermined thickness and having physical properties such as excellent reflectance and scratch resistance at the same time.

One embodiment of the present invention, CPI film; A hard coating layer formed on the CPI film; And a low-reflection coating layer formed on the hard coating layer, wherein a refractive index of the low-reflection coating layer is lower than that of the hard coating layer.

In an exemplary embodiment, the refractive index of the low-reflective coating layer may be 0.01-0.5 lower than that of the hard coating layer.

In an exemplary embodiment, the refractive index of the low-reflective coating layer may be 1.1-1.3.

In an exemplary embodiment, the thickness of the low-reflective coating layer may be 350-450 nm.

In an exemplary embodiment, the low-reflective coating layer may include an acrylate base resin.

In an exemplary embodiment, the refractive index of the hard coating layer may be 1.3-1.6.

In an exemplary embodiment, the thickness of the hard coating layer may be 1 μm or more.

In an exemplary embodiment, the hard coating layer may include an acrylate base resin.

In an exemplary embodiment, the low-reflective CPI film may have a haze of 1% or less or a total light transmittance of 90% or more under a D65 light source condition.

In an exemplary embodiment, the low-reflective CPI film may have a hardness of 1H or more.

In an exemplary embodiment, the low-reflection CPI film may be for a flexible display.

In embodiments of the present invention, it is intended to provide a CPI film that can be applied as a substitute for a cover glass of a flexible display. To this end, it is intended to provide a flexible film having a low reflectivity.

In addition, in embodiments of the present invention, it is intended to provide a film having a predetermined thickness and having physical properties such as excellent reflectance and scratch resistance at the same time.

1 is a schematic diagram showing a three-layer structured low-reflective CPI film according to an embodiment of the present invention, where AR denotes a low-reflective coating layer and HC denotes a hard coating layer.
2 shows a graph comparing the reflectance of a low-reflective CPI film according to the presence or absence of a low-reflection coating layer.
3 is a graph comparing the reflectance of the low-reflection CPI film when the refractive index of the hard coating layer is set to 1.5, the refractive index of the low-reflection coating layer is 1.5 or more and 1.5 or less.
4 is a graph showing the reflectance of the low-reflective CPI film of Examples 1-35, and when the refractive index of the hard coating layer is 1.5, the reflectance of the low-reflective film layer is compared according to the refractive index and thickness.

Hereinafter, embodiments of the present invention will be described in more detail.

The embodiments of the present invention disclosed in the text are illustrated for purposes of explanation only, and the embodiments of the present invention may be implemented in various forms and should not be construed as being limited to the embodiments described in the text. .

The present invention is not intended to limit the present invention to a specific disclosed form, as various changes may be added and various forms may be added, and all changes, equivalents, or substitutes included in the spirit and scope of the present invention It should be understood to include.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

One embodiment of the present invention includes a CPI film, a hard coating layer formed on the CPI film, and a low reflection coating layer formed on the hard coating layer, wherein the refractive index of the low reflection coating layer is lower than the refractive index of the hard coating layer. Provide a film.

Referring to FIG. 1, the low-reflective CPI film according to an embodiment of the present invention may include a CPI film, and may be used without limitation as long as it can be used as a cover glass substitute for a flexible display. For example, the CPI film may be a color-corrected polyimide (PI) material.

For example, the thickness of the CPI film may be 25-100 μm. The thickness of the CPI film can be flexible at a thickness of 25-100 µm and have excellent physical properties.

It may also include a hard coating layer formed on the CPI film. The hard coating layer may be coated on one surface of the CPI film to improve hardness, abrasion resistance, and/or impact resistance of the film.

In particular, in an exemplary embodiment, the thickness of the hard coating layer may be 1 μm or more, for example, 1 μm to 1 mm, 1 to 100 μm, 1 to 10 μm, or 1 to 5 μm. When the thickness of the hard coating layer is 1 μm or more, it may have excellent scratch resistance. For example, a film including a hard coating layer having a thickness of 1 μm or more may have a hardness of 1H or more. Therefore, the low-reflective CPI film according to an embodiment of the present invention has excellent scratch resistance and can be easily applied to a flexible display.

In an exemplary embodiment, the hard coating layer may include an acrylate base resin. Specifically, the acrylate base resin may include a polyacrylate 　 monomer, and the polyacrylate monomers are methacrylate, methyl acrylate, ethyl acrylate, 2-chloroethyl vinyl ether, and 2-ethylhexyl acrylate. Rate, hydroxyethyl methacrylate, butyl acrylate, methyl methacrylate, dipentaerythritol hexaacrylate, butyl methacrylate, or trimethylolpropane triacrylate (TMPTA), but is not limited thereto.

Referring to FIG. 1, a low-reflective CPI film according to an embodiment of the present invention may include a low-reflective coating layer formed on the hard coating layer. When a low reflection coating layer is further included, it may be advantageous for low reflection compared to a case including only the hard coating layer. For example, when the low-reflective coating layer is further included, the reflectance may be about 5-10% lower than that in the case of including only the hard coating layer (see FIG. 2).

In an exemplary embodiment, the low-reflection coating layer may include an acrylate base resin, and the acrylate base resin may be the same as that included in the hard coating layer.

In an exemplary embodiment, the hard coating layer and the low-reflection coating layer are commonly used 　 coating methods, such as dip coating, flow 　 coating, gravure 　 coating, Mayer bar 　 coating, slot die 　 coating, air knife 　 coating 　 and doctor knife 　 coating It may be formed by and is not particularly limited.

In an exemplary embodiment, the refractive index of the low-reflection coating layer may be lower than that of the hard coating layer. For example, when the low-reflective coating layer is overcoated using a material lower than the refractive index of the hard coating layer, there is an effect of lowering the refractive index, and the reflectance of the low-reflective CPI film thus prepared can be lowered. That is, through optical design in which a low-reflective coating layer having a special refractive index is treated on the surface of the CPI film, the effect of lowering the reflectance can be obtained.

In an exemplary embodiment, when the refractive index of the low reflection coating layer is lower than the refractive index of the hard coating layer, for example, when the refractive index of the hard coating layer is about 1.5 and the refractive index of the low reflection coating layer is less than 1.5, the reflectance may be lowered, while the low reflection coating layer When the refractive index of is greater than the refractive index of the hard coating layer, for example, when the refractive index of the hard coating layer is about 1.5 and the refractive index of the low-reflective coating layer is greater than 1.5, the reflectance may increase.

Specifically, the refractive index of the low-reflective coating layer may be 1.1-1.3. At this time, the refractive index of the hard coating layer may be 1.3-1.6. For example, the refractive index of the low-reflective coating layer may be 0.01-0.5 lower than that of the hard coating layer.

In general, the lower the refractive index of the low reflection coating layer, the lower the average reflectance of the low reflection CPI film. However, the reflectance may vary depending on the thickness of the low-reflective coating layer.

In an exemplary embodiment, the thickness of the low-reflective coating layer may be 100-500 nm. When the thickness of the low-reflective coating layer is less than 100 nm, scratch resistance may be poor, and when it is more than 500 nm, reflectance may be lowered.

The thickness of the low-reflective coating layer may be combined with the refractive index of the low-reflective coating layer to obtain excellent reflectivity. For example, when the refractive index of the low reflection coating layer is 1.1-1.3 and the thickness of the low reflection coating layer is 100-200 nm, the reflection rate of the low reflection CPI film may be excellent, for example, less than 10%, preferably less than 5%. have.

In an exemplary embodiment, the thickness of the low-reflective coating layer may be 350-450 nm. When the thickness of the low reflection coating layer is 350-450 nm, not only excellent reflectance but also excellent scratch resistance can be obtained.For example, the refractive index of the low reflection coating layer is 1.1-1.3 and the thickness of the low reflection coating layer is 350-450 The low-reflective CPI film of nm can have excellent reflectivity and scratch resistance at the same time.

Therefore, the low-reflection CPI film according to the embodiment of the present invention has a three-layer structure including a CPI film, a hard coating layer, and a low-reflection coating layer, and the low-reflection coating layer has a specific refractive index and thickness, so that excellent reflectivity and scratch resistance Can be implemented at the same time.

In an exemplary embodiment, the low-reflection CPI film may have a haze of 1% or less or a total light transmittance of 90% or more under conditions of a D65 light source and a wavelength of 380 nm to 780 nm.

In an exemplary embodiment, the low-reflective CPI film may have a hardness of 1H or more. Specifically, the 　 coating 　 film. According to JIS K-5600, the pencil hardness measured under an angle of 45o and a load of 750 g using a Mitsubishi pencil uni may be 1H or more. Here, the pencil hardness can be expressed as 9F, 8F, 7F, 6F, 5F, 4F, 3F, 2F, F, HB, 1H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H. It is soft and harder as it goes to 9H.

In an exemplary embodiment, the low-reflection CPI film may be for a flexible display.

Hereinafter, the present invention will be described in more detail through examples. These examples are for illustrative purposes only, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not construed as being limited by these examples.

Example

Example 1-7: Low-reflection CPI film (AR layer thickness of 100 nm)

On the CPI film, a hard coating layer having a refractive index of 1.5 with an acrylate base resin and a low-reflective coating layer having a thickness of 100 nm are sequentially applied with Mayer Bar, followed by drying under conditions of about 90℃ and 90s. And light quantity is about 150mJ/cm ² Curing is performed by irradiating the light in the above UVA area.

At this time, the refractive index of the low-reflection coating layer was 1.1 (Example 1), 1.2 (Example 2), 1.3 (Example 3), 1.4 (Example 4), 1.5 (Example 5), and 1.6 (Example 6). ), 1.7 (Example 7).

Example 8-14: Low-reflective CPI film (AR layer thickness of 200 nm)

A low-reflection CPI film was prepared in the same manner as in Example 1, except that the thickness of the low-reflection coating layer was set to 200 nm.

The refractive indices of the low-reflection coating layer were 1.1 (Example 8), 1.2 (Example 9), 1.3 (Example 10), 1.4 (Example 11), 1.5 (Example 12), 1.6 (Example 13), and 1.7, respectively. It was set as (Example 14).

Example 15-21: Low-reflection CPI film (AR layer thickness 300nm)

A low-reflection CPI film was prepared in the same manner as in Example 1, except that the thickness of the low-reflection coating layer was set to 300 nm.

The refractive indices of the low-reflection coating layer were 1.1 (Example 15), 1.2 (Example 16), 1.3 (Example 17), 1.4 (Example 18), 1.5 (Example 19), 1.6 (Example 20), and 1.7, respectively. It was set as (Example 21).

Examples 22-28: Low-reflective CPI film (AR layer thickness of 400 nm)

A low reflection CPI film was prepared in the same manner as in Example 1, except that the thickness of the low reflection coating layer was set to 400 nm.

The refractive indices of the low-reflection coating layer were 1.1 (Example 22), 1.2 (Example 23), 1.3 (Example 24), 1.4 (Example 25), 1.5 (Example 26), 1.6 (Example 27), and 1.7, respectively. It was set as (Example 28).

Example 29-35: Low-reflection CPI film (AR layer thickness 500 nm)

A low-reflection CPI film was prepared in the same manner as in Example 1, except that the thickness of the low-reflection coating layer was 500 nm.

The refractive index of the low-reflection coating layer was 1.1 (Example 29), 1.2 (Example 30), 1.3 (Example 31), 1.4 (Example 32), 1.5 (Example 33), 1.6 (Example 34), and 1.7, respectively. It was set as (Example 35).

Comparative Example 1: Hard coating CPI film

A hard-coated CPI film was prepared in the same manner as in Example 1, except that the low-reflective coating layer was not coated on the hard coating layer.

[Experimental Example 1] Reflectance experiment

A reflectance measurement experiment was conducted under the condition of a D65 light source and a wavelength of 380 to 780 nm (UV-2450 from Shimadzu).

Figure 2 shows a graph comparing the reflectance of the low-reflective CPI film according to the presence or absence of the low-reflection coating layer.As a result, compared to the case of coating the hard coating layer alone on the CPI, the reflectance decreases when additional AR coating is applied thereon. I could confirm.

Figure 3 shows a graph comparing the reflectance of the low-reflective CPI film when the refractive index of the hard coating layer is set to 1.5, the refractive index of the low-reflective coating layer is 1.5 or more and 1.5 or less, as a result of which the AR layer is uncoated. In other words, when compared with the HC alone state (n=1.5), when high refractive index and low refractive index are respectively coated thereon, a difference in reflectance occurs. It can be seen that when the AR layer having a refractive index of 1.5 or less is coated, the reflectance is lowered, and when the AR layer having a refractive index of 1.5 or more is coated, the reflectance is increased.

4 is a graph showing the reflectance of the low-reflective CPI film of Example 1-35, and when the refractive index of the hard coating layer is 1.5, the reflectance according to the refractive index and thickness of the low-reflective film layer is compared. It can be seen that if the AR layer with a refractive index lower than 1.5 is coated, the reflectance is lowered. In particular, the lowest reflectance is shown at a specific refractive index and a specific thickness. When the refractive index of the hard coating layer is 1.5, the low reflection film layer It can be seen that the refractive index has excellent reflectivity characteristics at 1.1 to 1.3 and the thickness at 100 nm.

[Experimental Example 2] Scratch Resistance Test

The hardness was measured by a method of checking the scratches by scratching the surface with 750 g load, Mitsubishi pencil 1H, 5 times, and a steel wool test was performed in which the surface scratch was produced by repeating 10 times with #0000 steel wool material under 700 g load.

The test was conducted by varying the thickness of the low-reflective coating layer, and it was evaluated by comparing the number of scratches generated. The results are shown in Table 1.

Low reflection coating layer thickness (nm) Scratch 100 nm (Example 1-7) 10 or more scratches occurred 200 nm (Examples 8-14) 10 or more scratches occurred 300 nm (Examples 15-21) 10 or more scratches occurred 400 nm (Examples 22-28) No scratch 500 nm (Examples 29-35) No scratch

From the evaluation results, when the thickness of the low-reflective coating layer is in the range of 300-400 nm or more, it can be confirmed that there is no scratch. Accordingly, when the reflectance test result of Experimental Example 1 is considered together, when the thickness of the low-reflection coating layer is 350-450 nm, It can be seen that not only excellent reflectance but also excellent scratch resistance can be obtained. Therefore, the low-reflection CPI film having a refractive index of 1.1-1.3 and a thickness of the low-reflection coating layer of 350-450 nm may have excellent reflectivity and scratch resistance at the same time.

The embodiments of the present invention described above should not be construed as limiting the technical idea of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and those of ordinary skill in the technical field of the present invention can improve and change the technical idea of the present invention in various forms. Therefore, such improvements and changes will fall within the scope of the present invention as long as it is apparent to those of ordinary skill in the art.

Claims (11)

As a low reflection CPI film,
CPI film;
A hard coating layer formed on the CPI film; And
Includes; a low-reflective coating layer formed on the hard coating layer,
The refractive index of the low-reflection coating layer is lower than the refractive index of the hard coating layer and is 1.1-1.3,
The thickness of the low reflection coating layer is 350-450 nm,
The low-reflection CPI film is a D65 light source, having a haze of 1% or less or a transmittance of 90% or more in a wavelength condition of 380 nm to 780 nm, a low-reflection CPI film. The method of claim 1,
The refractive index of the low reflection coating layer is 0.01-0.5 lower than the refractive index of the hard coating layer, low reflection CPI film. delete delete The method of claim 1,
The low reflection coating layer comprises an acrylate base resin, low reflection CPI film. The method of claim 1,
The refractive index of the hard coating layer is 1.3-1.6, a low-reflective CPI film. The method of claim 1,
The thickness of the hard coating layer is 1 μm or more, a low-reflective CPI film. The method of claim 1,
The hard coating layer includes an acrylate base resin, a low-reflective CPI film. delete The method of claim 1,
The low-reflection CPI film has a hardness of 1H or more, low-reflection CPI film. The method according to any one of claims 1, 2, 5 to 8, and 10,
The low reflection CPI film is for a flexible display, low reflection CPI film.

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