KR102689065B1 - Manufacturing method for making flexible polyimide film, the film and display substrate comprising the film - Google Patents

Abstract

The present invention relates to a method for manufacturing a nano-sized flexible polyimide film, the flexible polyimide film, and a display substrate containing the film. The polyimide film is formed by spin coating and is characterized by satisfying both hardness and modulus.

Description

Manufacturing method of flexible polyimide film, the film, and display substrate comprising the film {Manufacturing method for making flexible polyimide film, the film and display substrate comprising the film}

The present invention relates to a manufacturing method of a flexible polyimide film, a film manufactured by the manufacturing method, and a display substrate including the film.

Thin display devices are implemented in the form of touch screen panels and are used in various smart devices, including smart phones, tablet PCs, and various wearable devices. .

Display devices using such touch screen panels are equipped with a window cover containing tempered glass or plastic film over the display panel to protect the display panel from scratches or external impacts. However, tempered glass is not suitable for lightweighting and has the problem of being vulnerable to external shocks.

In the case of plastics, polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polyacrylate (PAR), polycarbonate (PC), polyimide (PI), polyaramid (PA), etc. is being used, and in particular, the demand for polyimide-based films that show little change in mechanical and optical properties even under high temperature and high humidity conditions is increasing.

However, the polyimide film manufactured in a conventional manner was excellent in terms of hardness, but did not have the modulus to have flexible characteristics, and there was a problem of scratches occurring due to the pressure of the touch pen.

Korean Patent Publication No. 2013-0076154

The purpose of the present invention is to provide a method for manufacturing a polyimide film that has a nano size and satisfies both hardness and modulus.

The present invention includes the steps of forming a polyimide layer by spin-coating a solution containing polyimide (S1);

Forming an OCR layer by spin coating a solution containing an optically transparent material (OCR) on the polyimide layer (S2); and

A step (S3) of forming a polyimide layer by spin-coating a solution containing polyimide on the OCR layer,

Spin coating in step S2 is,

A method for manufacturing a flexible polyimide film is provided, which is performed at a temperature of 60° C. or higher and a speed of 9000 rpm or higher.

In one embodiment of the present invention, steps S1 and S2 are repeated multiple times.

In another embodiment of the present invention, spin coating in steps S1 and S3 is performed at room temperature at a speed of 2000 rpm or more.

In another embodiment of the present invention, the solution containing the polyimide is characterized in that the polyimide and the solvent are mixed in a weight ratio of 5:5 to 5:1.

In another embodiment of the present invention, the solution containing the OCR is characterized in that it contains 50 to 70% by weight of solvent.

In another embodiment of the present invention, the polyimide layer is characterized by having a thickness of 10 to 1000 nm.

In another embodiment of the present invention, the OCR layer is characterized by having a thickness of 10 to 1000 nm.

Additionally, the present invention provides a flexible polyimide film manufactured by the above manufacturing method.

In addition, the present invention provides a display substrate including the film.

The flexible polyimide film manufactured by the manufacturing method of the present invention has a structure in which polyimide layers and OCR layers are formed alternately, and each layer has a nano-level size, so it is scratch-resistant when used in a touch display substrate. It is characterized by excellent properties. In addition, the polyimide film manufactured by the above manufacturing method can satisfy both hardness and modulus.

Figure 1 is a diagram showing the results of measuring the thickness of the polyimide layer according to spin coating rotation speed.
Figure 2 shows a photograph confirming the cross section of the polyimide layer.
Figure 3 shows the results of measuring the thickness of the OCR layer according to the solvent content.
Figure 4 shows a photograph confirming the cross section of the OCR layer.
Figure 5 shows a photograph confirming the thickness of the OCR layer according to temperature.
Figure 6 shows a graph confirming the change in thickness of the OCR layer according to temperature.
Figure 7 shows a photograph confirming the thickness of the OCR layer according to the rotation speed of spin coating.
Figure 8 shows a graph confirming the change in thickness of the OCR layer according to the rotation speed of spin coating.
Figure 9 shows a film with a triple-layer structure manufactured by the manufacturing method of the present invention.
Figure 10 shows a film with a five-layer structure manufactured by the manufacturing method of the present invention.
Figure 11 shows the results of measuring the radius of curvature of the film manufactured in Example.
Figure 12a shows the results of confirming the scratch resistance of the PI film manufactured in Example.
Figure 12b shows the results of confirming the scratch resistance of the 3-layer (PI-OCR-PI) film prepared in the example.
Figure 12c shows the results of confirming the scratch resistance of the 5 layer (PI-OCR-PI-OCR-PI) film prepared in the example.
Figure 12d shows the results of confirming the scratch resistance of the films manufactured in Examples.

The present invention includes the steps of forming a polyimide layer by spin-coating a solution containing polyimide (S1);

Forming an OCR layer by spin coating a solution containing an optically transparent material (OCR) on the polyimide layer (S2); and

A step (S3) of forming a polyimide layer by spin-coating a solution containing polyimide on the OCR layer,

Spin coating in step S2 is,

A method for manufacturing a flexible polyimide film is provided, which is performed at a temperature of 60° C. or higher and a speed of 9000 rpm or higher.

Additionally, the present invention can provide a flexible polyimide film manufactured by the above manufacturing method and a display substrate including the film.

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

The present invention provides a polyimide film that can be used in a display substrate. The polyimide film may have a structure in which several layers are stacked, and an OCR layer may be formed between the polyimide layers.

In the present invention, the polyimide film has a structure in which polyimide layers and OCR layers are alternately stacked by repeating steps S1 and S2 multiple times, and both the polyimide and OCR are optically clear. It is characterized by

The OCR (Optically Clear Resin) can function as an adhesive between polyimide layers and may be made of polyurethane, epoxy, silicone, or polyacrylate materials, but if it is optically transparent, it is limited to these materials. It doesn't work.

Each layer of the film is formed by spin coating, which is performed by applying a coating material on a plate and then rotating it. In the present invention, spin coating can be performed using a conventional spin coater.

As an embodiment of the present invention, spin coating in step S2 may be performed at a temperature of 60 ℃ or higher and a speed of 9,000 rpm or higher, and preferably at a temperature of 60 ℃ to 300 ℃ and a speed of 9,000 rpm to 30,000 rpm. It can be done. In relation to this, it has been confirmed in FIGS. 5 and 7 of the present invention that an OCR layer having a nano-sized thickness of 1000 nm or less is created under the above conditions. However, if the OCR material is silicon, temperature may not be applied.

As another embodiment of the present invention, spin coating in steps S1 and S3 may be performed at room temperature at a speed of 2000 rpm or more, and preferably at a speed of 2000 rpm to 30000 rpm. In relation to this, in Figure 1 of the present invention, it has been confirmed that a polyimide layer having a nano-sized thickness of 1000 nm or less is produced under the above conditions.

As another embodiment of the present invention, the solution containing the polyimide may be a solution in which polyimide and a solvent are mixed in a weight ratio of 5:5 to 5:1. Preferably, a thin polyimide layer can be formed due to the viscosity of the solution mixed at a ratio of 5:4.5 to 5:3.5.

As another embodiment of the present invention, the solution containing the OCR may contain 50 to 70% by weight of solvent. A thin OCR layer can be formed with the viscosity of the solution containing the solvent in the above range.

Hereinafter, embodiments will be described in detail with reference to the attached drawings. However, various changes can be made to the embodiments, so the scope of the patent application is not limited or limited by these embodiments. It should be understood that all changes, equivalents, or substitutes for the embodiments are included in the scope of rights.

The terms used in the examples are for descriptive purposes only and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that it does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the embodiments belong. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. No.

In addition, when describing with reference to the accompanying drawings, identical components will be assigned the same reference numerals regardless of the reference numerals, and overlapping descriptions thereof will be omitted. In describing the embodiments, if it is determined that detailed descriptions of related known technologies may unnecessarily obscure the gist of the embodiments, the detailed descriptions are omitted.

<Example>

One. Polyimide film manufacturing

Polyimide was diluted with NMP solvent to prepare polyimide solutions with weight ratios of PI:NMP of 5:4 and 5:3, respectively. The prepared solution was spin-coated at 500 to 9000 rpm to prepare a film.

The film thickness according to the spin coating rotation speed was measured and shown in Figure 1.

As a result, the film thickness appeared thinner in the 5:4 solution with a relatively large NMP content, and it was confirmed that the rotation speed was preferably 2000 rpm or more.

A film (top) prepared by diluting PI:NMP in a 5:4 ratio and rotating it at 3500 rpm for 50 seconds, and a film (bottom) prepared by diluting PI:NMP in a 5:5 ratio and rotating it at 3500 rpm for 50 seconds. The cross section is shown in Figure 2.

2. Preparation of OCR film

2.1. Check the thickness of OCR layer according to viscosity

OCR was diluted with HMDSO (Hexamethyldisiloxane, viscosity 0.5 cps) to prepare an OCR solution with a solvent content of 0 to 65% by weight. Each prepared solution was spin-coated at 10,000 rpm for 50 seconds to prepare a film. The temperature during spin coating was 60°C.

The film thickness according to the solvent content was measured and shown in Figure 3.

As a result, as the solvent content increased and the viscosity of the OCR solution decreased, the thickness of the OCR layer became thinner. In particular, since the thickness was significantly reduced when more than 50% by weight of solvent was used, it was confirmed that it is preferable to use the solvent content at more than 50% by weight.

In addition, the cross-section of the film (top) prepared by rotating the OCR solution at 80°C at 9000rpm for 50 seconds and the cross-section of the film prepared by rotating the OCR solution at 100°C at 9000rpm for 50 seconds are shown in Figure 4.

2.2. Check the thickness of OCR layer according to temperature

An OCR solution was prepared. The prepared solution was spin-coated at 10,000 rpm for 50 seconds to prepare films at temperatures of 25, 50, 60, 80, and 100°C.

The film thickness at each temperature was measured and shown in Figure 5, and the results are summarized and shown in Figure 6.

As a result, as the coating temperature increased, the thickness of the OCR layer became thinner. In particular, when coating was performed at a temperature of 60°C or higher, the thickness of the OCR layer was reduced to 1 μm or less, so it was confirmed that coating was preferable at a temperature of 60°C or higher.

2.3. Check the thickness of the OCR layer according to rotation speed

An OCR solution (containing solvent: 0 to 87.5% by weight) was prepared. Films were prepared from the prepared solution at 60°C for 50 seconds at speeds of 2000, 3500, 5000, 7000, and 9000 rpm.

The film thickness according to each spin coating rotation speed was measured and shown in Figure 7, and the results are summarized and shown in Figure 8.

As a result, as the rotation speed increased, the thickness of the OCR layer became thinner. In particular, when coating was performed at a speed of 9000 rpm or higher, the thickness of the OCR layer was reduced to 1 μm or less, so it was confirmed that it was preferable to perform coating at a speed of 9000 rpm or higher.

3. Preparation of PI-OCR lamination film

Under the conditions confirmed through the above results, a lamination film in which a PI layer and an OCR layer were formed alternatingly was manufactured. The content ratio of PI and NMP solvent was 5:4 (10 wt%), and the solvent content in the OCR solution was 86%. Spin coating of the PI solution was performed at _3500_rpm for 50 seconds at 25°C, and spin coating of the OCR solution was performed at 60°C for 50 seconds at 10000 rpm.

Figure 9 shows a lamination film in which three layers of a polyimide layer, an OCR layer, and a polyimide layer are sequentially formed, and Figure 10 shows a polyimide layer, an OCR layer, a polyimide layer, an OCR layer, and a polyimide layer. A sequentially formed 5-layer lamination film was shown.

Since each of the coating layers has a nanoscale thickness of less than 1 um, it was expected to be excellent in the relationship between hardness and elastic modulus.

4. Check the physical properties of the film

As a result of measuring the radius of curvature of the manufactured film, as shown in Figure 11, it had a very low radius of curvature of less than 1 mm. In addition, as a result of nanoindentation measurement, it was confirmed that it had a high elastic modulus and low modulus (high H/E ratio) as shown in Table 1 below.

In addition, the scratch resistance of the manufactured film was confirmed and shown in Table 2 and Figure 12. As a result, it was confirmed that the final Rd (nm) indentation depth of 3 layer (b) and 5 layer (c) was smaller than that of PI layer (a), showing better scratch resistance.

Although the embodiments have been described with limited drawings as described above, those skilled in the art can apply various technical modifications and variations based on the above. For example, the described techniques are performed in a different order than the described method, and/or components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or other components are used. Alternatively, appropriate results may be achieved even if substituted or substituted by an equivalent.

Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the following claims.

[National research and development project that supported this invention]

[Assignment number]2020123100

[Assignment number]GRRC dankook 2016-B13

[Ministry Name] Gyeonggi-do

[Project management (professional) organization name] Gyeonggi-do

[Research Project Name]GRRC

[Research project name] (Response) Development of organic/inorganic composite materials processing technology for higher order structures (GRRC-organic/inorganic 3 applications, 6th year)

[Contribution rate]1/1

[Name of project carrying out institution] Dankook University

[Research period]2021.07.01 ~ 2022.06.30

Claims (9)

Forming a polyimide layer by spin coating a solution containing polyimide (S1);
Forming an OCR layer by spin coating a solution containing an optically transparent material (OCR) on the polyimide layer (S2); and
A step (S3) of forming a polyimide layer by spin-coating a solution containing polyimide on the OCR layer,
Spin coating in steps S1 and S3,
It is carried out at a speed of 2000 rpm or more at a temperature of 60 ℃ or more,
Spin coating in step S2 is,
It is carried out at a speed of 9000 rpm or more at a temperature of 60 ℃ or more,
The solution containing the polyimide is a solution in which polyimide and solvent are mixed in a weight ratio of 5:5 to 5:1,
The solution containing the OCR contains 50 to 70% by weight of solvent,
Method for manufacturing flexible polyimide film. According to paragraph 1,
A method of manufacturing a flexible polyimide film, characterized in that steps S1 and S2 are repeated multiple times. delete delete delete According to paragraph 1,
A method of manufacturing a flexible polyimide film, wherein the polyimide layer has a thickness of 10 to 1000 nm. According to paragraph 1,
A method of manufacturing a flexible polyimide film, characterized in that the OCR layer has a thickness of 10 to 1000 nm. A flexible polyimide film manufactured by the manufacturing method of any one of claims 1, 2, 6, and 7. A display substrate comprising the film of claim 8.