KR20120078514A - The transparent polyimide substrate and the method for producing it - Google Patents

Abstract

PURPOSE: A transparent polyimide substrate and a manufacturing method thereof are provided to enhance solvent resistance and thermal resistance of polyimide film surfaces by forming an inorganic silicon oxide layer on one side or both sides of transparent polyimide films. CONSTITUTION: A transparent polyimide substrate comprises transparency polyimide films and a silicon oxide layer. The silicon oxide layers are formed on a single-side or both sides of the transparent polyimide film and comprises silicon oxide consisting of units represented by chemical formula. In the chemical formula 1, m and n are respectively integers of 0-10. The thickness of the silicon oxide layer is 0.3-2.0 micro meters. The surface roughness(RMS) of the silicon oxide layer is 5 nano meters or less. A manufacturing method of transparent polyimide substrate comprises the following steps: coating and drying a solution including polysilazane on a single-side or both sides of the transparent polyimide film; and curing the coated polysilazane.

Description

The transparent polyimide substrate and the method for producing it

The present invention relates to a transparent polyimide substrate usable as a flexible display substrate material and a method of manufacturing the same.

Recently, flexible electronic devices such as color EPDs, plastic LCDs, TSPs, and OPVs, including flexible OLEDs, have been attracting attention as displays that can bend or bend as one of the next-generation displays. In order to enable such a flexible display that can bend or bend, a new type of substrate is required instead of the existing glass substrate. In addition, such a substrate needs to maintain sufficient chemical resistance, heat resistance, and light transmittance in order to protect components included in the display device. In addition, such a substrate requires particularly high solvent resistance to solvents used in the process of cleaning, peeling, etching and the like, which is a manufacturing process of a display device, and high heat resistance that can withstand even a high temperature.

As such a flexible display substrate material, various plastic substrates have been examined as candidates, and among them, transparent polyimide films have been examined as major candidates.

And in order to supplement the solvent resistance of the transparent polyimide film examined as a flexible display substrate material, although the method of forming an acryl-type or epoxy-type organic hardening film on the surface of a transparent polyimide film was used conventionally, such an organic hardening film is about 200 degreeC. There was a problem that the heat resistance is poor at the high temperature or more than about 300 ℃.

The present invention seeks to provide a transparent polyimide substrate having excellent solvent resistance and high heat resistance.

It is another object of the present invention to provide a method for producing a transparent polyimide substrate having excellent solvent resistance and high heat resistance.

The transparent polyimide substrate of the present invention is characterized in that it comprises a silicon oxide layer including a transparent polyimide film and a silicon oxide formed on one side or both sides of the transparent polyimide film, the unit structure of formula (1).

[Formula 1]

Here, m and n are integers of 0-10, respectively.

That is, an inorganic silicon oxide layer is formed on one side or both sides of the transparent polyimide film, thereby making it excellent in solvent resistance and high heat resistance of the surface of the polyimide film. In addition, when n or m is 0 in Formula 1, solvent resistance and high heat resistance may be maximized as a pure inorganic layer, and in some cases, in order to improve flexibility of the transparent polyimide substrate, n or It is advantageous for m to be an alkyl chain of suitable length as one or more natural numbers. However, when n or m is 10 or more, the coating liquid may aggregate when coating due to hydrophobic properties.

Here, the silicon oxide layer is preferably a thickness of 0.3 ~ 2.0㎛. That is, it is preferable to make thickness into 0.3 micrometer or more in order to ensure appropriate solvent resistance enough, and to make it possible to eliminate the concern that the flexibility of a transparent polyimide substrate falls, it is preferable to make thickness into 2.0 micrometer or less.

Thus, the transparent polyimide substrate of the present invention having the silicon oxide layer formed thereon may be used in tetramethylammonium hydroxide (TMAH), potassium hydroxide (KOH), N-Methylpyrrolidone (NMP), MEK, which are used in etching and etching processes in the manufacturing process of display devices. Even when dipping for about 30 minutes at room temperature in organic solvents such as (Methyl Ethyl Ketone) and MASO2 (a solvent containing about 16.9 ~ 20.3% HCl as Dongwoo Fine Cam Co., Ltd.) The solvent resistance is excellent.

In addition, since the silicon oxide layer is formed on the surface of the transparent polyimide substrate of the present invention, the surface roughness (RMS) of the surface may be 5 nm or less, which brings the advantage of planarization of the substrate. This planarization advantage may facilitate the movement of carriers when forming electrodes or TFTs.

The method for producing a transparent polyimide substrate of the present invention is a method for forming a silicon oxide layer on one or both surfaces of the transparent polyimide substrate of the present invention described above, and includes polysilazane on one or both surfaces of the transparent polyimide film. Coating and drying the solution, and curing the coated polysilazane.

That is, in the method of manufacturing a transparent polyimide substrate of the present invention, a -NH- group present in the unit structure of Chemical Formula 2 is coated by curing polysilazane to form a silicon oxide layer on the surface of the transparent polyimide film It is characterized by forming a silicon oxide layer by converting the -O- group present in the unit structure.

As a conventional general deposition method for forming an inorganic material on the surface, PECVD or sputtering has a disadvantage in that the deposition area is limited due to the vacuum equipment limitation, but the method of coating a solution and curing the inorganic material with an inorganic material is a simple casting process at atmospheric pressure. It is possible to have a very advantageous advantage in large area and continuous process.

Here, the polysilazane may include a unit structure of Formula 2, and have a weight average molecular weight of 3,000 to 5,000.

[Formula 2]

m and n are the integers of 0-10, respectively.

In Formula 1, m and n may be appropriately selected depending on the characteristics of the silicon oxide to be finally formed. The weight average molecular weight of the polysilazane is 1,000 or more to ensure better solvent resistance and high heat resistance, and to 5,000 or less to ensure uniform coating of the solution.

Coating of a solution containing polysilazane (Polysilazane) on one or both sides of the transparent polyimide film can be performed in various ways such as spray coating, bar coating, spin coating, dip coating, and the like. The appropriate method can be selected and performed.

Here, the method of converting the -NH- group present in the unit structure of Formula 2 of the coated polysilazane to the -O- group present in the unit structure of Formula 1 to form a silicon oxide layer includes a thermosetting method and an ultraviolet curing method. This can be considered.

In the thermosetting method, polysilazane is formed of a silicon oxide film, which is advantageous to have a network structure, which makes the film properties more rigid, thereby making it excellent in chemical resistance and heat resistance, while raising the process temperature to about 200 to 300 ° C. In the ultraviolet curing method, polysilazane may be formed of silicon oxide film by irradiating UV in a short time, but there is a concern that the film property may not be rigid because the structure of the formed film has a network structure partially compared to the thermal curing method. Therefore, it can be selected according to the physical properties required for the final product and the advantages and disadvantages of the manufacturing process.

When the thermosetting method is selected, it may be possible by heat-treating the coated polysilazane at a temperature of 200 to 300 ° C. At this time, when the heat treatment temperature is 200 ° C. or higher, the polysilazane is cured into the silicon oxide layer, and the curing time can be shortened. When the temperature is 300 ° C. or lower, the thermal expansion coefficient of the transparent polyimide film and the silicon oxide layer does not match and is distorted. It is desirable to prevent the problem that a phenomenon may occur.

When the ultraviolet curing method is selected, the UV curing agent is further included in the solution containing the polysilazane in the coating of the solution containing the polysilazane and the 312 or 365 nm in the step of curing the coated polysilazane. The ultraviolet ray of a wavelength can be irradiated at 1500-4000 J / m <^2>, and can harden an ultraviolet-ray.

Here, the ultraviolet curing agent may be at least one selected from among ultraviolet curable benzoin ethers including a photoinitiator selected from a benzoin ether photoinitiator, a benzophenone photoinitiator, or a mixture thereof.

The present invention provides a transparent polyimide substrate having excellent solvent resistance and high heat resistance.

Moreover, this invention provided the method of manufacturing the transparent polyimide substrate which has the outstanding solvent resistance and high heat resistance.

Hereinafter, the present invention will be described in more detail with reference to Examples.

&Lt; Comparative Example 1 &

The transparent polyimide film of the state which did not do any treatment to the surface of a film is prepared, and it is set as the comparative example 1.

&Lt; Example 1 >

In Formula 2, m and n are 0, and a solution of polysilazane having a molecular weight of about 2,000 at 2wt% in DBE (Dibutyl ether) is coated with a wire on one surface of the transparent polyimide film of Comparative Example 1 and then about 80 ° C. It dried at the temperature of and formed the polysilazane film | membrane of thickness 1micrometer.

Thereafter, the mixture was left at room temperature for about 5 minutes and thermally cured at a temperature of about 250 ° C. to form a silicon oxide layer.

<Example 2>

In Example 1, polysilazane was performed in the same manner as in Example 1 except that polysilazane in Formula 2 was used, wherein m was 0, n was 1, or m and n were 1 and the molecular weight was about 3,000.

<Example 3>

In Example 1, it carried out similarly to Example 1 except having apply | coated the polysilazane solution to one side of the transparent polyimide film on both surfaces.

<Example 4>

In Example 2, the same procedure as in Example 2 was carried out except that the polysilazane solution was applied on one side of the transparent polyimide film.

<Example 5>

In Formula 2, m and n are 0 and the polysilazane having a molecular weight of about 2,000 is dissolved in DBE at 2wt%, and the solution dissolved by adding an ultraviolet curing agent is applied to one surface of the transparent polyimide film of Comparative Example 1 with a wire. After drying to a temperature of about 80 ℃ to form a polysilazane film having a thickness of 1㎛.

Thereafter, two wavelengths were simultaneously irradiated with energy of 27 W / m ² for 60 seconds using an ultraviolet curing machine of 312 nm and 365 nm to obtain a colorless transparent polyimide film having a silicon oxide film formed thereon.

Solvent resistance and other physical properties were measured using the colorless transparent polyimide films prepared in Examples and Comparative Examples as follows.

[Measurement of physical properties]

The physical properties were measured by the following method, and the results are shown in Table 1.

Content-based

The coating film was subjected to solvent resistance evaluation by dipping test for 30 minutes at room temperature in each of the organic solvents shown in Table 1, and there was no change in appearance when visually examined, and if the RMS difference before and after chemical test was less than 1 nm, ◎ It was evaluated as ○ when the RMS difference before and after the chemical test was 1 nm or more, and when a white cloud phenomenon or spot occurred when the naked body was observed, the results are shown in Table 1.

Average light transmittance (%)

Optical transmittance at 350-700 nm was measured using a spectrophotometer (CU-3700D, KONICA MINOLTA).

Yellow road

Yellowness was measured using a spectrophotometer (CU-3700D, KONICA MINOLTA).

Coefficient of thermal expansion (CTE) (ppm / ℃)

Using a thermal analyzer (TA Instrument Q-400), the coefficient of thermal expansion at 50 ~ 250 ℃ was measured.

Oxygen permeability (cc / cm ² * day)

Oxygen permeability was measured using an oxygen permeability meter (MOCON / US / Ox-Tran 2-61).

Surface Roughness (RMS) (nm)

It measured by 20 * 20um using PSIA XE100 AFM.

Adhesive

Measured by tapping 100 times with a standard (ASTM D3359).

Heat resistance

After sufficiently removing the moisture of the film, the weight change rate was measured after standing for 24 hours in a hot air oven in a nitrogen atmosphere of 300 ℃, the weight change rate was less than 1% excellent, 1% or more was evaluated as poor.

division IPA TMAH KOH NMP MEK MASO2 Example 1 ◎ ◎ ◎ ◎ ◎ ◎ Example 2 ◎ ◎ ◎ ◎ ◎ ◎ Example 3 ◎ ◎ ◎ ◎ ◎ ◎ Example 4 ◎ ◎ ◎ ◎ ◎ ◎ Comparative Example 1 ◎ ○ X X X ○

division Average
Light transmittance (%) Yellow road CTE
(ppm / ℃) Oxygen Permeability
(cc / cm ² * day) RMS
(nm) Adhesive Heat resistance
(300 ℃ / 30 minutes) Example 1 92 2.29 26.95 1.90 0.582 5B Great Example  2 91 2.01 26.98 1.87 0.581 5B Great Example 3 90 1.95 26.55 1.14 0.583 5B Great Example 4 90 2.86 26.71 1.28 0.553 5B Great Comparative example  One 89 3.06 28.78 6.48 3.798 - Great

As shown in Table 1, the solvent resistance test results of the Examples and Comparative Examples Examples 1 to 4 are not visible changes when the solvent resistance to the naked eye to all solvents ◎, the RMS difference before and after the chemical test is evaluated as less than 1nm However, it can be seen that the comparative example was poor except for some solvents.

In addition, in the case of the embodiment, the silicon oxide layer is formed on the surface, thereby improving light transmittance, yellowness, CTE, oxygen permeability, surface roughness (RMS), adhesiveness, and the like, compared to Comparative Example 1, in which no treatment is performed on the surface. It can be seen that.

Claims (10)

Transparent polyimide film and
A transparent polyimide substrate formed on one or both surfaces of the transparent polyimide film, the silicon oxide layer comprising a silicon oxide made of a unit structure of the formula (1).
[Formula 1]

Here, m and n are integers of 0-10, respectively. The method of claim 1,
The silicon oxide layer is a transparent polyimide substrate having a thickness of 0.3 ~ 2.0㎛. The method of claim 1,
The silicon oxide layer is a transparent polyimide substrate having a surface roughness (RMS) of 5nm or less. Coating and drying a solution containing polysilazane on one or both sides of the transparent polyimide film; And
Method of manufacturing a transparent polyimide substrate comprising the step of curing the coated polysilazane. The method of claim 4, wherein
The polysilazane is a method for producing a transparent polyimide substrate comprising a unit structure of formula (2).
(2)

Here, m and n are integers of 0-10, respectively. The method of claim 5,
The polysilazane is a method for producing a transparent polyimide substrate having a weight average molecular weight of 1,000 ~ 5,000. The transparent polyimide substrate of claim 4, wherein a thickness of the polysilazane layer coated by coating and drying a solution containing polysilazane on one or both surfaces of the transparent polyimide film is 0.3 to 2.0 μm. . The method of claim 4, wherein
Curing the coated polysilazane is a method of producing a transparent polyimide substrate that is heat-cured by heat treatment at a temperature of 200 ~ 300 ℃. The method of claim 4, wherein the solution containing the polysilazane in the step of coating the solution containing the polysilazane further comprises an ultraviolet curing agent,
The curing of the coated polysilazane is a method of manufacturing a transparent polyimide substrate which is UV cured by irradiating short wavelength ultraviolet rays of 312 nm or 365 nm at 1500 to 4000 J / m ² . The method of claim 7, wherein the UV curing agent is at least one selected from among UV-curable benzoin ether-based photoinitiator comprising a photoinitiator selected from a benzoin ether photoinitiator, a benzophenone-based photoinitiator, or a mixture thereof. Way.