KR20190010119A - Electroconductive coating composition and transparent conductive film for flexible display comprising conductive layer prepared from the composition - Google Patents

Abstract

The present invention relates to an electroconductive coating liquid composition and to a transparent conductive film for a flexible display comprising a conductive layer prepared from the composition, wherein the transparent conductive film has a low surface resistivity change after bending for a number of times, and has a low haze and high light transmittance, enabling the transparent conductive film to be suitable for the flexible display.

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent conductive film for a flexible display comprising a conductive coating liquid composition and a conductive layer prepared therefrom. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a transparent conductive film for a flexible display,

The present invention relates to a transparent conductive film for a flexible display comprising a conductive coating liquid composition and a conductive layer prepared therefrom, wherein the transparent conductive film has a small change in surface resistance even after multi-bending, has low haze and high light transmittance, Suitable for application.

ITO (Indium Tin Oxide) is the most widely used transparent electrode material for displays. However, when the transparent electrode is formed of ITO, it is disadvantageous in that an excessive cost is required and it is difficult to realize a large area. In particular, when ITO is coated on a large area, there is a disadvantage that the luminance and luminous efficiency of the display are reduced due to a large change in surface resistance. In addition, indium, a major raw material of ITO, is a rare mineral, and is rapidly depleting as the display market expands. In order to overcome the disadvantages of ITO, research to form transparent electrode using poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT / PSS) with excellent flexibility and simple coating process .

On the other hand, as the use of liquid crystal display devices is increasing, the use of materials constituting the liquid crystal display devices is also increasing. Among them, various transparent plastic materials replacing materials such as metal and glass are widely used in places where high transparency is required. Among these, the surface of the panel of the liquid crystal display element is exposed to the outside, and thus a transparent substrate for protecting the panel from various external stimuli is widely used.

However, when PEDOT / PSS is used as a transparent electrode and a display is formed using polyethyleneterephthalate (PET) as a transparent substrate, unreacted oligomers are released from the PET to the surface during the heat treatment process and the haze value The surface resistance of the transparent electrode may be increased and the surface resistance may be increased. Also, since the surface resistance change due to the multi-step bending is large, it is not suitable for application to a flexible display requiring high physical stability in multi- -0095915).

Korea Patent Publication No. 2011-0095915

Accordingly, an object of the present invention is to provide a conductive coating liquid composition capable of producing a conductive layer suitable for use in a flexible display with a low change in surface resistance even after multi-bending, a low haze and a high light transmittance, and a conductive layer made therefrom To provide a transparent conductive film.

In order to accomplish the above object, the present invention provides a process for preparing poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT / PSS), an organic binder, an organic solvent, a silane coupling agent and a surfactant , And a conductive coating liquid composition.

In order to achieve still another object,

A transparent base film, and a conductive layer,

Wherein the conductive layer is formed from the conductive coating liquid composition.

The transparent conductive film for a flexible display including the conductive layer formed from the conductive coating liquid composition according to the present invention has a small surface resistance change after multi-bending, low haze and high light transmittance.

1 is a cross-sectional view of a transparent conductive film for a flexible display according to an embodiment of the present invention.
2 is a cross-sectional view of a film in which a metal layer is laminated on one side of a transparent conductive film for a flexible display according to an embodiment of the present invention.

The conductive coating liquid composition of the present invention includes poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT / PSS), an organic binder, an organic solvent, a silane coupling agent and a surfactant.

Wherein the conductive coating liquid composition comprises 10 to 70 wt% PEDOT / PSS, 1 to 20 wt% organic binder, 10 to 80 wt% organic solvent, 0.05 to 1 wt% silane coupling agent, and 0.02 to 0.4 wt% . ≪ / RTI > Specifically, the conductive coating liquid composition comprises 30 to 60 wt% of PEDOT / PSS, 1 to 10 wt% of organic binder, 40 to 65 wt% of organic solvent, 0.1 to 1 wt% of silane coupling agent, and 0.1 to 0.4 wt% Of a surfactant. More specifically, the conductive coating liquid composition comprises 35 to 50 wt% of PEDOT / PSS, 1 to 5 wt% of organic binder, 45 to 60 wt% of organic solvent, 0.5 to 1 wt% of silane coupling agent and 0.1 to 0.4 wt% % ≪ / RTI > of a surfactant.

The PEDOT / PSS is a water-dispersed conductive polymer in which poly (3,4-ethylenedioxythiophene) (PEDOT) is doped with poly (4-styrenesulfonate) (PSS). The PEDOT / PSS has an ethylene dioxy group in the form of a ring in the structure of thiophene, and has an electron donating effect by ethylenedioxy groups substituted at positions 3 and 4 to form thiophene (760 nm to 780 nm or 1.6 eV to 1.7 eV), and it is possible to change the color depending on the potential difference of oxidation / reduction and to have transparency because the absorption band exists in the infrared region in the oxidized state have.

The organic binder may include at least one selected from the group consisting of a melamine resin, a polyester resin, a polyurethane resin, and a polyacrylic resin. Further, the organic binder may be a water-dispersible resin.

The weight average molecular weight of the organic binder may range from 5,000 to 30,000 g / mol. Specifically, the weight average molecular weight of the organic binder may be 10,000 to 20,000 g / mol.

The organic solvent may include an alcohol-based organic solvent and an amide-based organic solvent. Specifically, the organic solvent may include an alcohol-based organic solvent and an amide-based organic solvent at a weight ratio of 10 to 30: 1. More specifically, the organic solvent may include an alcoholic organic solvent and an amide organic solvent at a weight ratio of 10 to 25: 1, a weight ratio of 15 to 25: 1, or a weight ratio of 17 to 25: 1. When the mixing ratio of the organic solvent and the amide organic solvent is within the above range, the conductivity of the conductive coating liquid composition is increased after coating, and a coating layer having a low surface resistance can be obtained.

The alcohol-based organic solvent improves the coating property by lowering the surface tension of the conductive coating liquid composition. Specifically, the alcohol-based organic solvent may be an alcohol having 1 to 4 carbon atoms. More specifically, it may be methanol, ethanol, propanol, isopropanol or n-butyl alcohol.

The amide-based organic solvent serves to improve the conductivity of the prepared conductive layer. Specifically, the amide-based organic solvent may include at least one selected from the group consisting of acetamide, N-methylacetamide, N-dimethylacetamide and N-methylpyrrolidone.

The silane coupling agent improves the adhesion of the conductive coating liquid composition and facilitates the lamination of the conductive layer on the transparent substrate film. Specifically, the silane coupling agent may include at least one selected from the group consisting of trimethoxysilane, triethoxysilane, tetramethoxysilane and tetraethoxysilane.

The triethoxysilane silane may be selected from the group consisting of 2- (3,4-epoxycyclohexyl) ethyltriethoxy silane, (3-aminopropyl) triethoxysilane ((3 -aminopropyl) triethoxy silane, (pentafluorophenyl) triethoxy silane, (3-glycidyloxypropyl) triethoxy silane or (4-glycidyloxypropyl) - (4-chlorophenyl) triethoxy silane).

The trimethoxystyrene silane can be selected from the group consisting of (3-glycidyloxypropyl) trimethoxy silane, (3-chloropropyl) trimethoxy silane, (3-mercaptopropyl) trimethoxy silane, (3-glycidyloxypropyl) trimethoxy silane, (3-aminopropyl) trimethoxy silane, (3-aminopropyl) trimethoxy silane, [3- (2-aminoethylamino) propyl] trimethoxysilane, (N- (N, N-dimethylaminopropyl) trimethoxy silane, (3-bromopropyl) trimethoxy silane or (3-isopropyl) trimethoxy silane, Silane ((3-iodopropyl) trimethoxy silane).

The surfactant may be a silicone surfactant or an acetylenic surfactant.

The silicone surfactant may be a modified silicone surfactant. For example, BYK-378 from BYK is a commercially available product of the silicone surfactant.

For example, a commercial product of the acetylenic surfactant is Dynol 604 from Air Products.

The conductive coating liquid composition may further include a pH adjusting agent. Specifically, the pH adjusting agent is selected from the group consisting of 2-dimethylaminoethanol, 2,2'-iminodiethanol and 2,2 ', 2 "-nitrile triethanol (2, 2 ', 2' '- nitrilotriethanol).

Based on the total weight of the conductive coating composition, a pH adjusting agent in an amount of 0.001 to 0.01% by weight. Specifically, it may contain 0.001 to 0.005 wt% of a pH adjusting agent based on the total weight of the conductive coating liquid composition.

The transparent conductive film for a flexible display of the present invention

A transparent base film, and a conductive layer,

The conductive layer is formed from a conductive coating fluid composition comprising PEDOT / PSS, an organic binder, an organic solvent, a silane coupling agent, and a surfactant.

The conductive layer is formed from a conductive coating liquid composition comprising PEDOT / PSS, an organic binder, an organic solvent, a silane coupling agent, and a surfactant. The conductive coating liquid composition is as described above.

The average thickness of the conductive layer may be 100 to 1,000 nm. Specifically, the average thickness of the conductive layer may be 100 to 700 nm.

The transparent base film may include polyethylene terephthalate (PET), polyimide (PI), or colorless transparent polyimide (PI). Specifically, the transparent base film may be composed of polyethylene terephthalate (PET) or colorless transparent polyimide (PI).

The transparent base film may have an average thickness of 12 to 200 탆. Specifically, the transparent base film may have an average thickness of 15 to 150 mu m, 15 to 130 mu m, or 20 to 130 mu m.

The transparent conductive film may have a surface resistance change of -5.0 to 5.0% calculated by using the following formula 1 after bending 300,000 times to a bending radius of 3 mm while applying a voltage of 5 V . Specifically, the transparent conductive film is formed by bending 300,000 times to a bending radius of 3 mm while applying a voltage of 5 V, and then changing the surface resistance by 0 to 5.0% .

[Equation 1]

.

.

The transparent conductive film may have a surface resistance of 100 to 200? /? Or 150 to 200? / ?, and a haze measured after cutting into 10 cm 占 10 cm 占 50 占 퐉 (width 占 length 占 thickness) have. Specifically, the transparent conductive film may have a surface resistance of 150 to 180 Ω / □ and a haze measured after cutting into 10 cm × 10 cm × 50 μm (width × length × thickness) of less than 0.7%.

The transparent conductive film may have a transmittance to visible light of 80% or more and a contact angle to water of 60 to 85 °. The transparent conductive film may have a transmittance to visible light of 80% or more and a contact angle to water of 63 to 84 °.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are intended to illustrate the present invention, but the scope of the present invention is not limited thereto.

[ Example ]

The compounds and the names of the compounds used in the following Examples and Comparative Examples are shown in Table 1 below.

division manufacturer product name Remarks PEDOT-PSS Heraeus Clevios ™ PH1000 - Organic binder-1 Lubrizol Sancure® 825 Polyurethane resin Organic binder-2 Base Korea EW-210 Polyester resin Silane Binder-1 Sigma aldrich (3-glycidyloxypropyl) trimethoxysilane - Silane Binder-2 Sigma aldrich 2- (3,4-epoxycyclohexyl) ethyl triethoxysilane - Surfactant-1 Air Products Dynol 604 Acetylenic surfactant Surfactant-2 BYK BYK-378 Silicone surfactant pH adjusting agent Sigma aldrich 2-dimethylaminoethanol - Organic solvent-1 Sigma aldrich N-methyl-2-pyrrolidone Amide-based organic solvent Organic solvent-2 Sigma aldrich Isopropanol Alcoholic organic solvent

Example  1. Preparation of transparent conductive film

A mixture of 42.9 g of aqueous dispersed PEDOT-PSS, 2.524 g of organic binder-1, 0.9 g of Silane Binder-1, 0.3 g of Surfactant-1, 0.003 g of pH adjusting agent, 2.6 g of organic solvent-1 and 50.773 g of organic solvent- Thereby obtaining a conductive coating liquid composition. Then, the conductive coating liquid composition was wet-coated on one side of a PET base film (manufacturer: SKC, product name: TU63, average thickness: 50 μm), dried at 80 ° C. for 3 minutes and thermally cured to form a conductive layer having an average thickness of 620 nm To prepare a transparent conductive film having an average thickness of 50.62 mu m.

Example  2 to 8.

A transparent conductive film having an average thickness of 50.62 占 퐉 was prepared in the same manner as in Example 1 except that PEDOT-PSS, an organic binder, a silane coupling agent, a surfactant, a pH adjuster and the kind and content of the organic solvent were changed.

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 PEDOT-PSS 42.9 g 42.9 g 42.9 g 42.9 g 42.9 g 42.9 g 42.9 g 42.9 g Organic binder-1 2.524 g 2.524 g 2.524 g 2.524 g - - - - Organic binder-2 - - - - 2.524 g 2.524 g 2.524 g 2.524 g Silane Binder-1 0.9 g 0.9 g 0.9 g 0.9 g - - - - Silane Binder-2 - - - 0.9 g 0.9 g 0.9 g 0.9 g Surfactant-1 0.3 g 0.15 g - - 0.3 g 0.15 g - - Surfactant-2 - - 0.3 g 0.15 g - - 0.3 g 0.15 g pH adjusting agent 0.003 g 0.003 g 0.003 g 0.003 g 0.003 g 0.003 g 0.003 g 0.003 g Organic solvent-1 2.6 g 2.6 g 2.6 g 2.6 g 2.6 g 2.6 g 2.6 g 2.6 g Organic solvent-2 50.773 g 50.923 g 50.773 g 50.923 g 50.773 g 50.923 g 50.773 g 50.923 g

Example  9.

A transparent conductive film having an average thickness of 50.62 占 퐉 was prepared in the same manner as in Example 1, except that a polyimide film (manufacturer: SKC, product name: CtPI, average thickness: 50 占 퐉) was used as a base film.

Experimental Example  1. Evaluation of Properties of Transparent Conductive Film

The properties of the transparent conductive films of Examples 1 to 9 were evaluated as follows and shown in Table 3.

(1) Surface resistance

The transparent conductive film was cut into 500 mm × 500 mm (width × length), and the surface resistance of the conductive layer was measured using MCP-T370 manufactured by Mitsubishi chemical analytech.

(2) Hayes

The transparent conductive film was cut into a size of 10 cm x 10 cm x 50 m (width x length x thickness), and haze was measured according to ISO 14782 standard using NDH2000N manufactured by Nippon Denshoku.

(3) Transmittance

The transmittance of the transparent conductive film to visible light (380 to 780 nm) was measured using Nippon Denshoku's NDH2000N.

(4) Contact angle

The transparent conductive film was cut into 1 cm × 5 cm × 50 μm (width × length × thickness), and a drop of water was dropped. The angle of tangential line between the coated surface and the water droplet was measured to determine the contact angle.

(5) Attachment  (Cross hatch cut, cross hatch cut)

The transparent conductive film was cut into 20 cm × 20 cm × 50 μm (width × length × thickness), and then the adhesion through cross hatch cut was measured according to ISO 2409 standard.

Surface resistance Hayes Transmittance Contact angle Attachment Example 1 152.5 Ω / □ 0.54% 85.19% 72.90 ˚ 5B Example 2 158.6 Ω / □ 0.59% 85.24% 67.41 ˚ 4B Example 3 153.5 Ω / □ 0.36% 85.03% 71.59 ˚ 4B Example 4 160.8 Ω / □ 0.47% 85.21% 64.87 ˚ 4B Example 5 161.1 Ω / □ 0.50% 85.04% 83.89 ˚ 5B Example 6 162.7 Ω / □ 0.51% 85.32% 74.19 ˚ 5B Example 7 166.9 Ω / □ 0.49% 84.39% 76.28 ˚ 5B Example 8 170.9 Ω / □ 0.40% 85.20% 81.44˚ 5B Example 9 150.0 Ω / □ 0.58% 85.79% 75.90 ˚ 5B

Experimental Example  2. Flexibility evaluation of transparent conductive film

In order to evaluate the flexibility of the transparent conductive films of Examples 1 and 9, the transparent conductive film was cut into a 15 mm x 50 mm (width x length) and then cut into a clamp facing each other (hereinafter, . The length of the sample between the two clamps was adjusted from 50 mm to 13 mm so that the bending radius was 1 mm or 3 mm in the structure where the clamps of both sides were adjacent to each other and the sample was bended. The surface resistance was measured by applying a voltage of 5 V DC while bending for 300,000 times. The bending was performed so that the conductive layer was outward (tensile) or inward (compressed) when folded, and the maximum value and the minimum value of the surface resistance and the surface resistance after bending 300,000 times were measured. The measurement results of the film of Example 1 are shown in Table 4, and the measurement results of the film of Example 9 are shown in Table 5.

Bend radius 1mm 3mm Bending direction Inside the conductive layer Outside the conducting layer Inside the conductive layer Outside the conducting layer Surface resistance before bending 152 Ω / □ 155 Ω / □ 153 Ω / □ 154 Ω / □ Surface resistance after bending 155 Ω / □ 155 Ω / □ 155 Ω / □ 155 Ω / □ Surface resistance change rate 2.0% 0.0% 1.3% 0.6% Surface resistance minimum value 152 Ω / □ 152 Ω / □ 149 Ω / □ 152 Ω / □ Maximum surface resistance 155 Ω / □ 155 Ω / □ 155 Ω / □ 155 Ω / □ Surface resistance measurement error 2.0% 2.0% 4.0% 2.0%

Bend radius 1mm Bending direction Inside the conductive layer Outside the conducting layer Surface resistance before bending 150 Ω / □ 151Ω / □ Surface resistance after bending 151Ω / □ 153Ω / □ Surface resistance change rate 0.7% 1.3% Surface resistance minimum value 149Ω / □ 149Ω / □ Maximum surface resistance 153Ω / □ 152Ω / □ Surface resistance measurement error 2.7% 2.0%

As shown in Tables 4 and 5, it was found that the transparent conductive film of the example had a small rate of change in surface resistance after bending, and that the surface resistance after bending was within the measurement error range before bending.

Experimental Example  3. Evaluation of metal adhesion of transparent conductive film

Copper (Cu) or silver (Ag) was laminated on the conductive layer of the transparent conductive film of Example 1 by a roll-to-roll metal sputtering method according to the vacuum degree, line speed, pretreatment conditions, and film forming conditions shown in Table 6. The physical properties were evaluated as shown in Table 7 below.

Metal type Cu Ag Vacuum degree Base pressure 7.0E-6 Torr 7.0E-6 Torr Working pressure 3.0E-3 Torr 3.0E-3 Torr Line speed 0.5 m / min. 1 m / min. Pretreatment condition Ar Plasma, DC Power 30 W Ar Plasma, DC Power 30 W Film formation conditions Partial pressure Ar 800 sccm Ar 1000 sccm Power DC Power 9 kW DC Power 9 kW

(1) resistivity and surface resistance

The transparent conductive film was cut into 10 cm × 10 cm (width × length), and the surface resistivity of the resistivity and conductive layer was measured using MCP-T370 manufactured by Mitsubishi chemical analytech.

(2) Attachment  (Cross hatch cut, cross hatch cut)

The transparent conductive film was cut into 20 cm × 20 cm × 50 μm (width × length × thickness), and then the adhesion through cross hatch cut was measured according to ISO 2409 standard.

Types of deposited metal Copper (Cu) Silver (Ag) Resistivity 1.72E-08? M 1.59E-08? M Surface resistance 0.17 Ω / □ 0.15 Ω / □ The thickness of the metal layer 101 nm 106 nm Attachment 5B (OK) 5B (OK) Exterior Good (Hazy, no Pinhole) Good (Hazy, no Pinhole)

As shown in Table 7, it was found that the transparent conductive film of the present invention is excellent in adhesion to metal, has low surface resistance after metal deposition, and is suitable for application to a narrow bezel display.

100: transparent conductive film 10: conductive layer
20: transparent base film 30: metal layer

Claims (19)

A conductive coating fluid composition comprising a poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT / PSS), an organic binder, an organic solvent, a silane coupling agent, and a surfactant.
The method according to claim 1,
Wherein the conductive coating liquid composition comprises 10 to 70 wt% PEDOT / PSS, 1 to 20 wt% organic binder, 10 to 80 wt% organic solvent, 0.05 to 1 wt% silane coupling agent, and 0.02 to 0.4 wt% ≪ / RTI >
3. The method according to claim 1 or 2,
Wherein the organic binder comprises at least one selected from the group consisting of a melamine resin, a polyester resin, a polyurethane resin, and a polyacrylic resin.
3. The method according to claim 1 or 2,
Wherein the organic solvent comprises an alcohol-based organic solvent and an amide-based organic solvent.
5. The method of claim 4,
Wherein the alcohol-based organic solvent is an alcohol having 1 to 4 carbon atoms.
5. The method of claim 4,
Wherein the amide organic solvent comprises at least one selected from the group consisting of acetamide, N-methylacetamide, N-dimethylacetamide and N-methylpyrrolidone.
5. The method of claim 4,
Wherein the organic solvent comprises an alcohol-based organic solvent and an amide-based organic solvent in a weight ratio of 10 to 30: 1.
3. The method according to claim 1 or 2,
Wherein the silane coupling agent comprises at least one selected from the group consisting of trimethoxystyrene silane, triethoxystyrene silane, tetramethoxystyrene silane, and tetraethoxystyrene silane.
3. The method according to claim 1 or 2,
Wherein the surfactant is a silicone surfactant or an acetylenic surfactant.
3. The method according to claim 1 or 2,
Wherein the conductive coating liquid composition further comprises a pH adjusting agent.
11. The method of claim 10,
The pH controlling agent may be selected from the group consisting of 2-dimethylaminoethanol, 2,2'-iminodiethanol and 2,2 ', 2 "-nitrile triethanol (2,2' 2 " -nitrilotriethanol). ≪ / RTI >
11. The method of claim 10,
Wherein the conductive coating liquid composition comprises 0.001 to 0.01 wt% of a pH adjusting agent based on the total weight of the conductive coating liquid composition.
A transparent base film, and a conductive layer,
Wherein the conductive layer is formed from a conductive coating liquid composition comprising poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT / PSS), an organic binder, an organic solvent, a silane coupling agent and a surfactant, Transparent conductive film for flexible display.
14. The method of claim 13,
Wherein the conductive coating liquid composition comprises 10 to 70 wt% PEDOT / PSS, 1 to 20 wt% organic binder, 10 to 80 wt% organic solvent, 0.05 to 1 wt% silane coupling agent, and 0.02 to 0.4 wt% And a transparent conductive film for a flexible display.
The method according to claim 13 or 14,
Wherein the transparent base film comprises polyethylene terephthalate (PET) or colorless transparent polyimide (PI) and has an average thickness of 12 to 200 탆.
The method according to claim 13 or 14,
Wherein the conductive layer has an average thickness of 100 to 1,000 nm.
The method according to claim 13 or 14,
The transparent conductive film was produced by flexing 300,000 times to a bending radius of 3 mm while applying a voltage of 5 V and then changing the surface resistance to -5.0 to 5.0% Transparent conductive film for display:
[Equation 1]

.
The method according to claim 13 or 14,
Wherein the transparent conductive film has a surface resistance of 100 to 200 Ω / □ and a haze measured after cutting into 10 cm × 10 cm × 50 μm (width × length × thickness) of less than 1%.
The method according to claim 13 or 14,
Wherein the transparent conductive film has a transmittance to visible light of 80% or more and a contact angle to water of 60 to 85 占 The transparent conductive film for a flexible display.

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