KR102103860B1 - 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 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 surface resistance change even after multiple bending, low haze, and high light transmittance to a flexible display. Suitable for application.

Description

A transparent conductive film for a flexible display comprising a conductive coating solution composition and a conductive layer prepared therefrom.

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 surface resistance change even after multiple bending, low haze, and high light transmittance to a flexible display. Suitable for application.

Currently, the most commonly used transparent electrode material for display is ITO (Indium Tin Oxide). However, when the transparent electrode is formed of ITO, there is a disadvantage in that it is difficult to implement a large area as well as excessive cost. Particularly, when ITO is coated on a large area, a change in surface resistance is large, so that the brightness and luminous efficiency of the display are reduced. In addition, indium, the main raw material of ITO, is a rare mineral, and is rapidly depleted as the display market expands. In order to overcome the shortcomings of this ITO, a study of forming a transparent electrode using polyethylene dioxythiophene / polystyrene sulfonate (PEDOT / PSS), which is excellent in flexibility and has a simple coating process Is going on.

Meanwhile, as the use of liquid crystal display devices has recently increased, the use of materials constituting it has also increased. Among them, various transparent plastic materials, which have replaced materials such as metal or glass in areas where high transparency is required, are widely used. Since the panel surface of the liquid crystal display element is exposed to the outside, a transparent substrate for protecting the panel from various external stimuli is widely used.

However, when a display is formed using PEDOT / PSS as a transparent electrode and polyethylene terephthalate (PET) as a transparent substrate, a haze value is generated while unreacted oligomer is eluted from the PET to the surface during the heat treatment process. In addition, the rise or damage of the transparent electrode may cause an increase in surface resistance. In addition, since the change in surface resistance due to multiple bending is large, it is unsuitable for application to a flexible display requiring high physical property stability during multiple bending (Republic of Korea Patent Publication No. 2011) -0095915).

Republic of Korea Patent Publication No. 2011-0095915

Accordingly, the object of the present invention includes a conductive coating liquid composition capable of producing a conductive layer suitable for application to a flexible display, and has a low haze and high light transmittance even after multiple bending, and a conductive layer prepared therefrom It is to provide a transparent conductive film.

In order to achieve the above object, the present invention comprises polyethylene dioxythiophene / polystyrene sulfonate (poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate; PEDOT / PSS), an organic binder, an organic solvent, a silane binder and a surfactant. , It provides a conductive coating liquid composition.

In order to achieve another object, the present invention

It includes a transparent base film and a conductive layer,

It provides a transparent conductive film for a flexible display, the conductive layer is formed from the conductive coating liquid composition.

The transparent conductive film for a flexible display including a conductive layer formed from the conductive coating solution composition according to the present invention has advantages of low surface resistance change after multiple 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 surface 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 polyethylene dioxythiophene / polystyrene sulfonate (PEDOT / PSS), an organic binder, an organic solvent, a silane binder, and a surfactant.

The conductive coating solution composition is 10 to 70% by weight of PEDOT / PSS, 1 to 20% by weight of an organic binder, 10 to 80% by weight of an organic solvent, 0.05 to 1% by weight of a silane binder, and 0.02 to 0.4% by weight of a surfactant It may include. Specifically, the conductive coating solution composition is 30 to 60% by weight of PEDOT / PSS, 1 to 10% by weight of organic binder, 40 to 65% by weight of organic solvent, 0.1 to 1% by weight of silane binder, and 0.1 to 0.4% by weight It may include a surfactant. More specifically, the conductive coating solution composition is 35 to 50% by weight of PEDOT / PSS, 1 to 5% by weight of organic binder, 45 to 60% by weight of organic solvent, 0.5 to 1% by weight of silane binder, and 0.1 to 0.4% by weight % Surfactant.

The PEDOT / PSS is a water-dispersible conductive polymer doped with poly (3,4-ethylenedioxythiophene) (PEDOT) 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 thiophene due to an electron donating effect by ethylene dioxy groups substituted at positions 3 and 4. It has a lower optical band gap (760 nm to 780 nm or 1.6 eV to 1.7 eV), discoloration is possible depending on the potential difference of oxidation / reduction, and the absorption band is present in the infrared region in the oxidation state, so that it is possible to secure transparency. have.

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

The organic binder may have a weight average molecular weight of 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 in a weight ratio of 10 to 30: 1. More specifically, the organic solvent may include an alcohol-based organic solvent and an amide-based organic solvent in 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-based organic solvent is within the above range, the conductivity may be increased after coating the conductive coating liquid composition to obtain a coating layer having a low surface resistance.

The alcohol-based organic solvent serves to improve the coating properties 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 binder improves the adhesion of the conductive coating liquid composition and serves to facilitate the lamination of the conductive layer on the transparent base film. Specifically, the silane binder may include at least one selected from the group consisting of trimethoxy-based silane, triethoxy-based silane, tetramethoxy-based silane, and tetraethoxy-based silane.

The triethoxy silane is 2- (3,4-epoxycyclohexyl) ethyltriethoxy silane (2- (3,4-epoxycyclohexyl) ethyltriethoxy silane), (3-aminopropyl) triethoxysilane ((3 -aminopropyl) triethoxy silane, (pentafluorophenyl) triethoxy silane, (3-glycidyloxypropyl) triethoxy silane ((3-glycidyloxypropyl) triethoxy silane) or (4 It may be -chlorophenyl) triethoxy silane.

The trimethoxy silane is (3-glycidyloxypropyl) trimethoxy silane ((3-glycidyloxypropyl) trimethoxy silane), (3-chloropropyl) trimethoxy silane ((3-chloropropyl) trimethoxy silane), ( 3-mercaptopropyl) trimethoxy silane, (3-glycidyloxypropyl) trimethoxy silane, (3-aminopropyl) tri Methoxysilane ((3-aminopropyl) trimethoxy silane), [3- (2-aminoethylamino) propyl] trimethoxy silane, (N, N-dimethyl (Aminopropyl) trimethoxy silane ((N, N-dimethylaminopropyl) trimethoxy silane), (3-bromopropyl) trimethoxy silane or (3-idopropyl) trimethoxy It may be a silane ((3-iodopropyl) trimethoxy silane).

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

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

For example, commercially available products of the acetylene surfactant include Dynol 604 from Air Products.

The conductive coating liquid composition may further include a pH adjusting agent. Specifically, the pH adjusting agent is 2-dimethylaminoethanol, 2,2'-iminodiethanol and 2,2 ', 2' '-nitrilotriethanol (2, 2 ', 2' '-nitrilotriethanol).

Based on the total weight of the conductive coating solution composition may include a pH adjusting agent of 0.001 to 0.01% by weight. Specifically, a pH adjusting agent of 0.001 to 0.005% by weight based on the total weight of the conductive coating solution composition may be included.

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

It includes a transparent base film and a conductive layer,

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

The conductive layer is formed from a conductive coating liquid composition comprising PEDOT / PSS, organic binder, organic solvent, silane binder, and 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), or 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 μm. Specifically, the average thickness of the transparent base film may be 15 to 150 μm, 15 to 130 μm, or 20 to 130 μm.

The transparent conductive film may be bent 300,000 times so that the bending radius is 3 mm while applying a voltage of 5 V, and the surface resistance change calculated using Equation 1 below may be -5.0 to 5.0%. . Specifically, the transparent conductive film was bent 300,000 times so that the bending radius is 3 mm while applying a voltage of 5 V, and the surface resistance change calculated using Equation 1 below was 0 to 5.0%. You can.

[Equation 1]

.

.

The transparent conductive film has a surface resistance of 100 to 200 Ω / □ or 150 to 200 Ω / □, and the haze measured after cutting to 10 cm × 10 cm × 50 μm (width × length × thickness) may be less than 1%. have. Specifically, the transparent conductive film has a surface resistance of 150 to 180 Pa / □, and a haze measured after cutting to 10 cm × 10 cm × 50 μm (width × length × thickness) may be less than 0.7%.

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

Hereinafter, the present invention will be described in more detail by the following examples. However, the following examples are only for illustrating the present invention and the scope of the present invention is not limited to them.

[Example]

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

division manufacturer product name Remark 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) trimethoxy silane - Silane Binder-2 Sigma aldrich 2- (3,4-epoxycyclohexyl) ethyltriethoxy silane - Surfactant-1 Air Products Dynol 604 Acetylene surfactant Surfactant-2 BYK BYK-378 Silicone surfactant pH adjuster Sigma aldrich 2-dimethylaminoethanol - Organic solvent-1 Sigma aldrich N-methyl-2-pyrrolidone Amide-based organic solvent Organic solvent-2 Sigma aldrich Isopropanol Alcohol-based organic solvent

Example 1. Preparation of a transparent conductive film 42.9 g of water-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-2 to obtain a conductive coating solution composition. Thereafter, the conductive coating liquid composition was wet coated on one surface of a PET base film (manufacturer: SKC, product name: TU63, average thickness: 50 μm), dried and thermally cured at 80 ° C. for 3 minutes to form a conductive layer having an average thickness of 620 nm. , A transparent conductive film having an average thickness of 50.62 μm was prepared.

Examples 2 to 8.

A transparent conductive film having an average thickness of 50.62 μm was prepared in the same manner as in Example 1, except that the type and content of the PEDOT-PSS, organic binder, silane binder, surfactant, pH control agent, and 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 adjuster 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 μm was prepared in the same manner as in Example 1, except that a polyimide film (manufacturer: SKC, product name: CtPI, average thickness: 50 μm) was used as the base film.

Experimental Example 1. Evaluation of physical properties of transparent conductive film

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

(1) Surface resistance

After cutting the transparent conductive film into 500 mm × 500 mm (horizontal × vertical), the surface resistance of the conductive layer was measured using MCP-T370 manufactured by Mitsubishi chemical analytech.

(2) Haze

After the transparent conductive film was cut into 10 cm × 10 cm × 50 μm (width × length × thickness), haze was measured according to ISO 14782 using NDH2000N of Nippon denshoku.

(3) transmittance

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

(4) Contact angle

After cutting the transparent conductive film into 1 cm × 5 cm × 50 μm (horizontal × vertical × thickness), a drop of water was dropped, and the angle forming the tangent between the coating surface and the droplet was measured to determine the contact angle.

(5) Adhesion (cross hatch cut)

After the transparent conductive film was cut into 20 cm × 20 cm × 50 μm (horizontal × vertical × thickness), adhesion was measured through a cross hatch cut using ISO 2409 standard.

Surface resistance Haze Transmittance Contact angle Adhesion 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. Evaluation of the flexibility of the transparent conductive film To evaluate the flexibility of the transparent conductive films of Examples 1 and 9, the transparent conductive film was cut into 15 mm × 50 mm (horizontal × vertical) and then cut into clamps facing each other. Attach one transparent conductive film (hereinafter referred to as 'sample'). 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 a structure in which the clamps located between both clamps were adjacent to each other, and the bending sample was placed between them. Surface resistance was measured by applying a voltage of DC 5 V while bending 300,000 times. In addition, the bending was carried out so that the conductive layer becomes outer (tensile) or inner (compressed) when folded, and the maximum and minimum values of the surface resistance, and the surface resistance after bending 300,000 times. Table 4 shows the measurement results of the film of Example 1 and Table 5 shows the measurement results of the film of Example 9.

Bending radius 1 mm 3 mm Winding direction Conductive layer inside The conductive layer is outside Conductive layer inside The conductive layer is outside 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% Minimum surface resistance 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%

Bending radius 1 mm Winding direction Conductive layer inside The conductive layer is outside Surface resistance before bending 150Ω / □ 151Ω / □ Surface resistance after bending 151Ω / □ 153Ω / □ Surface resistance change rate 0.7% 1.3% Minimum surface resistance 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 Examples had a small change rate of surface resistance after bending, and 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) on the conductive layer of the transparent conductive film of Example 1 was laminated with a metal layer by a roll-to-roll metal sputtering method according to the vacuum degree, line speed, pretreatment conditions and film formation conditions of Table 6. Then, the 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 conditions Ar Plasma, DC Power 30 W Ar Plasma, DC Power 30 W Deposition conditions Partial pressure Ar 800 sccm Ar 1000 sccm Power DC Power 9 kW DC Power 9 kW

(1) Resistivity and surface resistance After cutting the transparent conductive film into 10 cm × 10 cm (horizontal × vertical), the specific resistance and surface resistance of the conductive layer were measured using Mitsubishi chemical analytech's MCP-T370.

(2) Adhesion (cross hatch cut)

After the transparent conductive film was cut into 20 cm × 20 cm × 50 μm (horizontal × vertical × thickness), adhesion was measured through a cross hatch cut using ISO 2409 standard.

Type of metal deposited Copper (Cu) Silver (Ag) Resistivity 1.72E-08 Ω ㆍ m 1.59E-08 Ω ㆍ m Surface resistance 0.17 Ω / □ 0.15 Ω / □ Metal layer thickness 101 nm 106 nm Adhesion 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 has excellent metal adhesion, low surface resistance after metal deposition, and good appearance, and thus is suitable for application to narrow bezel displays.

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

Claims (7)

It includes a transparent polyimide (PI) base film and a conductive layer,
The conductive layer is 35 to 50% by weight of polyethylene dioxythiophene / polystyrene sulfonate (poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate; PEDOT / PSS), 1 to 5% by weight of organic binder, 45 to 60% by weight It is formed from a conductive coating liquid composition comprising an organic solvent, 0.5 to 1% by weight of a silane binder, 0.1 to 0.4% by weight of a surfactant, and 0.001 to 0.01% by weight of a pH adjusting agent,
The organic binder comprises a polyurethane resin having a weight average molecular weight of 10,000 to 20,000 g / mol,
The organic solvent comprises an alcohol-based organic solvent and an amide-based organic solvent in a weight ratio of 17 to 25: 1, a transparent conductive film for a flexible display.
According to claim 1,
The transparent polyimide base film has an average thickness of 12 to 200 μm, a transparent conductive film for a flexible display.
According to claim 1,
A transparent conductive film for flexible display having an average thickness of 100 to 1,000 nm of the conductive layer.
According to claim 1,
The transparent conductive film is flexible after bending 300,000 times so that a bending radius is 3 mm while applying a voltage of 5 V, and the surface resistance change calculated using Equation 1 below is -5.0 to 5.0%. Transparent conductive film for display:
[Equation 1]

.
According to claim 1,
The transparent conductive film has a surface resistance of 100 to 200 Ω / □, and the haze measured after cutting to 10 cm × 10 cm × 50 μm (width × length × thickness) is less than 1%, and the transparent conductive film for flexible display.
According to claim 1,
The transparent conductive film has a transmittance to visible light of 80% or more, and a contact angle to water of 60 to 85 °, a transparent conductive film for a flexible display.
According to claim 1,
The alcohol-based organic solvent is an alcohol having 1 to 4 carbon atoms,
The amide-based organic solvent includes at least one selected from the group consisting of acetamide, N-methylacetamide, N-dimethylacetamide and N-methylpyrrolidone,
The silane binder comprises at least one member selected from the group consisting of trimethoxy-based silane, triethoxy-based silane, tetramethoxy-based silane and tetraethoxy-based silane,
The surfactant comprises a silicone-based surfactant or an acetylene-based surfactant,
The pH adjusting agent is 2-dimethylaminoethanol, 2,2'-iminodiethanol and 2,2 ', 2''-nitrolotriethanol(2,2', 2 ''-nitrilotriethanol), a transparent conductive film for a flexible display, including at least one selected from the group consisting of.

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