TWI681022B - 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 conductive coating liquid composition and a transparent conductive film for a flexible display including a conductive layer manufactured thereby. Even after multiple bendings, the surface resistance changes little, the haze is low, and the light transmission The rate is high, so it is suitable for flexible displays.

Description

Conductive coating liquid composition and transparent conductive film for flexible display including conductive layer manufactured thereby

The present invention relates to a conductive coating liquid composition and a transparent conductive film for a flexible display including a conductive layer manufactured therefrom. Even after multiple bendings, the surface resistance changes little, the haze is low, and light transmission The rate is high, so it is suitable for flexible displays.

At present, the most used transparent electrode material for displays is Indium Tin Oxide (ITO). However, when ITO is used to form a transparent electrode, it has the following disadvantages, which not only requires excessive cost, but also makes it difficult to realize a large area. In particular, when ITO is coated over a large area, there is a disadvantage that the brightness and luminous efficiency of the display are reduced due to a large change in surface resistance. In addition, indium, which is the main raw material of ITO, is a rare mineral and is rapidly depleting as the display market expands. In order to overcome these shortcomings of ITO, poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT/PSS) with excellent flexibility and simple coating process is being used ) Research on forming transparent electrodes.

On the other hand, as the use of liquid crystal display elements has increased recently, the use of its constituent materials has also increased. Among them, various transparent plastic materials that replace materials such as metal or glass are widely used in parts requiring high transparency. Among them, the panel surface of the liquid crystal display element is exposed to the outside, so transparent substrates for protecting the panel from various external stimuli are widely used.

However, when using PEDOT/PSS as a transparent electrode and polyethylene terephthalate (PET) as a transparent substrate to form a display, unreacted oligomers are poured out of PET during the heat treatment process To the surface, thereby increasing the haze value or damaging the transparent electrode, resulting in an increase in surface resistance. In addition, since the surface resistance changes greatly after multiple bendings, it is not suitable for flexible displays that require high physical stability after multiple bendings (see Korean Patent Publication No. 2011-0095915).

Therefore, the object of the present invention is to provide a conductive coating liquid composition and a transparent conductive film including the conductive layer manufactured thereby, even after multiple bendings, the surface resistance changes are still small, the haze is low, and the light transmittance is high, Thus, a conductive layer suitable for flexible displays can be manufactured.

In order to achieve the above object, the present invention provides a conductive coating liquid composition comprising poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT/PSS) , Organic binders, organic solvents, silane coupling agents and surfactants.

To achieve another object, the present invention provides a transparent conductive film for a flexible display, including a transparent base film and a conductive layer, wherein the conductive layer is formed of the conductive coating liquid composition.

The transparent conductive film for flexible displays of the present invention includes a conductive layer formed of a conductive coating liquid composition, and the transparent conductive film has the following advantages: even after multiple bendings, the surface resistance changes are still small, the haze is low, and the light transmission The rate is high.

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

The conductive coating liquid composition may include 10 to 70 wt% of PEDOT/PSS, 1 to 20 wt% of organic binder, 10 to 80 wt% of organic solvent, 0.05 to 1 wt% of silane coupling agent and 0.02 to 0.4 wt % Surfactant. Specifically, the conductive coating liquid composition may include 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 ~0.4wt% surfactant. More specifically, the conductive coating liquid composition may include 35-50 wt% of PEDOT/PSS, 1-5 wt% of organic binder, 45-60 wt% of organic solvent, 0.5-1 wt% of silane coupling agent and 0.1~0.4wt% surfactant.

The PEDOT/PSS is a water-dispersible conductive polymer doped with poly(4-styrenesulfonate) (PSS) in poly(3,4-ethylenedioxythiophene) (PEDOT). The PEDOT/PSS has an ethylene dioxy group in the form of a ring in the thiophene structure, and the electron supply effect by the ethylene dioxy group substituted to the 3 and 4 positions is lower than that of thiophene. The optical band gap (760nm to 780nm or 1.6eV to 1.7eV) can change color according to the oxidation/reduction potential difference. In the oxidation state, there is an absorption band in the infrared region to ensure transparency.

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

The weight average molecular weight of the organic binder may be 5000-30,000 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, and a weight ratio of 17 to 25:1. When the mixing ratio of the alcohol-based organic solvent and the amide-based organic solvent is within the above range, the electrical conductivity increases after the conductive coating liquid composition is applied, so that a coating with low surface resistance can be obtained.

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

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

The silane coupling agent functions to improve the adhesion of the conductive coating liquid composition to facilitate the lamination of a conductive layer on the transparent base film. Specifically, the silane coupling agent may include one or more selected from the group consisting of trimethoxy-based silane, triethoxy-based silane, tetramethoxy-based silane, and tetraethoxy-based silane.

The triethoxysilane may be 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (2-(3,4-epoxycyclohexyl)ethyltriethoxysilane), (3-aminopropyl ) Triethoxysilane ((3-aminopropyl) triethoxysilane), (pentafluorophenyl) triethoxysilane ((pentafluorophenyl) triethoxysilane), (3-glycidyl ether oxypropyl) triethoxysilane ( (3-glycidyloxypropyl)triethoxysilane) or (4-chlorophenyl)triethoxysilane ((4-chlorophenyl)triethoxysilane).

The trimethoxysilane may be (3-glycidyloxypropyl) trimethoxysilane ((3-glycidyloxypropyl) trimethoxysilane), (3-chloropropyl) trimethoxysilane ((3-chloropropyl) trimethoxysilane), (3-mercaptopropyl)trimethoxysilane ((3-mercaptopropyl)trimethoxysilane), (3-aminopropyl)trimethoxysilane ((3-aminopropyl)trimethoxysilane), [3-(2-amino Ethylamino)propyl]trimethoxysilane ([3-(2-aminoethylamino)propyl]trimethoxysilane), (N,N-dimethylaminopropyl)trimethoxysilane ((N,N-dimethylaminopropyl)trimethoxysilane ), (3-bromopropyl) trimethoxysilane ((3-bromopropyl) trimethoxysilane) or (3-iodopropyl) trimethoxysilane ((3-iodopropyl) trimethoxysilane).

The surfactant may be a silicon-based surfactant or an acetylene-based surfactant.

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

For example, the commercially available product of the acetylene surfactant is Dynol 604 of Air Products.

The conductive coating liquid composition may further contain a pH adjuster. Specifically, the pH adjusting agent may comprise selected from the group consisting of 2-dimethylaminoethanol, 2,2'-iminodiethanol and 2,2',2'' -More than one of the group consisting of nitrilotriethanol (2,2',2''-nitrilotriethanol).

Based on the total weight of the conductive coating liquid composition, it may contain 0.001 to 0.01 wt% of a pH adjuster. Specifically, based on the total weight of the conductive coating solution composition, a pH adjuster of 0.001 to 0.005 wt% may be included.

The transparent conductive film for a flexible display of the present invention includes a transparent base film and a conductive layer formed of a conductive coating liquid composition containing PEDOT/PSS, an organic binder, an organic solvent, a silane coupling agent, and a surfactant .

The conductive layer is formed of a conductive coating liquid composition containing 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 100-1000 nm. Specifically, the average thickness of the conductive layer may be 100-700 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 average thickness of the transparent base film may be 12-200 μm. Specifically, the average thickness of the transparent base film may be 15-150 μm, 15-130 μm, or 20-130 μm.

The transparent conductive film can be bent 300,000 times with a 5V voltage applied so that the bending radius (bending radius) reaches 3 mm, and then the surface resistance change calculated using the following formula (1) can be -5.0 to 5.0%. Specifically, the transparent conductive film may be bent 300,000 times with a voltage of 5V applied so that the bending radius (bending radius) reaches 3 mm, and then the surface resistance change calculated using the following formula (1) may be 0 to 5.0%.

[Formula 1]

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

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

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

[Example]

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

Table 1

Example 1. Preparation of transparent conductive film

42.9g of aqueous dispersion PEDOT-PSS, 2.524g of organic binder-1, 0.9g of silane coupling agent-1, 0.3g of surfactant-1, 0.003g of pH adjuster, 2.6g of organic solvent -1 and 50.773 g of organic solvent-2 were mixed to obtain a conductive coating liquid composition. Then, the conductive coating liquid composition was wet coated on the side of the PET base film (manufacturer: SKC, trade name: TU63, average thickness: 50 μm), dried at 80° C. for 3 minutes, and thermally cured To form a conductive layer with an average thickness of 620 nm, thereby preparing a transparent conductive film with an average thickness of 50.62 μm.

Examples 2-8.

Except for changing the types and contents of PEDOT-PSS, organic binders, silane coupling agents, surfactants, pH adjusters, and organic solvents, the same method as in Example 1 was used to prepare a transparent conductive film with an average thickness of 50.62 μm .

Table 2

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 the base film used a polyimide film (manufacturer: SKC, trade name: CtPI, average thickness: 50 μm).

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 shown in Table 3.

( 1 ) Surface resistance

The transparent conductive film was cut into 500 mm×500 mm (length×width), and MCP-T370 of Mitsubishi Chemical Analytech was used to measure the surface resistance of the conductive layer.

( 2 ) Haze

The transparent conductive film was cut into 10 cm×10 cm×50 μm (length×width×thickness), and the haze was measured using NDH2000N from Nippon Denshoku according to the ISO 14782 standard.

( 3 )Transmittance

The NDH2000N from Nippon Denshoku Corporation was used to measure the transmittance of the transparent conductive film to visible light (380 to 780 nm).

( 4 )Contact angle

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

( 5 ) Adhesion (cross cutting, cross hatch cut )

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

table 3

Experimental Example 2. Evaluation of the flexibility of the 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 15 mm×50 mm (length×width), and then the cut transparent conductive films (hereinafter, described as samples) were installed opposite to each other On the fixture. Adjust the length of the sample between the two clamps from 50mm to 13mm, so that the clamps on both sides are adjacent to each other, the sample between them becomes a bending structure and the bending radius (bending radius) reaches 1mm or 3mm, and the bending is 300,000 During this period, a DC voltage of 5V was applied and the surface resistance was measured. In addition, the bending causes the conductive layer to be outward (stretched) or inward (compressed) when folded, and the maximum and minimum values of the surface resistance and the surface resistance after bending 300,000 times are 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.

Table 4

table 5

As shown in Tables 4 and 5, the transparent conductive film of the embodiment has a small surface resistance change rate after bending, and the surface resistance after bending is within the measurement error range before bending.

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

According to the vacuum degree, linear velocity, pretreatment conditions, and film formation conditions in Table 6, a metal layer, such as copper (Cu) or silver, was laminated on the conductive layer of the transparent conductive film of Example 1 by the roll-to-roll metal spraying method Ag). The physical properties were evaluated as described below and shown in Table 7.

Table 6

( 1 )Resistivity ) And surface resistance

The transparent conductive film was cut into 10 cm×10 cm (length×width), and MCP-T370 of Mitsubishi Chemical Analytech was used to measure the resistivity and the surface resistance of the conductive layer.

( 2 ) Adhesion (cross cutting, cross hatch cut )

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

Table 7

As shown in Table 7, it can be seen that the transparent conductive film of the present invention not only has excellent metal adhesion, low surface resistance after metal deposition, but also has a good appearance, so it is suitable for narrow bezel displays.

100‧‧‧Transparent conductive film 10‧‧‧Conductive layer 20‧‧‧Transparent base film 30‧‧‧Metal layer

FIG. 1 is a cross-sectional view of a transparent conductive film for a flexible display provided by an embodiment of the present invention.

2 is a cross-sectional view of a thin film in which a metal layer is laminated on one surface of a transparent conductive film for a flexible display provided by an embodiment of the present invention.

100‧‧‧Transparent conductive film

10‧‧‧conductive layer

20‧‧‧Transparent base film

Claims (13)

A conductive coating liquid composition, which contains 35-50 wt% of poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT/PSS), 1~5wt% organic binder, 45~60wt% organic solvent, 0.5~1wt% silane coupling agent, 0.1~0.4wt% surfactant and 0.001~0.01wt% pH adjuster, among which The organic binder includes a polyurethane resin having a weight average molecular weight of 10,000 or even 20,000 g/mol, the organic solvent includes an alcohol-based organic solvent and an amide-based organic solvent, the alcohol-based organic solvent and the amide-based organic solvent The weight ratio of the solvent is 17 or even 25:1. The conductive coating liquid composition according to item 1 of the patent application range, wherein the organic binder contains one or more kinds selected from the group consisting of melamine resin, polyester resin, polyurethane resin, and polyacrylic resin. The conductive coating liquid composition according to item 1 of the patent application range, wherein the alcohol-based organic solvent is an alcohol having 1 to 4 carbon atoms. The conductive coating liquid composition as described in item 1 of the patent application range, wherein the amide-based organic solvent comprises a compound selected from the group consisting of acetamide, N-methylacetamide, N-dimethylacetamide and One or more types of N-methylpyrrolidone. The conductive coating liquid composition as described in item 1 of the patent application range, wherein the silane coupling agent comprises a group selected from the group consisting of trimethoxysilane, triethoxysilane, tetramethoxysilane and tetraethyl One or more of the group consisting of oxysilanes. The conductive coating liquid composition according to item 1 of the patent application range, wherein the surfactant is a silicon-based surfactant or a acetylene-based surfactant. The conductive coating liquid composition according to item 1 of the scope of the patent application, wherein the pH adjusting agent comprises a member selected from the group consisting of 2-dimethylaminoethanol, 2,2′-iminodiethanol (2 , 2'-iminodiethanol) and 2,2',2"-nitrilotriethanol (2,2',2"-nitrilotriethanol) more than one group. A transparent conductive film for flexible display, which includes a transparent base film and a conductive layer, the conductive layer is formed by the conductive coating liquid composition described in the patent application items 1 to 7, the conductive coating liquid The composition contains 35~50wt% poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT/PSS), 1~5wt% organic binder , 45~60wt% organic solvent, 0.5~1wt% silane coupling agent, 0.1~0.4wt% surfactant and 0.001~0.01wt% pH adjuster, wherein the organic binder contains weight average molecular weight Polyurethane resin of 10,000 or even 20,000g/mol, the organic solvent includes an alcohol-based organic solvent and an amide-based organic solvent, the weight ratio of the alcohol-based organic solvent and the amide-based organic solvent is 17 or even 25 :1. The transparent conductive film for flexible displays as described in item 8 of the patent application range, wherein the transparent base film contains polyethylene terephthalate (PET) or colorless transparent polyimide (PI), average thickness It is 12~200μm. The transparent conductive film for flexible displays as described in item 8 of the patent application range, wherein the average thickness of the conductive layer is 100 to 1000 nm. The transparent conductive film for flexible displays as described in item 8 of the patent application range, wherein the transparent conductive film is bent 300,000 times with a voltage of 5 V applied so that the bending radius (bending radius) reaches 3 mm, and then the following formula is used (1) The calculated surface resistance change is -5.0~5.0%:

The transparent conductive film for flexible displays as described in item 8 of the patent application range, wherein the surface resistance of the transparent conductive film is 100~200Ω/□, cut into 10cm×10cm×50μm (length× Width × thickness) measured haze is less than 1%. The transparent conductive film for flexible displays as described in item 8 of the patent application range, wherein the transparent conductive film has a visible light transmittance of 80% or more and a contact angle with water of 60 to 85°.

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