KR20150084689A - Transparent conductive electrode and method for producing the same - Google Patents

Abstract

Disclosed are a transparent conductive electrode containing metal nanowires and capable of improving reliability by suppressing the migration of metal ions, and a method for manufacturing the same. The transparent conductive electrode comprises: a transparent conductive electrode layer formed on a substrate, and including metal nanowires; and an over coating layer which coats the upper part of the transparent conductive electrode layer to suppress the migration of metal ions. The over coating layer comprises a material selected from the group consisting of (1) an acrylate polymer, (2) an epoxy resin, and (3) a siloxane polymer.

Description

[0001] Transparent conductive electrode and method for producing same [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent conductive electrode and a method of manufacturing the same. More particularly, the present invention relates to a transparent conductive electrode comprising metal nanowires, wherein migration of metal ions is suppressed, And a manufacturing method thereof.

2. Description of the Related Art In recent years, various types of display devices such as a liquid crystal display (LCD), a plasma display panel (PDP), and an organic electroluminescent device (OELD) In such flat panel display devices, a transparent electrode using a transparent conductive film is necessarily used. In addition, a transparent conductive film must be essentially used for various electronic devices such as a touch panel, a cellular phone, and an electronic paper. As such a transparent conductive film, various metal thin films such as Au, Ag, Pt, and Cu, indium oxide (ITO, IZO) doped with tin or zinc, metal oxides such as zinc oxide (AZO, GZO) doped with aluminum or gallium Thin films and the like are mainly used. In addition to these inorganic thin films, organic thin films made of conductive polymers are also used. Of these, indium tin oxide (ITO) is excellent in both light transmittance and conductivity and can be easily formed into a thin film by a vacuum deposition method, a sputtering method, an ion plating method, etc., and is widely used as a transparent conductive electrode in various electronic apparatuses . However, most of these ITO film forming methods require expensive equipment and a large amount of energy, and the formed ITO thin film is heavy and inflexible.

Recently, a method of forming a transparent conductive film composed of metal nanowires by coating a substrate with a dispersion of a metal nanowire (NW) and drying the substrate has been researched. In such a nanowire transparent conductive film, since conductivity is exhibited by an electrical network of nanowires having a very small size, both conductivity and transparency are excellent, and there is no need to heat the transparent conductive film at a high temperature. A transparent conductive film may be formed on the resin substrate. Particularly, silver (Ag) is excellent in conductivity and it is known as the most practical conductive film forming material since silver (Ag) nanowire can be easily produced in an aqueous system (see, for example, U.S. Patent Publication No. 2005/0056118 Reference). However, in the case of a transparent conductive film made of a silver (Ag) nanowire, when a voltage is applied for a long time, part of the silver (Ag) nanowire migrates in the conductive film due to ionization of the (Ag) Lt; / RTI > When the Ag + ions migrate and grow on the surface of the insulating part contacting the transparent conductive film and / or the conductive film, the shape of the conductive film and / or the insulating part changes and the resistance value changes or short- There is a problem that stability and durability of the conductive film deteriorate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a transparent conductive electrode which suppresses migration of metal ions and improves reliability in a transparent conductive electrode comprising metal nanowires and a method for producing the same.

It is another object of the present invention to provide a transparent conductive electrode capable of preventing deterioration of electrical characteristics such as a short due to deformation of an electrode and an insulating portion, and a manufacturing method thereof.

According to an aspect of the present invention, there is provided a light emitting device comprising: a transparent conductive electrode layer formed on a substrate and including metal nanowires; And an overcoat layer coated on top of the transparent conductive electrode layer to inhibit movement of metal ions, wherein the overcoat layer comprises (1) an acrylate polymer, (2) an epoxy resin and (3) a siloxane polymer And a transparent conductive electrode.

According to another aspect of the present invention, there is provided a method of fabricating a transparent conductive electrode, comprising: forming a transparent conductive electrode layer by applying a coating composition in which metal nanowires are dispersed in a dispersion solvent; And forming the overcoat layer on the transparent conductive electrode layer.

INDUSTRIAL APPLICABILITY The transparent conductive electrode and the method of manufacturing the same according to the present invention can prevent the migration of metal ions, improve the reliability of the electrode, and prevent deterioration of electrical characteristics due to deformation of the electrode and the insulating portion.

1 is a cross-sectional view illustrating a structure of a transparent conductive electrode according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view illustrating a structure of a transparent conductive electrode according to an embodiment of the present invention. 1, a transparent conductive electrode according to a first embodiment of the present invention includes a transparent conductive electrode layer 20 formed on a substrate 10 and including a metal nanowire 22, And an over coating layer 30 coated on top of the transparent conductive electrode layer 20 to suppress movement of metal ions.

The transparent conductive electrode layer 20 includes a metal nanowire 22 as a transparent conductive material and a transparent binder 24 for improving the adhesion between the metal nanowire 22 and the substrate 10, , and a binder. As is well known, the transparent conductive electrode layer 20 may have the form of a layer having a predetermined thickness, and may be patterned in a predetermined electrode form, if necessary. As the metal nanowires 22, ordinary metal nanowires can be used without any particular limitation (see, for example, JP-A-2009-127092 and JP-A-2013-122053). The metal nanowires 22 may be composed of metal elements such as Ag, Au, Ni, Cu, Pd, Pt, Rh, Ir, Fe, Co and Sn. The shape of the metal nanowires 22 is not particularly limited and may be appropriately selected according to the purpose. For example, the metal nanowires 22 may have any shape such as a columnar shape, a rectangular parallelepiped shape, and a columnar shape having a polygonal cross section. The long axis average length of the metal nanowires 22 is 1 占 퐉 or more, preferably 5 占 퐉 or more, more preferably 10 占 퐉 or more, for example, 1 to 1000 占 퐉. If the length of the metal nanowires 22 is less than 1 탆, the junction of the metals may be reduced and the resistance may increase when the transparent conductive electrode layer 20 is formed. In addition, the short axis average length (diameter) of the metal nanowires 22 may be 1 to 200 nm, preferably 5 to 100 nm. If the diameter of the nanowire 22 is too small, the heat resistance of the nanowire 22 may deteriorate. If the diameter is too large, the haze due to scattering of the metal increases, The light transmittance and visibility of the electrode layer 20 may be lowered.

As the transparent binder 24, a usual transparent polymer resin which is excellent in adhesion to the substrate 10 and the metal nanowires 22 and capable of uniformly dispersing the metal nanowires 22 can be used without any particular limitation . Specific examples of the transparent binder 24 include thermoplastic resins such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polymethyl methacrylate, nitrocellulose, chlorinated polyethylene or polypropylene, vinylidene fluoride, melamine acrylate, Heat, light, electron beam, or radiation curable resin such as urethane acrylate, epoxy resin, urethane resin, polyimide resin, and acrylic modified silicate may be used. In the transparent conductive electrode layer 20, the content of the transparent binder 24 is 0 to 80% by weight, preferably 5 to 50% by weight, more preferably 10 to 30% by weight. If the content of the transparent binder 24 is too large, the conductivity of the transparent conductive electrode layer 20 may deteriorate. If the content of the transparent binder 24 is too small, the adhesion between the substrate 10 and the metal nanowires 22 may decrease . The thickness of the transparent conductive electrode layer 20 may be appropriately set according to the line width and required resistance of the electrode to be implemented and is preferably 5.0 μm or less, more preferably 1.0 μm or less, for example, 0.05 to 0.5 Mu m. The substrate on which the transparent conductive electrode layer 20 is formed may be appropriately selected in accordance with the purpose without particular limitation and includes, for example, a polymer film such as a polyethylene terephthalate (PET) film, a triacetylcellulose (TAC) film, May be used.

The overcoat layer 30 is formed on the upper part of the transparent conductive electrode layer 20 in order to suppress migration of metal ions, particularly Ag + ions, moving through moisture or the like and improve the reliability of the transparent conductive electrode. . The overcoat layer 30 is preferably formed of a barrier polymer having a low water vapor transmission rate (WVTR), and specifically includes (1) an acrylate polymer, (2) an epoxy resin Or (3) a siloxane polymer. Examples of the acrylate polymer (1) include methyl methacrylate, methyl acrylate, ethyl acrylate, 2-chloroethyl vinyl ether, 2-ethylhexyl acrylate, A polymerization product of a conventional photocurable or thermosetting acrylate monomer such as hydroxyethyl methacrylate, butyl acrylate and butyl methacrylate can be used. Examples of the epoxy resin (2) include bisphenol A type epoxy resin, Novolac epoxy resin, and aliphatic epoxy resin, which are used alone or in combination . Examples of the siloxane polymer (3) include tetraethyloxysilane (TEOS), vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (? -Methoxyethoxy) silane,? -Methacryloxypropyltrimethoxysilane A polymerization product of a conventional polymerizable silane-based monomer such as trimethylsilane, trimethylsilane, trimethylsilane, trimethylsilane, trimethylsilane, trimethylsilane, trimethylsilane, trimethylsilane, The thickness of the overcoat layer 30 is 10 nm to 100 mu m, preferably 1 to 50 mu m, more preferably 5 to 20 mu m.

The overcoat layer 30, particularly the overcoat layer 30 formed of a siloxane polymer, preferably further comprises a chelating agent 40 capable of binding metal ions. The chelating agent 40 dispersed in the overcoat layer 30 binds to a metal ion, particularly Ag + ions, and inhibits the migration of metal ions, thereby improving the reliability of the transparent conductive electrode layer 20 have. The chelating agent is _{NH 3, H 2 NR-NH} 2 , such as an amine compound, RS ^- containing phosphorus (P) or sulfur (S), such _{as, R 2 S, S 2 O} 3 2-, PR 3 -, S 2 An ionic compound such as a compound (R: an alkyl group having a carbon number of 1 to 10), an unsaturated alkene such as C ₂ H ₄ , H ^- , I ^- , CN ^- , or CO may be used alone or in combination. Compound, phosphorus (P) or sulfur (S) -containing compound, and more preferably an amine compound. In the overcoat layer 30, the content of the chelating agent 40 is 0.1 to 20% by weight, preferably 1 to 15% by weight, more preferably 4 to 11% by weight. If the content of the chelating agent (40) is too small, the migration of the metal ions can not be sufficiently suppressed. If the content of the chelating agent (40) is too large, there is a fear that the physical properties of the overcoat layer have.

Next, a method of manufacturing a transparent conductive electrode according to the present invention will be described.

In order to manufacture the transparent conductive electrode according to the first embodiment of the present invention, a coating composition in which the metal nanowires 22 are dispersed in a dispersion solvent is first applied to a substrate 10 and dried to form a transparent conductive electrode layer 20 ). If necessary, the coating composition may further include additives such as a transparent binder 24, a dispersant, a surfactant, a wetting agent, and a leveling agent. As a dispersion solvent for the coating composition, water, an organic solvent, and other solvents capable of dispersing the metal nanowires 22 can be used without any particular limitation. However, water is used and an organic solvent which is miscible with water is used in an amount of 50 wt% By weight or less. Examples of the organic solvent include alcohols such as methanol, ethanol, isopropanol and butanol, glycols such as ethylene glycol and glycerin, acetates such as ethyl acetate, butyl acetate, methoxypropyl acetate and carbitol acetate, Ethers such as methyl cellosolve, butyl cellosolve, diethyl ether, tetrahydrofuran and dioxane, ketones such as methyl ethyl ketone, acetone, dimethyl formamide and 1-methyl-2-pyrrolidone, Aromatic solvents such as benzene, toluene and xylene, halogen substitution solvents such as chloroform and methylene chloride, acetonitrile, dimethylsulfoxide and the like may be used in excess or mixed with each other. In the coating composition, the content of the metal nanowires 22 is not particularly limited, but is 0.1 to 99% by weight, preferably 1 to 95% by weight, more preferably 5 to 50% by weight. If the content of the metal nanowires 22 is too small, the load of the drying process becomes large when the transparent conductive electrode layer 20 is formed. If the content is too large, the nanowires 22 may aggregate. As a method of applying the coating composition to the substrate 10, a conventional film forming method can be used, and examples thereof include a spin coating method, a roll coating method, a spray coating method, a dip coating method, Flow coating, doctor blade and dispensing, inkjet printing, offset printing, screen printing, pad printing, gravure printing, flexography printing, stencil printing, imprinting, (imprinting) method may be used. The drying temperature of the coating composition can be freely selected so long as it does not affect the properties of the object such as the substrate 10, the nanowire 22, and the like, and can be generally performed at a temperature of 80 to 200 ° C. At this time, the coating composition dried in the form of a film having a predetermined thickness is coated on the substrate 10 in the form of an electrode in the form of a predetermined electrode by coating (coating) Patterning can be performed.

After the transparent conductive electrode layer 20 is formed as described above, an overcoat layer 30 is formed on the transparent conductive electrode layer 20. The overcoat layer 30 may be formed by a known ordinary film forming method. For example, when the overcoat layer 30 is made of a photo-curable polymer, the photo-curable monomer is coated on the transparent conductive electrode layer 20 and light such as ultraviolet (UV) is applied to the overcoat layer 30 ) Can be formed. At this time, when the chelating agent 40 is included in the material forming the overcoat layer 30, the overcoat layer 30 including the chelating agent 40 is formed. The material forming the overcoat layer 30 may be a binder such as hydroxypropylcellulose (HPC), a surface-smoothing agent such as polyvinylpyrrolidone, or the like, in addition to the monomer forming the above (1) acrylate polymer, (2) Leveling agents, defoaming agents, and the like.

Hereinafter, the present invention will be described in more detail with reference to specific examples. The following examples illustrate the present invention and are not intended to limit the scope of the present invention.

[Production Examples 1 to 5 and Comparative Examples] Preparation of composition for forming a siloxane polymer overcoat layer

A composition for forming a siloxane polymer overcoat layer containing a chelating agent was prepared according to the ingredients and content shown in Table 1 below. In the following Table 1, TEOS represents a tetraethyloxysilane (TEOS) monomer, EtOH represents an ethanol solvent, and HPC represents a hydroxypropylcellulose binder.

Chelating agents and
Content (% by weight) TEOS
(weight%) EtOH
(weight%) HPC
(weight%) Comparative Example - 60 30 10 Production Example 1 NH ₃ , 1 wt% 60 29 10 Production Example 2 NH ₃ , 5 wt% 60 25 10 Production Example 3 NH ₃ 10 wt% 60 20 10 Production Example 4 H ₂ N (CH ₂ ) ₂ NH ₂ , 1 wt% 60 29 10 Production Example 5 H ₂ N (CH ₂ ) ₂ NH ₂ , 5 wt% 60 25 10

[Production Examples 6 to 8] Preparation of composition for forming an epoxy polymer overcoat layer

Based on the components and contents shown in Table 2 below, a composition for forming an epoxy polymer overcoat layer was prepared.

Bisphenol A type epoxy resin (%) Novolac
Epoxy
resin (%) Aliphatic epoxy
resin (%) Thermal Initiator
(%) Leveling
agent (%) Defoaming
agent (%) Production Example 6 39.3 30 30 0.1 0.1 0.5 Production Example 7 30 39.3 30 0.1 0.1 0.5 Production Example 8 30 30 39.3 0.1 0.1 0.5

[Examples 1 to 8 and Comparative Examples] Formation of transparent conductive film and evaluation of optical properties

1 g of the nanowire was dispersed in 8 g of ethanol, applied to a substrate, and dried to form a conductive film having a thickness of about 10 mu m. Next, the overcoat layer forming composition of Comparative Examples and Preparation Examples 1 to 8 was applied to the top of the formed conductive film and polymerized to form an overcoat layer having a total thickness of 15 占 퐉. Transmittance (Transmittance: Trans), haze, and resistance value change (85/85 Test) were evaluated in order to confirm the optical characteristics and reliability of the transparent conductive film having the overcoat layer formed thereon. Table 3 shows the results. In the following Table 3, when the resistance value change (85/85 Test) is maintained at 85% humidity and 85 ° C temperature for 1000 hours, if the resistance value change is kept within 10% of the initial value, , &Quot; O "is indicated when it is maintained within 20%, and" X "

Sheet resistance (Ω / □) HAZE (%) Trans (%) 85/85 TEST Comparative Example 1 130.60 1.07 91.82 X Example 1 110.07 0.92 91.70 ○ Example 2 101.74 0.95 91.36 ◎ Example 3 105.19 0.91 90.71 ◎ Example 4 120.10 0.98 91.66 ◎ Example 5 800.15 0.90 91.75 ◎ Example 6 102.46 0.92 91.85 ◎ Example 7 110.13 0.89 91.99 ◎ Example 8 105.87 0.84 92.01 ○

As shown in Table 3, when the siloxane polymer overcoat layer containing the chelating agent was formed, the NH ₃ content was 5 to 10 wt% and the H ₂ N (CH ₂ ) ₂ NH ₂ content was 1 to 5 wt% Example 2 ~ 5) showed better results than the resistance change test. In the case of the epoxy polymer overcoat layer, the resistance value change characteristics in Examples 6 and 7 were better. From Table 3, it can be seen that the siloxane polymer overcoat layer containing the chelating agent and the epoxy polymer overcoat layer have the effect of improving the optical characteristics and reliability of the transparent conductive film.

Claims (4)

A transparent conductive electrode layer formed on the substrate and including a metal nanowire; And
And an overcoat layer coated on the transparent conductive electrode layer to suppress movement of metal ions,
Wherein the overcoat layer is made of a material selected from the group consisting of (1) an acrylate polymer, (2) an epoxy resin, and (3) a siloxane polymer. The transparent conductive electrode according to claim 1, wherein the overcoat layer further comprises a chelating agent capable of binding to a metal ion. The transparent conductive electrode according to claim 2, wherein the chelating agent is selected from the group consisting of amine compounds and phosphorus (P) or sulfur (S) containing compounds. Applying a coating composition in which metal nanowires are dispersed in a dispersion solvent to a substrate and drying the coating composition to form a transparent conductive electrode layer; And
And forming an overcoat layer on the transparent conductive electrode layer, the overcoat layer suppressing migration of metal ions,
Wherein the overcoat layer is made of a material selected from the group consisting of (1) an acrylate polymer, (2) an epoxy resin, and (3) a siloxane polymer.

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