KR20150084690A - Metal nanowire, method for producing the same, and transparent conductive film including the same - Google Patents

Abstract

Disclosed are a metal nanowire capable of reducing diffused reflection, a method for producing the same, and a transparent conductive film, which is made of the metal nanowire and has excellent transparency and visibility. The metal nanowire is configured to be formed with a carbon coating film on the surface thereof. The method includes the steps of: coating the metal nanowire with a carbon precursor compound; and forming the carbon coating film on the surface of the metal nanowire by treating the metal nanowire, coated with the carbon precursor compound, with heat. The transparent conductive film includes the metal nanowire having the carbon coating film formed on the surface thereof.

Description

TECHNICAL FIELD The present invention relates to a metal nanowire, a method of manufacturing the same, and a transparent conductive film including the same

More particularly, the present invention relates to a metal nanowire capable of reducing irregular reflection of light, a method of manufacturing the same, and a transparent conductive film formed of the metal nanowire and having excellent transparency and visibility .

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 to a TV, 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 have also been developed. 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, or an ion plating method, and thus is widely used as a transparent 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 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 particularly excellent in conductivity and is known as the most practical conductive film forming material since silver (Ag) nanowires can be easily produced from a water system (see, for example, U.S. Patent Publication No. 2005/0056118 See also

However, in the case of metal nanowires, the light diffuses irregularly on the surface of the nanowire, and the haze value of the conductive film made of the nanowire increases, thereby lowering the visibility (transparency) of the conductive film. Therefore, a method for improving the visibility of the nanowire conductive film by suppressing irregular reflection occurring on the surface of the nanowire is being studied. For example, JP-A-2013-122053 discloses a method for adsorbing a colored compound (colored dye) on the surface of a metal nanowire to suppress irregular reflection of light generated on the surface of the metal nanowire, Patent Document 10-2013-0092857 discloses a method for reducing the pattern line width and improving the visibility of the nanowire conductive film by forming a transparent electrode fine pattern made of a metal wire while changing the laser power.

It is an object of the present invention to provide a metal nanowire with reduced diffuse reflection of light on the surface and a method of manufacturing the same.

Another object of the present invention is to provide a transparent conductive film having reduced haze due to irregular reflection of light and consequently having improved visibility.

In order to attain the above object, the present invention provides a metal nanowire, wherein a carbon coating film is formed on the surface. The present invention also provides a method of fabricating a semiconductor device, comprising: coating a metal nanowire with a carbon precursor compound; And heat treating the metal nanowires coated with the carbon precursor compound to form a carbon coating layer on the surface of the metal nanowires. The present invention also provides a transparent conductive film comprising a metal nanowire having a carbon coating film formed on its surface.

Since the metal nanowire according to the present invention suppresses irregular reflection of light on the surface, the transparent conductive film made of the metal nanowire reduces haze due to irregular reflection of light, resulting in improved visibility.

Hereinafter, the present invention will be described in detail.

[Metal nanowire]

The metal nanowire according to the present invention is characterized in that a carbon coating film is formed on the surface. In the present invention, the content of the carbon coating layer is 0.01 to 50 parts by weight, preferably 1 to 30 parts by weight, more preferably 5 to 20 parts by weight, based on 100 parts by weight of the metal nanowire. Here, the carbon coating film refers to a carbon film formed by carbonizing a carbon precursor compound (organic material). If the content of the carbon coating film is too small, the irregular reflection of light on the surface of the metal nanowire can not be sufficiently suppressed. If the content of the carbon coating film is too large, the electrical properties of the metal nanowire are lowered . Conventionally, a colored dye or the like is attached to a surface of a metal nanowire. In the present invention, a carbon coating film is partially or wholly formed on a surface of the metal nanowire so that the metal nanowire itself can partially or wholly have a color.

As the metal nanowires usable in the present invention, ordinary metal nanowires can be used without any particular limitation. The metal nanowires may be made of metal elements such as Ag, Au, Ni, Cu, Pd, Pt, Rh, Ir, Fe, Co and Sn. The shape of the metal nanowire is not particularly limited and may be appropriately selected according to the purpose. For example, the shape of the metal nanowire may be 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 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, specifically, 5 to 100 占 퐉. When the length of the metal nanowires is less than 1 m, there is a fear that the junctions of the metals are reduced when the transparent conductor is produced, thereby increasing the resistance. The average short axis length (diameter) of the metal nanowire is 1 to 200 nm, preferably 5 to 100 nm, more preferably 10 to 50 nm. If the diameter of the nanowire is too small, heat resistance of the nanowire may be deteriorated. If it is too large, haze due to scattering of the metal is increased, and the light transmittance and visibility of the transparent conductor containing the metal nanowire are deteriorated There is a concern.

[Manufacturing Method of Metal Nanowire]

The method for manufacturing a metal nanowire according to the present invention includes a step of coating a metal nanowire with a carbon precursor compound (organic material) and performing a heat treatment to form a carbon coating film on the surface of the metal nanowire. The coating of the carbon precursor compound may be carried out by adding a metal nanowire solution to a solution of a metal nanowire in a solution of sucrose, lactose, maltose, trehalose, turanose, cellobiose, raffinose, melezitose, Aldohexose, polyvinylalcohol, aldehydes, ketones, ketones, aldehydes, ketoglucose, ketoglutarate, ketoglutarate, ketoglutarate, tartrate, acarbose, stachyose, dihydroxyacetone, May be carried out by adding a carbon precursor compound such as polyvinylpyrrolidone or a mixture thereof, mixing them uniformly, removing the solvent if necessary, and attaching a carbon precursor compound to the surface of the metal nanowire . The solvent of the metal nanowire solution is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include water, propanol, acetone, and ethylene glycol. These may be used alone, or two or more kinds may be used in combination. The heat treatment of the carbon precursor compound may be performed at a temperature capable of carbonizing the carbon precursor compound and may vary depending on the kind of the carbon precursor compound used. Typical heat treatment temperature is 50 to 400 ° C, preferably 70 To 300 캜, and the heat treatment time is usually 30 seconds to 5 minutes. If the heat treatment temperature is too low, the organic precursor may not sufficiently carbonize. If the heat treatment temperature is too high, the Ag nanowire itself may be melted and the shape of the Ag nanowire may be changed. For this reason, when the carbonization proceeds at a too high temperature, the shape of the Ag nanowire may be deformed and the network of the Ag nanowire may be weakened, thereby deteriorating the overall conductivity.

[Transparent conductive film made of metal nanowire]

The transparent conductive film according to the present invention is characterized by including a metal nanowire having a carbon coating film formed on its surface. The transparent conductive film according to the present invention can be produced by applying a coating composition in which the metal nanowires are dispersed in a dispersion solvent to a substrate and drying the coating composition. If necessary, the coating composition may further include additives such as a dispersant, a binder, a surfactant, a wetting agent, a leveling agent, and the like. As the dispersion solvent of the coating composition, water, an organic solvent, and the like can be used without any particular limitation, but water is mainly used, and an organic solvent which is miscible with water is contained in an amount of 50 wt% Is preferably used in combination. 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, Heptane, dodecane and paraffin oil, aromatics such as benzene, toluene and xylene, and halogen-substituted solvents such as chloroform and methylene chloride, acetonitrile, dimethylsulfoxide and the like may be further mixed and used. As the binder, a polymer resin having excellent adhesion to a substrate such as cellulose acetate, polyvinyl chloride, polyurethane, polyester, alkyd resin, epoxy resin, peroxy resin, melamine resin and phenol resin can be used.

In the coating composition, the content of the metal nanowires 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 is too small, the load of the drying process becomes large when the conductive film is produced. If the content is too large, the nanowire particles may aggregate. The substrate on which the transparent conductive film is formed can be appropriately selected according to the purpose without particular limitation. For example, a polymer film such as a polyethylene terephthalate (PET) film, a triacetylcellulose (TAC) film, glass, have. As a method of applying the coating composition to a substrate, 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 printing, doctor blade and dispensing, inkjet printing, offset printing, screen printing, pad printing, gravure printing, flexography printing, stencil printing, imprinting, Method can 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 substrate, nanowire, etc., and can be generally carried out at a temperature of 80 to 200 ° C.

The thickness of the transparent conductive film according to the present invention may be appropriately set according to the line width and required resistance conditions 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 μm to be. The metal nanowire according to the present invention has a colored carbon coating film formed on its surface to efficiently absorb light and suppress haze due to irregular reflection of light and consequently to provide a transparent conductive film made of metal nanowires Can be improved.

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.

[Examples 1 to 3] Surface Coating of Metal Nanowires Using Surface Carbonization

(Ag NW) was coated with the components and the contents of the carbon precursor compound (organic material) shown in the following Table 1, and then heat treatment was performed using microwave at 300 to 500 W (about 120 to 350 ° C) Thus, the carbon precursor compound was carbonized to prepare a metal nanowire having a carbonized surface layer. The silver nanowires used were of an ideal elliptical structure with a length of about 35 μm and a diameter of about 25 nm.

Of the carbon precursor compound
Type and usage 1 wt% Ag NW
solution (g) Microwave
Power (W) Heat treatment
Time (min) Example 1 Polyvinylpyrrolidone, 1 mg 10 300 One Example 2 Polyvinylpyrrolidone, 1 mg 10 300 2 Example 3 Polyvinylpyrrolidone, 1 mg 10 500 One

[Examples 4 to 6, Comparative Example 1] Formation of a transparent conductive film using metal nanowires and evaluation of optical properties

1 g of the silver nanowire having the carbonized surface layer prepared in Examples 1 to 3 was dispersed in 8 g of ethanol and then coated on a substrate and dried to form a conductive film having a thickness of about 10 탆 (Example 4 To 6). In addition, a conductive film was formed in the same manner using silver nanowires having no carbonized surface layer (Comparative Example 1). Sheet resistance, transmittance (T.Trans), and turbidity (Haze) were evaluated as optical characteristics of the formed transparent conductive film, and the results are shown in Table 2 below.

Microwave
Treatment condition Sheet resistance
(Ω / □) Haze (%) T.Trans (%) Comparative Example 1 - 130.60 1.04 91.92 Example 4 300 W, 1 min 89.42 0.76 91.99 Example 5 300 W, 2 min 89.32 0.75 92.1 Example 6 500 W, 1 min 137.2 0.80 92.26

As shown in Table 2, the conductive films (Examples 4 to 6) formed of silver nanowires having a carbonized surface layer were superior to the conductive films (Comparative Example 1) formed of silver nanowires having no carbonized surface layer , Sheet resistance and permeability were equal or more, and haze was excellent. On the other hand, when the heat treatment condition was 300 W (150-200 ° C), not only the turbidity but also the sheet resistance were also excellent.

Claims (6)

And a carbon coating film is formed on the surface of the metal nanowire. The metal nanowire according to claim 1, wherein the content of the carbon coating layer is 0.01 to 50 parts by weight based on 100 parts by weight of the metal nanowire. Coating the metal nanowire with a carbon precursor compound; And
And forming a carbon coating layer on the surface of the metal nanowire by heat treating the metal nanowire coated with the carbon precursor compound. The method of claim 3, wherein the carbon precursor compound is selected from the group consisting of sucrose, lactose, maltose, trehalose, turanose, cellobiose, raffinose, melechetose, maltotriose, acarbose, stachyose, dihydroxyacetone, Wherein the metal nanowire is selected from the group consisting of ketotetraose, ketopentose, aldopentose, deoxy sugar, ketohexose, aldohexose, polyvinyl alcohol, polyvinylpyrrolidone, ≪ / RTI > 4. The method according to claim 3, wherein the carbon precursor compound has a heat treatment temperature of 70 to 300 占 폚. And a metal nanowire having a carbon coating film formed on its surface.