Method for manufacturing silver nanowires using ionic liquid

Abstract

The present invention relates to a method of preparing silver nanowires having a diameter of less than 100 nm and a length of 10 μm or more, and, more particularly, to a method of uniformly preparing silver nanowires having a high aspect ratio using an ionic liquid as an additive in addition to a silver salt precursor, a reducing solvent and a capping agent in a polyol process. When the technology of the present invention is used, silver nanowires having a diameter of less than 100 nm and a length of 10 μm or more can be uniformly prepared. Further, when a transparent conductive film is formed by applying a silver nanowire-dispersed solution onto a base film, the transparent conductive film has a surface resistivity of 10 1 ˜10 3 Ω/□ and a light transmittance of 90% or more to the base film.

1 . A method of preparing silver nanowires by a polyol reduction reaction of a mixed solution including a silver salt precursor, a reducing solvent and a capping agent,
 wherein the polyol reduction reaction of the mixed solution is performed by adding an ionic liquid to the mixed solution as an additive,   wherein the ionic liquid is a compound comprising an organic cation having an imidazolium group and an organic or inorganic anion, the compound being represented by Formula 1 below in the form of a monomer or being represented by Formula 2 below in the form of a polymer:   
       
         
           
           
               
               
           
         
         where R1, R2 and R3 are identical to or different from each other, each of which is hydrogen or a hydrocarbon group of 1 to 16 carbon atoms, and each of which includes at least one heteroatom selected from the group consisting of oxygen, sulfur, nitrogen, phosphorus, fluorine, chlorine, bromine, iodine and silicon; X— is an anion, and is an organic or inorganic compound including a halogen ion such as a chlorine ion (Cl − ) or a bromine ion (Br − ); and n is a repetitive unit, and is a natural number. 
       
     
     
         2 . (canceled) 
     
     
         3 . The method of  claim 1 , wherein, in the ionic liquid, the monomeric cationic compound is selected from the group consisting of 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-octyl-3-methylimidazolium, 1-decyl-3-methylimidazolium, 1-dodecyl-3-methylimidazolium and 1-tetradecyl-3-imidazolium, and the polymeric cationic compound is selected from the group consisting of poly(1-vinyl-3-alkylimidazolium), poly(1-allyl-3-alkylimidazolium) and poly(1-(meth)acryloyloxy-3-alkylimidazolium). 
     
     
         4 . The method of  claim 3 , wherein, in a mixing ratio of a silver salt precursor, a capping agent and an ionic liquid, the capping agent is included in an amount of 1 to 2 mol based on 1 mol of the silver salt precursor, and the ionic liquid is included in an amount of 0.001 to 0.2 mol based on 1 mol of the silver salt precursor. 
     
     
         5 . The method of  claim 4 , wherein a reaction temperature for synthesizing silver nanowires is 50˜180° C. 
     
     
         6 . The method of  claim 5  wherein the silver salt precursor includes a silver cation and an organic or inorganic anion, and includes at least one selected from the group consisting of AgNO 3 , AgClO 4 , AgBF 4 , AgPF 6 , CH 3 COOAg, AgCF 3 SO 3 , Ag 2 SO 4 , CH 3 COCH═COCH 3 Ag. 
     
     
         7 . The method of  claim 1 , wherein the reducing solvent is a solvent including diol, polyol or glycol having two or more hydroxy groups in a molecule thereof. 
     
     
         8 . The method of  claim 5 , wherein the capping agent is polyvinylpyrrolidone (PVP) or polyvinylalcohol (PVA). 
     
     
         9 . (canceled) 
     
     
         10 . A silver nanowire-dispersed solution prepared by dispersing 0.1˜5 wt % of the silver nanowires having an aspect ratio of 100 or more, prepared by the method of  claim 1  in 95˜99.9 wt % of a solvent. 
     
     
         11 . The silver nanowire-dispersed solution of  claim 10 , wherein the solvent includes at least one selected from the group consisting of water, methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, iso-butanol, hexanol, benzyl alcohol, diacetone alcohol, ethyleneglycol, propyleneglycol, glycerol, 1,4-dioxane, tetrahydrofuran (THF), ethyleneglycol monomethyl ether, ethylenglycol monoethyl ether, ethyleneglycol dimethyl ether, propyleneglycol monomethyl ether, propyleneglycol monoethyl ether, propyleneglycol dimethyl ether, N,N-dimethylformamide, N-methylformamide, N,N-dimethylacetamide (DMA), acetonitrile, acetaldehyde, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethylsulfoxide, n-butyrolactone, nitromethane, and ethyl lactate. 
     
     
         12 . The silver nanowire-dispersed solution of  claim 11 , further comprising 0.01 to 10 parts by weight of a dispersant and 0.01 to 10 parts by weight of a thickener based on 100 parts by weight of the silver nanowire-dispersed solution. 
     
     
         13 . The silver nanowire-dispersed solution of  claim 12 , wherein the dispersant includes at least one selected from the group consisting of polyoxyethylene aliphatic ether, polyoxyethylene phenyl ether, polyimine, alkyl phosphate, an alkylammonium salt, a polyester alkylolammonium salt, a polyacrylic alkylolammonium salt, polydimethylsilane, polyacrylic acid, polysulfonic acid and polyvinylpyrrolidone, and the thickener includes at least one selected from the group consisting of a urethane-modified thickener, an acrylic thickener, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose. 
     
     
         14 . A transparent conductive film formed by applying the silver nanowire-dispersed solution including the silver nanowires prepared by the method of  claim 1  onto a base film. 
     
     
         15 . The transparent conductive film of  claim 14 , wherein the transparent conductive film has a surface resistivity of 10 1 ˜10Ω/□ and a light transmittance of 90% or more to the base film. 
     
     
         16 . The method of  claim 3 , wherein the reducing solvent is a solvent including diol, polyol or glycol having two or more hydroxy groups in a molecule thereof. 
     
     
         17 . The method of  claim 4 , wherein the reducing solvent is a solvent including diol, polyol or glycol having two or more hydroxy groups in a molecule thereof. 
     
     
         18 . The method of  claim 5 , wherein the reducing solvent is a solvent including diol, polyol or glycol having two or more hydroxy groups in a molecule thereof. 
     
     
         19 . The method of  claim 6 , wherein the reducing solvent is a solvent including diol, polyol or glycol having two or more hydroxy groups in a molecule thereof. 
     
     
         20 . A silver nanowire-dispersed solution prepared by dispersing 0.1˜5 wt % of the silver nanowires having an aspect ratio of 100 or more, prepared by the method of  claim 7  in 95˜99.9 wt % of a solvent. 
     
     
         21 . The silver nanowire-dispersed solution of  claim 20 , further comprising 0.01 to 10 parts by weight of a dispersant and 0.01 to 10 parts by weight of a thickener based on 100 parts by weight of the silver nanowire-dispersed solution. 
     
     
         22 . The silver nanowire-dispersed solution of  claim 21 , wherein the dispersant includes at least one selected from the group consisting of polyoxyethylene aliphatic ether, polyoxyethylene phenyl ether, polyimine, alkyl phosphate, an alkylammonium salt, a polyester alkylolammonium salt, a polyacrylic alkylolammonium salt, polydimethylsilane, polyacrylic acid, polysulfonic acid and polyvinylpyrrolidone, and the thickener includes at least one selected from the group consisting of a urethane-modified thickener, an acrylic thickener, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose.