Coatings and processing of transparent conductive films for stabilization of sparse metal conductive layers
Transparent conductive films comprising sparse metal conductive layers are processed after coating with an overcoat to lower the sheet resistance of the film. The sparse metal conductive layer can comprise a fused metal nanostructured network. A coating, such as a polymer overcoat or a polymer undercoat can noble metal ions that can further reduce the sheet resistance with the application of heat and optionally humidity. In particular, silver ions in a coating are demonstrated to provide important stabilization of sparse metal conductive layers, whether or not fused, upon the application of heat and humidity. A coating can further comprise a metal salt stabilization composition.
1. A transparent conductive film comprising a transparent polymer substrate, a sparse metal conductive layer supported by the substrate, and a polymer overcoat adjacent the sparse metal conductive layer, wherein the transparent conductive film has a transmittance of visible light of at least about 88% and a sheet resistance of no more than about 120 ohm/sq and wherein the polymer overcoat comprise polymer and from about 0.01 wt % to about 20 wt % noble metal ions wherein the noble metal ions comprise ions of silver, gold, platinum, indium, osmium, ruthenium or rhodium.
2. The transparent conductive film of claim 1 wherein the overcoat has an average thickness from about 5 nm to about 250 nm.
3. The transparent conductive film of claim 1 wherein the polymer of the overcoat comprises comprises a polysiloxane, a polysilsesquioxane, a polyurethane, an acrylic resin, an acrylic copolymer, a cellulose ether and/or ester, nitrocellulose, other water insoluble structural polysaccharide, a polyether, a polyester, polystyrene, polyimide, fluoropolymer, a styrene-acrylate copolymer, a styrene-butadiene copolymer, an acrylonitrile butadiene styrene copolymer, polysulfide, an epoxy containing polymer, copolymers thereof, and mixtures thereof.
4. The transparent conductive film of claim 1 wherein the polymer overcoat comprises from about 0.1 wt % to about 9 wt % of a vanadium (+5) stabilization composition.
5. The transparent conductive film of claim 1 wherein the polymer overcoat has an average thickness from about 10 nm to about 125 nm, wherein the polymer of the overcoat comprises polyacrylate, and wherein the polymer overcoat further comprises from about 0.5 wt % to about 5 wt % of a vanadium (+5) stabilization composition that comprises ammonium metavanadate (NH 4 VO 3 ), tetrabutylammonium vanadate (NBu 4 VO 3 ), potassium metavanadate (KVO 3 ), sodium metavanadate (NaVO 3 ), sodium orthovanadate (Na 3 VO 4 ), vanadium oxytripropoxide, vanadium oxytriethoxide, vanadium oxytriisopropoxide, vanadium oxytributoxide, or mixtures thereof.
6. The transparent conductive film of claim 1 wherein the sparse metal conductive structure comprises a fused metal nanostructured network comprising silver and wherein the noble metal ions comprise silver ions.
7. The transparent conductive film of claim 1 wherein the transparent conductive film has a transmittance of at least about 90% and a sheet resistance of no more than about 90 ohm/sq.
8. The transparent conductive film of claim 1 wherein the polymer overcoat comprise from about 0.25 wt % to about 12 wt % silver ions that are provided as silver tetrafluoroborate (AgBF 4 ), silver hexafluorophosphate (AgPF 6 ), silver perchlorate (AgClO 4 ), silver hexafluoroantimonate (AgSbF 6 ), silver trifluoroacetate (AgCF 3 COO), silver heptafluorobutyrate (AgC 4 HF 6 O 2 ,) and silver methylsulfonate (AgCH 3 SO 3 ), silver tolylsulfonate (AgCH 3 C 6 H 4 SO 3 ), or mixtures thereof.
9. The transparent conductive film of claim 1 wherein the sparse metal conductive layer is patterned.