Transparent conductive coatings based on metal nanowires and polymer binders, solution processing thereof, and patterning approaches
Polymer binders, e.g., crosslinked polymer binders, have been found to be an effective film component in creating high quality transparent electrically conductive coatings or films comprising metal nanostructured networks. The metal nanowire films can be effectively patterned and the patterning can be performed with a high degree of optical similarity between the distinct patterned regions. Metal nanostructured networks are formed through the fusing of the metal nanowires to form conductive networks. Methods for patterning include, for example, using crosslinking radiation to pattern crosslinking of the polymer binder. The application of a fusing solution to the patterned film can result in low resistance areas and electrically resistive areas. After fusing, the network can provide desirable low sheet resistances while maintaining good optical transparency and low haze. A polymer overcoat can further stabilize conductive films and provide desirable optical effects. The patterned films can be useful in devices, such as touch sensors.
1. A coated substrate comprising a substrate with a conductive coating over at least a portion of the substrate comprising a fused nanostructured metal network and a crosslinked polymer binder and having a sheet resistance of no more than about 270 ohms/square, an optical transmittance through the conductive coating of greater than about 90% and a haze of no more than about 1%, wherein the fused nanostructured metal network comprises nanowire segments fused into the network with an average diameter of no more than about 40 nm.
2. The coated substrate of claim 1 wherein the polymer binder comprises a polyurethane, acrylic resin, acrylic copolymer, cellulose or mixture thereof.
3. The coated substrate of claim 1 wherein the nanostructured metal network comprises silver and has a loading on the surface from about 0.5 mg/m 2 to about 200 mg/m 2 .
4. The coated substrate of claim 1 wherein the coating has a sheet resistance of no more than about 150 ohm/sq.
5. The coated substrate of claim 1 wherein the coating has a sheet resistance of no more than about 95 ohm/sq.
6. The coated substrate of claim 1 wherein the coating has an optical transmittance of greater than about 94% and a haze of no more than about 0.9%.
7. A conductive film processing system comprising a metal nanowire ink and a fusing solution, wherein
the metal nanowire ink comprises a first solvent, from about 0.01 weight percent (wt %) to about 2 wt % metal nanowires, from about 0.02 wt % to about 5 wt % crosslinkable organic polymer and from about 0.05 wt % to about 2 wt % processing additive wherein the metal nanowires have an average diameter of no more than about 40 nm, and
the fusing solution comprises a second solvent and a fusing agent selected from the group consisting of a halide anion, or a reducing agent combined with a metal ion source, or a combination thereof.
8. The conductive film processing system of claim 7 wherein the processing additive comprises a wetting agent, a polymer dispersant, a thickener or a mixture thereof.
9. The conductive film processing system of claim 7 wherein the processing additive comprises a thickener.
10. The conductive film processing system of claim 7 wherein the crosslinkable organic polymer comprises a polyurethane, acrylic resin, acrylic copolymer, cellulose or mixture thereof.
11. The conductive film processing system of claim 7 wherein the metal nanowire ink further comprises from about 0.0005 wt % to about 1 wt % crosslinking agent.
12. The conductive film processing system of claim 7 wherein the first solvent is an aqueous solvent.
13. The conductive film processing system of claim 7 wherein the fusing agent comprises a reducing agent.
14. The conductive film processing system of claim 7 wherein the metal nanowire ink comprises from about 0.05 wt % to about 1 wt % metal nanowires, from about 0.05 wt % to about 2 wt % crosslinkable organic polymer and from about 0.1 wt % to about 1.5 wt % processing additive.
15. The conductive film processing system of claim 7 wherein the second solvent comprises alcohol.
16. The conductive film processing system of claim 12 wherein the aqueous solvent comprises an organic solvent.