Metal nanowire ink and method for forming conductive film
Fusing nanowire inks are described that can also comprise a hydrophilic polymer binder, such as a cellulose based binder. The fusing nanowire inks can be deposited onto a substrate surface and dried to drive the fusing process. Transparent conductive films can be formed with desirable properties.
1. A method for forming a conductive film, the method comprising:
depositing a fusing metal nanowire ink onto a substrate surface, wherein the metal nanowire ink comprises from about 0.001 wt % to about 4 wt % metal nanowires, from about 0.05 wt % to about 5 wt % hydrophilic polymer binder, and from about 0.00025 wt % to about 0.5 wt % metal ions;
drying the metal nanowire ink to form fused metal nanowires in the form of a fused metal nanostructured network, which is transparent; and
applying a polymer overcoat on the fused metal nanostructured network to form the conductive film having a sheet resistance no more than about 250 ohms/sq.
2. The method of claim 1 wherein the metal nanowires comprise silver nanowires and the metal ions comprise silver ions, and wherein the depositing is performed to cover all or a portion of the substrate surface at a metal loading at covered locations from about 0.1 mg/m 2 to about 300 mg/m 2 .
3. The method of claim 1 wherein the hydrophilic polymer binder comprises a polymeric polyol.
4. The method of claim 1 wherein the hydrophilic polymer binder comprises a polysaccharide.
5. The method of claim 1 wherein the hydrophilic polymer binder comprises a cellulose based polymer or chitosan based polymer.
6. The method of claim 1 wherein the metal nanowires comprise silver nanowires, and wherein the metal nanowire ink comprises from about 0.1 wt % to about 2 wt % polysaccharide polymer binder, and from about 0.001 to about 0.2 wt % metal ions selected from the groups consisting of silver, gold, platinum, palladium, zinc, nickel and combinations thereof.
7. The method of claim 1 wherein the metal nanowire ink further comprises from about 5 wt % to about 60 wt % liquid alcohol.
8. The method of claim 1 wherein the drying is performed by heating to a temperature from about 50° C. to about 150° C. for no more than about 2 hours.
9. The method of claim 1 wherein the drying is performed by heating to a temperature from about 65° C. to about 135° C. for about 30 seconds to about 20 minutes.
10. The method of claim 1 wherein the metal nanowire ink further comprises a curable polymer binder and the method further comprising curing the binder.
11. The method of claim 1 wherein the conductive film has a sheet resistance of no more than about 100 ohms/sq.
12. The method of claim 1 wherein the conductive film has a transparency of at least about 90%.
13. The method of claim 1 wherein the conductive film has a sheet resistance of no more than about 140 ohms/sq, a % TT of at least about 95% and a haze of no more than about 1.2%, wherein the metal nanostructured network comprises silver.
14. The method of claim 1 wherein the dried film is washed with alcohol.
15. The method of claim 1 , wherein the conductive film is transparent.
16. A metal nanowire ink comprising an aqueous blend of from about 0.001 wt % to about 4 wt % metal nanowires, from about 0.0001 to about 0.5 wt % metal ions, and from about 0.05 wt % to about 5 wt % polymeric polyol binder comprising functional groups.
17. The metal nanowire ink of claim 16 wherein the polymeric polyol binder comprises a polysaccharide.
18. The metal nanowire ink of claim 16 wherein the polymeric polyol binder comprises a cellulose based polymer or chitosan based polymer.
19. The metal nanowire ink of claim 16 comprising from about 0.01 wt % to about 2 wt % of the metal nanowires, the metal nanowires comprising silver nanowires, from about 0.1 wt % to about 2 wt % of the polymeric polyol binder, the polymeric polyol binder comprising a polysaccharide, and from about 0.001 to about 0.2 wt % of the metal ions, the metal ions comprising silver ions.
20. The metal nanowire ink of claim 16 comprising from about 0.01 wt % to about 2 wt % of the metal nanowires, from about 0.1 wt % to about 2 wt % of the polymeric polyol binder, the polymeric polyol binder comprising a polysaccharide, and from about 0.001 wt % to about 0.2 wt % of the metal ions, the metal ions selected from the group consisting of silver, gold, platinum, palladium, zinc, nickel and combinations thereof.
21. The metal nanowire ink of claim 16 having a pH from about 5.5 to about 7.5 pH units.
22. The metal nanowire ink of claim 16 wherein no visible settling can be observed after one hour of sitting without stirring.
23. The metal nanowire ink of claim 16 further comprising anions selected from the group consisting of nitrates, sulfates, perchlorates, acetates, fluorides, chlorides, bromides, and iodides.