Thin flexible structures with surfaces with transparent conductive films and processes for forming the structures
Structures are described having thin flexible polymer substrates with electrically conductive films on each opposing surface while having high optical transmittance and good optical properties. The structures can have total thicknesses of no more than about 30 microns and good flexibility. Processing approaches are described that allow for the coating of the very thin structures by providing support through the coating process. The structures are demonstrated to have good durability under conditions designed to test accelerated wear for touch sensor use.
1. A double sided conductive structure comprising:
a transparent polymer substrate comprising a polymer and having a first surface and a second surface, wherein the polymer substrate has an average thickness of no more than about 27 microns and the polymer in a configuration of the transparent polymer substrate has a transmittance from 400 nm to 750 nm of at least about 88% and over the UV spectrum from 330 nm to 375 nm of no more than about 15%;
a first sparse metal conductive layer supported on the first surface of the transparent polymer substrate;
a second sparse metal conductive layer supported on the second surface of the transparent polymer substrate; and
first and second polymer overcoats over the first and second sparse metal conductive layers, respectively, wherein each of the first and second polymer overcoats has an average thickness from about 10 nm to about 200 nm;
wherein each surface of the double sided conductive structure has a sheet resistance of no more than about 120 Ohms/sq.
2. The double sided conductive structure of claim 1 further comprising a first hardcoat layer and a second hardcoat layer, each having an average thickness of from about 50 nm to about 3 microns, wherein the first hardcoat layer is between the first surface of the transparent polymer substrate and the first sparse metal conductive layer, wherein the second hardcoat layer is between the second surface of the transparent polymer substrate and the second sparse metal conductive layer, and wherein both hardcoat layers comprise a crosslinked polyacrylate polymer.
3. The double sided conductive structure of claim 2 wherein each hardcoat layer has a thickness from about 100 nm to about 2.5 microns and comprises a highly crosslinked polyacrylate.
4. The double sided conductive structure of claim 1 wherein the double sided conductive structure can be assembled into a test structure with an optically clear adhesive and a 125 micron thick PET film over each surface and subjected to accelerated wear testing at 85° C. and 85% relative humidity for 500 hours with an increase in sheet resistance of no more than about 20%.
5. The double sided conductive structure of claim 1 wherein the transparent polymer substrate comprises polyimide.
6. The double sided conductive structure of claim 1 wherein the polymer substrate has an elongation of at least about 10%, a tensile strength of at least about 50 MPa, and a Young's modulus from about 1.5 GPa to about 7.0 GPa.
7. The double sided conductive structure of claim 1 wherein the transparent polymer substrate comprises polysulfide, polysulfone, polyethylene naphthalate or polyethersulfone.
8. The double sided conductive structure of claim 1 wherein each of the first and second sparse metal conductive layers comprises a fused metal nanostructured network and wherein the double sided conductive structure can be bent around a 1 mm diameter mandrel repeatedly for at least 200,000 times with the sheet resistance of the conductive surfaces changing by no more than 10%.
9. The double sided conductive structure of claim 8 wherein each surface of the double sided conductive structure has a sheet resistance of no more than about 100 Ohms/sq.
10. The double sided conductive structure of claim 9 having a transmittance of visible light of at least about 88%, a haze of no more than about 2.5% and a value of b* of no more than about 4.0.
11. The double sided conductive structure of claim 1 having an average thickness of no more than about 30 microns,
a % TT of at least 89%, a haze of no more than 2.5%, and a b* of no more than about 3.5, and each surface of the double sided conductive structure has a sheet resistance of no more than 100 Ohms/sq,
wherein the double sided conductive structure can be assembled into a test structure with an optically clear adhesive (3M, 8146) and a 125 micron thick PET film over each surface and subjected to accelerated wear testing at 85° C. and 85% relative humidity for 500 hours with an increase in sheet resistance of no more than about 40%.
12. The double sided conductive structure of claim 11 further comprising a first hardcoat layer and a second hardcoat layer, each having an average thickness of from about 50 nm to about 3 microns, wherein the first hardcoat layer is between the first surface of the transparent polymer substrate and the first sparse metal conductive layer, wherein the second hardcoat layer is between the second surface of the transparent polymer substrate and the second sparse metal conductive layer, and wherein both hardcoat layers comprise a crosslinked polyacrylate polymer.
13. The double sided conductive structure of claim 12 wherein each hardcoat layer has a thickness from about 100 nm to about 2.5 microns and comprises a highly crosslinked polyacrylate.
14. The double sided conductive structure of claim 11 wherein the double sided conductive structure can be assembled into a test structure with an optically clear adhesive and a 125 micron thick PET film over each surface and subjected to accelerated wear testing at 85° C. and 85% relative humidity for 500 hours with an increase in sheet resistance of no more than about 20%.
15. The double sided conductive structure of claim 11 wherein the transparent polymer substrate comprises polyimide.
16. The double sided conductive structure of claim 11 wherein the polymer substrate has an elongation of at least about 10%, a tensile strength of at least about 50 MPa, and a Young's modulus from about 1.5 GPa to about 7.0 GPa.
17. The double sided conductive structure of claim 11 wherein the transparent polymer substrate comprises polysulfide, polysulfone, polyethylene naphthalate, or polyethersulfone.
18. The double sided conductive structure of claim 11 wherein each of the first and second sparse metal conductive layers comprises a fused metal nanostructured network and wherein the double sided conductive structure can be bent around a 1 mm diameter mandrel repeatedly for at least 200,000 times with the sheet resistance of the conductive surfaces changing by no more than 10%.
19. The double sided conductive structure of claim 11 wherein each surface of the double sided conductive structure has a sheet resistance of no more than about 75 ohm/sq.
20. The double sided conductive structure of claim 1 having an average thickness of no more than about 30 microns.
21. The double sided conductive structure of claim 1 wherein the first and/or second sparse metal conductive layers are patterned.
22. The double sided conductive structure of claim 1 wherein the first and/or second sparse metal conductive layers are independently patternable with UV light.