Preparation of articles with conductive micro-wire pattern
Conductive articles and devices have conductive micro-wires formed by curing a photocurable layer on a transparent flexible substrate that has a distortion temperature of less than 150° C. The photocurable layer has a viscosity <5,000 Pascal-seconds at the temperature micro-channels formation and the micro-channels having an average width of less than or equal to 4 μm and an average depth to average width ratio that is greater than or equal to 1. The photocurable layer is exposed to curing ultraviolet radiation to form a pattern of photocured micro-channels and a conductive composition comprising metal nano-particles is formed in the photocured micro-channels. The conductive composition is cured in the pattern of photocured micro-channels to provide a pattern of conductive micro-wires in the pattern of photocured micro-channels on the transparent flexible substrate. Each of at least 50% of the conductive micro-wires has a sheet resistance of less than 0.025 ohms/sq.
1. A method for making a micro-wire pattern in an article, the method comprising:
providing a photocurable layer on a transparent flexible substrate that has a distortion temperature of less than 150° C.,
forming a pattern of micro-channels within the photocurable layer that has a viscosity of less than 5,000 Pascal-seconds at the temperature at which the micro-channels are formed, the micro-channels having an average width of less than or equal to 4 μm and an average depth to average width ratio that is greater than or equal to 1,
exposing the photocurable layer to curing ultraviolet radiation to form a pattern of photocured micro-channels within a photocured layer on the transparent flexible substrate, the photocured micro-channels having an average width of less than or equal to 4 μm and an average depth to average width ratio that is greater than or equal to 1,
applying a conductive composition comprising metal nano-particles to the photocured micro-channels,
removing any excess conductive composition outside the photocured micro-channels while leaving conductive composition within the pattern of photocured micro-channels,
curing the conductive composition in the pattern of photocured micro-channels to provide a pattern of conductive micro-wires in the pattern of photocured micro-channels on the transparent flexible substrate, and
optionally, polishing the pattern of conductive micro-wires on the transparent flexible substrate,
wherein each of at least 50% of the conductive micro-wires has a sheet resistance of less than 0.025 ohms/sq.
2. The method of claim 1 , comprising:
forming a pattern of micro-channels within the photocurable layer so that the average depth to average width ratio of the micro-channels is greater than 1 and up to and including 3, and
exposing the photocurable layer to curing ultraviolet radiation to form a pattern of photocured micro-channels having an average width of less than or equal to 3 μm and an average depth to average width ratio that is greater than 1 and up to and including 3.
3. The method of claim 1 , comprising forming the pattern of micro-channels at a temperature less than or equal to 130° C.
4. The method of claim 1 , comprising curing the conductive composition at a temperature greater than or equal to 90° C.
5. The method of claim 1 , comprising removing any excess conductive composition using mechanical means.
6. The method of claim 1 , wherein the photocurable layer comprises a crosslinkable material.
7. The method of claim 1 , wherein the conductive composition comprises silver nano-particles.
8. The method of claim 1 , wherein the conductive micro-wires independently have an average width of at least 0.5 μm and up to and including 4 μm.
9. The method of claim 1 , wherein the photocurable layer comprises a compound that generates an acid upon exposure to radiation of at least 190 nm and up to and including 500 nm, a multifunctional epoxy compound having an epoxy equivalent molecular weight of less than 1,000, and an epoxysilane oligomer that is represented by the following Structure (I):
wherein R and R 1 are independently substituted or unsubstituted alkyl groups, R 2 is a substituted or unsubstituted linear, branched, or cyclic alkyl group or an alkyl ether residue substituted with an epoxide, R 3 is hydrogen or a substituted or unsubstituted alkyl, and x+y≧2.
10. A conductive article prepared according to the method of claim 1 , the article comprising a transparent flexible substrate and a pattern of conductive micro-wires disposed thereon, which conductive micro-wires have an average width of less than or equal to 4 μm and an average depth to average width ratio greater than 1, and each of at least 50% of the conductive micro-wires has a sheet resistance of less than 0.025 ohm/sq.
11. The conductive article of claim 10 that exhibits a haze of less than 10% and a light transmission of at least 80%.
12. The conductive article of claim 10 that exhibits a haze of less than 5% and a light transmission of at least 85%.
13. The conductive article of claim 10 , wherein the pattern of conductive micro-wires comprises conductive silver, palladium, platinum, copper, nickel, or indium tin-oxide.
14. The conductive article of claim 10 , wherein the pattern of conductive micro-wires comprises at least silver, the average width of the micro-wires is at least 0.5 μm and less than or equal to 4 μm and the average depth to average width ratio is greater than 0.5 and up to and including 3.