Lithographic imaging with printing members having metal imaging bilayers
View Patent ↗Printing members include very thin metal imaging bilayers that combine to trap and utilize imaging radiation and, due to their minimal thicknesses, ablate easily. The bilayer may include a first (bottommost) metal layer having a high extinction coefficient in the imaging wavelength range (e.g., 600-1200 nm) and, thereover, a second metal layer having a high transmittance and low emissivity for imaging radiation.
1. A printing member comprising:
a) a polymeric substrate;
b) disposed over the substrate, first and second radiation-responsive layers adjacent and in contact with each other and each having a thickness below an optical penetration depth thereof for near-IR radiation, wherein the first radiation-responsive layer consists essentially of a metal having a coefficient of extinction of at least 3 in a wavelength range of 600-1200 nm, and (ii) the second radiation-responsive layer consists essentially of a metal having a transmittance of at least 30% in a wavelength range of 600-1200 nm; and
c) a topmost layer disposed over the first and second radiation-responsive layers, the topmost layer and the substrate having opposite affinities for at least one of ink or a liquid to which ink will not adhere.
2. The printing member of claim 1 , wherein the second radiation-responsive layer overlies the first radiation-responsive layer.
3. The printing member of claim 1 , wherein the first and second radiation-responsive layers have melting points below 1100° C.
4. The printing member of claim 3 , wherein the second radiation-responsive layer has a melting point below 500° C.
5. The printing member of claim 1 , wherein the substrate scatters imaging radiation and the second radiation-responsive layer reflects imaging radiation.
6. The printing member of claim 1 , wherein the first radiation-responsive layer consists essentially of at least one of aluminum, copper, silver or gold.
7. The printing member of claim 1 , wherein the second radiation-responsive layer consists essentially of at least one of tin, zinc, indium or gallium.
8. The printing member of claim 1 , wherein the first radiation-responsive layer has a thickness ranging from 8 to 16 nm.
9. The printing member of claim 8 , wherein the first radiation-responsive layer has a thickness of 12 nm.
10. The printing member of claim 1 , wherein the second radiation-responsive layer has a thickness ranging from 4 to 8 nm.
11. The printing member of claim 1 , wherein the second radiation-responsive layer has a thickness of 5 nm.
12. The printing member of claim 1 , wherein the first and second radiation-responsive layers have a combined thickness ranging from 12 to 24 nm.
13. The printing member of claim 1 , wherein the substrate is oleophilic and the topmost layer is polymeric and oleophobic.
14. The printing member of claim 13 , wherein the substrate is polyester and the topmost layer is silicone.
15. The printing member of claim 1 , wherein the substrate is oleophilic and the topmost layer is polymeric and hydrophilic.
16. The printing member of claim 15 , wherein the substrate is polyester and the topmost layer is polyvinyl alcohol.