Printing members having permeability-transition layers and related methods
View Patent ↗Permeability transitions rather than ablation mechanisms facilitate selective removal of the imaging layer of a lithographic plate, which allows for imaging with low-power lasers that need not impart ablation-inducing energy levels.
1. A lithographic imaging member comprising:
(a) an insoluble first layer that undergoes, in response to heat, a transition from an impermeable state to an insoluble thermally rearranged state exhibiting enhanced permeability;
(b) an insoluble second layer, disposed below the first layer, that undergoes, in response to heat, a transition to a soluble state; and
(c) a substrate beneath the second layer,
wherein the first layer and at least one of the second layer and the substrate have opposite affinities for at least one of ink and a liquid to which ink will not adhere.
2. The member of claim 1 wherein the thermally rearranged state is permeable to a solvent.
3. The member of claim 1 wherein the impermeable state is crystalline.
4. The member of claim 1 wherein the permeable state is amorphous.
5. The member of claim 1 wherein the insoluble state is crystalline.
6. The member of claim 1 wherein the soluble state is amorphous.
7. The member of claim 1 wherein the first layer comprises a material that absorbs imaging radiation and transfers heat to the second layer.
8. The member of claim 7 wherein the first layer is polymeric and the material comprises an IR-absorbing pigment dispersed therein.
9. The member of claim 7 wherein the first layer is polymeric and the material comprises an IR-absorbing dye dispersed therein.
10. The member of claim 1 wherein the second layer comprises a material that . absorbs imaging radiation.
11. The member of claim 10 wherein the second layer is polymeric and the material comprises an IR-absorbing pigment dispersed therein.
12. The member of claim 10 wherein the second layer is polymeric and the material comprises an IR-absorbing dye dispersed therein.
13. The member of claim 1 wherein the first and second layers each comprise a material that absorbs imaging radiation.
14. The member of claim 1 wherein the first layer comprises polyoxyalkylene polyols.
15. The member of claim 1 wherein the first layer and the substrate have opposite affinities for at least one of ink and a liquid to which ink will not adhere.
16. The member of claim 15 wherein the first layer and the second layer have opposite affinities for at least one of ink and a liquid to which ink will not adhere.
17. The member of claim 15 wherein the first layer and the second layer have the same affinity for at least one of ink and a liquid to which ink will not adhere.
18. The member of claim 1 wherein the first layer and the substrate have the same affinity for at least one of ink and a liquid to which ink will not adhere.
19. The member of claim 18 wherein the first layer and the second layer have opposite affinities for at least one of ink and a liquid to which ink will not adhere.
20. The member of claim 1 wherein substantially all of the first layer exposed to the imaging radiation undergoes the transition.
21. The member of claim 1 wherein the substrate comprises a metal.
22. The member of claim 1 wherein the substrate comprises a polymer.
23. The member of claim 1 further comprising a third layer between the second layer and the substrate, the third layer being soluble and having an affinity opposite to that of the first layer for at least one of ink and a liquid to which ink will not adhere.
24. The member of claim 23 wherein the third layer comprises a material that absorbs imaging radiation.
25. The member of claim 23 wherein the third layer and the substrate have the same affinity for at least one of ink and a liquid to which ink will not adhere.
26. The member of claim 1 further comprising a top layer disposed above the first layer, the top layer being permeable to a solvent and having the same affinity as the first layer for at least one of ink and a liquid to which ink will not adhere.
27. The member of claim 26 wherein the top layer comprises a material that absorbs imaging radiation.
28. The member of claim 1 further comprising a substrate modifier disposed above the substrate, the substrate modifier imparting the substrate affinity for at least one of ink and a liquid to which ink will not adhere.