Ablation-type lithographic imaging with silicone acrylate layers
View Patent ↗In ablation-type printing plates involving silicone acrylate top layers, curing at high oxygen levels not only substantially reduces or eliminates toning, but does not adversely affect plate durability or printing performance.
1. A method of printing comprising:
a. providing a printing member fabricated according to steps comprising (i) providing a precursor structure having an oleophilic surface; (ii) coating a silicone acrylate over the precursor, the silicone acrylate not including a trivalent phosphite additive; and (iii) following step (a)(ii), curing the silicone acrylate by electron-beam exposure at an ambient oxygen level of at least 100 ppm;
b. following the curing step, selectively exposing, in a pattern representing an image, the printing member to imaging radiation so as to remove or render removable selected portions of the silicone acrylate layer;
c. cleaning the printing member to remove the silicone acrylate layer where the printing member has been exposed to imaging radiation, thereby directly producing an array of oleophilic image features separated by remaining portions of the silicone acrylate layer; and
d. repeatedly (i) applying ink to the printing member, and (ii) transferring the ink to a recording medium,
wherein the ink is transferred, substantially without toning, only from the oleophilic image features and not from portions of the printing member therebetween.
2. The method of claim 1 , wherein the ambient oxygen level is at least 200 ppm.
3. The method of claim 1 , wherein the electron-beam exposure delivers a dose of at more than 2 MRad.
4. The method of claim 1 , wherein the electron-beam exposure delivers a dose of at least 7 MRad.
5. The method of claim 1 , wherein the electron-beam exposure delivers a dose of at least 14 MRad.
6. The method of claim 1 , wherein the precursor comprises an ablation-resistant, oleophilic substrate and an ablatable imaging layer thereover.
7. The method of claim 1 , wherein the silicone acrylate consists of an acrylate-modified polydimethylsiloxane polymer.