Lithographic imaging and printing without defects of electrostatic origin

Abstract

Embodiments of the present invention involve three-layer printing members having a central layer that is non-conductive yet abalatable at commercially realistic fluence levels. In various embodiments, the central layer is polymeric with a dispersion of nonconductive carbon black particles therein at a loading level sufficient to provide at least partial layer ablatability and water compatibility of the resulting ablation debris.

1 . A lithographic printing member comprising:
 (a) a first layer presenting a hydrophilic or oleophobic lithographic affinity;   (b) a second layer comprising a polymeric matrix and, dispersed therein, nonconductive carbon black particles at a loading level sufficient to provide at least partial layer ablatability and water compatibility following ablation; and   (c) a third layer presenting an oleophilic lithographic affinity, the second layer being disposed between the first and third layers.   
     
     
         2 . The member of  claim 1  wherein ablation debris of the second layer is removable by contact with an aqueous liquid. 
     
     
         3 . The member of  claim 1  wherein the loading level is sufficient to confer at least partial ablatability at a fluence of 400 mJ/cm 2  or less. 
     
     
         4 . The member of  claim 1  wherein the loading level is sufficient to confer at least partial ablatability at a fluence of 300 mJ/cm 2  or less. 
     
     
         5 . The member of  claim 1  wherein the third layer is a polyester substrate. 
     
     
         6 . The member of  claim 1  wherein the third layer is polyester and further comprising a metal sheet to which the third layer is attached. 
     
     
         7 . The member of  claim 1  wherein the third layer is a metal sheet. 
     
     
         8 . The member of  claim 1  wherein the first layer comprises or consists essentially of silicone. 
     
     
         9 . The member of  claim 1  wherein the first layer comprises or consists essentially of polyvinyl alcohol. 
     
     
         10 . The member of  claim 1  wherein the loading level is at least 25 wt %. 
     
     
         11 . The member of  claim 1  wherein the loading level is at least 35 wt %. 
     
     
         12 . The member of  claim 1  wherein the loading level is at least 40 wt %. 
     
     
         13 . The member of  claim 1  wherein the second layer has a dry coating weight of at least 0.2 g/m 2 . 
     
     
         14 . The member of  claim 1  wherein the second layer has a dry coating weight of at least 0.8 g/m 2 . 
     
     
         15 . A method of forming an imageable lithographic printing member, the method comprising the steps of:
 (a) applying, to an ink-receptive layer, an imaging layer comprising a polymeric matrix and, dispersed therein, nonconductive carbon black particles at a loading level sufficient to provide at least partial layer ablatability and water compatibility of ablation debris;   (b) drying the imaging layer;   (c) applying, to the dried imaging layer, a topmost coating which, when dried, presents a hydrophilic or oleophobic lithographic affinity; and   (d) drying the topmost coating.   
     
     
         16 . A method of imaging a lithographic printing member, the method comprising the steps of:
 (a) providing a lithographic printing member comprising (i) a first layer presenting a hydrophilic or oleophobic lithographic affinity, (ii) a second layer comprising a polymeric matrix and, dispersed therein, nonconductive carbon black particles at a loading level sufficient to provide at least partial layer ablatability, and (iii) a third layer presenting an oleophilic lithographic affinity, the second layer being disposed between the first and third layers;   (b) exposing the printing member to imaging radiation in an imagewise pattern so as to at least partially ablate the second layer where exposed and thereby de-anchor the first layer; and   (c) subjecting the printing member to an aqueous liquid to remove imaged portions of the imaging layer, thereby creating an imagewise lithographic pattern on the printing member.   
     
     
         17 . The method of  claim 16  wherein the aqueous liquid consists essentially of water. 
     
     
         18 . The method of  claim 17  wherein the aqueous liquid is plain tap water. 
     
     
         19 . The method of  claim 16  wherein the aqueous liquid comprises water and not more than 20% by weight of an organic solvent. 
     
     
         20 . The method of  claim 19  wherein the aqueous liquid comprises not more than 15% by weight of an organic solvent. 
     
     
         21 . The method of  claim 19  wherein the solvent is an alcohol. 
     
     
         22 . The method of  claim 21  wherein the alcohol is a glycol. 
     
     
         23 . The method of  claim 21  wherein the alcohol is at least one of propylene glycol, benzyl alcohol or phenoxyethanol. 
     
     
         24 . The method of  claim 16  wherein the aqueous liquid comprises a surfactant. 
     
     
         25 . The method of  claim 16  wherein the aqueous liquid is heated to a temperature greater than about 80° F. 
     
     
         26 . A method of lithographic printing, the method comprising the steps of:
 (a) providing a lithographic printing member comprising (i) a first layer presenting an oleophobic lithographic affinity, (ii) a second layer comprising a polymeric matrix and, dispersed therein, nonconductive carbon black particles at a loading level sufficient to provide at least partial layer ablatability, and (iii) a third layer presenting an oleophilic lithographic affinity, the second layer being disposed between the first and third layers;   (b) exposing the printing member to imaging radiation in an imagewise pattern so as to at least partially ablate the second layer where exposed and thereby de-anchor the first layer;   (c) subjecting the printing member to an aqueous liquid to remove imaged portions of the imaging layer, thereby creating an imagewise lithographic pattern on the printing member;   (d) following the removal step, applying ink to the printing member, the ink adhering only to imaged portions of the printing member; and   (e) transferring the applied ink from the printing member to a recording medium, wherein the applying and transferring step occur without deleterious buildup of triboelectric charge.