Imaging members with ionic multifunctional epoxy compounds
View Patent ↗An imaging member, such as a negative-working printing plate or on-press cylinder, can be prepared using a hydrophilic imaging layer comprising a hydrophilic heat-sensitive polymer containing a crosslinking agent comprising ionic groups and epoxy groups. This polymer may comprise quaternary ammonium carboxylate groups which may include at least one substituted-alkylene(C 1 -C 3 )-phenyl group. The imaging member also includes an infrared radiation sensitive material to provide added sensitivity to heat that can be supplied by laser irradiation in the IR region. The heat-sensitive polymer may be “switchable” in response to heat, and provides a lithographic image without wet processing.
1. A coating composition comprising:
(a) a hydrophilic polymer;
(b) a crosslinking agent comprising one or more ionic groups and a plurality of epoxy groups; and
(c) a photothermal conversion material.
2. The coating composition of claim 1 , wherein the one or more ionic groups of the crosslinking agent are cationic groups.
3. The coating composition of claim 2 , wherein the cationic groups are the same or different organophosphonium moieties, the same or different organosulfonium moieties, the same or different organoammonium moieties, or the same or different N-alkylated positively charged nitrogen-containing heterocyclic moieties.
4. The coating composition of claim 1 , wherein the one or more ionic groups of the crosslinking agent are anionic groups.
5. The coating composition of claim 4 , wherein the anionic groups are the same or different sulfonate or thiosulfate groups.
6. The coating composition of claim 1 , wherein the plurality of epoxy groups and the one or more ionic groups of the crosslinking agent are in a ratio ranging from about 19:1 to about 1:19.
7. The coating composition of claim 1 , wherein the hydrophilic polymer comprises thiosulfate groups.
8. The coating composition of claim 1 , wherein the hydrophilic polymer comprises carboxylate groups and a backbone, wherein the carboxylate groups are linked either directly or indirectly to the polymer backbone.
9. The coating composition of claim 1 , wherein the hydrophilic polymer comprises quaternary ammonium carboxylate groups and a backbone, wherein the carboxylate groups are linked either directly or indirectly to the polymer backbone, and the quaternary ammonium groups comprise at least one substituted alkylene(C 1 -C 3 )-phenyl group.
10. The coating composition of claim 9 , wherein the hydrophilic polymer comprises at least 1 mole of quaternary ammonium carboxylate groups per 1000 g of polymer.
11. The coating composition of claim 1 , wherein the hydrophilic polymer is represented by Structure 1 below wherein “A” represents recurring units derived from ethylenically unsaturated polymerizable monomers, R 1 , R 2 and R 3 are independently alkyl or aryl groups, or any two or all three of R 1 , R 2 and R 3 can be combined to form one or two heterocyclic rings with the quaternary nitrogen atom, R 4 is a substituted alkylenephenyl group in which the alkylene portion has 1 to 3 carbon atoms, and B represents non-carboxylated recurring units, m is 0 to about 75 mol %, n is from about 25 to 100 mol %, and y is 0 or 1.
12. The coating composition of claim 1 wherein the photothermal conversion material is a carbon black.
13. The coating composition of claim 12 , wherein the carbon black is a polymer-grafted carbon black, an anionic surface-functionalized carbon black, or a polymer-grafted, anionic surface-functionalized carbon black.