Method of processing elements with coalesced particles
View Patent ↗Imageable elements can be imaged and then processed using a solution containing core-shell particles that are designed to complex with non-coalesced particles in the non-exposed regions of imaged element. A separate development step is not needed, but the non-coalesced particles and complexed core-shell particles can be removed from the resulting printing plate before using the resulting lithographic printing plate for printing.
1. A method of providing an image comprising:
A) thermally imaging a negative-working imageable element that comprises a hydrophilic substrate and has thereon a thermally-sensitive imageable layer comprising an infrared radiation absorbing compound and polymeric particles that coalesce upon thermal exposure,
to provide an imaged element with exposed regions and non-exposed regions, the exposed regions comprising coalesced polymeric particles, and
B) contacting the imaged element with a processing solution having a pH greater than 7 to about 14 to remove polymeric particles in the non-exposed regions, the processing solution comprising water-swellable core-shell polymeric particles that are different from the polymeric particles in the imageable layer,
wherein the core of the water-swellable core-shell polymeric particles is composed of a hydrophobic thermoplastic polymer, and
the shell of the water-swellable core-shell polymeric particles is composed of a hydrophilic polymer that is covalently bonded to the core hydrophobic thermoplastic polymer.
2. The method of claim 1 further comprising rinsing and drying the imaged element prior to contacting it with the processing solution.
3. The method of claim 1 wherein the hydrophilic polymer comprises recurring units derived from (meth)acrylamides, (meth)acrylphosphonates, (meth)acrylphosphates, (meth)acrylsulfates, vinyl imidazoles, polyethyleneoxide (meth)acrylates, polypropylene oxide(meth)acrylates, polyethylene-co-propylene oxide(meth)acrylates, [3-(methacryloylamino)propyl]dimethyl(3-sulfopropyl)ammonium hydroxide inner salt, [2-methacryloyloxy]ethyl[dimethyl(3-sulfopropyl)ammonium hydroxide inner salt hydrate.
4. The method of claim 1 wherein the imageable layer comprises less than 10 weight % of free polymeric binder.
5. The method of claim 1 wherein the core hydrophobic thermoplastic polymer comprises at least one copolymer comprising repeating units derived from at least one styrene or styrene derivative, (meth)acrylate, methylenelactone, vinyl chloride, (meth)acrylonitriles, or vinyl ester, or a combination thereof.
6. The method of claim 1 wherein the water-swellable core-shell polymeric particles have an average particle size of from about 25 to about 150 nm.
7. The method of claim 1 wherein the shell of the water-swellable core-shell polymeric particles has an average thickness of from about 1 to about 10 nm and comprises from about 5 to about 25% of the volume of the water-swellable core-shell particles, on average, and the core has an average diameter of from about 20 to about 120 nm.
8. The method of claim 1 wherein the coalesced polymeric particles are also core-shell polymeric particles.
9. The method of claim 1 wherein the outer surface of the coalesced polymeric particles has a different composition than the shell of the water-swellable core-shell polymeric particles in the processing solution.
10. The method of claim 1 wherein the processing solution has a pH of from about 7 to about 12.
11. The method of claim 1 wherein the water-swellable core-shell particles are present in the processing solution in an amount of at least 1 and up to 75 weight %, based on total processing solution weight.
12. The method of claim 1 wherein the infrared radiation absorbing compound is present in the single thermally-sensitive imageable layer in an amount of from about 1 to about 30%, based on the total imageable layer dry weight.
13. The method of claim 1 wherein the imaging is carried out using an infrared laser at a wavelength of from about 700 to about 1250 nm.
14. The method of claim 1 wherein the imageable element is a lithographic printing plate precursor that has an aluminum-containing substrate having a hydrophilic surface.
15. The method of claim 1 wherein the imageable layer consists essentially of the coalesceable polymeric particles and the infrared radiation absorbing compound.
16. The method of claim 1 wherein the infrared radiation absorbing compound is present only in the imageable layer.
17. A method of providing an image comprising:
A) thermally imaging a negative-working imageable element that comprises a hydrophilic substrate and has thereon a thermally-sensitive imageable layer comprising an infrared radiation absorbing compound and polymeric particles that coalesce upon thermal exposure,
to provide an imaged element with exposed regions and non-exposed regions, the exposed regions comprising coalesced polymeric particles, and
B) contacting the imaged element with a processing solution having a pH greater than 7 to about 14 to remove polymeric particles in the non-exposed regions, the processing solution comprising water-swellable core-shell polymeric particles that are different from the polymeric particles in the imageable layer, where the core of the water-swellable core-shell polymeric particles is composed of a hydrophobic thermoplastic polymer, and
wherein the core hydrophobic thermoplastic polymer has a glass transition temperature greater than 40° C.
18. A method of providing an image comprising:
A) thermally imaging a negative-working imageable element that comprises a hydrophilic substrate and has thereon a thermally-sensitive imageable layer comprising an infrared radiation absorbing compound and polymeric particles that coalesce upon thermal exposure,
to provide an imaged element with exposed regions and non-exposed regions, the exposed regions comprising coalesced polymeric particles, and
B) contacting the imaged element with a processing solution having a pH greater than 7 to about 14 to remove polymeric particles in the non-exposed regions, the processing solution comprising water-swellable core-shell polymeric particles that are different from the polymeric particles in the imageable layer, the shell of the water-swellable core-shell polymeric particles is composed of a hydrophilic polymer, and
wherein during the contacting step, the hydrophilic polymer in the shell of the water-swellable core-shell polymeric particles forms a non-covalent or non-ionic complex with the polymer in the outer surface of non-coalesced particles in the non-exposed regions.