Developer regenerators
View Patent ↗The present invention provides an aqueous regenerator for addition to an aqueous developer that contains an organic solvent, a dispersing agent and a weak base, and has a pH of between about 8 and less than about 13. The aqueous regenerator includes an organic solvent, dispersing agent, and an effective amount of a strong base such that the regenerator has a greater pH than the developer into which the regenerator is to be added.
1. A method for treating an aqueous developer after developing at least a portion of one printing plate precursor, the aqueous developer comprising an organic solvent, a dispersing agent and a weak base, and having a pH between about 8 and less than about 13, the method comprising:
adding to the aqueous developer an effective amount of an aqueous regenerator to maintain the activity of the aqueous developer, the aqueous regenerator comprising an organic solvent, a dispersing agent, and an effective amount of at least one strong base such that the regenerator has a greater pH than the developer, wherein the K b of the strong base is greater than the K b of the weak base,
wherein the aqueous regenerator has a pH at least 0.7 higher than the pH of the aqueous developer, and
said printing plate precursor comprises a radiation-sensitive composition applied to a substrate, said radiation-sensitive composition comprising a plurality of layers including a first layer that is soluble in aqueous developer, and a second layer applied to said first layer, the second layer comprising a polymeric material that is not soluble in the aqueous developer.
2. The method of claim 1 comprising adding an effective amount of the aqueous regenerator to maintain the pH or conductivity of the aqueous developer.
3. The method of claim 1 wherein the adding step comprises maintaining the pH of the aqueous developer at between about 8 and about 12.
4. The method of claim 1 wherein the adding step comprises maintaining the pH of the aqueous developer at between about 9.5 and about 10.5.
5. The method of claim 1 comprising adding an effective amount of the aqueous regenerator to maintain the organic solvent concentration of the aqueous developer.
6. The method of claim 1 wherein the adding step comprises maintaining the organic solvent concentration of the aqueous developer at between about 2 and about 8 weight percent.
7. The method of claim 1 comprising adding an effective amount of the aqueous regenerator to maintain the dispersing agent concentration of the aqueous developer at between about 7 and about 15 weight percent dispersing agent.
8. The method of claim 1 comprising adding an effective amount of a replenisher and the aqueous regenerator to maintain the activity of the aqueous developer.
9. The method of claim 1 wherein the weak base has a K b of between about 1×10 −2 to about 1×10 −5 and the strong base has a K b of about 1 or greater.
10. The method of claim 1 wherein the aqueous regenerator has a pH at least 1.0 higher than the pH of the aqueous developer.
11. The method of claim 1 wherein the organic solvent in the aqueous regenerator comprises an alcohol.
12. The method of claim 1 wherein the weak base comprises an amine, sodium carbonate, potassium carbonate, sodium bicarbonate, trisodium phosphate, tripotassium phosphate, or a combination thereof and the strong base comprises a hydroxide.
13. The method of claim 1 further comprising:
after the aqueous regenerator is added to the aqueous developer, contacting a portion of at least one additional imaged printing plate precursor with the aqueous developer.
14. The method of claim 1 wherein the radiation-sensitive composition is laser imageable.
15. The method of claim 14 wherein the radiation-sensitive composition comprises an infrared absorbing compound.
16. The method of claim 1 wherein the radiation-sensitive composition comprises a polymeric material that comprises an acidic or weakly basic functionality.
17. The method of claim 1 comprising:
repeating the developing of a least a portion of a printing plate precursor with the aqueous developer and adding the aqueous regenerator to the aqueous developer, a plurality of times.
18. The method of claim 1 wherein prior to the developing step,
imagewise exposing a plurality of printing plate precursors to radiation using stochastic screening to form a plurality of imaged printing plate precursors, wherein the stochastic screening comprises first or second order stochastic screening, or combined screening that includes both stochastic screening and conventional screening.