Ablatable elements for making flexographic printing plates
Flexographic printing plates and other relief images can be formed from a laser-ablatable element having a laser-ablatable layer that is from about 300 to about 4,000 μm in thickness. The laser-ablatable layer includes a film-forming material that is a laser-laser-ablatable material or the film-forming material has dispersed therein a laser-ablatable material. The laser-ablatable material is a polymeric material that when heated to 300° C. at a rate of 10° C./minute, loses at least 60% of its mass to form at least one predominant low molecular weight product. The laser-ablatable material also comprises at least 0.01 weight % of a depolymerization catalyst that is a Lewis acid or organometallic based catalyst. The element can be imaged by ablation at an energy of at least 1 J/cm 2 to provide a relief image.
1. A method of making a flexographic printing plate comprising:
A) providing a flexographic printing precursor having a laser-ablatable layer having a thickness of from about 300 to about 4000 μm and comprising a film-forming material,
wherein the film-forming material is a laser-ablatable material or the film-forming material has dispersed therein a laser-ablatable material,
the laser-ablatable material being a polymeric material that when heated to 300° C. at a rate of 10° C./minute, loses at least 60% of its mass to form at least one predominant low molecular weight product, and
the laser-ablatable layer comprises at least 0.01 weight % of a depolymerization catalyst that is a zinc-containing organometallic based catalyst comprising a zinc center and two organic ligands, and
B) imagewise directly ablating the laser-ablatable layer with a laser at an energy of at least 1 J/cm 2 to provide a relief image having a depth of at least 100 μm.
2. The method of claim 1 wherein the laser-ablatable material is a poly(cyanoacrylate) that forms a cyanoacrylate as the predominant low molecular weight product, or a polycarbonate or polycarbonate block copolymer that forms a cyclic alkylene carbonate as the predominant low molecular weight product.
3. The method of claim 1 wherein the laser imaging is at a wavelength of from about 800 to about 1100 nm using an infrared laser at an energy of from about 20 to about 1000 J/cm 2 .
4. The method of claim 1 wherein the relief image has a depth of from about 300 to about 600 μm.
5. The method of claim 1 wherein the laser-ablatable, relief image-forming layer comprises a film-forming material, an IR-radiation absorbing material, and inactive microvoided particulate materials or inert microvoided microspheres.
6. The method of claim 1 wherein the depolymerization catalyst is one of the compounds shown in the following TABLE:
(BDIEt)ZnOAc
(BDIiPr)ZnOAc
7. The method of claim 1 wherein the laser-ablatable material is a polycarbonate or polycarbonate block copolymer that forms a cyclic alkylene carbonate as the predominant low molecular weight product.
8. The method of claim 1 wherein the laser-ablatable layer further comprises a carbon black or an infrared radiation absorbing dye.
9. The method of claim 1 wherein the film-forming material is the laser-ablatable material and represents at least 10 weight % of the laser-ablatable layer.
10. The method of claim 1 wherein the film-forming material is the laser-ablatable material and the laser-ablatable layer further comprises inactive particulate materials or microcapsules.
11. The method of claim 1 wherein the film-forming material comprises a laser-ablatable material dispersed within the film-forming material.
12. The method of claim 11 wherein the laser-ablatable layer further comprises inactive particulate materials or microcapsules dispersed therein.
13. The method of claim 1 wherein the film-forming material is a first laser-ablatable material and has dispersed therein a second laser-ablatable material.
14. The method of claim 1 wherein the laser-ablatable layer is the outermost layer of the flexographic printing precursor and is disposed on a substrate.
15. The method of claim 1 wherein the laser-ablatable layer is underneath an outermost capping smoothing layer having a thickness of from about 1 μm to about 200 μm.
16. The method of claim 1 wherein the laser-ablatable layer has a dry thickness of from about 300 μm to about 4,000 μm and the relief image has a depth of from about 300 μm to about 600 μm.
17. The method of claim 1 wherein the laser-ablatable layer is disposed on a substrate and the flexographic printing precursor further comprises an adhesive layer between the substrate and the laser-ablatable layer.