Laser Ablation of Plate
Digital photopolymer flexographic plate imaging uses no film. Conventional plate making generates chemical waste from film processing and solid waste from the films. Multiple generations of films are usually produced during job approval and for conventional analog proofing. Digital plate making only generates a thin black integral mask as waste. It promotes the transition to an all-digital workflow that employs digital proofing for job approval and final proofs.
For digital photopolymer plates, a phototool is created directly on the unimaged photopolymer plate surface from a black layer that is manufactured on top of the plate. The black layer covers the entire plate. It absorbs ultraviolet radiation like film and it also is sensitive to infrared radiation. An imaging device (much like an imagesetter) uses a high-power infrared laser or lasers to remove the black layer corresponding to the image to be transferred to the plate, revealing the unimaged photopolymer underneath. This removal process is called laser ablation and it creates the photo-tool or integral mask. The underlying photopolymer does not absorb the infrared laser radiation. Thus, it is not affected by the laser ablation.
After laser ablation imaging, the digital plate receives ultra-violet exposure through the integral mask. The remaining black layer absorbs the ultraviolet radiation. The ultraviolet radiation polymerizes the photopolymer where the black layer has been removed. The plate is washed, dried, and finished with the same process as a conventional plate.
Best Management Practices & Pollution Prevention
Solid Waste/Waste Solvent/Waste Water
The black layer that is ablated off the plate during imaging of a digital photopolymer plate is captured by a debris removal system. In most cases, the black layer remaining on the plate is soluble in solvent and is removed from the plate during the plate wash out. Solids end up in the still bottoms of the solvent recovery distillation process. Sometimes, the black layer is water-soluble and is washed off the plate before the plate is washed out in solvent. In either case, the waste is disposed of by conventional methods and is a tiny fraction of the volume of film that is used for conventional plate making.
For access to vendors who may supply alternative materials and equipment, see the PNEAC Vendor Directory.
Health & Safety
Formaldehyde and vinyl acetate are hazardous materials and, if possible, should be eliminated from the adhesive formulation. If the formaldehyde and vinyl acetate cannot be eliminated from the glue formulation, employees should be monitored for exposure to excessive levels of formaldehyde and vinyl acetate, especially since these materials can lead to long term health affects.