Formulation And Optimization On Platemaking Process For Flexographic Printing Plate

Photosensitive resin composition and process parameters for flexographic printing plate were studied in order to enhance the properties of the plate. Photosensitive resin system were formulated with polystyrene-block-polybutadiene-block-polystyrene(SBS) as main resin. Kinds of the crosslinkers, photoinitiators, and liquid polybutadiene(L-PB) were investigated in term of gel fraction, hardness, swelling degree, and crosslinked depth. The impacts of the platemaking factors on the printing plate's resolution, including back exposure, main exposure, development, and post exposure, were further studied.The results indicated that properties of the photosensitive resin as gel fraction, hardness, swelling degree were strongly affected by the concentration of L-PB. Hardness was dropped with increasing of the L-PB concentration. The hardness of the plates could be tuned by adding various levels of L-PB. But swelling ratio was increased because of a looser polymer network. To choice the optimum amount of L-PB must take account of both hardness and swelling ratio. Photoinitiators had a great impact on the rate of crosslinking reaction and crosslinked depth. A complex photoinitiator system turned out to perform best which accelerated the reaction and deepened the crosslinked depth.Through the investigation of platemaking technique, we found that back exposure time, main exposure time, and degree of vacuum were the most important factors which influenced resolution of the plate. To control these process parameters must base on the gel fraction of the photosensitive resin.The result of the investigation have been used to fine-tune the photosensitive resin composition and process parameters to significantly improve the image quality of flexographic printing plate with high resolution.