Phase-inversion applications beyond membrane formation. I. Lithography films

Polymeric films cast from a polymer solution can develop a bulk porosity, i f the conditions are favorable for phase inversion (PI), a physical chemica l process based on fluid-fluid demixing of which there are two known major variants: wet and dry PI. As the formation of polymeric coatings often invo lves a polymeric solution or gel precursor, dry or wet PI phenomena may aff ect the structure formation of the final solvent-free coating. In this arti cle we identify the situations under which lithographic films can develop a PI structure and focus on solid polymer layers undergoing postcasting wet processing. Examples are provided from the wet processing of a fractionated epoxy novolac resin currently used in lithographic patterning. (C) 2000 Jo hn Wiley & Sons, Inc.