NOVEL NEGATIVE-TYPE SOLUBLE PHOTOSENSITIVE POLYIMIDES - SYNTHESIS ANDCHARACTERIZATION

In the present paper, we describe the synthesis and characterization o f a novel negative-type soluble photosensitive polyimide (PSPI). A gro up of new photosensitive polyimides has been prepared by condensation of dianhydrides bearing photoreactive ester groups and aromatic diamin es in N-methylpyrrolidone (NMP), followed by chemical imidization usin g acetic anhydride without acid accepters such as pyridine or triethyl amine. Thus, the starting monomer used in the synthesis of a commercia l aromatic polyimide has been chemically modified with four different photosensitive groups (chlorine-free synthesis). All the intermediates as well as the resulting polymers have been characterized. The PSPI e sters were found to be soluble in N-alkyl-substituted amides. Their ir radiation with UV light induces cross-linking of the photoreactive est er groups. These systems change from being weakly to being heavily cro ss-linked during irradiation and do not swell during development. The remaining PSPI esters do not require thermal imidization because they are already imidized, and shrinkage is about 20% due to volatilization of photoreactive groups.