Novel Partial Esterification Reaction in Poly(amic acid) and Its Application for Positive-Tone Photosensitive Polyimide PrecursorPartial Esterification in Poly(amic acid) for Photo-Polyimide

We found novel quantitative esterification in poly(amic acid) (PAA) by reacting with N,N-dimethylformamide dialkyl acetals (DFAs). Different alkyl ester was obtained by changing the alkyl group in DFAs. The esterification ratio was determined by amount of DFAs. The reaction proceeds under mild condition without any catalysis. It has not been reported such a kind of quantitative partial esterification before. The partial esterification allowed us to control the solubility of PAA to alkaline solutions. The strict solubility rate control to alkaline solution of PAA was quite important for positive tone photosensitive polyimide (posi PSPI). The partial esterification of PAA gave us a way to strict dissolution control. By using it, we could obtain posi PSPI just mixing with diazonaphthoquinone compound.