A soluble multiblock copolyimide without specific functional groups such as OH and COOH was prepared by a direct one-pot polycondensation of two types of dianhydrides and diamines in the presence of ␥-valerolactone/pyridine catalyst using N-methylpyrrolidone (NMP)/toluene mixture as a solvent. The polyimide film containing the photosensitive agent diazonaphthoquinone (DNQ) compound gave positive-tone behavior by UV irradiation, followed by development in a mixture of ethanolamine/ NMP/H 2 O (1/1/1 by weight). The scanning electron microscopic photograph of the resultant image showed fine patterns with about 20 m film thickness. Its pattern forming was based on the photorearrangement of diazonaphthoquinone, a process in which the ring-opening reaction of imide units of the polyimide with the amine used as a developer and the following degradation of the polymer are induced. Such a new imaging technique combines principles of photolithography and etching of a polyimide to give, what we call, reaction development patterning in which the main chemical reactions directly related to the pattern formation occur during development.
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