ion upon exposure to light and a reverse reaction inhibitor the reaction of a hydrogen ion generated by the photochemical acid generator with the base resin eliminates the protecting group which renders the base resin soluble in the basic developer with concomitant generation of a new hydrogen ion so that solubilization of the photoresist in the basic developer is amplified the reverse reaction inhibitor inhibits recombination of the eliminated protecting group with the base resin application_number US 33272999 A description in the chemical photoresist of this invention a polyhydroxystyrene resin may be used as the base resin in the chemical photoresist of this invention the protecting group may be an acetal based protecting group in the chemical photoresist of this invention the reverse reaction inhibitor may be one containing at least an alkyl halide as the alkyl halide a member selected from the group consisting of an alkyl fluorosulfonate an alkyl bromosulfonate and an alkyl iodosulfonate each having a molecular weight of 100 to 1 000 or mixtures of two or more of them can be used the content of the alkyl halide is 1 to 20 wt based on the base resin hereafter embodiments of this invention will be explained the explanation will be made concretely by examples the positive type chemical.