Abstract: A photocurable and thermosetting resin composition comprising (A) a photosensitive prepolymer having a carboxyl group in combination with at least two ethylenically unsaturated double bonds in its molecule, (B) a polymerization initiator, (C) a diluent, (D) an oxetane compound having at least two oxetanyl groups in its molecule, and (E) a curing promotor is developable with an alkaline solution and can be formulated as a one package preparation. Such a photocurable and thermosetting resin composition and a photosensitive dry film prepared by the use thereof are useful as various resist materials and electrical insulating materials, particularly as solder resists for printed circuit boards, interlaminar insulating materials for build-up multi-layer printed circuit boards, and the like.

Abstract: In the catalyst-applying treatment, the sensitization treatment is carried out by dipping the base material which has been subjected to the preliminary treatment in a tin chloride solution applied with a predetermined amount of fluorine type anionic surfactant, and the activation treatment is carried out by dipping the base material which has been subjected to the preliminary treatment in a palladium chloride solution applied with a predetermined amount of fluorine type anionic surfactant.

Abstract: A novel polyaddition copolymer having repetition units represented by the following general formula: ##STR1## where R: a lower alkyl group, Ar: a bisphenol compound residue, and X: a CH.sub.2 O group or a COO group, is obtained by copolymerization reaction of a bisoxetane compound represented by the following general formula: ##STR2## and a bisphenol compound.

Abstract: A curable composition comprising a polyfunctional oxetane compound and a polyphenol compound or phenol resin, where a quaternary onium salt or Crown ether compound is preferably further contained as a curing catalyst, provides a novel use for reactions of the oxetane compound as a 4-membered cyclic ether compound.