Abstract: A photosensitive resin composition comprising (A) a polymer obtained by reacting an isocyanate compound having an ethylenic unsaturated group with a polymer which is a reaction product of a tetracarboxylic acid dianhydride and a diamine, and (B) a photoinitiator, can provide a thick film excellent in heat resistant, adhesiveness, flexibility, electrical and mechanical properties, and is particularly suitable for producing a photosensitive element.

Abstract: A flexible printed-circuit board covered with a coverlay is produced by bonding (a) a flexible printed-circuit board that comprises a flexible base having a surface bearing a circuit and (b) a polyimide film having a surface treated to increase adhering property and another surface not treated to increase adhering property, each of the surfaces being coated with an adhesive layer, with the adhesive layer on the surface treated to increase adhering property interposed between the polyimide film and the surface bearing the circuit, and then peeling off the adhesive layer coating the polyimide film on the surface not treated to increase adhering property.

Abstract: Resol type phenol resins containing scarcely or no phenol mononucleus compounds (monomers) and phenol dinuclei compounds (dimers) and their methylolated derivatives and scarcely containing molecules having an apparent molecular weight of more than 2500 are produced by reacting phenol with formaldehyde in the presence of an alkaline catalyst in a molar ratio of 3.0 to 6.0 moles of formaldehyde and 0.05 to 2.0 moles of the alkaline catalyst per mole of phenol, neutralizing the reaction solution with an acid to pH 4.5 to 6.5 and precipitating the resulting product for separation.