Abstract: A solvent-soluble siloxane polyimide comprising a copolymer obtained by reaction of a diamine compound mixture comprising a diaminopolysiloxane, an alicyclic diamine and an aromatic diamine with an aromatic tetracarboxylic acid anhydride, followed by polyimidization reaction of the resulting polyamic acid forms a heat-resistant adhesive by adding an epoxy resin, a diamine-based curing agent and an organic solvent thereto, The formed adhesives provides a distinguished curling resistance without any warp when the resulting siloxane polyimide soluble in ordinary organic solvents is used as a main component of the adhesive for bonding between a base material and a copper foil of a flexible printed substrate.

Abstract: A solvent-soluble siloxane polyimide comprising a copolymer obtained by reaction of a diamine compound mixture comprising a diaminopolysiloxane and an alicyclic diamine with an aromatic tetracarboxylic acid anhydride, followed by polyimidization reaction of the resulting polyamic acid forms a heat-resistant adhesive by adding an epoxy resin, a diamine-based curing agent and an organic solvent thereto, The formed adhesives show a distinguished heat-resistant adhesiveness when the resulting siloxane polyimide soluble in ordinary organic solvents is used as a main component of the adhesive for bonding between a base material and a copper foil of a flexible printed substrate. By further addition of a fluorinated resin to the heat-resistant adhesive, the adhesiveness can be more improved.