Abstract: A crosslinked resin excellent in heat resistance, toughness, moisture resistance and adhesiveness can be obtained by the use of an epoxy compound having both alcoholic hydroxyl groups and epoxy groups in its molecule and an isocyanate compound having isocyanate groups in its molecule by first reacting the alcoholic hydroxyl groups of said epoxy compound and the isocyanate groups of said isocyanate compound to produce an epoxy prepolymer having urethane linkages stable at room temperature, followed by dissociating the urethane linkages of the prepolymer to regenerate the isocyanate groups and reacting said isocyanate groups with the epoxy groups of said epoxy compound.

Abstract: There are disclosed a flexible printed circuit base board produced as an elemental material suitable for a flexible printed circuit board by coating a heat-resistant resin composition composed of a heat-resistant resin having a heterocyclic ring and an epoxy resin dissolved in an organic solvent on a metal foil and drying it to form a film directly on said foil, and a method for producing the same. Said flexible printed circuit base board is more excellent in heat resistance, flame retardancy, adhesiveness, electric insulation, and heat deterioration characteristics than the conventional base board obtained by integrating a heat-resistant film and a metal foil through an adhesive. These properties are of great importance in practical applications of the printed circuit base board. As compared with the conventional products, the production is easy, and hence, the present base board can be produced at a low cost.

Abstract: A heat-resistant resin composition suitable for use in multilayer super high density printed circuit boards, comprising a polyaminobismaleimide, a polyepoxy compound, and an aromatic vinyl copolymer containing as structural unit maleic anhydride and/or an alkyl maleate. This resin composition is excellent in thermal resistance and dimensional stability, which are important properties of a resin composition for practical use in lamination, and when used in lamination, exhibits favorable flow and curing properties so that it can be easily and economically processed under conventional laminating conditions. When used as a multilayer printed circuit board material, it is also characterized by excellent adhesion to a copper foil, particularly in bonding an inner circuit copper foil to the board.

Abstract: A metal-clad laminate as a base board for a flexible printed circuit, consisting of a metal foil and a base sheet composed of a fibrous base material impregnated with a resin composition comprising a polyepoxy compound and a styrene copolymer containing structural units of maleic anhydride and/or a monoalkyl maleate. The said resin composition cures rapidly, so that the fibrous base material impregnated with said composition can be laminated in a continuous way with a metal foil and, moreover, the composition imparts to the resulting laminate flexibility and heat resistance suitable for flexible printed circuits. Said resin composition may comprise, in addition to the above-said components, a reactive epoxy diluent, an acrylonitrile-butadiene copolymer, and/or a mixture of a saturated polyester resin and a polyisocyanate compound, in order to improve the flexiblity and adhesion of the base sheet to metal foil.

Abstract: This invention provides an adhesive composition for use in flexible printed circuits, comprising a phenol-formaldehyde resin, a polyepoxy compound, an acrylonitrile-butadiene copolymer and/or a polyvinylacetal resin, and a styrenic copolymer containing as structural units maleic anhydride and/or an alkyl maleate. Being excellent in adhesive strength, flow property, rapid curability, and heat resistance after curing, the present composition is especially suitable for the continuous bonding of insulating plastic films, particularly a polyimide film, to conductor foils by use of a roll-laminator and gives heat-resistant metal-clad laminates excellent for flexible printed circuits which can be soldered at high temperatures.