PURPOSE: To obtain a lignt-weignt and high-bending stiffness diaphragm without requiring adhesive by spraying special modified polyurethane resin onto the surface of a porous structure material in a random thread form to form a sealing layer.
CONSTITUTION: A porous structure material such as a foamed material and a honey-comb structure material of resin or metal is used as a core material, and special modified polyurethane resin diluted into a proper concentration is sprayed onto one or both discontinuous surfaces of this porous structure material in a random thread form to form a sealing layer. Spraying of special modified polyurethane resin forms a film which becomes a continuous ground layer. and much narrow threads are sprayed onto the arachnoid ground layer, which is formed in this ground process, to make this layer dense, and an intermediate layer having a fixed thickness is formed, and a close top layer is formed on the surface of this intermediate layer. Thus, a light-weight and high-bending stiffness diaphragm can be obtained.
RINAMI MASAHIRO
ISHII YASUHIRO
