Patents Assigned to Mitubishi Petrochemical Co., Ltd.
  • Piezoelectric and foam resin sheet speaker
    Patent number: 4807294
    Abstract: A sheet speaker comprised of a planar piezoelectric ceramic sheet encapsulated in a planar sheet of hard resin foam, comprised of a polystyrene, urethane, urea or phenolic. The planar piezoelectric ceramic sheet is centered in the planar hard resin from sheet which provides a surface area of 10-50 times the surface area of the planar piezoelectric sheet. The surface of the planar hard resin foam may be lined with cloth, paper, or plastic film.
    Type: Grant
    Filed: June 17, 1987
    Date of Patent: February 21, 1989
    Assignee: Mitubishi Petrochemical Co., Ltd.
    Inventors: Yoichi Iwata, Nubuo Tanaka, Junichi Katurayama