(19)
(11) EP 0 457 474 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
16.09.1992 Bulletin 1992/38

(43) Date of publication A2:
21.11.1991 Bulletin 1991/47

(21) Application number: 91304093.7

(22) Date of filing: 07.05.1991
(51) International Patent Classification (IPC)5: H04R 7/02, H04R 31/00
(84) Designated Contracting States:
DE FR GB

(30) Priority: 18.05.1990 JP 126819/90

(71) Applicants:
  • SONY CORPORATION
    Tokyo (JP)
  • AJINOMOTO CO., INC.
    Tokyo 104 (JP)

(72) Inventors:
  • Uryu, Masaru, c/o Sony Corp.
    Shinagawa-ku, Tokyo (JP)
  • Kurihara, Noboru, c/o Ajinomoto Co. Inc.
    Chuo-ku, Tokyo (JP)

(74) Representative: Ayers, Martyn Lewis Stanley et al
J.A. KEMP & CO. 14 South Square Gray's Inn
London WC1R 5LX
London WC1R 5LX (GB)


(56) References cited: : 
   
       


    (54) Method of producing an acoustic diaphragm


    (57) An acoustic diaphragm obtained by forming micro-fibrillated cellulose into a web by a process similar to a paper-making process is disclosed. the micro-fibrillated cellulose is the cellulose obtain by beating to a Canadian standard freeness of not more than 300 ml, or the bacterial cellulose. Since the micro-fibrillated cellulose has only poor wet strength, it is reinforced by a reinforcement element and, in this state, is formed into the web on a wire screen. The reinforcement element may be detached after forming the web, or may be left laminated with the cellulose web so that the resulting composite product is used as the acoustic diaphragm.






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