(19)

(11)

EP 0 469 053 A1

(12)

(43) Date of publication: 05.02.1992 Bulletin 1992/06 (21) Application number: 90907212.0 (22) Date of filing: 20.04.1990

(51) International Patent Classification (IPC):  C01G 23/ 00( . ) C04B 35/ 49( . ) C04B 35/ 626( . ) C01G 25/ 00( . ) C04B 35/ 491( . ) H01L 41/ 24( . ) (86) International application number: PCT/GB1990/000612 (87) International publication number: WO 1990/012755 (01.11.1990 Gazette 1990/25)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB IT LI LU NL SE (30) Priority: 21.04.1989 GB 19890009107 10.05.1989 GB 19890010717 (71) Applicant: ALCAN INTERNATIONAL LIMITED Montreal Quebec H3A 3G2 (CA)	(72) Inventors: GROVES, Paul Oxford OX5 1EY (GB) STEWARD, Nigel, I. Oxon OX16 7UD (GB) LANDHAM, Rowena, Roshanthi West Midlands B91 1PF (GB) TEAT, Simon, J. Banbury Oxon OX16 8BU (GB) WARRENDER, Theresa, E. Oxford OX5 1QN (GB) (74) Representative: Pennant, Pyers  Stevens, Hewlett & Perkins 1 Serjeants' Inn Fleet Street London EC4Y 1LL London EC4Y 1LL (GB)