(19)

(11)

EP 0 414 841 A1

(12)

(43) Date of publication: 06.03.1991 Bulletin 1991/10 (21) Application number: 90902315.0 (22) Date of filing: 29.01.1990

(51) International Patent Classification (IPC):  C30B 29/ 04( . ) C23C 16/ 27( . ) C23C 16/ 16( . ) C30B 25/ 02( . ) (86) International application number: PCT/GB1990/000122 (87) International publication number: WO 1990/009465 (23.08.1990 Gazette 1990/20)

(84) Designated Contracting States: DE FR GB IT NL (30) Priority: 20.02.1989 GB 19890003793 (71) Applicant: PLESSEY OVERSEAS LIMITED Ilford Essex IG1 4AQ (GB)	(72) Inventor: WORT, Christopher, John Towcester Northants NN12 8JY (GB) (74) Representative: Elliott, Frank Edward  GEC Patent Department (Chelmsford Office) GEC-Marconi Research Centre West Hanningfield Road Great Baddow Chelmsford Essex CM2 8HN Great Baddow Chelmsford Essex CM2 8HN (GB)