GB867352A - Improvements in or relating to the manufacture of electron discharge tubes having a photo-conductive target - Google Patents

Abstract

867,352. Coating by vapour deposition. MULLARD LTD. Nov. 7, 1958 [Feb. 21, 1958], No. 5707/58. Class 82(2) [Also in Group XL(a)] In a method of depositing a photo-conductive target layer on a supporting base within an electron discharge tube, the supply of photo-conductive material is formed on part of the internal structure for the tube prior to the insertion of this structure within the envelope. After sealing a foot or base to the envelope, the envelope is evacuated through an exhaust tube and the photo-conductive material is evaporated either in vacuo or in a gas such as argon at low pressure, to form the target layer. In the former case the exhaust tube may be sealed-off either before or after evaporating the material. A layer 25, Fig. 3, of photo-conductive material, preferably pure red antimony trisulphide, may first be formed on a collector grid 1 by evaporation in vacuo, Fig. 2, not shown. The grid 1 of fine copper mesh is sandwiched between rings 2, 3 of copper-nickel alloy, each of the members 1, 2, 3 being first nickel-plated and then rhodium-plated. Alternatively a supply of photo-conductive material may be provided in an inturned portion 35, Fig. 5, of the anode 20. In each case, the photoconductive material may be evaporated by means of heating coil 38, the upper part of the Vidicon envelope 18 being surrounded by a cooling jacket 29 containing water. The target layer 25<SP>1</SP> is formed on a transparent conducting coating of tin oxide on the glass end plate 18<SP>1</SP> which is sealed to the envelope through a ring 19 of fernico alloy, undue heating of this ring being prevented by cylinder 33. Specification 707,125 is referred to.