GB1160253A - Cathode Ray Tube Display Device - Google Patents

Abstract

1,160,253. Cathode-ray display tubes. SYLVANIA ELECTRIC PRODUCTS Inc. 3 Oct., 1966 [21 Oct., 1965], No. 44117/66. Heading H1D. [Also in Division C4] For use in navigational and tactical distance determination and surveillance systems, a display system for distinguishing fixed and moving objects comprises a C.R.T. with a multilayer luminescent screen including an outer layer 47 of two cathode luminescent phosphors 49 and 51 with U.V. and visible emissions and shorter and longer persistences respectively, an inner screen layer 39 of a radiant energy excitable phosphor with visible emission of a wavelength different to the second phosphor and of a persistence longer than the first and second phosphors, and a filter layer 43 between the outer and inner layers which is transparent to radiant energy wavelengths emitted by the first and second phosphors but impervious to the electron beam. Upon soda lime glass support 27, layer 39 (and subsequently layer 43) may be formed by settling, slurrying or dusting to a thickness of 0À001 to 0À002 inches. Phosphor 39 may be ZnS : Cu with yellow-green emission at 5400Š and persistence longer than one second, or (Zn, Cd) S : Cu emitting at 5500Š. Phosphor 49 may be 2CaO.MgO.2SiO 2 : Ce with 3800Š in emission and persistence less than one microsecond and phosphor 51 a Y, Gd and/or Lu trivalent vanadate or oxide host compound activated by Eu and/or Sm (e.g. YVO 4 : Eu with 6110Š red emission and several milliseconds persistence); alternatively, phosphor 51 may be KMgF 3 : Mn of orange-red emission at 5900Š and persistence in excess of 100 milliseconds. Layer 47 may comprise a mixture of the phosphors with 60 to 85% by wt. of the shorter persistence phosphor. An electron beam representative of a fixed object produces a resultant white emission corresponding to the complementary addition of red emission B of phosphor 51 and yellow-green emission of phosphor 41. A moving object is represented by a resultant reddish hue B<SP>1</SP> (Fig. 3, not shown) corresponding mainly to the phosphor 51 red emission and to a small extent by phosphor 41 yellow-green emission. Barrier 43 may be settled or sprayed by suspending a silicon compound in the form of a leadless glass frit in a hexylene glycol-water vehicle spraying and firing or alternatively, layer 39 may be first covered with a methacrylate toluene lacquer, SiO deposited and baked to form SiO 2 barrier layer. An Al film may be evaporated over layer 39.