Cathode-ray storage tube having semicontinuous phosphor layer on continuous electron bombardment induced conductivity layer

Claim 1

A bistable cathode-ray storage tube with a high writing speed characteristic comprising: A. an evacuated envelope; B. a storage screen within said envelope comprising: 1. a control layer of electrically conductive material; 2. a continuous layer of insulating charge-storage material having electron bombardment induced conductivity which overlays said control layer; and 3. a semicontinuous layer of secondary electron emissive charge-storage material which overlays said layer of insulating material; C. a writing electron gun disposed within said envelope on the semicontinuous layer side of the storage screen, for scanning over the storage screen a narrow beam of relatively high energy electrons which penetrate said semicontinuous layer and impinge on the insulating layer, thereby to provide localized conductive paths through the insulating layer between the semicontinuous layer and the control layer so that, when the surface of the semicontinuous layer nearer the writing electron gun and the control layer are initially at potentials respectively below and above the first crossover value of the secondary electron emission characteristic of the material of the semicontinuous layer, the potential of said surface of the semicontinuous layer at regions corresponding to said localized conductive paths is raised to a value above said first crossover value; and D. a flood electron gun, disposed within the envelope on the semicontinuous layer side of the storage screen, for flooding the whole of said surface of the semicontinuous layer with relatively low energy electrons so as to maintain a chargestorage pattern on the semicontinuous layer by virtue of secondary electron emission at said regions where said surface of the semicontinuous layer is at a potential above the first crossover value, the surface of said semicontinuous layer facing said guns being completely exposed over its entire area to direct impingement by electrons emitted by said guns, said semicontinuous layer being a phosphor emissive of radiation at a potential above said first crossover value, whereby the electron bombardment induced conductivity layer accelerates the formation by the writing gun of a charge storage pattern on said surface.