PHOSPHOR SCREENS FOR FLAT CATHODE-RAY TUBES

In the Zeus display panel, as in other flat-panel cathode ray tubes, t he anode voltage is limited to a few kV. The effects of the anode volt age on phosphor screen performance are discussed which include energy conversion ross processes at the phosphor surface and variation of the number of luminescent centres available. Phosphor efficiency saturati on has been measured in the range of 1 to 10 kV, using a pulse-width-m odulation scheme. The luminance performance at different excitation co nditions is predicted and confirmed experimentally. Coulomb degradatio n of phosphor screens is shown to increase with decreasing anode volta ge. Novel ultra-thin and dense anti-degradation coatings have been dev eloped for zinc sulphide phosphors which effectively prevent fast degr adation due to chemical surface reactions. In this way a satisfactory solution has been found to obtain in the Zeus display a luminance leve r about equal to the best conventional tubes.