High current density oxide cathode for CRTs

Image quality of CRTs has been improved by applying new technologies of electron gun, cathode, deflection yoke and image screen. Recently, new types of cathodes with higher current density have been developed, and contributing to higher definition and brightness of CRTs. We also have developed a technology to realize a higher current density oxide cathode through the following three steps of the technical innovation. 1) In 1986, the invention of Sc/sub 2/O/sub 3/-dispersed-cathode materialized four folds (2A/cm/sup 2/) of the then current density. 2) The tungsten (W) film-coated oxide cathode increased further the current density up to 3.6A/cm/sup 2/. 3) A technology to reduce the cut-off voltage drift was developed for the high current density cathode.