The effect of In2O3 conductive coating on the luminescence and zeta potential of ZnS:Cu, Al phosphors

Phosphors used in CRTs have been coated with In2O3 conductive layer derived from the hydrolysis of indium chloride. It was found that brightness of the phosphors rises initially with the amount of InCl3, reaches a maximum at 10 wt.% InCl3 and then decreases when more InCl3 was added. With 10 wt.% InCl3 coating, the brightness of ZnS:Cu, Al phosphor increases by 24% at 800 V and 1 μA while very little changes were observed in the luminescent emission peak and CIE color loci. The luminescence decay times increase with the increase of the conductive coating. However, they are shorter than 0.7 μs for samples with the amount of coating ranging from 0 to 20 wt.% InCl3 and are suitable for display applications. Conductive coating affects the surface chemistry of the phosphor particles, enhances the zeta potential of ZnS:Cu, Al in IPA solution, and, consequently, increases the electrophoretic deposition rate of the phosphors onto substrate. The zeta potential of 10 wt.% InCl3 coated ZnS:Cu, Al in isopropyl alcohol solution is 32 mV as compared to 1.2 mV of that of the uncoated ZnS:Cu, Al. Besides, the electrophoretic deposition rate of the 10 wt.% InCl3 coated ZnS:Cu, Al (0.23 mg/s) is larger than that of the uncoated phosphor (0.17 mg/s).