Synthesis of submicron-sized spherical green phosphors by reverse emulsion method and their application to phosphor inks for ink-jet process in PDP

Sphere-shaped green phosphor, Zn₂SiO₄:Mn, with 100-500 nm of average diameter was successfully prepared by the reverse emulsion method to formulate the phosphor ink for ink-jet processing. It was found that the aqueous phosphor ink exhibited excellent dispersion stability by introducing organic low molecular weight additives such as nonionic type of fatty acid containing ethylene oxide (BYK 192^®), 3-(2-aminoethyl)aminopropyl trimethoxy silane (SA0700^®) and acetic acid, due to the combination of the steric hindrance originated from BYK 192^® and charge repulsion from SA0700^® and acetic acid. The patterned phosphor layers with thickness uniformity (±0.008 μm to ± 0.055 μm depending on the formulation of phosphor inks) and precisely controlled thickness (in the range of 5-50 μm) in between barrier ribs could be obtained by using ink-jet printing with optimized process parameters such as nozzle diameter, dispensing pressure and nozzle moving speed. Optical properties of the resulting phosphor layers fired at different temperatures were compared in terms of PL emission intensity and color coordinate.