The decay time of green phosphors and the life of blue phosphors for full-color PDPs have been investigated. Optimization of Mn content of Zn_2SiO_4Mn^<2+> to 2.6 (weight%) caused the decay time (1/e) of 3.9ms, which is sufficient for practical use, and other characteristics is also better than conventional phosphors. Luminance of conventional blue phosphor (BaMgAl_<14>O_<23>:Eu^<2+>) decreased with discharging time, the emission spectra also changed. Improved phosphor (BaMgAl_<10>O_<17>Eu^<2+>) dose not change the emission spectra, and the life is longer than conventional phosphor by from two to three times.
