PURPOSE: To improve the luminance of a flat type image displaying apparatus by heightening the concentration of activators of red, green and blue phosphors and altering the particle sizes of phosphor particles.

CONSTITUTION: A fluorescent screen with high luminance and excellent color reproducibility even at low acceleration voltage can be obtained by heightening the concentration of activators of red, green, and blue phosphors and altering the particle sizes of phosphor particles. That is, regarding Y2O2S:Eu, the concentration of Eu as a fluorescent ion is increased more than the conventional concentration, 2-4 mole %, in order to improve the luminance. Regarding ZnS:Cu, Al, the concentration of Cu and Al as activators is increased more than the conventional concentration, 100-200ppm, in order to improve the luminance. Moreover the particle sizes of all the phosphors are made 2-6μm, which is smaller than those of conventional phosphors in order to make electron beam enter the phosphors sufficiently even at low acceleration voltage and improve the luminance.