PURPOSE: To improve the moisture resistance of a phosphor which uses La2O2S as the matrix by subjecting the phosphor to a moistureproofing treatment and thereby to enable the use of the phosphor as an electron beam excited phosphor.
CONSTITUTION: On the surface of a particle of a phosphor matrix represented by La2O2S is formed a transparent protective film comprising at least one metal oxide pref. selected from the group consisting of Al2O3, SiO2, TiO2, and GeO2. If the amt. of the film formed is 50-2,000ppm based on the matrix, better results are obtd. When the amt. exceeds 40ppm, the luminance of a phosphor rapidly increases ; at above about 3,000ppm, the luminance decreases to lower than conventionally obtd. The amt. of 50-2,000ppm is pref. as the amount of the protective film for the phosphor to obtain a relative luminance of 110 or higher, one usually considered pref.
SATO YOSHITAKA
KAGAWA NORITAKA
