PHOSPHOR WHICH EMITS LIGHT WHEN STIMULATED BY X-RAY AND X-RAY SENSITIZED SHEET USING SAID PHOSPHOR

摘要

PURPOSE:To remarkably improve the after-glow characteristic of a phosphor by incorporating at least one kind of bivalent metal among Be, Mg, Ca, Sr, Ba, Zn and Cd in a specific range into the phosphor. CONSTITUTION:The base body of the phosphor is expressed by formula I and the activator thereof is any of Tm, Pr, Sm, Eu, Tb, Dy, Yb or self activation. M is at least one kind of the bivalent element selected from the group of Be, Mg, Ca, Sr, Ba, Zn and Ln is at least one kind of elements among Y, Gd, La and Lu. D includes either or both of Ta and Nb and (a) is the numerical value in a 1X10-5=a=1 range. The after-glow characteristic is improved if the content of M which is the bivalent metal to be incorporated into the phosphor is high but the light emission efficiency decreases if the content is too high. (a) Of formula I indicating the content of the bivalent M is determined by taking the after-glow characteristic and light emission efficiency into consideration. The light emission efficiency decreases if Tm, Pr, Sm, Eu, Tb, Dy and Yb which are the activator are too much.