抄録
Persistent internal polarization of ZnS and ZnCdS phosphors is investigated. Polarization P is found to be expressed by an exponential function of illumination intensity I and polarization time t as
P=P∞ [1-exp(-βIt)] Polarization P∞, after a long polarization time is determined by the applied voltage alone, and β is a constant depending on the phosphor materials and the cell structures. This leads to a conclusion that such an exponential characteristic is due to the decrease in effective internal field with the formation of polarization and not caused by all the trape being filled up.
On the basis of the experimental results, the polarization effect is applied to an electric static photography. On the authors' phosphor sheets, excellent latent images were obtained which were made visible by charged particles applied on them. Illumination intensity of 40lx, polarization time of 5 seconds and applied voltage of 600 volts per 70 microns were used for this attempt.
