Лако-красочные материалы — производство

In long-afterglow phosphors, optical excitation energy is stored in the lattice by trap­ping photoexcited charge carriers. The most prominent example is SrAl2O4:Eu, Dy: after optical excitation of Eu2+, Eu2+ is oxidized to Eu3+ and Dy3+ is reduced to Dy2+. Thermal excitation of Dy2+ to Dy3+, followed by capture of the electron by Eu3+ and subsequent Eu2+ emission results in time-delayed Eu2+ emission. The thermal ex­citation process of Dy2+ determines the time delay. This particular material still generates visible emission after several hours in the dark.

Long-afterglow phosphors can be used in watch fingers, and also in safety appli­cations, e. g., in exit signs, which still operate in the case of a current blackout. Other long-afterglow materials are e. g. ZnS:Cu or SrS:Bi.

5.5.4