Production of a luminescent material used for marking valuable documents comprises charging an ion exchanger with rare earth metal cations and thermally treating the charged ion exchanger

摘要

Production of a luminescent material comprises charging an ion exchanger with rare earth metal cations and thermally treating the charged ion exchanger. Preferred Features: The charged ion exchanger is crushed, preferably by grinding before or after the thermal treatment to a pigment size. The ion exchanger is a silicate, preferably a zeolite. The rare earth metal cations are Yb cations or a mixture of Yb and Er cations or Nd and Cr cations or Yb and Y cations. Thermal treatment is carried out at 1100-1200, preferably 1150 deg C for 2-5 hours.