Security paper with authenticity features in the form of substances luminescing only in the invisible region of the optical spectrum and process for testing the same

摘要

Security paper with luminescing authenticity characteristics which after excitation with invisible light emit exclusively invisible light of different wavelengths as authenticity signal. The luminophores can be included in the printing ink used or they can be added to the paper material in the manufacture of the paper material. A corresponding test apparatus makes it possible to check the authenticity of the security paper in the presence of customers but unnoticed by them; thereby the invisibility of the test signal and the authenticity signal are taken advantage of and the test device is hidden behind a plate non- transmissive for visible light which however is transmissive for the test signal and for the authenticity signal.