| abstract |
Paper security with luminescent authenticity mark which, after excitation by an invisible light, emits only invisible light of a different wavelength. The luminescent substance may be added to the printing dye or to the paper during manufacturing. A corresponding checking device allows the checking of the authenticity of the paper security in the presence of the customer but without his knowledge. It could be taken advantage of the fact that the test signal and the authenticity signal remain invisible in order to place the apparatus behind an opaque plate (2) for the visible light but transparent for the authenticity and test signals. |