Fluorescent marking ink for documents, etc. - contains inorganic pigment doped with rare earth element

摘要

The ink comprises >=1 organic binder and a pigment constituted by n inorganic matrix, in which the spectrums of excitation and fluorescence are respectively the visible spectrum and/or the near UV on the one hand and the near IR on the other. The pigment is doped with >=1 rare earth element. The characters printed on a support with the above ink are read using an appts. comprising appts. for luminous excitation and appts. for photosensitive detection. The spectrum of rays of the excitation appts. ranges at most in the visible and UV and the detection appts. is sensitive to fluorescence of wave lengths >0.8 mu m. The inks are used for documents, cheques, etc. for automatic indexing. They have the advantage of not requiring UV source or expensive detectors to eliminate fluorescence dur to the paper. The procedure for detection is therefore simpler, cheaper and more convenient.