INVISIBLE, X-RAY OPAQUE, FLUORESCENT PRINTING MEDIUM FOR MULTIPLEX READING

摘要

Materials for printing information that is invisible under normal white or visible light but is x-ray opaque and ultraviolet fluorescent or absorbent and is used for multiplex reading. The invention permits a reader to use x-ray radiation, ultraviolet light or visible light to read printed information. With the x-ray reading capability, it is possible to read pages in sealed envelopes, thick documents or unopened attache cases.