We developed a novel photoluminescent ink for rewritable security papers.  The ink consists of a dendritic Cu(I) pyrazolate complex and dichroically emits phosphorescence due to a structural bistability of the columnar assembly of the complexes.  Photoluminescent images have been developed on the security paper by using conventional thermal printers, which are readable only on exposure to ultraviolet light, and more importantly, are thermally erasable for rewriting.