| 摘要 |
A novel security item is proposed which is characterised by at least one security element having at least one segment comprising at least one latent UV or IR absorber (III). A latent absorber is a compound or composition capable of liberating a UV absorber on demand. Preferentially, the latent absorber is converted to its absorbing form in a spatially resolved manner (III) thus providing the desired information as latent image. Information imprinted within a substrate containing said absorbers is invisible to the naked eye. Moreover, the information is also invisible under UV irradiation. Only if a photoluminescent screen or background is used under UV irradiation, the "imprinted" information becomes apparant as a shadow image on the photoluminescent screen, since, in the areas where the latent absorber has been converted to the UV absorber, the UV light is being absorbed and does not reach the photoluminiscent device. <IMAGE> |
