Security device with hidden optically variable feature

摘要

A security device comprises an array of lines printed or provided on a substrate, the lines 1 comprising materials which have the same appearance under visible light illumination (figure 6) but which appear different from each other 1A and 1B under a combination of visible and non-visible ultraviolet illumination (figure 7); whereby at least some of the lines appear different from other lines. The device also comprises a second surface relief array of lines (3, figure 6) imposed on the first array, possibly by blind intaglio embossing. The orientation, line widths and spacings of the first and second arrays being such that the device exhibits a variable appearance as it is tilted and viewed along direction 12 (figure 7) whilst exposed to a combination of visible and non-visible illumination, a gradual switch between one appearance and another will be observed.