| 摘要 |
A security device is disclosed, comprising: an at least semi-transparent layer exhibiting a first pattern of regions having a high optical density and/or a raised surface profile relative to intervening regions of the layer; and a colour layer exhibiting a second pattern of elements of at least one colour. The first and second patterns at least partially overlap one another and are configured such that, when the device is viewed from at least one side, the appearance of the device varies at different viewing angles. Where the first pattern is of raised regions, the colour layer follows the contours of the raised regions. Also disclosed is a method of manufacturing the security device. In addition, a security device is disclosed comprising: a first photosensitive film exhibiting a pattern of regions of relatively high and relatively low optical density, respectively, the pattern arising from exposure of the photosensitive film to radiation of a predetermined wavelength to which the photosensitive film is responsive; and a colour layer overlapping the pattern exhibited by the first photosensitive film. The photosensitive film is adapted to exhibit an increase in optical density upon exposure to radiation of a predetermined wavelength and concurrent or subsequent heating,the increase in optical density being due to the formation of bubbles within the photosensitive film. |
