IMPROVEMENTS IN SECURITY DEVICES

摘要

The present invention relates to improvements in security devices that can be used in varying shapes and sizes for various authenticating or security applications, particularly a device which on the application of heat uses a shape memory polymer material to induce a colourshift in a liquid crystal material. The invention therefore relates to a security substrate (10) comprising a polymeric liquid crystal material (13) and a shape memory polymer film (14), wherein the application of a predetermined external stimuli to the substrate (10) which causes the shape memory polymer film (14) to change shape which, in turn causes the liquid crystal material (13) to stretch or contract and thereby induce in the liquid crystal material (13) a temporary colour change.