Optical LPP/LCP devices: A new generation of optical security elements

With Linear Photo-Polymerization (LPP) ROLIC has developed a new photo-patternable technology which enables to align not only conventional liquid crystals but also Liquid Crystals Polymers (LCP). ROLIC's optical, security device technology derives from its LPP/LCP technology. LPP/LCP security devices are created by structured photo-alignment of an LPP layer through photo-masks, thus generating a high resolution, photo-patterned aligning layer which carries the aligning information of the image to be created and which is machine readable. The subsequent LCP layer transforms the aligning information into an optical phase image. Among a large number of possible LPP/LCP optical effects that lead to LPP/LCP security devices - all of them with distinct optical appearance - we will concentrate on the following LPP/LCP security elements: Reflective and transmissive LPP/LCP security devices for 2(nd) level inspection applications. LPP/LCP images are invisible when viewed with the naked eye but becomes visible when viewed through a polarizer. Rotation of the polarizer leads to contrast inversion: i.e. the image changes from 'positive' to 'negative' which is an additional unique security feature. Other types of LPP/LCP security devices are based on cholesteric films. We will present 2(nd) level cholesteric LPP/LCP devices which can be used as overlays and superimposed on printed information which remains visible through the overlay.