Optical security devices using UV-curable nematic liquid crystals

Abstract

This chapter begins by reviewing current counterfeit-proofing concepts and the security applications of liquid crystal (LC) materials that have been proposed to date. Next, security devices that use intrinsic random features for applications in a variety of fields are reviewed and the core concept of use of random features is discussed. The random optical textures that occur in LC phases, which have generally been considered to be defects for the purposes of most engineering applications, can then be regarded as favourable characteristics for security devices; the use of the unique patterns of these optical textures as identification information, which was previously proposed by the author, is then explained. Because security measures that use these intrinsic random features appear to be an unfamiliar concept for most LC researchers, a more detailed explanation is provided that traces the concept of security measures that use the random features in LC materials, and real data from actual fabricated devices is then provided.