Broadband Encrypted Mirror Fabricated via Stacking Cholesteric Liquid Crystal Polymer Network Films and a Patterned Half‐Wave Plate

ABSTRACT Cholesteric liquid crystal polymer network (CLCN) mirrors featuring a broad reflection band have attracted considerable interest for use in optical filters and decorative applications. To date, however, the development of mirrors with encryption capabilities remains unexplored. In this work, a series of chiral additives were synthesized from isosorbide and 4′‐ n ‐alkyl‐(1,1′‐biphenyl)‐4‐carboxylic acids. Using polymerization‐induced chiral additive diffusion, we then prepared a set of CLCN films exhibiting broad reflection bands. By stacking these films with an optically clear adhesive, a broadband CLCN mirror with high reflectance was fabricated. Furthermore, a patterned half‐wave plate was fabricated using a nematic liquid crystal polymer network (NLCN) in combination with a CLCN. A modified mirror was constructed by incorporating the patterned half‐wave plate during the stacking process. When illuminated with circularly polarized light, this configuration revealed vivid colored images. These results demonstrate the potential of such mirrors for encryption purposes.