Cholesteric Liquid Crystal Polymer Network/Patterned Quarter‐Waveplate Composite Film for Anti‐Counterfeiting

Cholesteric liquid crystal (CLC) polymer network (CLCN) patterns for decoration have been well‐developed. However, those for anti‐counterfeiting are still limited. Herein, the CLCN films were used for selectively reflecting circularly polarized light that matches their handedness, and the nematic liquid crystal polymer network (NLCN) films with different thicknesses were used as the waveplates for manipulating the polarization states of the lights. A CLC mixture was prepared using LC242 and a photoisomerizable chiral dopant. Upon the irradiation of the 365‐nm UV light, this CLC mixture changes to a nematic liquid crystal mixture due to the photoisomerization of the chiral dopant. Then, a patterned quarter‐waveplate composed of CLCN and NLCN was prepared using this CLC mixture and a photomask through a two‐step approach. The CLCN/patterned quarter‐waveplate composite film was prepared by directly coating and curing a CLC mixture on the patterned quarter‐waveplate surface. Since the quarter‐waveplate can change the circularly polarized light to linearly polarized light, although the pattern is invisible under natural light, it is visible under linearly polarized light. The results shown here not only give us a better understanding of the effect of waveplates, but also lay the foundation for the anti‐counterfeiting CLCN/NLCN composite film.