Highly reflective cholesteric liquid crystal films based on nematic isolation layers: broadband infrared regulation and polarization anti-counterfeiting applications

Abstract

To address the limitations of conventional single-layer polymer-stabilized cholesteric liquid crystals (PSCLCs), which are restricted to reflecting circularly polarized light of a single handedness within a limited spectral bandwidth, this study proposes a method for fabricating a three-layer broadband high-reflection PSCLC film. Left- and right-handed broadband reflective PSCLC films are separately prepared using photoinduced molecular diffusion coupled with polymer network stabilization. A polymer-stabilized nematic liquid crystal (PSNLC) is employed as an intermediate isolation barrier to suppress chiral cancellation caused by the cross-layer diffusion of chiral dopants. Consequently, the resulting film achieves a high reflectivity exceeding 80% across the infrared region. The effects of the polymerizable monomer C6M content, the ultraviolet absorber UV-327 concentration, and UV intensity on the reflection bandwidth are systematically investigated to determine the optimal fabrication parameters. Thermal insulation tests demonstrate that the proposed film significantly reduces internal temperature rise in a simulated building model, exhibiting superior energy-saving performance compared to single-layer PSCLCs. Furthermore, by adjusting the chiral dopant concentration, patterned films operating in the visible region can be fabricated for polarization-responsive optical anti-counterfeiting. This method provides a simple and feasible fabrication strategy, offering a new approach for the preparation of liquid crystal-based infrared reflective materials and anti-counterfeiting devices.