Single-Layer Polymer-Stabilized Cholesteric Liquid Crystal Films: Broadband High Reflection and Electro-Tunable Polarization Anticounterfeiting

In this work, broadband polymer-stabilized cholesteric liquid crystal (PSCLC) films with gradient helical pitches along the thickness were fabricated via UV-induced diffusion polymerization in a single liquid-crystal cell. The UV absorber UV-327 created a vertical light intensity gradient inside the cell, which drove the diffusion of polymerizable chiral monomer HCM-006 and nonpolymerizable chiral dopant S1011 in opposite directions. A continuous gradient of cholesteric helical pitch thus formed, enabling the simultaneous broadband reflection of both left- and right-handed circularly polarized light. We systematically investigated how chiral dopant content, polymerizable monomer ratio, UV absorber concentration, UV irradiation intensity, and polymerization time affected the reflection bandwidth. Optimized formulations and processing conditions achieved a maximum reflection bandwidth of 357 nm. Patterned PSCLC films were further produced by stepwise UV polymerization with photomasks. Benefiting from the orientation memory effect of cross-linked polymer networks, the films exhibited reversible electrically tunable optical switching between a reflective planar state and transparent homeotropic state under an alternating voltage. By adjusting the chiral component loading, the reflection color of films could be customized. Relying on circular polarization selectivity, the patterned films supported polarization encryption and anticounterfeiting. This study proposes a simple single-cell fabrication route for broadband PSCLC and offers experimental guidance for developing electroresponsive cholesteric liquid crystal optical devices.