Aiming at the drawbacks of traditional polymer-dispersed liquid crystals (PDLC), such as single anti-counterfeiting mode, invisibility in dark-field conditions and low contrast ratio (CR), a multimodal PDLC anti-counterfeiting film integrating electrically controlled dimming, multicolor luminescence and long-afterglow properties was constructed in this work. PDLC films with excellent comprehensive performance were fabricated by optimizing the monomer ratio and liquid-crystal content. On this basis, red fluorescent powder R-FL and long-afterglow green phosphor G-PH were introduced separately. The effects of doping concentration on the micromorphology, electro-optical properties and luminescence behaviors of PDLC were systematically investigated. The optimal doping ratios were determined to be 2 wt% for R-FL and 2.5 wt% for G-PH, by which the CR values were increased to 192.79 and 243.94, respectively. Under ultraviolet excitation, the devices exhibited red emission at 658 nm and green emission at 506 nm, and the G-PH-doped system possessed long-afterglow characteristics. Combined with screen-printing technology, dynamic anti-counterfeiting patterns that can be switched among bright-field, UV-excited and dark-field afterglow states were fabricated. The multi-responsive PDLC system constructed in this study greatly improves anti-counterfeiting security level and display contrast, and provides a feasible fabrication strategy for high-security information-encryption devices.

Key words: Polymer dispersed liquid crystals, Photoluminescence, long afterglow, Dynamic Optical Anti-counterfeiting, multiple responses