Advanced PDLC films with dual-responsive fluorescence and phosphorescence for multicolor pattern display, quadruple information encryption and anti-counterfeiting

In recent years, polymer dispersed liquid crystals (PDLCs) have demonstrated remarkable application potential in the field of display, information encryption and anti-counterfeiting, but they still have the drawbacks of single color change, suboptimal contrast ratio (CR) and simple anti-counterfeiting modes. Herein, novel PDLC films with electro-optical dual-responsive fluorescence and phosphorescence are prepared to achieve multicolor pattern display and quadruple information encryption by using the strategy of combining phosphorescence and fluorescence with electrically responsive PDLC. The phosphorescent green (PG) and phosphorescent blue (PB) doped PDLC has high CR of 164 and 226. The color pattern display of PDLC is achieved by the electro-optical synergy effect of increasing or decreasing the excitation probability of the light emitting molecules through multiple scattering or transmission of ultraviolet (UV) light by electrically responsive PDLC. Fluorescent red (FLR) particles were incorporated into the PDLC films to augment the anti-counterfeiting ability of PDLC. Various shapes of PDLC films were prepared utilizing screen-printing method, which can manifesting multiple optical states of scattered (white), fluorescent (red), and phosphorescent (green and blue) colors under natural light, UV light, and UV light-off, respectively. Furthermore, a sophisticated PDLC (static + dynamic) anti-counterfeiting pattern with quadruple information encryption has been developed by taking advantage of the differences in the afterglow times of different concentrations and types of phosphorescent materials. The PDLC films additionally demonstrate utility in UV pattern printing. In conclusion, this work establishes a solid foundation for the development of future PDLC display, information encryption and anti-counterfeiting materials.