Cholesteric liquid crystal based polymer anti-counterfeit lamination films with broadband hyper-reflective properties and effective shielding against infrared laser beams†

Abstract

We innovatively propose broadband hyper-reflective bilayer polymer dispersed cholesteric liquid crystal (PDCLC) films with difficult diffusion between the upper and lower films. Single-layer PDCLC films with broadband reflective properties were prepared using light-induced molecular diffusion and a polymer network-anchored pitch. Then, bilayer PDCLC films with broadband hyper-reflective properties were prepared by filling liquid crystal mixtures of opposite rotations into a specially designed bilayer liquid crystal cassette, and further broadened the reflective broadband by constructing a bilayer liquid crystal system. In the upper liquid crystal polymerisation layer, a pitch gradient is formed inside the liquid crystal film by controlling the content of the polymerisable monomer RM257 and the polymerisation conditions to produce broadband reflections. Subsequently, the left-handed liquid crystal composite system was filled under the upper film, which made it difficult for the lower chiral compounds to diffuse into the upper layer due to the dense mesh structure of the upper layer. The S5011 content was controlled so that the reflection broadband of the lower liquid crystal film overlapped with that of the upper liquid crystal film, and the whole liquid crystal composite system achieved a broadband hyper-reflective effect with a maximum reflection broadband of 1104 nm. We have verified the film's application in infrared reflection and anti-counterfeiting with good results by making temperature simulation models and patterning the film.