Low-temperature processable transparent liquid crystal light shutter

Abstract

Tunable light shutters show their great potential as smart windows, especially when energy efficiency is greatly entailed. Polymer-dispersed liquid crystals (PDLCs) are one of the most well-known and promising methods for smart window applications, but there are many obstacles to overcome or to develop further. At first, PDLCs require high voltages not only when to switch from an opaque to a transparent state but also to maintain the transparent state. A transparent mode, which can be produced by polymer-stabilizing homeotropic alignment of LCs, can be one of the ways to reduce energy consumption significantly from this perspective. However, the most efficient material for the induction of the homeotropic alignment, polyimide requires high temperature for the surface treatment process. Here we demonstrate a low-temperature process for plastic substrates, allowed via a homeotropic alignment induction molecule, premixed in LCs. The mixture before polymerization contains LCs, a reactive mesogen, and a homeotropic alignment inducer. The homeotropic alignment inducer plays a role of polymer-stabilization as well. We believe the result clearly suggests a novel approach to resolve the issues in establishing initial structures and energy consumption of PDLCs for smart windows.