Balanced electro-optical properties and off-axis haze performance of a polymer-dispersed liquid crystal film via refractive index matching

Abstract

As a type of smart dimming film, polymer-dispersed liquid crystals (PDLCs) show great prospects in the fields of indoor partition, electronic curtains, and automobile windows. However, its high off-axis haze greatly impacts the application scope. This obvious shortcoming is mainly caused by the serious mismatch between the effective refractive index of the liquid crystal (n_eff) and the refractive index of the polymer matrix (n_p) at large viewing angles. Thereby, factors affecting the viewing angle of a PDLC film are analyzed in this research, including the birefringence of the liquid crystal (Δn), film thickness, and the refractive index of the polymer matrix (n_p). Balanced electro-optical properties are guaranteed simultaneously. It is found that high on-state transmittance and low off-axis haze can be achieved at large viewing angles in the suggested optimized case where Δn is within the range of 0.1–0.13; the film thickness is between 20 μm and 15 μm; and n_p approaches n_o but the difference does not exceed 0.03.