Preparation and characterization of PDLC films formed using a two‐step procedure

Abstract

ABSTRACT:A novel polymer-dispersed liquid crystal composite film was prepared using liquid crystal and dual resins, namely, UV-curable urethane diacrylate and thermo-curable epoxy, with a fixed LC content of 50 wt%. A combination treatment of UV irradiation and heat was performed in sequential steps. At first, the urethane diacrylate resin was cross-linked through UV irradiation and a pre-UV-cured film was formed. Then, the pre-UV-cured film was heat treated for curing the thermo-curable epoxy resin. As the thermal polymerization continued, LC droplets were formed and became embedded POLYMER-DISPERSED LIQUID CRYSTAL COMPOSITE FILMSwithin the polymer matrix. PDLC films obtained from the polymer matrix with refractive indices in a range from 1.511 to 1.523 (1.517 ± 0.006) have optimal electro-optical properties. Films with a refractive index higher than 1.523 have high contrast ratio (CR), threshold voltage (V th ), and V 90 , whereas those with a low refractive index of 1.508 have low CR, V th , and V 90 . In this study, we found that PDLC composite films with optimal compositions prepared by dual resins (UV/thermal) have good electro-optical properties.

Advanced liquid crystal-based switchable optical devices for light protection applications: principles and strategies

“…In addition, the solubility of dichroic dyes in LCs and the order parameter (S) greatly affect the performance of guest-host light protection devices. Both factors determine the absorbance and contrast of the device [78][79][80][81][82][83][84][85] , as shown in Fig. 6b.…”