Abstract
The effects of dichroic dye (SI361) on electro-optical properties of polymer dispersed liquid crystal (PDLC) films and morphology of liquid crystal droplets are discussed in this study. From the observation with polarizing optical microscopy (POM), the characteristics of phase separation in liquid crystal (E63)、dye (SI361)、epoxy (DER736) and amine (An2143) and the phase diagram in E63/SI361/DER736, E63/SI361/An2143 and E63/ SI361/DER736/An2143 mixture can be obtain. The time and temperature for thermal reaction are determined by means of differential scanning calorimeter (DSC) and thermogravimeter analyzer (TGA). Then, we analyze electro-optical properties including V-T curve, response time and hysteresis in PDLC films with different dye concentration. Besides, the morphology of liquid crystal is analyzed from the scanning electron microscope (SEM).Because dye is nucleus in E63/DER736 or E63/ DER736/An2143 mixture, the phase separation temperature of liquid crystal with dye is higher than that without dye. On the other hand, dichroic dye would absorb UV light, thus time that PDLC films expose to UV light must increase to UV curl completely. Besides, owing to incorporation of dye, thermal curing temperature of PDLC films with dye is also higher than that without dye. Nevertheless, in corporation of dye substantially improves the contrast of PDLC films. Although dye has this advantage, rise time could increase at 20V because it cannot be rotated by liquid crystal.We discover that the increasing thermal curling time of PDLC films increases threshold voltage, contrast ratio, rise time, hysteresis and anchoring. Besides, we also find the increasing thermal curing time of PDLC film leads to the alignment of the LC droplets to the substrate.