Nematic Liquid Crystals Doped with Carbon Nanomaterials:haracteristics and Measurement for Dynamic Response
Date Issued
2009
Date
2009
Author(s)
Lee, Chian-Wen
Abstract
Liquid crystals and carbon nanomaterials have been of high interest recently. The switching behavior of liquid crystals plays an important role on the application of display technologies. However, the inevitable impurity ions exist in liquid crystals and affect the device performance. Carbon nanomaterials as dopants fortuitously supply us alternatives to improve the performances of liquid crystals. In this work, nematic liquid crystals doped with several kinds of carbon nanomaterials including multi-wall carbon nanotubes (tube length 5~15μm), carbon nanofibers, multi-wall carbon nanotubes (tube length 1~2μm), helical carbon nanotubes, single-wall carbon nanotubes and fullerenes(C60) were examined in planar-aligned liquid crystal cells by measuring their electrical properties. As indicated by the measurement results, carbon nanomaterials certainly suppress the ion-charge effect to some degree, simultaneously lowering the threshold voltage and effectively improving the hysteresis width of liquid crystals. From the analysis of capacitance-voltage curve, the liquid crystal doped with MWCNT (tube length 5~15μm) sample reduced the hysteresis width and the threshold voltage 34.25% and 52.5%, respectively lower than the undoped E7 sample. Moreover, we defined and ranked the ion trapping coefficient for each carbon nanomaterials to represent the ability of trapping ions. Based on the results, MWCNT (tube length 5~15μm) served as the best dopants in liquid crystals to suppress the ion-charge effect and improve the performance of the liquid crystal.
Subjects
liquid crystals
carbon nanomaterials
carbon nanotube
ion-charge effect
hysteresis
Type
thesis