Abstract
The spontaneous vertical alignment of liquid crystals (LCs) in gelator (12-hydroxystearic acid)-doped LC cells was studied. Gelator-induced alignment can be used in both positive and negative LC cells. The electro-optical characteristics of the gelator-doped negative LC cell were similar to those of an LC cell that contained a vertically aligned (VA) host. The rise time of the gelator-doped LC cell was two orders of magnitude shorter than that of the VA host LC cell. The experimental results indicate that the gelator-induced vertical alignment of LC molecules occurred not only on the surface of the indium tin oxide (ITO) but also on the homogeneous alignment layer. Various LC alignments (planar, hybrid, multistable hybrid, and vertical alignments) were achieved by modulating the doped gelator concentrations. The multistable characteristic of LCs doped with the gelator is also presented. The alignment by doping with a gelator reduces the manufacturing costs and provides a means of fabricating fast-responding, flexible LC displays using a low-temperature process.
Highlights
The alignment of liquid crystals (LCs) is very important for LC devices such as sensors [1,2,3,4], light shutters [5,6,7], and displays [8,9], because it causes them to exhibit a specific uniform orientation
These results demonstrate that the ability of 12-hydroxystearic acid (12-HSA) to align vertically the LC molecules is comparable with that of the conventional alignment material DMOAP
LC cell was only ~2.4% of that of the vertically aligned (VA) host LC cell when the step-voltage driving scheme was used. These results indicate that the gelator-doped LC cell was two orders of magnitude faster than the VA
Summary
The alignment of liquid crystals (LCs) is very important for LC devices such as sensors [1,2,3,4], light shutters [5,6,7], and displays [8,9], because it causes them to exhibit a specific uniform orientation. LCs can be aligned using several methods; in the liquid crystal display (LCD) industry, the molecular orientation of LCs is mainly achieved by rubbing polyimide films. Langmuir–Blodgett films that are formed by mixing fatty acids with LCs can cause LC molecules to be aligned perpendicularly to substrate surfaces [14,15]. Gelator-doped LCs have shown to possess the multistable characteristic, and some devices, such as phase gratings and phase-retardation plates based on gelator-doped LCs have been realized [26,27]. In this investigation, the spontaneous vertical alignment of gelator-doped LC cells was examined. The multistable property and various alignments in gelator-doped LCs are presented
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