Vertical Alignment of Liquid Crystal on Film of Plant-based Polysaccharide Derivatives

In this study, we investigate the liquid crystal (LC) alignment of LC cells created from plant-based polysac-charide derivatives, such as guar gum. Guar gum films exhibit satisfactorily high optical transparency in the visible light region (400-750 nm). For example, the transmittance of polyimide films, which are the most typically used LC alignment layers, is 87%, whereas that of guar gum films deposited onto a glass substrate at a wavelength of 550 nm is approximately 99%. The observed LC alignment depends on the rubbing depth. For example, an LC cell comprising a guar gum film fab-ricated via rubbing at rubbing depths of 0.1, 0.2, 0.3, and 0.4 mm exhibits a planar LC alignment, whereas it exhibits a ver-tical LC alignment at a rubbing depth of 0.5 mm. Additionally, the LC alignment is shown to be correlated with the total surface energy of the guar gum films. When the total surface energy of a rubbed guar gum film exceeds 58.10 mJ/m2, an LC cell comprising the guar gum film exhibits a stable and vertical LC alignment. Therefore, guar gum can be used to real-ize the vertical alignment system of LC via a simple adjustment of the rubbing depth.