Study on the vertical alignment of nematic liquid crystals by fumed silica doping

The alignment of liquid crystals is important in the manufacturing of devices. Usually, the alignment layer is prepared using a thin-film coating, thermal processing and processes such as rubbing or photo-alignment. Several trials without processes related to the alignment layer were performed for realizing vertical alignment. The main approaches were to utilize the self-assembly of the alignment agent on the substrate. Here, tiny amount of fumed silica, a kind of nano-particle, was added to nematic liquid crystals. With a low frequency electric field and thermal treatment, the region of vertical alignment was obtained. In addition, the efficiency of alignment was related to the polarity of the electric field. The vertical alignment by the fumed silica was active for negative polarity. This results in an easy and convenient way of obtaining vertical alignment.