Low-frequency dielectric processes in deformed helix ferroelectric liquid crystals

Alignment layer and helix controlled unconventional operational switching in ferroelectric liquid crystal

“…In the cell LAHS-2, where the p-UHM is dominant, the optical switching can be obtained at very low field, which means that the surface molecules are crucially playing an important role for low field switching in the FLC materials. As already discussed somewhere else [16] whenever, p-UHM process appears, the surface molecules at the electrode surface are in partially unwound state and needs very low field to get activated in the direction of the electric field. These surface molecules force the bulk molecules to respond, in the same way, resulting into the overall optical change in the FLC cell.…”

“…These two molecular dynamics can be visualized very clearly if the intensity of both dielectric processes is comparable to each other. The characteristics of these two molecular dynamics are totally different as observed by dielectric and electro optical investigations in FLC materials [16,29]. In thick FLC cells of more than 20 µm, the bulk molecular dynamics is very dominant and the surface molecular effect gets neglected.…”

“…The desired square shaped electrode pattern of ITO surfaces was casted by using photolithographic technique. Both the glass substrates having desired pattern of 4.5 mm × 4.5 mm size was coated with polymer nylon 6/6 and the same were rubbed 25 times manually by using velvet cloth, wrapped on a cylinder, along the desired direction for the alignment of liquid crystal molecules [16]. The spacing between two glass plate electrodes was maintained by inserting the Mylar (biaxiallyoriented polyethylene terephthalate, sheet as a spacer) spacer of 8 µm thickness in between two glass plates.…”

“…Similarly, in thin cells (less than 5 µm), the surface effect is dominant and bulk effect gets neglected. In moderately thick cells in between 5 and 20 µm, the surface and bulk effects can be seen, of course, it also depends upon the surface anchoring energy, P s , pitch value etc of the FLC materials [16,17].…”

“…The new relaxation process, caused by the interface of FLC and strongly anchored alignment layer interaction, is always found at lower frequency than the phase fluctuation i.e. GM process and is found dependent on various other parameters like probing AC voltage [14], DC bias voltage, temperature [15,16], spontaneous polarization (P s ) [17]. On the other hand, if the rubbing strength is kept weak, the new relaxation mode is observed in surface stabilized cells [6].…”