Polymer-Stabilized Ferroelectric Liquid Crystals Photocured at Nematic Phase

Abstract

Polymer-stabilized ferroelectric liquid crystals (PSFLCs), in which a photocurable mesogenic monomer is doped into a ferroelectric liquid crystal and a UV photocure is carried out in the SmA or the SmC Ã phase under the application of a bipolar AC electric field, show the monostable and V-shaped electrooptical characteristics, and thus are expected to be a newly developed materials for LC devices. In this study, in order to increase the thermal reliability of PSFLCs, we fabricate a new PSFLC photocured at the nematic (N) phase, and then investigate its characteristics in terms of the electrooptical effect and the X-ray diffraction. Results show that the PSFLC photocured at the N phase does not become monostable because the chevron angle does not coincide with the tilt angle.

Influence of Fabrication Conditions on Monostability of Polymer-Stabilized Ferroelectric Liquid Crystals

“…12,28) To realize the monostable situation of PS-FLCs photocured in the SmA phase, the smectic layer tilt angle (chevron angle) must be equal to the tilt angle of FLC molecules. [22][23][24] It is well known empirically that in a conventional FLC, is not equal to but almost 0:8 owing the energy balance between the layer structure modification from bookshelf in SmA to chevron in SmC Ã and the surface anchoring of the alignment film. In this situation, there exist two energically stable states at the quiescent condition, and thus conventional FLC cells may exhibit bistability.…”

“…However, the bistability of FLC devices is disadvantageous for LC displays, which possess grayscale or full-color capability. 13) In previous papers, [13][14][15][16][17][18][19][20][21][22][23][24] we reported that polymer-stabilized FLCs (PS-FLCs), in which a photocurable mesogenic monomer is doped into an FLC and UV photocuring is carried out in the SmC Ã phase under the application of a bipolar AC electric field or in the SmA phase at the quiescent condition, may show monostable and V-shaped electrooptical characteristics with a grayscale capability without a threshold. The PS-FLCs with V-shaped electrooptical characteristics are usually called PSV-FLCs.…”

“…The PS-FLCs with V-shaped electrooptical characteristics are usually called PSV-FLCs. Many papers concerned with PSV-FLCs photocured in the SmC Ã phase were published, whereas there have been only few for PSV-FLCs photocured in the SmA phase [22][23][24] and the characteristics are not known in detail. In this study, we focus on the PSV-FLCs photocured in the SmA phase since the fabrication process and conditions are not relatively complicated, and research in detail how the fabrication conditions of PSV-FLCs such as polymer concentration, cell gap, and further alignment film materials influence the monostable capability.…”