Dielectric relaxation spectroscopy and electro-optical studies of a new, partially fluorinated orthoconic antiferroelectric liquid crystal material exhibiting V-shaped switching

Abstract

In this paper we report the results from detailed electro-optical and dielectric studies in various antiferroelectric and ferroelectric phases of an orthoconic antiferroelectric liquid crystal (OAFLC) material . The material possesses high tilt and high spontaneous polarisation. Such an OAFLC, because of its high tilt, provides an excellent dark state. The material exhibits V-shaped switching in the SmC* phase. Dielectric studies reveal the existence of another phase during heating in the range between 78.6 and 92 C which did not appear in the DSC curve and in polarising microscopy. This phase has been identified as the SmC * phase and is extremely sensitive with respect to the cell conditions, aligning material, purity, etc. Three dielectric modes have been assigned in the above-mentioned temperature range and their origins are discussed.

Electro-optic and dielectric investigations of a perfluorinated compound showing orthoconic antiferroelectric liquid crystal

“…The relaxation frequencies of both relaxations show roughly constant behavior with temperature. Mode IIB is Goldstone mode as the relaxation frequency is constant (of the order of 1 to 2 kHz) and its dielectric strength is high [18]. As reported earlier [24], low frequency mode (LFM) is also found to exist much below the GM in our case around 70 Hz for the 10 μm thick cell.…”

“…The investigated high tilted AFLC sample was newly synthesized by R Dabrowski et al [17,18] by using partly fluorinated compounds of a common formula as given below in Fig. 1.…”

“…The phase sequence of the sample is given as below [17,18] The indium tin oxide (ITO) coated planar aligned EHC glass cells with thickness of 4 μm were used for electro-optic study and cells of 10 μm thickness were used for dielectric study. The effective area of the cell was 16 mm 2 .…”

Dielectric and visco-elastic properties of laterally fluorinated liquid crystal single compounds and their mixture

“…The compounds (1)(2)(3)(4)(5) were procured from AWAT Co. Ltd., Warsaw, Poland, and were used without further ISSN 0267-8292 print/ISSN 1366-5855 online Table 1. Chemical structure and transition temperatures of compounds 1-5.…”

“…Laterally fluorinated liquid crystals with negative dielectric anisotropy ( ε < 0) [1][2][3] find wide application in vertically aligned (VA) mode [4,5] devices, ranging from flat-panel liquid crystal display (LCD) devices to high-resolution projection micro displays using Liquid Crystal on Silicon (LCoS) panels [6,7]. Devices operating in the VA mode usually exhibit an excellent contrast in combination with high-speed switching.…”