Nematic Liquid Crystals for Active Matrix Displays: Molecular Design and Synthesis

Abstract

Substances forming calamitic mesophases have been known for more than 100 years but only the recent, rapid advance in active matrix liquid crystal display (AM‐LCD) technology helped these materials to achieve the crucial position in flat panel display technology they hold today. Due to their high contrast, large viewing angle, and rapid switching times, modern AM‐LCDs offer a superior picture quality even compared to conventional cathode ray tubes. Their flatness, low weight, and low energy consumption render them the technology of choice for all kinds of portable devices. Some of the future promises of AM‐LCD technology are centered around the development of liquid crystalline materials for the different subtypes of active matrix applications. This development is aimed, on the one hand, towards improved electrooptical and viscoelastic properties; on the other hand, the increasing performance of LCDs leads to extremely stringent reliability demands on the liquid crystals. Responding to these high standards of performance and quality, most liquid crystals for contemporary AM‐LCD applications are multiply fluorinated compounds with very high purities, as is typical for materials used in the electronics industry. The synthesis of these superfluorinated materials (SFMs) often requires specialized methods, which, in several cases, had to be introduced for the first time into the canon of industrial production. The immense market pressure, as well as the rapid advance of AM‐LCD technology on the side of the display manufacturers, urges an increasing pace of the materials development. This demand for new materials can no longer be fulfilled by conventional trial‐and‐error approaches. As in the pharmaceutical industry, in the search for new, superior liquid crystals, the purely empirical methods are increasingly supported by a rational design based on computational methods.

Determination of Orientational Order Parameters of Two Tri-Component Mixtures from Optical Birefringence and X-Ray Diffraction Measurements

“…In contrast, the vertically aligned (VA) mode LCD's [1][2][3][4][5], based on liquid crystal materials with negative dielectric anisotropy, offers a superior picture quality with wide viewing angle [6,7], high contrast [8] and video-compatible switching times [9,10]. Liquid crystalline materials suitable for VA mode LCD's are mainly focused on dielectrically negative fluorinated liquid crystals comprising of 1,2-difluorobenzene building block [11] which combine the necessary polarity with chemical stability and low polarizability [12,13] suitable for their application in VA mode LCD's. Difluorinated alkoxy compounds are suitable for preparation of VA mixtures because of their large negative dielectric anisotropy and low optical birefringence.…”

Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

“…All these factors create additional sources of ions of organic origin [82]. However, recent advances in the chemical synthesis of novel liquid crystal materials exhibiting improved chemical stability reduced the probability of such events significantly [83][84][85][86]. Liquid crystals can get contaminated with ionic impurities during the process of chemical synthesis.…”

“…By applying the proper chemical design along with the methods of chemical synthesis and post-synthetic techniques, many improved liquid crystal materials were successfully produced and tested in numerous applications [2,28,[83][84][85][86]. The high resistivity liquid crystals are characterized by extremely low levels of ionic impurities.…”

Synthetic chemistry and biological activity of pentafluorosulphanyl (SF5) organic molecules

“…The review is structured in three main sections: (1) Synthesis of SF 5 containing molecules (primary reactivity); (2) Reactions of SF 5 -containing molecules (secondary reactivity); (3) Biological properties. Different aspects of the chemistry and properties of SF 5 compounds have been reviewed, mainly in book chapters [4][5][6][7][8][9]. To our knowledge the most recent general review covering SF 5 -compounds dates back to 2005 [10] and comprehensively covers the literature until 2000, with scattered references to articles published in the following two years.…”