Nematic Liquid Crystals with Negative Dielectric Anisotropy: Molecular Design and Synthesis

Abstract

Despite their relatively uniform structural appearance, the synthesis of liquid crystalline materials for modern display applications involves a broad range of different synthetic methods, such as heterocyclic chemistry, ortho-metallation, transition metal catalyzed carbon-carbon coupling reactions or stereoselective hydrofluorination. This account aims to give an impression of the ongoing challenge to introduce these complex techniques into industrial practice, and to keep pace with the more and more rapid advance of display technology.

High Performance Negative Dielectric Anisotropy Liquid Crystals for Display Applications

“…We also calculated the gray-to-gray (GTG) response times of the VA LCOS, and results are summarized in Table 2. Taking green color as an example, the VR curve was uniformly divided into eight gray levels (1)(2)(3)(4)(5)(6)(7)(8) and the response time between every two gray levels was calculated. Here both rise time and decay time are calculated between 10% and 90% reflectance change.…”

“…However, the free relaxation time is intrinsically dependent on the LC properties and cell configuration. By substituting E = 0 into Equation (1), we can obtain the equation for the free relaxation process: (2) By solving Equation (2), we obtain the free relaxation time of the LC directors:…”

“…Negative dielectric anisotropy (Δε = ε // − < 0) liquid crystals (LCs) [1,2], in which the parallel permittivity (ε // ) is smaller than the perpendicular one ( ), have been widely used for direct-view and projection displays. The common feature of a negative Δε LC is that lateral polar substituents induce a dipole moment perpendicular to the principal molecular axis [3][4][5].…”

Evaluation of carborane‐containing nematic liquid crystals for electro‐optical applications

“…Strategic placement of fluorine atoms in benzene rings is an effective way to construct polar nematic materials with low viscosity and high resistivity (3)(4)(5)(6)(7)(8)(9). In this context, we recently began a systematic investigation of partially fluorinated mesogens containing p-carborane (A and B) and comparison of their properties with those of carbocyclic analogs containing bicyclo[2.2.2]octane (C), cyclohexane (D), and benzene (E) rings ( Figure 1).…”

Liquid Crystals and their Applications in the THz Frequency Range

“…In negative dielectric anisotropic (NDA) LCs, the different dielectric anisotropic behavior is, for example, caused by the laterally substituted cyanide (CN) or fluorine (F) groups [57][58][59]. As a result, a strong permanent dipole moment is formed in the direction perpendicular to the molecular long axis.…”