Abstract
The alignment of chiral nematic liquid crystals in the so-called uniform lying helix geometry allows for the observation and exploitation of the flexoelectro-optic effect. However, high-quality uniform lying helix alignment is difficult to achieve reliably, and this can potentially impact the accuracy of the measurements made on the flexoelectro-optic switching behaviour. Here, we show that, using an appropriate method, it is possible to make measurements of the flexo-electric coefficients that are not substantially influenced by the alignment quality.
Highlights
The molecules that exhibit thermotropic liquid crystal (LC) phases commonly possess a significant electric dipole, which gives rise to the well-known dielectric properties and dielectric anisotropy
In 1969, Meyer suggested a direct coupling between director distortion and the bulk polarization in LCs through distortion-induced molecular ordering and a consequent ordering of the molecular dipoles.[1]
We have demonstrated that a time-resolved measurement method can be used to determine the flexoelectro-optic tilt angle that does not rely on the formation of a high-quality uniform lying helix alignment
Summary
The molecules that exhibit thermotropic liquid crystal (LC) phases commonly possess a significant electric dipole, which gives rise to the well-known dielectric properties and dielectric anisotropy (the difference between the relative dielectric permittivities parallel and perpendicular to the LC director). This anisotropy in the dielectric properties is exploited in the electro-optic behaviour of most LC-based display technologies. For in-plane switching technologies, the dielectric permittivity parallel to the director constitutes the larger component due to the presence of dipoles that are oriented preferentially along the molecule. This came to be referred to as “flexoelectricity,” and its interaction with electric fields is commonly designated as the “flexoelectric effect.” The degree of molecular ordering, and the strength of the induced flexoelectric polarization, depends on the LC director distortion field, which is generally expressed as Pflexo 1⁄4 e1n^(r Á n^) þ e3(r  n^)  n^ ,
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