Alignment control technology of liquid crystal molecules

Abstract

Liquid crystal displays are now indispensable in everyday life. The display characteristics considerably depend on the configuration of liquid crystal (LC) molecules and interactions between the LC molecules and an alignment film surface. In this paper, we introduce various methods to control parameters that dominate the LC alignment. These parameters include order parameters, the pretilt angle, the director direction, and surface anchoring strength. We also introduce their evaluation methods. In particular, recent alignment film‐free technology is explained in detail. In addition, details of how these parameters are related to the display characteristics, particularly wide viewing angles and fast response characteristics, are described primarily with reference to recent technologies.

On the measurement of the bend elastic constant in nematic liquid crystals close to the nematic-to-SmA and the nematic-to-NTBphase transitions

“…The capacitance C ⊥ was then calculated by taking φ a = 2 • in Eqs. (10) and (12) and the dielectric constants ⊥ and were calculated by dividing C ⊥ and C by the capacitance C 0 of the empty cells. From these measurements the dielectric anisotropy a and the factor γ were obtained.…”

“…Such surface treatments exist but we did not have them. We can cite, for instance, the surface treatment by deposition under oblique incidence of a layer of SiO, at least under certain conditions [36], or certain treatments with photopolymers [12]. This method also requires to have an adequate polymer to obtain a strong homeotropic anchoring, which was the case with 8CB and the mixture 8CB-CB7CB used in this paper.…”

“…It allowed us to prepare all the plates in the same experimental conditions. This was important to always obtain the same pretilt as we know that the latter depends on the rubbing conditions [12]. Nickel wires were used as a spacer to fix the sample thickness and an epoxy glue was used to stick them.…”

Vertical Orientation of Liquid Crystal on Comb-Like 4-(trans-4-alkylcyclohexyl)phenoxymethyl-substituted Polystyrene Containing Liquid Crystal Precursor

“…For example, the vertical orientation of nematic LCs, wherein the director of the nematic LCs is oriented vertically to the surface of the substrate, has been studied for sensor applications because of its susceptibility to small perturbations and binding events [ 15 , 16 , 17 , 18 ], which can be observed by an optical apparatus such as a polarized optical microscopy (POM) [ 19 , 20 ]. It has been demonstrated that LC molecules can be aligned by the anisotropic characteristics of a surface via numerous contact and noncontact methods, such as mechanical rubbing, stretching, lithography, polarized ultraviolet (UV) radiation, and ion beam treatment [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. Among these, the mechanical rubbing of polymeric surfaces is the most commonly used contact method to obtain a uniform orientation of LC molecules because of its simplicity and rapidity [ 29 , 30 ].…”

From Molecular Achirality to Mesoscopic Helicity: Toward the Development of Circularly Polarized Luminescence‐Emitting Liquid Crystal Displays

“…[ 13 ] In the early stage LCD technology, LCs exhibiting twisted nematicity (TN) show better performance in LCD technology and many devices are still using TN–LCDs nowadays due to its fast response time. [ 14 ] In a TN–LCD, the nematic LC layer exists in a twisted or helical configuration between perpendicular alignment layers.…”