Effect of surface alignment layer and polymer network on the Helfrich deformation in cholesteric liquid crystals

Abstract

We show that the Helfrich deformation can be used for fast response time, low driving voltage reflective displays by using cholesteric liquid crystals under short voltage pulses (∼10 ms). Rather than turning planar domains into focal conic domains through a nucleation process, as used in bistable modes, the fast voltage pulse only deforms the cholesteric planar layers to form wrinkled layers. Since the deformed state is formed through a homogeneous process, quick response times and low operating voltage can be achieved. We studied the effects of alignment layer and dispersed polymer on the stability of the Helfrich deformed cholesteric layers, and found that homogeneous alignment layer and polymer network can inhibit the nucleation process responsible for breaking the layers.

Manipulation of Structural Colors in Liquid-Crystal Helical Structures Deformed by Surface Controls

“…However, for large angle α, we observed spectral blue shift of selective reflection from the CLC on the PPFVB surface. Similar results with these spectral shift and broadening of PBGs have been observed in transmission spectra of the electrical switching modes of CLC gels and the transient state with two-dimensional periodic undulations of helical structures induced by electric field applications, that is, the Helfrich deformation. ,− It is noted that deformed CLC structures on PPFVB surfaces are durable without additional solidification process and can be obtained from only surface controls without applications of external fields. In the present system, it was difficult to determine a threshold value of surface energy for cholesteric deformations on the PPFVB surface.…”

Estimating physical properties from liquid crystal textures via machine learning and complexity-entropy methods

“…Examples include the microscopic order parameter, from which several other parameters characterizing the nematic phase are dependent [3], and the pitch length of cholesteric liquid crystals. The latter is easily obtained under an optical microscope when the helical * rzola@utfpr.edu.br † hvr@dfi.uem.br axis lies perpendicular to the viewing direction [13], but cannot be estimated from the most commonly used experimental arrangements, where the helix orients parallel to the viewing direction (often called Grandjean texture, used in reflective displays) [14]. In this context, image-based characterization of liquid crystals can benefit hugely from state-of-the-art machine learning techniques [15].…”

Characteristics of dual mode reflective cholesteric display

“…Therefore, depending on the desired function of the Ch device, it can be stabilized in different textures; color tuning, bandwidth broadening, and optical attenuation have been reported by adding polymer network into Ch liquid crystals . Particularly, it has been demonstrated that the stability of Ch layers, which undergo Helfrich deformation, can be significantly enhanced as the planar texture is stabilized by introducing the polymer network …”

“…[18][19][20] Particularly, it has been demonstrated that the stability of Ch layers, which undergo Helfrich deformation, can be significantly enhanced as the planar texture is stabilized by introducing the polymer network. 21…”