Polymer‐stabilized blue phases: promising mesophases for a new generation of liquid crystal displays

Abstract

Blue phases—special chiral liquid crystalline mesophases—are promising candidates for electro‐optic devices with improved performance and simplified fabrication. A necessary precondition for possible applications is a significantly enhanced temperature range of their existence, which can be achieved by a cross‐linked polymer network formed by in situ polymerization. Unlike many other mesophases, blue phases are optically isotropic if no voltage is applied. Regarding the transmission of a blue phase cell placed between crossed polarizers, the optical isotropy enables—at least in principle—a perfect dark state, independent of the viewing angle, without the necessity of any alignment layer. The application of an in‐plane electric field induces a strong birefringence (Kerr effect). The effective Kerr constants are much larger than those of isotropic liquids, and the switching times between the dark and the induced bright state are in the submillisecond range. Some basic properties of blue phases, state‐of‐the‐art performance, and remaining challenges of the development of polymer‐stabilized blue phases are reviewed in this article. Copyright © 2014 John Wiley & Sons, Ltd.

‘Blue phases’ of highly chiral thermotropic liquid crystals with a wide range of near-room temperature

“…It is experimentally found that during cooling the existence of BPs has been observed in a wide temperature range about (9-15°C). This positive property can enable application of BPs in practice (for instance, for studies of colloidal particles in BPs [67] at nearroom temperature), as compared to the most wellknown pure thermotropic cholesterics and their mixtures, possessing BPs in narrow temperature ranges (0.5-2°C), that recently leaded to searches of new classes of the CLCs, possessing on the one hand, a wide temperature range of the blue phase, [40][41][42][43][44][45][46][47][48][49][50][51][52][53] in particular bimesogens, PS-BPLC or BPTN, [23,[25][26][27][28][29]33,39] and on the other hand CLCs, having BPs at low temperatures (i.e. at near-room temperature).…”

“…It was also shown that the usage of PS-BPLCs is promising for photonics including 3D lasers, [24,[30][31][32] tunable gratings [34] and displays. [33,[35][36][37][38]44] A fast switching broad-temperature range electrooptical material was demonstrated in [39] for BPTN (by using available nematic LC MLC2048 and chiral dopant (ChD) S-811, further this template was filled with nematic E7). In addition, as shown in, [43,46] the doping of pure CLC CE6 (or CE8 [46]) with hydrophobic surface-treated CdSe nanoparticles can lead to an essentially stabilised BP-III (i.e.…”

“…In this case the fabrication of materials with certain features based on CLCs and polymers (so-called polymer-stabilised blue phase liquid crystals (PS-BPLC) [22,[25][26][27]33]), the search of new LC molecules, such as bimesogens, [23] or the creation of BP polymer-templated nematic (BPTN) [39] are of increasing interest for different applications: solution of the storage problems, [25][26][27] existence of BPs at room temperature [22,23,28,29] and essential increase of BPs thermal range. [29,33,[40][41][42][43][44][45] A new class of BPs of the CLCs, which are stable over a wide temperature range −16-60°C, was recently reported in, [23] that potentially opens up new possibilities for their photonic applications. It was also shown that the usage of PS-BPLCs is promising for photonics including 3D lasers, [24,[30][31][32] tunable gratings [34] and displays.…”

Influence of alignment layers on crystal growth of polymer-stabilized blue phase liquid crystals

“…In order to extend a temperature range of the BPLCs for practical applications, polymer networks are added to BPLCs to stabilize blue phase structure under temperature fluctuations which is also known as polymer-stabilized blue phase liquid crystals (PS-BPLCs) [7]. The PS-BPLCs with a broad temperature range greatly impact device applications [8,9], such as three dimensional mirror-less lasers [10], microlens arrays [11], Fabry Perot filters [12], a dye-doped polarizer-free display [13], variable optical attenuators [14], and grating [15]. However, hysteresis and uniformity hinder the development of PS-BPLC-based devices.…”

Self-Organized 3D Photonic Superstructure: Blue Phase Liquid Crystal

“…Given the mature development of the operation modes for BP, many efforts were then shifted to embed BPLC in various display systems [86,137]. The research and development on BP based LCDs have been documented in detailed discussions [34,35,138,139].…”