Low voltage and hysteresis-free blue phase liquid crystal dispersed by ferroelectric nanoparticles

Abstract

Electro-optical switching with low voltage, free hysteresis and fast response speed is achieved in a facile manner by dispersing a small amount of ferroelectric nanoparticles (NPs) into blue phase liquid crystal. The large dipole moment of NPs contributes to the hysteresis-free switching, whereas the low voltage operation results from the introduction of the ferroelectric properties inherent to the NPs.Blue phase (BP) liquid crystal display (LCD) devices based on the optical Kerr effect are emerging as some of the leading candidates for the next-generation display technology because they exhibit the following revolutionary features: 1 (1) submillisecond gray-to-gray response time that enables field sequential display without using color filters, (2) no need for a surface alignment layer which greatly simplifies the fabrication process, (3) wide and symmetric viewing angle, and (4) cell-gap insensitivity provided that an in-planeswitching (IPS) electrode is employed. Recent developments that introduce BPs with an extended temperature range 2 make them more attractive for applications in LCDs, and Samsung Co. demonstrated the first BP LCD prototype based on polymer stabilized BPs (PSBP) in 2008. 3 However, some bottlenecks such as voltage-induced serious hysteresis and high driving voltage, still remain to be overcome before widespread applications of BP LCD can take off. The hysteresis-free BPLC has been previously achieved by introducing the polymers with flexible chains or the inorganic NPs with large dipole moment, 2d,4 but the high driving voltage (>50.0 V) is a big challenge on the road toward practical applications. Therefore, there is an urgent need to explore a novel strategy to reduce the driving voltage and develop the BP composites with low driving voltage and free hysteresis.It has already been theoretically predicted that the driving voltage (on-state voltage, V on ) is closely related to the Kerr constant of materials and the electrode configuration of devices, and a large Kerr constant or a uniform electric field which penetrates deeply into the bulk liquid crystal (LC) layer helps to reduce the driving voltage of BP LCD. 5 Extensive work on developing new BPLC materials and low-voltage device structures has been recently performed. On the one hand, to enlarge the Kerr constant, the materials with large intrinsic birefringence and dielectric anisotropy have been prepared by the conventional time-consuming and expensive chemically synthetic methods, 6 whereas enhancing the Kerr constant by increasing the Dn$D3 of host LCs unavoidably leads to increased viscosity, which in turn lengthens the response time. On the other hand, to optimize the device structures, several new electrode configurations, such as protrusion electrode, 7 wall-shaped electrode, 8 corrugated electrode 9 and vertical field switching (VFS) electrode, 10 have been proposed one after the other. Despite their remarkable achievements in reducing the driving voltage, many other problems such as sophisticated device fabrication, noticeab...

A comparison between size dependent paraelectric and ferroelectric BaTiO3 nanoparticle doped nematic and ferroelectric liquid crystals

“…6,[14][15][16][17][18][19][20][21][22] In addition to the size, the nanoparticle surface properties are also crucial for the manifestation of a well dispersed medium. Surface modification of NPs has been mainly been employed to achieve long-term stability of NPs in the LC medium and to smoothen director distortions around NPs, 23 thus reducing the cost of elastic energy.…”

“…This is often achieved by coating the surface with monomolecular organic materials, surfactants (stabiliser), or ligands. For instance, oleic acid, 7,10,17,20,21,[24][25][26][27] selenium docosane 28 and dodecylbenzenesulphonic acid 29,30 have been widely utilized for the coating of NPs.…”

Elastic constants, viscosity and response time in nematic liquid crystals doped with ferroelectric nanoparticles

“…16 For the twist mode, diffusivity was shown to decrease for the samples with nanoparticles. However, a full study of these parameters in the ferroelectric suspensions is essential for any prospective applications in displays, 1 blue phase structures 23 or optoelectronics that rely on an agile response and low energy consumption.…”

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

“…Luckily, since the defects can act as potential wells in the system, these impurities are trapped spontaneously in the defects. In the past few years, candidates including nanoparticles [24][25][26] and polymer network [27] were demonstrated to stabilize BPs either experimentally or theoretically [28][29][30]. Such stabilization raises not only the tolerance of thermal variation to a higher level but also the electro-optic threshold of lattice deformation [25] and phase transition to the cholesteric phase [31].…”