Rollable multicolor display using electrically induced blueshift of a cholesteric reactive mesogen mixture

Electrically controllable blueshift of the reflection band in a planar cholesteric reactive mesogen cell is observed. The responsible mechanism is electric-field-induced Helfrich deformation [J. Chem. Phys. 55, 839 (1971)]. The modified director configuration can be solidified by photopolymerizing the reactive mesogens when a voltage is applied. The correlation between the director configuration and optical properties is validated by the scanning electron microscope photos and the transmission spectra of a planar and an undulated cholesteric film. With masked curing at different voltages, a rollable multicolor display is demonstrated

Submillisecond-response polymer network liquid crystal phase modulators at 1.06-mu m wavelength

A fast-response and scattering-free polymer network liquid crystal (PNLC) light modulator is demonstrated at lambda = 1.06 mu m wavelength. A decay time of 117 mu s for 2 pi phase modulation is obtained at 70 degrees C, which is similar to 650 x faster than that of the host nematic LCs. The major tradeoff is the increased operating voltage. Potential applications include spatial light modulators and adaptive optics

Electro-optics of polymer-stabilized blue phase liquid crystal displays

Electro-optics of polymer-stabilized blue phase liquid crystal displays (BP LCDs) is analyzed and validated experimentally. A numerical model for characterizing and optimizing the electro-optical and display properties of BP LCDs in in-plane switching and fringe field switching cells is developed. The simulated voltage-dependent transmittance curves agree well with the measured results. To lower the operating voltage while keeping a high transmittance, both electrode width and gap, and large Kerr constant make important contributions. A wide-view BP LCD using a single biaxial compensation film is simulated

Anchoring energy and cell gap effects on liquid crystal response time

The anchoring energy and cell gap effects on liquid crystal response time (tau(0)) is analyzed theoretically and validated experimentally. Analytical expressions are derived using two different approaches: effective cell gap and surface dynamic equation methods. Consistent results are deduced from these two approaches. A simplified equation tau(0)similar to d(x) also fits the experimental data well, where d is the liquid crystal cell gap and x is the exponent. Under two extreme (strong and weak) anchoring limits, the exponent x approaches 2 and 1, respectively. This information is helpful for optimizing liquid crystal devices for display applications

P-153: High Birefringence Fluoro-terphenyls for Thin-cell-gap LCDs

Abstrac

Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals

We infiltrate liquid crystals doped with BaTiO3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum with the one achieved without dopant. New interesting features, such as frequency modulation response of the device and a transmission spectrum with tunable attenuation on the short wavelength side of the widest bandgap, suggest a potential application of this device as a tunable all-in-fiber gain equalization filter with an adjustable slope. The tunability of the device is achieved by varying the amplitude and the frequency of the applied external electric field. The threshold voltage for doped and undoped liquid crystals in a silica capillary and in a glass cell are also measured as a function of the frequency of the external electric field and the achieved results are compared

Sub-Millisecond Response Phase Modulator Using A Low Crossover Frequency Dual-Frequency Liquid Crystal

A high birefringence (Δn = 0.292 at λ = 633 nm, 25°C) and low crossover frequency (\u3c1 kHz at T = 25°C) dual-frequency liquid crystal (DFLC) mixture was developed. The high birefringence enabled us to use a thin liquid crystal cell, which is helpful for fast response time and low operating voltage. The initially low crossover frequency allowed us to operate the DFLC device at an elevated temperature, which significantly lowers the viscosity while keeping the crossover frequency in an acceptable range (\u3c10 kHz). We demonstrated a 2π phase shifter at λ = 633 nm using such a DFLC and obtained a sub-millisecond response time at T∼45°C. This type of DFLC mixture together with elevated temperature operation opens a new way for achieving fast response time. © 2008 Taylor & Francis

Liquid Crystal Droplet Array For Non-Contact Electro-Optic Inspections

We report a high density liquid crystal (LC) droplet array for non-contact inspection. The incident light is modulated by changing the shape of each droplet using a dielectric force even though the electrode and droplet array are separated by a fairly large air gap. The reshaped LC droplets cause colour change which is easily inspected by the human eye. In a sample with 30 μm thick polymer cavity and 130 μm air gap, LC droplet surface reshaping is clearly observed as the applied voltage exceeds 40 Vrms. Potential application of such a LC droplet array for inspecting the defected thin-film-transistor pixels is emphasized. © 2010 IOP Publishing Ltd

Electrically-Controllable Multi-Color Reflective Display Using A Single Cholesteric Liquid Crystal Cell

Blue shift of the reflection band through electrically-induced Helfrich deformation in cholesteric liquid crystal is demonstrated. The reflective color can be controlled by the applied voltage. This device can be used for reflective display if the transition to focal conic texture through oily streak can be suppressed. The color change can also be written into a thin polymer film by using cholesteric reactive mesogen to achieve rollable multi-color reflective displays. © Copyright 2006 Society for Information Display

Flexible Area-Color Reflective Displays Based On Electric-Field-Induced Blueshift In A Cholesteric Liquid-Crystal Film

An electrically controllable blueshift of the reflection band is observed in a cholesteric liquid crystal with either positive or negative dielectric anisotropy. The change in optical properties is a result of a two-dimensional periodic undulation of the cholesteric texture, known as Helfrich deformation. This blueshift mechanism was used to demonstrate area-color reflective displays in a cholesteric cell and a reliable polymeric film. © Copyright 2008 Society for Information Display