Sebastian Gauza

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.

Extended Kerr effect of polymer-stabilized blue-phase liquid crystals

Electric-field-induced birefringence of a polymer-stabilized blue-phase liquid crystal (BPLC) is investigated. In the low field region, conventional Kerr effect holds. As the electric field increases, the induced birefringence gradually saturates and deviates from Kerr effect. An exponential convergence model, called extended Kerr effect, is proposed to fit the experimental data. Good agreement between experiment and model is obtained. This extended Kerr effect will make a significant impact to the optimization of emerging BPLC display devices.

Submillisecond Gray-Level Response Time of a Polymer-Stabilized Blue-Phase Liquid Crystal

The gray-to-gray response time of a polymer-stabilized blue-phase liquid crystal is investigated. As the voltage increases, rise time decreases gradually but decay time remains unchanged. A set of analytical equations is used to fit the measured results, and an acceptable agreement is obtained.

Refractive indices of liquid crystals for display applications

This paper reviews the extended Cauchy model and the four-parameter model for describing the wavelength and temperature effects of liquid crystal (LC) refractive indices. The refractive indices of nine commercial LCs, MLC-9200-000, MLC-9200-100, MLC-6608, MLC-6241-000, 5PCH, 5CB, TL-216, E7, and E44 are measured by the Multi-wavelength Abbe Refractometer. These experimental data are used to validate the theoretical models. Excellent agreement between experiment and theory is obtained.

Temperature effect on liquid crystal refractive indices

A model describing the temperature effect of liquid crystal (LC) refractive indices is derived and confirmed by experiment. Two single LC compounds (5CB, 5PCH) and two mixtures (MLC-6241-000 and UCF-35) with different birefringence values were used to validate the model. This model fits all the experimental data well. For a low-birefringence LC mixture, if the operating temperature is far below its clearing point, the temperature-dependent refractive indices can be approximated as a parabolic form. This prediction is also experimentally validated. In addition, a linear relationship between 〈n2〉 and temperature is found.

Modeling of Blue Phase Liquid Crystal Displays

We propose a numerical model based on Kerr effect for simulating the electro-optics of polymer-stabilized blue phase liquid crystal displays (BP-LCDs). Parameters affecting the electro-optics of BP-LCDs in in-plane-switching (IPS) structures, such as wavelength, temperature, electrode dimension, and cell gap are investigated. In addition, viewing angle and color shift of IPS BP-LCDs are studied.

Tunable-focus flat liquid crystal spherical lens

A tunable-focus spherical lens using two flat substrates and inhomogeneous electric field over a homogeneous liquid crystal (LC) layer is demonstrated. The top flat substrate has an imbedded spherical indium–tin–oxide (ITO) electrode and the bottom has a planar ITO electrode on its inner surface. The inhomogeneous electric field generates a centrosymmetric gradient refractive index profile within the LC layer which causes the focusing behavior. The focal length of the LC lens can be tuned continuously from infinity to 0.6 m by the applied voltage.

Hysteresis Effects in Blue-Phase Liquid Crystals

Hysteresis effects of two blue-phase (BP) liquid crystals BP-I and BP-II, and polymer-stabilized BP-I and BP-II are investigated. BP-I exhibits a relatively slow response time and a large hysteresis. After polymer stabilization, its operating voltage is increased slightly, but its response time is dramatically reduced and hysteresis narrowed. In contrast, BP-II exhibits almost no hysteresis and submillisecond response time, but after polymer stabilization its hysteresis is amplified.

High Birefringence Isothiocyanato Tolane Liquid Crystals

The phase transition temperatures, birefringence and visco-elastic coefficient of several high birefringence isothiocyanato tolane compounds were evaluated. The polarizability of these compounds was calculated by the Austin Model 1 (AM1) and Modified Neglect of Diatomic Overlap (MNDO) methods. Using these compounds, we have formulated a eutectic mixture exhibiting a wide nematic range and high figure of merit.

Fast Switching Liquid Crystals for Color-Sequential LCDs

High birefringence (0.3 < Deltan < 0.4) and relatively low-viscosity liquid crystal mixtures containing isothiocyanato tolane and isothiocyanato terphenyl liquid crystals are developed. A twisted-nematic (TN) 1.6-mum thin cell for color-sequential liquid crystal display with ~1-ms response time is demonstrated.