Nanowire grid polarizer for energy efficient and wide-view liquid crystal displays

We report a liquid crystal display (LCD) using a nanowire grid polarizer (NWGP) to replace the bottom sheet linear polarizer (LP). The top LP and bottom NWGP configurations enable backlight recycling for enhancing optical efficiency while keeping a high contrast ratio and wide viewing angle. The electro-optic performance of this device configuration is studied based on the effective-medium theory and 4 x 4 matrix method. Results show that this configuration exhibits a 100: 1 contrast ratio over 75 S viewing cone in a film-compensated multidomain vertical alignment LCD and 10: 1 over 65 S viewing cone in a fringe-field switching LCD without any compensation film. (C) 2008 American Institute of Physics

Modeling Of Liquid Crystal Display And Photonic Devices

Liquid crystal (LC) materials have been widely applied in electro-optical devices, among which display is the most successful playground and numerous new applications in photonic areas (such as laser beam steering devices) are also emerging. To well guide the device design for optimum performance, accurate modeling is of prior and practical importance. Generally, the modeling of LC devices includes two parts in sequence: accurate LC molecule deformation extraction under external electric fields and optical calculation thereafter for the corresponding electro-optical behaviors. In this dissertation, first, hybrid finite element method and finite difference method are developed to minimize the free energy of the LC systems. In this part of study, with computer-aided derivation, the full forms of the LC free energy equations without any simplification can be obtained. Besides, Galerkin\u27s method and weak form technique are further introduced to successfully degrade the high order nonlinear derivative terms associated with the free energy equations into ones that can be treated by first order interpolation functions for high accuracy. The developed modeling methods for LC deformation are further employed to study display structures, such as 2D and 3D in-plane switching LC cells, and provides accurate results. Followed is the optical modeling using extended Jones matrix and beam propagation method to calculate the electro-optical performances of different devices, according to their amplitude modulation property or diffractive one. The developed methods are further taken to assist the understanding, development, and optimization of the display and photonic devices. For their application in the display area, sunlight readable transflective LCDs for mobile devices and the related optical films for wide viewing angle are developed and studied. New cell structure using vertically aligned liquid crystal mode is developed and studied to obtain a single cell gap, high light efficiency transflective LCD that can be driven by one gray scale control circuit for both transmissive and reflective modes. And employing an internal wire grid polarizer into a fringe field switching cell produces a single cell gap and wide viewing angle display with workable reflective mode under merely two linear polarizers. To solve the limited viewing angle of conventional circular polarizers, Poincare sphere as an effective tool is taken to trace and understand the polarization change of the incident light throughout the whole LC system. This study further guides the design of high performance circular polarizers that can consist of purely uniaxial plates or a combination of uniaxial and biaxial plates. The developed circular polarizers greatly enhance the viewing angle of transflective LCDs. Especially, the circular polarizer design using a biaxial film can even provide comparable wide viewing angle performance for the same vertically aligned cell as it is used between merely two linear polarizers, while using circular polarizers can greatly boost the display brightness. As for the beam steering device modeling, the developed LC deformation method is taken to accurately calculate the associated LC director distribution in the spatial light modulator, while beam propagation method and Fourier transformation technique are combined to calculate the near and far fields from such devices. The modeling helps to better understand the origins and formations of the disclinations associated with the fringe fields, which further result in reduced steering efficiency and output asymmetric polarizations between positive and negative diffractions. Optimization in both voltage profile and driving methods is conducted to well tune the LC deformation under strong fringe fields and improve the light efficiency

Wide-view and single cell gap transflective liquid crystal display using slit-induced multidomain structures

A wide-view transflective liquid crystal display (TR-LCD) using a single cell gap multidomain vertical alignment (MVA) cell is proposed. Unlike a conventional MVA which uses physical protrusions to form multidomain structures, our TR-LCD uses slit-induced longitudinal and fringe electric fields to generate multidomains. As a result, wide-view, high contrast ratio, and high transmittance are obtained. By varying the slit density in the transmissive and reflective regions, the optical path-length disparity between these regions can be balanced. Potential application of this TR-LCD for mobile displays is emphasized. (C) 2008 American Institute of Physics

Transflective Liquid Crystal Display with Fringing and Longitudinal Electric Field

A transflective liquid crystal display with uniform cell gap configuration throughout the transmissive and the reflective display region is invented. Mutually complementary common electrode pattern and reflector pattern or mutually complementary ITO pixel electrode pattern and reflector pattern produce an electric field in the transmissive display region that has a uniform longitudinal field and an electric field in the reflective display region that is a fringing field. An initially vertically aligned negative dielectric anisotropic nematic liquid crystal material between the electrodes forms a smaller tilt angle with respect to the substrate normal in the reflective display region while a larger tilt angle with respect to the substrate normal in the transmissive display region. Consequently, the ambient incident light experiences smaller phase retardation in the reflective display region while the light from the backlight source experiences larger phase retardation. Since the ambien

Transflective Liquid Crystal Display Having Mutually Complementary Patterned Electrode and Reflector

A transflective liquid crystal display with uniform cell gap configuration throughout the transmissive and the reflective display region is invented. Mutually complementary common electrode pattern and reflector pattern or mutually complementary ITO pixel electrode pattern and reflector pattern produce an electric field in the transmissive display region that has a uniform longitudinal field and an electric field in the reflective display region that is a fringing field. An initially vertically aligned negative dielectric anisotropic nematic liquid crystal material between the electrodes forms a smaller tilt angle with respect to the substrate normal in the reflective display region while a larger tilt angle with respect to the substrate normal in the transmissive display region. Consequently, the ambient incident light experiences smaller phase retardation in the reflective display region while the light from the backlight source experiences larger phase retardation. Since the ambien

Electro-optic properties of a homeotropic liquid crystal cell with 90 degrees surface rubbings and a reverse-handed chiral dopant

The electro-optic properties of a 90 degrees twisted-homeotropic liquid crystal (LC) cell with a chiral dopant whose handedness is opposite to the LC twist are studied. In the voltage-off state, the LC directors exhibit a homeotropic alignment. However, in the intermediate voltage state, the bulk LC directors behave like a homogeneous alignment due to the balanced torques between the electric field, surface anchoring, and reversed chiral dopant. Potential applications of this mode for liquid crystal displays, especially for dual-cell-gap transflective liquid crystal displays, are emphasized

Alignment layer effects on thin liquid crystal cells

Factors affecting the thin cell performance of a liquid crystal cell are analyzed. Examples based on vertically aligned thin cells are given to illustrate these effects. When the cell gap is below similar to 2 mu m, the liquid crystal alignment material, layer thickness, and anchoring energy all play important roles. The first two factors affect the threshold and on-state voltage, while the last one affects the operating voltage and response time. Three reflective liquid crystal cells are studied experimentally. Good agreement between experiment and theory is obtained. (c) 2008 American Institute of Physics

Liquid crystal display devices with high transmittance and wide viewing angle

Apparatus, methods, systems and devices for high aperture ratio, high transmittance, and wide viewing angle liquid crystal display having first and second substrates each with an alignment layer and polarizer on the interior and exterior surface thereof and a liquid crystal material therebetween forming plural pixels each having a common electrode group and a pixel electrode group each having at least one common and pixel electrode. A fringe field drives the molecules in the regions above and below the electrodes and a horizontal field drives the molecules between the electrode groups to achieve high transmittance. In an embodiment an insulating layer separates the substrate and alignment layer and the pixel electrodes are on the substrate and the common electrodes are on the insulating layer. In another embodiment a compensation film is layered between one of the substrates and corresponding polarizer

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

Transflective LCD Using Multilayer Dielectric Film Transflector

A novel transflective liquid crystal display (LCD) is provided with a multilayer dielectric film transflector. The dielectric transflector is composed of alternating high and low refractive index dielectric material layers deposited directly on the inner side of the LCD substrate to avoid parallax. The transmittance of the dielectric transflector can vary from approximately 5% to approximately 95% by simply adjusting the individual dielectric layer thickness and the arrangement of layers. The thickness of the 10-layer film is approximately 700 nm, which does not affect the voltage drop on the LC. Two structures of the dielectric film using different positions of the materials of construction are provided and demonstrated. Such a transflective LCD exhibits outstanding features, such as, robust dielectric film, single cell gap, no parallax, and a simple fabrication process