Abstract
Liquid crystal displays (LCDs) have been widely used in large variety of applications as information display devices due to the compact size and lighter weight. However, the light efficiency in current LCDs is only 4-7%. One of the major losses of LCDs is the absorption of down polarizers. In order to obtain polarized light for liquid crystal layer to manipulate light, over 50% of energy is absorbed. Solutions have been proposed to edge-lit and direct-lit backlight system respectively for enhancing light transmission efficiency in this thesis. For edge-lit backlight unit, a high extinction ratio, high brightness enhancement, and low color shift backlight unit has been proposed which features with a aperture-limited light guide plate and a hybrid wire-grid polarizer. Concept of polarization recycling and brightness enhancement are realized in the backlight unit so as a high efficiency backlight unit. To evaluate the design, a 2.5 inches backlight unit with a commercial wire-grid polarizer and components fabricated by ultra-precision diamond tooling is demonstrated. By experimental results, polarized brightness is enhanced by 74%, and optical efficiency is improved by 39%. For direct-lit backlight system, a white light polarized LED module has been proposed. It can be also used in other application such as anti-glare illumination. The module features with a dielectric-metal multilayer nanostructure wire-grid polarizer and half-wave retarders to realize the polarization conversion. The module increase the degree of polarization at the outlet of the whole packaged LED module, so as to improve the overall energy efficiency of direct-type LED backlighting. To evaluate the design, a commercial wire-grid polarizer was laminating with a nano photoresist film made by nano imprint process to become the cross stacking wire-grid polarizer. The cross stacking wire-grid polarizer and UV resin was packaged on a LED chip. By experimental results, polarization efficiency is increased to 72%, and the overall gain is 1.4X.