BACKLIGHT OUTPUT ENHANCEMENT USING CHOLESTERIC LIQUID-CRYSTAL FILMS

Dichroic polarizers are used to produce linearly polarized light in di rect view displays; however, these elements introduce an inordinate am ount of loss. Alternatively, a cholesteric liquid crystal (CLC) film a nd a quarter-wave plate (QWP) combination can be utilized in a display backlight to both polarize and enhance backlight output. A 45% increa se in forward propagating light intensity from a notebook computer bac klight outfitted with a broadband CLC film and a QWP is demonstrated h ere. Polarized backlight output is studied for two types of CLC films: one, a single layer broadband CLC, and the other, a stack of red-, gr een- and blue-reflecting CLC films. In addition, light output was meas ured at different positions on the backlight and for different types o f rear reflectors.