Edge-lit LCD backlight unit for 2D local dimming.

Local dimming technology has been highly desired for integration with liquid crystal displays (LCDs) in order to improve their contrast ratios (CRs) as well as to overcome power efficiency bottlenecks. In this paper, we propose and demonstrate a slim (~1 mm) edge-lit LCD backlight unit (BLU) capable of 2D local dimming. We designed a semi-partitioned light guide plate (LGP) patterned with inverse-trapezoidal microstructures, which allows the ultra-slim BLU to function without prism sheets. Since light emitting diodes (LEDs) are placed in the middle of the LGP, the BLU can freely define illuminated areas and the whole BLU can be modularly expanded like a tile canvas. The fabricated BLU achieves uniformity in both local and global luminance distributions, as well as in high local dimming performance. Experimentally, the BLU increases the CR of the display up to two orders of magnitude compared to conventional BLUs.