Design of integrated light guide plate with functional structure of enhanced diffusion length for ultra-slim LED backlight unit

An integrated light guide plate (LGP) with a functional structure for a longer diffusion length to decrease the thickness was proposed and designed for the large area direct-type LED backlight unit (BLU). The integrated LGP is composed of a concave cone structure on the top surface and a rugged bottom surface. The light emitted from the LED sources can be reflected on the top surface and diffuse effectively inside the LGP and in the bottom air-gap, which is placed below the LGP to realize sufficient diffusion length even in the ultra-slim structure. After comparing the optical simulation results with the measured data from the fabricated hexagonal unit cell of an LGP, we verified our design concept and realized the integrated LGP. The final LGP for a 55-inch LED display shows a brightness uniformity of 90.5% with a reduced number of 81 LEDs and a thickness of 6 mm, a remarkably reduced value compared with previous direct-type large area LED backlight units.