Polarized light-emitting backlight unit using a retardation film for improving light efficiency in a twisted nematic mode liquid crystal module

Abstract

We propose and demonstrate a new polarized backlight unit (BLU) configuration to enhance light transmission in a twisted nematic (TN) mode liquid crystal (LC) panel. By adding an optimized phase retardation film (PRF) to the BLU, we efficiently controlled the polarization state of the light from the light guide plate (LGP), enabling it to be aligned along the transmission axis of the bottom polarizer of the LC panel. We designed and fabricated a 7 in. edge-lit BLU with a PRF. To obtain a uniform positional distribution in both light intensity and degree of polarization (DOP), the LGP was optimized with linear groove patterns. To maximize BLU light transmission through the bottom polarizer in a TN-mode LC panel, the slow axis of the PRF was aligned at 22.5° with respect to the LED array axis. We improved the transmittance from 45 to 72%.

Polarized backlight unit using a polarization-preserving light-redirecting film for improving luminance gain

“…1. Here, we used a polarized BLU configuration similar to that used in our previous study 20) but with a new LRF on the LGP. The BLU configuration consisted of a polymer LGP with fine prismatic line patterns produced by CO 2 laser ablation [21][22][23][24][25][26][27] on its back surface.…”

“…The LGP had prism patterns whose interval ranged from 280 to 600 µm to ensure a uniform luminance, as reported in our previous study. 20) The height and width of the prism were 23 and 44 µm, respectively. A silver bottom reflector was used to enhance the specular reflection.…”