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

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%.