We developed a highly efficient lightguide plate (LGP) using an anisotropic layer (AL) with polarization-separating microstructures. The microstructures were fabricated on a uniaxially stretched polymeric AL through a hot embossing process. Our LGP with asymmetric saw-tooth bistructures produces highly efficient polarized light along the direction normal to the AL by reducing the stray light propagating at large inclination angles. The backlight unit (BLU) with a newly designed LGP has about 30% higher luminance and integrated intensity than the conventional BLU with a reflective polarizer.