We devised a novel buried inverse-trapezoidal (BIT) micropattern that can enable light extracting to both front and back sides of the backlight unit (BLU). The proposed BLU comprised of only a single-sheet light-guide plate (LGP) having the BIT micropatterns only on the top surface of the LGP. The proposed BLU shows normal directional light emitting characteristics to both the front and back sides of the LGP and successfully acts as a planer light source for a dual-sided LCD. The proposed BLU has the potential to dramatically reduce the thickness, weight and cost of the dual-sided LCD thanks to its single-sheet nature.