A flat panel display device is provided with an increased viewing angle having good dark versus light imaging contrast. The display device includes a display panel, a first optical unit, and a second optical unit. The display panel includes a liquid crystal layer that is driven in a vertical alignment mode. The first optical unit includes a negative C-plate and a first polarizer having a first absorption axis. The second optical unit includes a biaxial compensation plate having a refractive indices coefficient, (nx−nz)/(nx−ny) of more than 0.45 and less than 0.55, and a second polarizer having a second absorption axis crossing the first absorption axis. The biaxial compensation plate has a refractive indices relationship of nx>nz>ny such that dispersion of polarization states of colored light rays passed through the C-plate and the liquid crystal layer may be minimized and gathered about an extinction point, thereby improving contrast at side viewing angles.