Adding to that, if you investigate how LCDs work you will understand that they (at least 'normal' LCDs) use the angle of light in conjunction with polarized filters and a reflector to create the dot/segment shapes. As you move away from the optimum viewing angle, the reflected light becomes more subject to blockage through the polarizing filter and the dark 'on' segments become less blocked by it. The overall effect is less contrast and at extreme angles a negative effect.
Brian.