Disclosed are an LCD and a method of illuminating a liquid crystal layer. A protecting sheet is disposed on a reflection polarization film for enhancing the brightness. The protecting sheet is made of polyethylene terephthalate based material manufactured by an extension process to enhance the brightness, to improve visual angle and to prevent a Moire phenomenon. The LCD and the illumination method of the present invention enable high brightness displaying, color modulation depending on the visual angle and a relatively low manufacturing cost.