BACK LIGHT DEVICE AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide an edge light type back light device improving utilization efficiency of light quantity of a light source and reducing weight for making enlargement of a liquid display device easy. SOLUTION: A light source 4 is arranged to face an entry end face 71 of a light guide body 7 having an entry end face 71 and an emission face 72. A polarizing reflection film 1 between the light source 4 and the entry end face 71 makes first straight polarized light from the light source 4 enter into the light guide body 7 and reflects second straight polarized light. The reflected second straight polarized light is diffused and reflected and receives rotation by polarization plane thereof by a reflector 5 for generating first straight polarization light component, which transmits the polarizing reflection film 1. The light guide body 7 transmits and emits the first straight polarized light entered from the entry end face 71 while maintaining a polarized condition thereof. This function is realized by having a thickness change part 75 such that the further the light guide body 7 is separated from the entry end face 71 the thinner a thickness is. The emission face 72 includes a prism sheet 8 arranged in a facing position and a liquid crystal display element 3 is arranged thereon.