| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-grade backlight for a liquid crystal display device with which a uniform space distribution and adequate orientation distribution are obtained and the moires by a prism structure are decreased. SOLUTION: This backlight has a cylindrical light source 1, a light transmission plate 3 which is the light transmission plate having an incident end face 20 parallel to this light source, an exit surface 21 arranged in parallel opposite to a liquid crystal panel and a base surface 22 facing the same in parallel thereto, is provided with plural wedge-like reflecting grooves 4 changed in their depths by the distances from the incident end face 20 and extended in parallel to the incident end face and parting plane dividing plane parts 5 for dividing the wedge-like reflecting grooves 4 on a base surface 22 and is provided with prism-like rugged parts 6 having a plurality of ridge lines extending in a direction orthogonal with the incident end face 20 on an exit surface 21. When the pitch of the wedge-like reflecting grooves 4 in a direction parallel to the axis of the cylindrical light source 1 is defined as A, the pitch in a perpendicular direction as A', the pitch of the prism-like rugged parts 6 as B, the pitch of the pixel electrodes of the liquid crystal panel in the direction parallel to the cylindrical light source as C and the pitch in the perpendicular direction as C', the prism pitch ratios A:B, C:A and C':A' are set within prescribed ranges. |
