| abstract |
PCT No. PCT/JP97/00328 Sec. 371 Date Sep. 30, 1997 Sec. 102(e) Date Sep. 30, 1997 PCT Filed Feb. 7, 1997 PCT Pub. No. WO97/29398 PCT Pub. Date Aug. 14, 1997A fluorescent lamp L is arranged in the vicinity of an incidence surface 2 of a light scattering guide plate 1. A prism sheet 4' having rows of prism elements and rows of lens elements on each side is arranged outside an exiting surface 5. The angles of inclination of slopes 4a and 4b satisfy a condition that phi a> phi b. The slopes 4a and 4b extend in the transverse direction of the light scattering guide plate 1, and slopes 4c and 4d extend in the longitudinal direction. A reflector 3 is arranged along a rear surface 6. Light emitted from the exiting surface 5 is efficiently propagated by an inner prism surface toward a forward direction, shifted in the transverse direction by an outer prism surface or the lens element surfaces 4c and 4d, and is then returned inwardly. The path histories of light emitted from the prism sheet 4' is diversified to improve visual characteristics. The peak level of brightness as viewed in the forward direction is improved and brightness is smoothly reduced according to deviation from the peak direction. |