Backlighting device with a transparent sheet having straight ridges

摘要

A linear light source is disposed adjacent to the side face of a transparent light conducting plate. The thickness of the light conducting plate decreases as the position goes away from the light source. Light diffusing elements are formed on the major surface of the light conducting plate opposite to its light exit surface. At least one transparent sheet has, on the same surface thereof, a number of prisms having straight ridges that are arranged substantially parallel with each other at small intervals. The transparent sheet is disposed on the side of the light exit surface of the light conducting plate so that extensions of the straight ridges intersect the light source substantially perpendicularly.