| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface light source apparatus having excellent visibility in both of reflecting and transmitting modes and easy to be switched by forming a tilting face having a specified polarized state retaining characteristic in the lower face of a light guiding plate provided with a light source which is made possible to be switched to on and off state in the incident side face. SOLUTION: In a light guiding plate 1 comprising an upper face 11, which is light emitting face, a lower face 12 having a reflecting layer 2, an incident side face 13, a side end part 15 with about 50% or thinner thickness of the face 13, and a side face 16, a light source 3 provided with a lighting and extinguishing switching mechanism constituted of a switch 32, an electric power source 33, etc., is installed in the incident side face 13. Consequently, the light source apparatus is made usable in both of reflective and transmissive modes using outside light and back light. Moreover, the reflecting layer 2 is constituted by alternately forming faces with long side at (-10)-10 deg. tilting angle to the upper face and faces with short side at 25-50 deg. tilting angle. As a result, incident light rays are introduced from the faces with long side and having wider surface area and efficiently reflected in polarized state with excellent orientation property and emitted out of the upper face. In the upper side of the upper face 11 of the surface light source apparatus, liquid crystal cells having polarizing plates in the front and rear sides are arranged to give a liquid crystal display unit usable in both reflective and transmissive modes. |
