| 摘要 |
PROBLEM TO BE SOLVED: To obtain a surface light source device with high displaying grade. SOLUTION: The surface light source device comprises a light source 1, a surface of incidence 11 into which, the light emitted from the light source 1 enters, an emitting surface 12 approximately crossing at right angle to the surface of incidence 11, emitting the light entered from the surface of incidence 11, and a light guide plate 10 having plural rows of prisms 15 formed on the surface opposite to the emitting surface 12 so as to extend from the surface of incidence 11 toward a surface 14 facing the surface of incidence 11. For the flat light source device of which, the length of effective light emission area of the light source along the longitudinal direction of the surface of incidence 11 is shorter than the length of the surface of incidence 11 in the longitudinal direction, at least the rows of prisms 15 extending from the area which is near to but other than the surface of incidence 11 and facing the effective light emission area, toward the surface opposite to the surface of incidence 11, are arranged so as to become distant from the perpendicular bisector of the longitudinal length of the surface of incidence. |
