SIDE LIGHT TYPE SURFACE LIGHT SOURCE DEVICE

摘要

PURPOSE: To obtain a side light type surface light source device which is simple in structure, has a high light utilization rate and allows the control of light emission intensity. CONSTITUTION: This side light type surface light source device has a scattering light transmission body 20, a primary light source (fluorescent lamp) L arranged alongside a light incident surface 22 side, a silver foil sheet R enclosing this light source, a prism sheet 4 arranged along a light taking-out surface 23 and a silver foil sheet S arranged along a rear surface 25. The rear surface 25 side of the sectional shape of the scattering light transmission body 20 is composed of three blocks I to III. The block I is a projecting arc section having a radius of curvature of 330mm. The tangent direction at the light incident surface 2 side end is parallel with this light taking-out surface 23. The tangent direction at the boundary with the block II inclines 4 deg. with the light taking-out surface 23. The block II and the block III are straight blocks inclined 4 deg. and 3.6 deg. with the light taking-out surface 23. The exit light intensity distribution of this surface light source device is made into the distribution where the high luminance is observed near the central part. The various exit light intensity distributions are realized by changing the transition of the inclination of the rear surface.