SURFACE LIGHT SOURCE DEVICE OF SIDE LIGHT TYPE
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United States of America Patent
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Issued Date -
Apr 25, 2002
app pub date -
Oct 2, 1998
filing date -
Oct 7, 1997
priority date (Note) -
Abandoned
status (Latency Note)
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Abstract
A surface light source device comprises a primary light source, a reflection sheet, a scattering transmission sheet, a guide plate and prism sheet functioning as a light control member. The scattering transmission sheet is provided with scattering power which is given through roughening both faces, uniform containing of fine particles or other means. Light leaked from a back face of the guide plate is reflected and return to the guide plate, being scattered by the scattering transmission sheet on the way. The reflection sheet is a reflection member of high reflectance. A fluorescent lamp emits illumination light which enters into the guide plate and propagates as repeating reflections between the back face and an emission face. Meanwhile, light components having incidence angles smaller than the critical angle with respect to the emission face is emitted from the emission face. The prism sheet and the back face of the guide plate are provided with projections (arrows B, C) which are repeatedly arranged to correct directivity toward the frontal direction in planes parallel and perpendicular with respect to an incidence face of the guide plate. The scattering transmission sheet may be removed, if the reflection sheet is provided with scattering power.
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