Mitsubishi Rayon Company, Limited

Muneo Yoneda

Kozo Ida

A surface illuminant device for illuminating a short-distance observation picture plane, capable of easily being enlarged in area without inviting a non-uniformity in visibility, the device comprising a light guide ( ), a light reflection member ( ), a linear light source disposed to extend in a Y-direction along a light incident end face in a Y-Z plane of the light guide ( ), and a prism sheet ( ) for converting a light advancing direction. The light guide ( ) has a light outgoing mechanism of a fine unevenness structure for emitting from a light outgoing surface ( - ) an incident light from the linear source, and a light focusing means for acting on the light passed through the light guide ( ) and the prism sheet ( ) to allow it to leave in a focused status. The light focusing means is formed so that a prism apex angle &agr;, an inclination &bgr; with respect to a normal to the prism sheet, a change rate &ggr; of &bgr; with respect to a prism arraying direction, and a prism arraying pitch P satisfy 55 deg.&lE;&agr;&lE;75 deg., &minus;20 deg.&lE;&bgr;&lE;&plus;20 deg., 0.2 deg./cm&lE;&ggr;&lE;1.5 deg./cm, 10 &mgr;m &lE;P&lE;1000 &mgr;m.

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Nagoya, Japan

Muneo Yoneda