SURFACE LIGHT SOURCE DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a backlight capable of improving luminance quality of a light guide body.

SOLUTION: A light source surface of a light emitting diode 13a is mounted oppositely to the lower end face 21a of the light guide body 21. The guide body 21 refracts the light from the diode 13a toward its surface 21b in a planar form to convert it into a planar light source. Both sidewall surfaces 21d of the guide body 21 are tilted so as to enter the light from the diode 13a at an angle not less than a critical angle. Thus, the light entering into both of the sidewall surfaces 21d of the guide body 21 from the diode 13a is totally reflected; refraction of the light illuminated to both of the sidewall surfaces 21d of the guide body 21 can be prevented; and energy loss of the light from the surface 21b of the guide body 21 can be prevented. The luminance quality of the whole surface 21b of the guide body 21 can be improved.

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