Importance

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Abstract

A wedge shaped parallelized light flux element made of a light scattering guide of an emitting directionality has a specified ranged effective scattering irradiation parameter and correlation distance 'a'. A light incident into the parallelized light flux element from a fluorescent lamp arranged facing a light incident surface of the parallelized light flux element is emitted from a light output surface as a parallelized light flux G1 by composite factors including forward scattering of the inside, repeated reflection on wedge shaped two sides, critical angular condition and boundary face transmittance for the light output surface. A total amount of parallel light flux G1 emitted from the parallel light flux emitting section F is reflected on a two side prism surface of two prism reflection element PR thereby being converted into sectional area enlarged light fluxes G2 and G3. They are incident on a liquid crystal panel LP through a light diffusion plate DF, and utilized as a backlight. Reflective appearance of a light supply source for supplying a light to the light scattering guide is prevented by forming a reverse slope portion or the like on back surface of the light output surface in adjacent to the light incident surface of the parallelized light flux element.

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First Claim