Importance

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Abstract

A light regulation element regulates both the travelling direction and diffusion state of a light emitted from a surface light source device. Lights from a cylindrical light source 2 such as a cold cathode tube is introduced in a light guide 1. The light guide 1 has an emission surface 1a on the side opposite to a reflection element 4, and a light regulation element 3 is arranged in opposition to the emission surface 1a. Protrusions 3a are formed on one surface or both surfaces of the light regulation element 3. Coated on the surface on the light emission side of the light regulation element 3 is a light diffusion layer 5. The turbidity of the light diffusion layer 5 falls within a range from 1900 cm.sup.-1 to 2400 cm.sup.-1 . The light emitted from the emission surface 1a of the light guide penetrates the light regulation element 3, thereby causing the light travelling direction to be regulated. Then, the light whose travelling direction has been regulated penetrates the light diffusion layer 5, thereby causing a light diffusion. The light diffusion layer 5 is formed, for example, by mixing fine particles of a glass having a light penetrability or of a synthetic resin such as acryl and silicone, or fine hollow particles of glass, acryl resin or the like, or air bubbles in a coating material having a light penetrability.

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First Claim