LENS FOR ILLUMINATION, LIGHT-EMITTING DEVICE, PLANE LIGHT SOURCE, AND LIQUID CRYSTAL DISPLAY

摘要

PROBLEM TO BE SOLVED: To provide a lens for illumination capable of further widening directionality of a light source.

SOLUTION: The lens for illumination 1 includes an incident surface 11 and an emission surface 12. The emission surface 12 includes a first emission surface 121 being convex toward a tip of a light axis A, and a second emission surface 122 enlarging from a peripheral edge part of the first emission surface 121 toward outside. The first emission surface 121 takes on a shape, in which an emission light with an angle from the light axis A to be a predetermined angle or more among emission lights reaching the first emission surface 121 emitted from an origin P which is to be a light source position on the light axis A is made to reach an illuminated surface 3 by being refracted at a second-time reaching point after total reflection at a first-time reaching point. The second emission surface 122 takes on a shape, which makes the emission light reach the second emission surface 122 emitted from the origin P to be refracted at its reaching point and reach the illuminated surface 3. The second emission surface 122 satisfies a relation of 0.21*cos2θ2<0.98 in a region of d/p<0.4.

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