Patent ID: 11886075
Assignee: KEIWA INCORPORATED
Field: Optics (Instruments)
Classification: CPC G  F | IPC G

Claim 0:
1. An optical sheet to be interposed between a plurality of small light sources and a prism sheet in a liquid crystal display device having the small light sources arranged in a dispersed manner at a side of the liquid crystal display device opposite to a display screen, wherein:
at least one surface of the optical sheet has unevenness having recesses, each recess having an inverted pyramid shape and being two-dimensionally arrayed,
a distance between the plurality of small light sources and the optical sheet is 2 mm or less, and
a total area of some of minute regions, which have surfaces inclined at inclination angles of 30° or more from an imaginary plane that is a flat surface appearing after imaginarily removing the unevenness, accounts for 30% or more of a total area of all the minute regions, for which the inclination angles are obtained by approximating the surfaces of the minute regions with the unevenness to flat surfaces, while two-dimensionally shifting the minute region with a projection area of 10 μm2 or less and a square shape with respect to the imaginary plane at equal intervals along the imaginary plane to obtain the minute regions at respective points on the imaginary plane.