To provide an optical sheet that is free from delamination due to heat and vibration, by limiting the relationship between the shape and the area of both sides of the optical sheet, in the improvement of the optical sheet for use in controlling a light path in a display backlight unit with the use of a liquid crystal display element.

A diffuser is positioned on one side in a thickness direction. An optical functional member, which controls either one of the direction of emission, range, color or luminance distribution of light, is positioned on the other side in the thickness direction. The optical sheet is obtained by integrating those diffusers and the optical functional members. As shown by oblique lines, the projected area of the optical functional member is equal to or smaller than that of the diffuser.