| abstract |
A backlight unit, comprising plural linear light sources, and an optical functional sheet, wherein a prism structure having plural prisms is formed on at least one surface of the optical functional sheet, and the values of (Hn-1+Hn)/(An-An-1) are approximately equivalent, wherein, in a brightness distribution graph that expresses a brightness distribution in the optical functional sheet, A1 is a peak site and H1 is a peak height of a first virtual image, A2 is a peak site and H2 is a peak height of a second virtual image adjacent to the first virtual image, -----, An is a peak site and Hn is a peak height of (n)th virtual image adjacent to (n-1)th virtual image, and these virtual images are derived from the plural linear light sources. |