Patent ID: 7729050

Claim:
A diffusion sheet that diffuses light incident thereon from a light incident side and causes the light to outgo from a light outgoing side, comprising: a plurality of approximately trapezoidal columnar unit lens portions disposed such that long-axis directions thereof are in parallel with each other, wherein all surfaces of the unit lens portions, which correspond to long bottom segments of approximately trapezoidal sections of the unit lens portions vertical to the long-axis directions thereof, are disposed on a light-incident-side flat surface; and a plurality of light absorbing portions interposed between adjacent unit lens portions of the plurality of unit lens portions to absorb external light incident from the light outgoing side, wherein the plurality of unit lens portions are arranged such that a part of the light incident on the unit lens portions from the light incident side is totally reflected on surfaces of the unit lens portions corresponding to side segments of the approximately trapezoidal sections vertical to the long-axis directions of the unit lens portions, each side segment of the approximately trapezoidal section of each of the unit lens portions vertical to the long-axis direction thereof is formed in a broken line shape projecting inward, and the approximately trapezoidal section of each of the unit lens portions vertical to the long-axis direction thereof has a first angle between one side segment, and a light-incident-side long bottom segment, and a second angle between the other side segment, and the light-incident-side long bottom segment, the first angle being different from the second angle.