Diffusion sheet, rear projection screen provided with diffusion sheet, method of manufacturing mold for diffusion sheet, and method of manufacturing diffusion sheet

摘要

In a diffusion sheet, a plurality of approximately trapezoidal columnar unit lens portions are disposed such that the long-axis directions thereof are in parallel with each other, and all the surfaces of the unit lens portions, which correspond to the long bottom segments of the approximately trapezoidal sections of the unit lens portions are disposed on a light-incident-side flat surface. Further, light absorbing portions are disposed in the grooves between adjacent unit lens portions to absorb and/or shield external light incident from a light outgoing side. In the diffusion sheet arranged as described above, light incident on the unit lens portions from a light incident side is totally reflected on the surfaces corresponding to the side segments of the approximately trapezoidal sections vertical to the long-axis direction of the unit lens portions and outgoes from the light outgoing side.