Patent ID: 6913365
Filing Date: 2005-07-05
Classification: G02B

Abstract:
1. A light diffusive protective film disposed in a surface light source device, said light diffusive protective film comprising a transparent plastic film and a concave/convex layer stacked on the surface of the transparent plastic film, said concave/convex layer satisfying requirements that: (1) the ten-point mean roughness of the uneven surface in the concave/convex layer is 0.5 μm to 2.0 μm; and (2) the count number of profile peaks is 16 to 60 as determined by measuring a roughness curve for the uneven surface of the concave/convex layer, providing a center line with respect to the roughness curve, providing an upper peak count level and a lower peak count level, which are lines parallel to the center line, provided respectively at positions of ±0.1 μm in a vertical direction from the center line, and observing the roughness curve for a center line length of 0.8 mm to determine the count number of profile peaks for the center line length of 0.8 mm based on the assumption that, in an interval between two points where, after the roughness curve crosses the lower peak count level, the roughness curve next crosses the lower peak count level, when the number of times of crossing between the roughness curve and the upper peak count level is one or more, the number of profile peaks in this interval is “one.”