A light diffusive protective film for a surface light source device for protecting
other base material and improving the luminance of information display is disclosed
which comprises a transparent plastic film and a concave/convex layer stacked on
the surface of the transparent plastic film and satisfies requirements that: (1)
the ten-point mean roughness of the uneven surface in the concave/convex layer
is 0.5 m to 2.0 m; 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 and determining the count number of profile peaks by a peak
count method.
