A polyvinyl alcohol-based polarizing film is provided, and the polarizing film
has excellent surface smoothness while the light transmittance and the polarization
degree are improved due to the high stretch ratio. The polarizing film is obtained
from a polyvinyl alcohol film having a thickness ranging from 85 m to 150
m by dyeing the film with a dichroic substance and stretching it to 4-7
times its original length. The polarizing film has a light transmittance ranging
from 35% to 50% and a polarization degree of at least 80%, and the surface roughness
in a direction perpendicular to the stretching axis is at most 0.04 m based
on a centerline average roughness. A transparent protective layer or a transparent
protective plate comprising the transparent protective layer is formed on at least
one surface of the polarizing film in order to provide a polarizing plate. The
transparent protective layer can be subject to a pre-treatment selected from a
hard-coat treatment and an anti-glare treatment. Additional optical layers are
laminated on the polarizing plate in order to provide an optical element. A polarizing
plate or an optical element comprising the above-mentioned polarizing film has
an excellent light transmittance and polarization degree, so that stripe-shaped
streaks inhibiting visibility will not be observed substantially even in a reflection mode.
