A multilayered polymer film includes a first set of optical layers and a second
set of optical layers. The first set of optical layers is made from a polyester
which is often birefringent. The polyesters of the first set of optical layers
typically have a composition in which 70-100 mol % of the carboxylate subunits
are first carboxylate subunits and 0-30 mol % are comonomer carboxylate subunits
and 70 to 100 mol % of the glycol subunits are first glycol subunits and 0 to 30
mol % of the glycol subunits are comonomer glycol subunits, where at least 0.5
mol % of the combined carboxylate and glycol subunits are comonomer carboxylate
or comonomer glycol subunits. The multilayered polymer film may be used to form,
for example, a reflective polarizer or a mirror.