| abstract |
In one embodiment, the present invention provides a method of producing a polyethylene terephthalate film comprising at least one layer comprising a biaxially oriented and birefringent film of polyethylene terephthalate film having a thickness of from 0.25 mm (10 mils) to 0.64 mm (25 mils) Wherein the film is selected from the group consisting of dimethyl terephthalate, terephthalic acid, or combinations thereof; Ethylene glycol; Diol or triol monomers other than ethylene glycol; And 0.9 to 3 mol% of a sulfonate monomer having an inorganic counterion, based on 100 mol% of dimethyl terephthalate, terephthalic acid, or a combination thereof, based on the total weight of the poly (ethylene terephthalate) . |