| abstract |
A copolycarbonate lens formed from a polycarbonate composition, a polycarbonate composition: a copolycarbonate comprising bisphenol A carbonate units and phthalimide carbonate, and optionally bisphenol A Homopolycarbonate; wherein the second carbonate unit is present in an amount of from 18 to 35 mol %, based on the sum of the moles of copolycarbonate and bisphenol A homopolycarbonate, the copolycarbonate comprising: Less than 2 ppm by weight of lithium, sodium, potassium, calcium, magnesium, ammonium, chlorine, bromine, fluorine, nitrite, nitrate, phosphite, phosphate, sulfate, formate, acetate, citrate , oxalate, trimethylammonium and triethylammonium ions, the polycarbonate composition has a bisphenol A purity of at least 99.7% as determined by high performance liquid chromatography. The polycarbonate composition has: a Vicat B120 of 155°C or higher; and an increase in yellowness index of less than 10 during heat aging at 155°C for 1000 hours. |