| 摘要 |
A process for producing low birefringence and low stress thermoplastic polycarbonate film having a birefringence of less than about 20 nm from polycarbonate resin. The process consists of feeding a polycarbonate resin to an extruder, melting the polycarbonate resin, extruding the melted polycarbonate resin downwardly through an extrusion nozzle having the configuration of, forming a continuous film of melted resin, advancing the melted resin downwardly by essentially gravity into a gap between two calendering rolls which lie in a plane essentially perpendicular to the downward extrusion of the resin, cooling the polycarbonate film to below its glass transition temperature and advancing the cooled polymer to storage. The calendering rolls lie in a plane essentially perpendicular to the downward extrusion of the melted resin to wherein one roll is in a plane at an angle of about 30° from said perpendicular. The film is useful for optical media applications.
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