Optically plane thermoplastic sheet - extruded under closely controlled conditions and passed through very uniformly running polishing rollers

摘要

An extruded sheet or film of rigid thermoplastic has optically plane surfaces with optical distortion degree (delta) 0.03-0.06. The polymer used is e.g. polymethyl methacrylate, polycarbonate or polystyrene i.e. one with heat distortion temp. (ASTM D-648) of at least 70 degrees C. The factory delta is defined as = total of all high areas + all low areas between two points divided by distance between those two points. Excellent optical properties compared with films produced by conventional methods (which slow e.g. stripes of varying thickness).