Patent ID: 6773649
Filing Date: 2004-08-10
Classification: B29C,B29K,B32B,Y10T

Abstract:
A continuous film extrusion process for producing a transparent or translucent thermoplastic film for optical media applications having a low birefringence, low stress and wherein at least one surface of the film has a roughness of less than about 4 microinches and a retardation value of less than about 100 nanometers, which process comprises:extruding a molten thermoplastic film, and passing the molten thermoplastic film through an opening between two opposing calendaring rolls wherein at least one calendaring roll is a finishing roll and subsequently cooling the hot thermoplastic film to a temperature below its solidification temperature of the thermoplastic film, said finishing roll is a multi component structure comprised of an inner steel shell, an intermediate resilient covering over the inner steel and a multi-layer metal sleeve outer covering comprised of at least two layers.