MANUFACTURING METHOD OF WHITE POLYESTER FILM AND REFLECTIVE SHEET USING THE SAME

摘要

PURPOSE: A method for manufacturing a white polyester film and a reflective sheet using the film are provided to lower the glossiness of the surface of the film with less than 40% by a high surface roughness, thereby lowering visibility for defects, and restraining lamp mura. CONSTITUTION: A method for manufacturing a white polyester film is as follows. A raw material composition containing a polyester resin as a main component is melted and extruded, and then is molded into a sheet shape in order to prepare a non-oriented sheet. The non-oriented sheet is cooled. The cooled sheet is uniaxially oriented. A uniaxially oriented film is prepared by controlling the centerline surface roughness(Ra) of at least one of an upper contact roll or a lower contact roll at 1 to 20 micrometers. The uniaxially oriented film is biaxially oriented, and is heated. The raw material composition contains 1 to 40 parts by weight of white inorganic particles against 100 parts by weight of a resin composition which is a mixture of the polyester resin and an amorphous cyclic olefin copolymer which is an incompatible resin with the polyester. The resin composition comprises 65 to 95 wt% of the polyester resin, and 5 to 35 wt% of the amorphous cyclic olefin copolymer. The amorphous cyclic olefin copolymer has a glass transition temperature of 120 to 200 Deg.C.