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, restraining lamp mura, and preventing the separation of the film and wet out. 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 in a casting drum(20). The centerline surface roughness(Ra) of the surface of the casting drum(20) is controlled at 3 to 30 micrometers. A pattern on the surface of the casting drum is transcribed on the surface of the non-oriented sheet. The cooled sheet is uniaxially oriented. The uniaxially oriented film is biaxially oriented, and is heated. The surface of the casting drum is patterned into a prism pattern or a lenticular pattern. 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.