METHOD FOR PRODUCING POLYESTER FILM, POLYESTER FILM, BACK SHEET FOR SOLAR CELL, AND SOLAR CELL MODULE

摘要

This invention provides a method for producing a laminated polyester film wherein a polyester starting resin A, which is formed from polyester starting resins A1 and A2 and has an IV between 0.60 and 0.85 equivalents/ton and an AV between 5 and 20 equivalents/ton, and a recycled material B of polyester resin, which has an IV between 0.55 to 0.80 equivalents/ton and an AV of 35 equivalents/ton or less, are prepared; the starting resin A1 and a mixed starting resin comprising the resin A2 and the recycled material B (10 to 40 mass%) are dried to have a water content of 100 ppm or less each and then coextruded from a T die such that the extruded molten resin temperature is between 280 and 300ºC; the product is cooled and solidified on a casting roll in a laminated state such that the thickness of the film of the second molten resin formed from the resin A1 is thicker than that of the film of the first molten resin formed from the resin A2 and the recycled material B and a laminated body formed from at least two layers is thereby formed; and then the laminated body is biaxially stretched.