| 摘要 |
PROBLEM TO BE SOLVED: To provide a biaxially oriented laminated polyester film which suppresses minute flaws generated in a processing step, has little crystallization of oligomer, has high transparency and is optimal as a base film for a lens sheet.SOLUTION: A base film for a lens sheet is provided, satisfying the following requirements (1) to (7). (1) The film has a multilayer structure having 3 or more layers formed by a coextrusion method; (2) both outermost layers of the film contain inert particles having an average particle diameter of 2.1 to 2.5 μm; (3) both outermost layers have a thickness 5 to 11 times the average particle diameter of the inert particles; (4) a proportion of surface projections having a ratio L/h, which is a ratio of a diameter L to a height h of the surface projection of the outermost layers, of 50 or less is 30% or less; (5) the film shows a haze change ▵Hz of less than 1.0 when heated at 170°C for 20 minutes; (6) the outermost layers have a content of terminal hydroxyl (OH) of 70 eq/ton or less; and (7) the outermost layers have a cyclic trimer content of 0.45 wt.% or less. |
