Multilayered biaxially oriented polyester film, method of its preparation and its use

摘要

Biaxially-oriented polyester film with a base layer (B) of thermoplastic polyester and outer layers (A) and (C), in which (A) has a very smooth surface with no external particles and is coated with an acrylic polymer (D), and (C) contains external particles, the number of bumps per unit area of surface being correlated with bump height by a special equation. Biaxially-oriented polyester film with a base layer (B) comprising at least 80% thermoplastic polyester and two outer layers (A) and (C), in which (a) layer (A) has a very smooth surface with essentially no external particles, (b) layer (C) contains external particles, the number of bumps Nc per mm2 of film surface being correlated with the height of the bumps (h) by the equation Ah1 - Bh1 . log10 h/microns at most log10 (Nc/mm2) .. (1) where h = 0.01-1 micron, Ah1 = 0.05 and Bh1 = 3.3, and (c) layer (A) is coated with an acrylate-containing layer (D). An Independent claim is also included for a method for the production of this film which involves extrusion or coextrusion to form multilayer flat melt film, coating the film with layer (D), stretching the film biaxially and heat-fixing the stretched film.