Multilayer polyester film of high optical density, having a total thickness of maximum 60 µm and comprising two external white layers and a basis layer containing carbon black

摘要

At least three-layered biaxially oriented polyester film comprises two white outer layers and a carbon black-filled base layer. The thickness of the layers is 4-15 mu m. The thickness of the base layer is >= the sum of the outer layer thicknesses. The white outer layers contain at least 15 wt.% of titanium dioxide. The base layer contains at least 4 wt.% of titanium dioxide. The base layer comprises 1-8 wt.% of carbon black. The standard viscosity (SV) of the film is at least 600. The weights of all components are based on the weight of the individual layer. An independent claim is also included for producing the polyester film, comprising compressing the polymer or polymer mixture of the individual layers in extruders, liquefying to form a melt, extruding the melt into a coextrusion die to form flat melt films, pressing the flat melt films by a slot die, drawing on a cooling roll and one or more nip rolls, where the formed film is cooled and solidified, stretching the film simultaneously or sequentially in the longitudinal and transverse directions, thermally fixing the film and coiling the film.