| 摘要 |
<p>A transparent biaxially oriented polyester film containing at least 80 wt.% thermoplastic polyester, and a pigment system in amount 0.05-0.5 wt.% relative to the total weight of film, and having (a) a mean grain diameter (d50 value) of 1.5-5 micron, and (b) a distribution deviation, expressed in terms of SPAN 98,≤1.9 is new. An Independent claim is included for preparation of the film by extrusion, where the polyesteris first compressed in the extruder, liquefied and homogenized, with, if necessary, addition of additives already present in the polyester, pressing of the melt through a flat nozzle, pulling of the pressed melt over one/or more calender rollers, strengthening to a pre-film, biaxial stretching and thermal fixing of this, corona or flame treatment of the surface to be handled. The temperature in longitudinal stretching is 80-130 degrees C and in the transverse direction 90-150 degrees C, at a longitudinal stretching ratio of 2.5:1 to 6:1, preferably 3:1 to 5.5:1, and in the transverse direction 3.0:1 to 5.0:1, preferably 3.5:1 to 4.5:1</p> |
