| 摘要 |
PURPOSE: Provided is a milky translucent, biaxially oriented polyester film which has improved ease of production, i.e. low production cost, a use of the film and a process for its production. CONSTITUTION: The milky translucent, biaxially oriented polyester film comprises at least one layer, wherein said layer includes a cycloolefin copolymer(COC) in an amount of not more than about 5 wt%, based on the weight of said layer. The film is produced by the steps of (i) extruding or coextruding the melt corresponding to a single-layer film or the melts corresponding to the individual layers of the film through a flat-film die, (ii) drawing off the resultant film on one or more rolls for solidification, (iii) biaxially stretching the film, heat-setting the biaxially stretched film and, if desired, corona- or flame-treating at least one surface of the film. The biaxial orientation is carried out in succession, first oriented longitudinally and then transversely. The temperature during the longitudinal stretching is within the range from about 80 to about 130 deg.C and the temperature during the transverse stretching is within the range from about 90 to about 150 deg.C. The longitudinal stretching ratio is within the range from about 2.5:1 to about 6:1, and the transverse stretching ratio is within the range from about 3.0:1 to about 5.0:1. |
