Method and apparatus for producing a polarized resin film

Abstract

An object of the present invention is to provide a polarized vinylidene fluoride/tetrafluoroethylene copolymer resin film that can significantly reduce, when used as an optical film, the deterioration of the quality of video or still images formed by display elements. The present invention provides a polarized vinylidene fluoride/tetrafluoroethylene copolymer resin film having 2,000 or fewer spot defects per m2, the number of spot defects being measured by a defect measurement method; the method using an surface inspection system in which a CCD camera is placed so as to detect defects at an angle of 45 degrees relative to an LED source, defects of the film are read within a rectangular range of 300 mm in a width direction (the direction perpendicular to the scanning direction), and 150 mm in a machine direction (the scanning direction), while the film is scanned under the camera at a rate of 20 m/min; wherein first, defects having a bright area of 1.5 mm2 or less and a dark area of 1.4 mm2 or less are selected; and next, in order to remove defects resulting from causes other than a corona treatment contained in these defects, a circumscribed rectangle of defect is set so as to have two sides along the scanning direction, and the number of only defects that have a circumscribed width of 2.88 mm or less, a circumscribed length of 2.3 mm or less, an aspect ratio of −39 to +27, an occupancy area ratio in the circumscribing rectangle of 4,000 to 6,950, and an area ratio of −3,100 to +5,200, is automatically counted as spot defects by the surface inspection system.

Dependencies are inferred from the claim text.