POLARIZED RESIN FILM AND PROCESS FOR PRODUCING SAME

摘要

The purpose of the present invention is to provide a polarized vinylidene fluoride/tetrafluoroethylene copolymer resin film which, when used as an optical film, causes little deterioration in the quality of video or other images formed by the display element. This polarized vinylidene fluoride/tetrafluoroethylene copolymer resin film has a feature wherein the number of dot defects determined by the following defect examination method is 2,000 per m2 or less. An appearance inspection device is used, and a CCD camera is disposed so that defects can be detected at an angle of 45 degrees with an LED light source. While the film is passed under the camera at a speed of 20 m/min, a rectangular area of the film having a width-direction (direction perpendicular to the scanning direction) dimension of 300 mm and a flow-direction (scanning direction) dimension of 150 mm is scanned for defects. First, defects in which the area of bright sites is 1.5 mm2 or less and the area of dark sites is 1.4 mm2 or less are chosen. Next, in order to remove defects attributable to any cause other than corona treatment from the chosen defects, a rectangle circumscribed about each defect is set so as to have two sides along the scanning direction, and only the defects wherein the circumscribed rectangle has a width of 2.88 mm or less, a length of 2.3 mm or less, and a length/width ratio of -3.9 to +2.7 and wherein the circumscribed rectangle has an areal occupation ratio of 4,000-6,950 and an areal proportion of -3,100 to +5,200 are taken as dot defects. The number of these defects is automatically counted by the appearance inspection device.