Abstract: A process for cooling a heated polymer film by applying to both surfaces of the heated film, a cooling liquid adapted for wetting contact with the film surfaces. The viscosity of the layers of liquid adhering to the film surfaces is significantly reduced to facilitate removal of such liquid layers. The viscosity can be reduced by significantly raising the temperature of the adhering liquid layers after the film has been sufficiently cooled or by changing the adhering liquid to a different liquid of lower viscosity. Preferably, the liquid layers are removed for the film surfaces by conveying the liquid carrying film upwardly to cause the liquid layers to each form into a generally triangular shape with the vertex extending upwardly and blowing air stream downwardly against each such vertex.

Abstract: A process of cooling a heated polyethylene terephthalate film by applying cooling liquid to both surfaces of the heated film and, after the temperature of the film has decreased sufficiently, removing the cooling liquid from the film, wherein the cooling liquid has a pH value between 6 and 3.

Abstract: A process of making biaxially oriented polyethylene terephthalate photographic film having a controlled amount of curl in the longitudinal direction, wherein the file is subjected to longitudinal stretching while being asymmetrically heated across its thickness, then wound into a stock roll, and the stock roll thus obtained is heat-tempered. The stock roll after heat-tempering may be longitudinally slit, cut and rewound into smaller rolls in a winding direction opposite to the direction of the longitudinal curl induced in the film during the longitudinal asymmetrical heat-stretching.

Abstract: In a known process of making biaxially oriented polyethylene terephthalate photographic film, a certain amount of curl in the longitudinal direction can be imparted to the film by carrying out the longitudinal stretching step of that process while the film is asymmetrically heated across its thickness to a temperature gradient Delta T across the film of at least 10.degree. C. while the longitudinal stretching tension applied to the film is less than 10 N/sq.mm.