MANUFACTURING METHOD OF RETARDATION FILM

摘要

PROBLEM TO BE SOLVED: To provide a manufacturing method of a polypropylene resin retardation film having high axis accuracy and a uniform retardation value.

SOLUTION: Provided is a manufacturing method of a retardation film containing longitudinal stretching and horizontal stretching of a film comprising a polypropylene resin which are sequentially carried out in this order, where the horizontal stretching has a preheating step of retaining the film for 2.5 minutes or longer at an atmospheric temperature not less than the melting-point of the polypropylene resin and a stretching step of stretching the preheated film in the horizontal direction over a period of 3 minutes or more and 4 minutes or less at an atmospheric temperature lower than the melting-point of the polypropylene resin. The stretching step in the horizontal stretching is preferably carried out at a stretching magnification of 3.4 times or more. The preheating step is carried out when the film passes through a preheating zone 31 and the stretching step is carried out when the film passes through a stretching zone 32.

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