Method of producing retardation film, method of producing circularly polarizing plate, and film-stretching apparatus, involving braking the moving speeds of film-holding clips

Abstract

Provided is a method capable of producing a retardation film having an elongated shape and having a slow axis in an oblique direction with high production efficiency while precisely controlling the direction of the slow axis and the variation of the direction. The method of producing a retardation film of the present invention includes: holding the left and right end portions of a film with left and right variable pitch-type clips configured to have clip pitches changing in a longitudinal direction, respectively; preheating the film; obliquely stretching the film; and releasing the clips holding the film. The oblique stretching includes making the change ratio of the clip pitch of the clips on one side in the traveling direction thereof and the change ratio of the clip pitch of the clips on the other side in the traveling direction thereof different from each other, and/or making the position at which the clip pitch of the clips on the one side in the traveling direction starts to change and the position at which the clip pitch of the clips on the other side in the traveling direction starts to change different from each other, while extending a distance between the left and right clips. In the present invention, the moving speeds of the clips are braked immediately before the holding step and/or during a time period from the holding step to the oblique stretching step.