Methods for producing phase-difference film and circularly polarizing plate involving simultaneous reduction of clip pitch on one side and increase of clip pitch on another side

A production method for a retardation film, comprising:

• holding 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;
• causing the clip pitches of the left and right clips to each independently change to obliquely stretch the film;
• reducing the clip pitches of the left and right clips to shrink the film in the longitudinal direction;
• and
• releasing the film from being held with the clips,
• wherein the oblique stretching comprises
• (i) increasing the clip pitch of the clips on one side out of the left and right clips, and simultaneously reducing the clip pitch of the clips on another side, and
• (ii) increasing the reduced clip pitch to the same pitch as the increased clip pitch to set the clip pitches of the clips on each side to a predetermined pitch.