Method for producing long stretched film, and device for producing long stretched film

A method for producing a long stretched film, comprising at least the steps of:

• forming a long film containing a thermoplastic resin;
• stretching the long film in an oblique direction greater than 0° but smaller than 90° with respect to a widthwise direction of the long film by feeding to an oblique stretching apparatus having an oblique stretching tenter, in a specific direction different from a direction along which the long film runs after being stretched, and then allowing the long film to run while widthwise ends of the long film are gripped by gripping tools of a gripping tool running device of the oblique stretching tenter;
• and
• winding the long film having been subjected to the oblique stretching, wherein:
• the oblique stretching is performed in a heating section including a preheating section, a stretching section, and a thermosetting section,
• the preheating section and the stretching section are separated from each other by a first partition wall, and the stretching section and the thermosetting section are separated from each other by a second partition wall,
• each of the partition walls has an opening for permitting the long film to pass, and first slide members independently movable on the opposite sides of the opening and in widthwise directions of the long film,
• the first slide members adjust a width of the opening and the widthwise position of the opening to adjust a flowing in of air that accompanies a run of the long film from a previous section of the preheating section, the stretching section, and the thermosetting section to a subsequent section of the preheating section, the stretching section, and the thermosetting section.