A method for film production includes the steps of obtaining information on the position of a defect (D) in a separator (12a) and providing marks (LA, LB) at the respective positions in the vicinity of the defect (D), the marks indicating the position of the defect.

A method for film production includes the steps of obtaining information on the position of a defect (D) in a separator (12a) and providing marks (LA, LB) at the respective positions in the vicinity of the defect (D), the marks indicating the position of the defect.

To easily specify the position of a defect in a separator, a method for producing a separator original sheet (12b) includes the steps of: forming a separator original sheet (12b) including a separator original sheet (12c) and a heat-resistant layer coated on the separator original sheet (12c); detecting a defect (D) in the separator original sheet (12b); and recording information including information on a position of the defect (D) which position is a position in the width direction of the separator original sheet (12b).

To easily specify the position of a defect in a separator, a method for producing a separator original sheet (12b) includes the steps of: forming a separator original sheet (12b) including a separator original sheet (12c) and a heat-resistant layer coated on the separator original sheet (12c); detecting a defect (D) in the separator original sheet (12b); and recording information including information on a position of the defect (D) which position is a position in the width direction of the separator original sheet (12b).

A method of film production includes the steps of obtaining defect information including information on the position of a defect (D) in a separator original sheet (12b), slitting the separator original sheet (12b) to produce a plurality of separators (12a), and determining, on the basis of the defect information on a single defect (D), that a separator (12a) actually having the defect (D) and another separator (12a) adjacent to the above separator (12a) are defective.

A method of film production includes the steps of obtaining defect information including information on the position of a defect (D) in a separator original sheet (12b), slitting the separator original sheet (12b) to produce a plurality of separators (12a), and determining, on the basis of the defect information on a single defect (D), that a separator (12a) actually having the defect (D) and another separator (12a) adjacent to the above separator (12a) are defective.

A method for film production includes the steps of obtaining information on the position of a defect (D) in a separator (12a) and providing marks (LA, LB) at the respective positions in the vicinity of the defect (D), the marks indicating the position of the defect.

A method for film production includes the steps of obtaining information on the position of a defect (D) in a separator (12a) and providing marks (LA, LB) at the respective positions in the vicinity of the defect (D), the marks indicating the position of the defect.

A separator producing method includes the steps of: winding up, around a core (81, 53), a separator (12a, 12b) having a defect (D) detected; and providing a defect code (DC2) including information on a position of the defect (D) in the longitudinal direction of the separator (12a, 12b) on (i) the outermost portion (86, 86b) of the separator (12a, 12b), wound around the core (81, 53), or (ii) the core (81, 53), around which the separator (12a, 12b) is wound.

A method of film production includes the steps of obtaining defect information including information on the position of a defect (D) in a separator original sheet (12b), slitting the separator original sheet (12b) to produce a plurality of separators (12a), and determining, on the basis of the defect information on a single defect (D), that a separator (12a) actually having the defect (D) and another separator (12a) adjacent to the above separator (12a) are defective.