Abstract: An unnecessary substance is removed from a film which is being washed, while problems that occur to the film being washed are resolved. A method for washing a film includes the steps of: (a) transferring a heat-resistant separator in a lengthwise direction so that the heat-resistant separator passes through washing water in a washing tank; and (b) upwardly or downwardly discharging the washing water which has been guided into the washing tank through an inner wall of the washing tank, which inner wall faces a widthwise end part of the heat-resistant separator.

Abstract: A desired drying capability is achieved while damage to a film is prevented. A film production method is arranged such that: a production process including a drying step is operated by setting a drying condition, under which to carry out the drying step, for each of at least two periods, the two periods being a first period and a second period later than the first period; the drying condition is changed in at least a part of the first period so as to be enhanced with time; and the drying condition is maintained in the second period so as to be substantially fixed.

Abstract: A film production method includes the steps of: (i) passing a heat-resistant separator above rollers located above a washing tank; (ii) lowering another roller into water through a space between the rollers; and (iii) moving at least one of the rollers and the another roller so as to increase a surface area by which the heat-resistant separator is in contact with the another roller. The method resolves a problem that occurs to a film which is being washed.

Abstract: The present invention provides a washing method and the like suitable for a long and porous battery separator and a separator producing method including the washing method. The washing method of the present invention includes the steps of (i) transferring a separator in its longitudinal direction and (ii) washing the separator by causing the separator, which is being transferred, to sequentially pass through washing waters in washing tanks.