Abstract: As a nonaqueous electrolyte secondary battery separator which has improved mechanical strength and which retains flexibility, provided is a nonaqueous electrolyte secondary battery separator including: a mixed layer which contains a heat-resistant resin and a porous base material that includes a porous film containing a polyolefin-based resin as a main component; and a heat-resistant layer which contains the heat-resistant resin and which is in contact with the mixed layer. When an SEM image which includes a cross section of the nonaqueous electrolyte secondary battery separator in a thickness direction is analyzed, luminance distribution of the mixed layer in the thickness direction satisfies specific conditions.

Abstract: As a nonaqueous electrolyte secondary battery separator which has excellent heat resistance and excellent voltage withstand characteristics, provided is a separator including a mixed layer which contains a heat-resistant resin and a porous base material that includes a polyolefin porous film. When attenuated total reflection infrared spectroscopy is carried out with respect to an opposite surface of the separator, a ratio between an intensity of a peak indicating the heat-resistant resin and an intensity of a peak indicating the polyolefin-based resin is not less than 0.02.

Abstract: As a nonaqueous electrolyte secondary battery separator which has improved mechanical strength and which retains flexibility, provided is a nonaqueous electrolyte secondary battery separator containing a heat-resistant resin that contains N (nitrogen) and a porous base material that includes a porous film containing a polyolefin-based resin as a main component. A ratio of N2 to N1 is not less than 50% and not more than 80%, where N1 is a proportion of N (nitrogen) present when an energy dispersive X-ray analysis is carried out at an acceleration voltage of 1.5 kV and N2 is a proportion of N (nitrogen) present when an energy dispersive X-ray analysis is carried out at an acceleration voltage of 5.0 kV.

Abstract: As a nonaqueous electrolyte secondary battery separator which has excellent heat resistance and excellent battery performance, provided is a nonaqueous electrolyte secondary battery separator including a mixed layer which contains a heat-resistant resin and a porous base material that includes a polyolefin porous film, in the mixed layer, a weight ratio (W1/W0) between a weight W1 of the heat-resistant resin and a weight W0 of the porous base material being not less than 0.07.

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 method of producing a film is provided. The film includes a base material layer which is shrunk by heat and a functional layer which is dried while being restricted by the base material layer. The method involves heating the film while applying a tensile force in a direction of a length of the film so as to convey the film, and subjecting the film to a heat treatment while, in a distribution along a width of the film, a center part is higher in temperature than end parts. A center part sample of the film is smaller in curling amount with respect to the width of the film than an end part sample, or a standard deviation in curling amount with respect to the width is not more than 1 mm between two samples from respective end parts and a sample from the center part of the film.

Abstract: A drying roller includes: a cylindrical member for drying a separator original sheet, with hot water which is supplied into the cylindrical member and ejected from inside the cylindrical member, the separator original sheet being wrapped on an outer peripheral surface of the cylindrical member; and a discharge pipe for discharging the hot water toward one inner end surface of the cylindrical member, the heating medium being discharged at a position where a distance to the one end surface of the cylindrical member is longer than a distance to the other inner end surface of the cylindrical member.

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 battery separator film that has a small curling amount and is highly handleable is provided. The battery separator film has a curling amount W of not more than 5 mm, the curling amount W being represented by the following equation (1): Curling amount W=W1?W2??(1) where W1 is a width of a film that has been cut out in a longer side direction of the battery separator film, and W2 is a projection width of a part of the film which part is smallest in projection width when seen from a direction perpendicular to a surface of the film while the film, to which a tension of 90 N/m is applied, is stretched between two rollers that are provided in parallel with each other at an interval of 1 m at a temperature of 23 degrees Celsius and a relative humidity of 50%.

Abstract: The present invention resolves a problem that occurs to a film which is being washed. A film production method of the present invention 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.

Abstract: A drying device includes a first cylindrical member and a second cylindrical member. The first cylindrical member has an outer peripheral surface having a surface temperature that is higher on one width wise side where an end is present than on the other widthwise side where another end is present, whereas the second cylindrical member has an outer peripheral surface having a surface temperature that is lower on the one widthwise side where an end is present than on the other widthwise side where another end is present.

Abstract: A battery separator film that has a small curling amount and is highly handleable is provided. The battery separator film has a curling amount W of not more than 5 mm, the curling amount W being represented by the following equation (1): Curling amount W=W1?W2 (1) where W1 is a width of a film that has been cut out in a longer side direction of the battery separator film, and W2 is a projection width of a part of the film which part is smallest in projection width when seen from a direction perpendicular to a surface of the film while the film, to which a tension of 90 N/m is applied, is stretched between two rollers that are provided in parallel with each other at an interval of 1 m at a temperature of 23 degrees Celsius and a relative humidity of 50%.

Abstract: A method of producing a film is provided. The film includes a base material layer which is shrunk by heat and a functional layer which is dried while being restricted by the base material layer. The method involves heating the film while applying a tensile force in a direction of a length of the film so as to convey the film, and subjecting the film to a heat treatment while, in a distribution along a width of the film, a center part is higher in temperature than end parts. A center part sample of the film is smaller in curling amount with respect to the width of the film than an end part sample, or a standard deviation in curling amount with respect to the width is not more than 1 mm between two samples from respective end parts and a sample from the center part of the film.

Abstract: A transfer system includes an expander roll for removing a wrinkle in a separator original sheet, and (i) the expander roll and (ii) a transfer roller immediately followed by or following the expander roll are spaced from each other at a distance of not less than 1 m and not more than 10 m.

Abstract: The present invention resolves a problem that occurs to a film which is being washed. A film production method of the present invention 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.

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: A transfer system includes an expander roll for removing a wrinkle in a separator original sheet, and (i) the expander roll and (ii) a transfer roller immediately followed by or following the expander roll are spaced from each other at a distance of not less than 1 m and not more than 10 m.

Abstract: A drying roller includes: a cylindrical member for drying a separator original sheet, with hot water which is supplied into the cylindrical member and ejected from inside the cylindrical member, the separator original sheet being wrapped on an outer peripheral surface of the cylindrical member; and a discharge pipe for discharging the hot water toward one inner end surface of the cylindrical member, the heating medium being discharged at a position where a distance to the one end surface of the cylindrical member is longer than a distance to the other inner end surface of the cylindrical member.

Abstract: A drying device includes a first cylindrical member and a second cylindrical member. The first cylindrical member has an outer peripheral surface having a surface temperature that is higher on one width wise side where an end is present than on the other widthwise side where another end is present, whereas the second cylindrical member has an outer peripheral surface having a surface temperature that is lower on the one widthwise side where an end is present than on the other widthwise side where another end is present.

Abstract: Contamination of a washing liquid in a washing tank is suppressed at a downstream side of a path for transferring a film. A washing device includes a roller for transferring a heat-resistant separator from a washing tank to another washing tank. Two rollers contact one surface of the heat-resistant separator, and a remaining roller, between the two rollers, contacts the other surface of the heat-resistant separator. A washing liquid removed from the heat-resistant separator by the remaining roller returns to the washing tank.