| 摘要 |
PROBLEM TO BE SOLVED: To obtain a safer low-shrinkable microporous film having a low shrinkage percentage even under a high-temperature condition, excellent basic characteristics of film such as air permeability, etc., to provide a method for producing the same, to obtain a separator for a battery comprising the low-shrinkable microporous film and a lithium ion secondary battery obtained by using the low-shrinkable microporous film as a separator for a battery. SOLUTION: This low-shrinkable microporous film has <1% shrinkage percentage in one direction after being allowed to stand in an atmosphere at 105 deg.C under a tension-free condition for one hour and <1% shrinkage percentage in the same direction after being allowed to stand in an atmosphere at 140 deg.C in a tension-free condition for one hour. This method for producing a low-shrinkable microporous film comprises a process for fixing a rolled sheetlike formed material in one direction (x-axis direction) while drawing the material in a direction (y-axis direction) perpendicular to the x-axis direction by three times or more and shrinking the length of the film in the x-axis direction by 20-80% in the fixed state of the film in the y-axis direction. This separator for a battery comprises the low-shrinkable microporous film. This lithium ion secondary battery is obtained by using the low-shrinkable microporous film as a separator for a battery. |
