PROBLEM TO BE SOLVED: To provide a film in which the influence of variations in film shape on film characteristics is minimized, and a designing method thereof. A ductile film has a summit of a length of a first slope portion, a length of a top portion, and a length of a second slope portion in a predetermined direction as L, and a top portion and a bottom surface in a direction orthogonal to the predetermined direction. When the distance between the parts is H and the sum of the length of the first slope, the length of the top, the length of the bottom and the length of the second slope in the predetermined direction is P, the value of U/L is 0. It becomes 19 or more and 0.83 or less, the value of L/P becomes 0.51 or more and 0.70 or less, and the value of H/L becomes 0.28 or more and 0.67 or less. [Selection diagram] Figure 1【課題】フィルム特性に対するフィルム形状のばらつきの影響を最小限に抑えたフィルム及びその設計方法を提供する。【解決手段】延性を備えたフィルムは、所定方向における第１斜面部の長さと頂上部の長さと第２斜面部の長さの和をＬとし、所定方向に直交する方向における頂上部と底面部の距離をＨとし、所定方向における第１斜面部の長さと頂上部の長さと底面部の長さと第２斜面部の長さの和をＰとしたとき、Ｕ／Ｌの値が０．１９以上、０．８３以下となり、Ｌ／Ｐの値が０．５１以上、０．７０以下となり、Ｈ／Ｌの値が０．２８以上、０．６７以下となる。【選択図】図１
