PROBLEM TO BE SOLVED: To provide a method for evaluating flexibility of a hair, which can highly accurately evaluate the flexibility of the hair while considering a cross-sectional structure of the hair and can evaluate the flexibility of the hair by relating an elastic modulus of the hair to an inner structure of the hair.SOLUTION: A cross-sectional shape of a hair having a cross-sectional structure composed of a plurality of layers is measured, and when the cross-sectional shape is approximated to an ellipse, a major axis and a minor axis of the ellipse are found out. One end of the hair is fixed and relation between load P and displacement of the hair on a predetermined distance l from the fixed position along at least either one of the major axis and the minor axis is measured. An inclination SE of a graph obtained when setting a horizontal axis as displacement and a vertical axis as Pl3/3I (I is cross-sectional secondary moment to a load direction of load P) and plotting measurement values is found out, and the elastic modulus and/or thickness of each layer of the hair is evaluated from the inclination SE.COPYRIGHT: (C)2013,JPO&INPIT【課題】毛髪の断面形状を考慮して柔軟性を高精度に評価することができ、さらに弾性率と毛髪の内部構造とを関連付けて評価を行うことができる毛髪の柔軟性評価方法を提供する。【解決手段】複数の層から成る断面構造を有する毛髪の断面形状を測定し、その断面形状を楕円近似したときの長軸と短軸とを求める。毛髪の一端を固定し、少なくとも長軸および短軸のいずれか一方に沿った、固定位置から所定の距離lの位置での毛髪の荷重Pと変位との関係を測定する。横軸を変位、縦軸をPl3/3I(Iは荷重Pの負荷方向に対する前記毛髪の断面二次モーメント)として測定値をプロットしたときのグラフの傾きSEを求め、その傾きSEから毛髪の各層の弾性率および/または厚みを評価する。【選択図】図2
