SPIRAL SPRING

PROBLEM TO BE SOLVED: To provide a hairspring for a mechanical watch having applied thereon thin film coating for improving impacts resistance and temperature characteristics, without causing influence on assemblability and attitude difference of the hairspring.SOLUTION: A hairspring 11 is formed of material having a crystalline structure, has its surface coated with thin film, and includes a spiral spring part 11a whose inner end is connected to a collet 11b having a penetration hole 12b for being connected to a rotation shaft body, whose outer end is connected to a stud 11c for being fixed to the other member, and which is wound around the collet 11b. In the spiral spring part 11a, the thin film formed on the side surface in the outer circumferential direction thereof includes a non-film forming region on at least one portion thereof.SELECTED DRAWING: Figure 1 【課題】ヒゲぜんまいの組立て性や姿勢差への影響を与えることなく、耐衝撃性や温度特性を向上させる薄膜コーティングを施機械時計用ヒゲぜんまいを提供する。【解決手段】内端を回転軸体と接続するための貫通孔１２ｂを有するヒゲ玉１１ｂに接続し、外端を他の部材に固定するためのヒゲ持ち１１ｃに接続し、ヒゲ玉１１ｂの周囲に巻回されるぜんまい部１１ａを有し、その表面に薄膜をコーティングした、結晶構造を有する材料で形成されたヒゲぜんまい１１であって、ぜんまい部１１ａの外周方向側面に形成された薄膜は、少なくとも一箇所に非成膜領域を含む構成とした。【選択図】図１