PROBLEM TO BE SOLVED: To prevent a tilt of a gasket in capping a syringe with a gasket, and to ensure sealing performance of the gasket.SOLUTION: A gasket for a prefilled syringe includes an umbrella part having a medical solution side slanting face protruded to a medical solution side (formed of a conical surface) and a body part which is equipped with a female screw part corresponding to a screw part on a tip end of a plunger and forms at least one seal surface by making contact with an inner peripheral surface of an outer cylinder. A relationship between an inclination angle θ1 of the medical solution side slanting face of the umbrella part and an inclination angle θ2 of a back face side slanting face thereof is represented as θ1-3°≤θ2≤θ1+5° (provided that θ1>0°, θ2>0°), and a thickness of the umbrella part is within a range of 2.5 to 5.0 mm.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2017,JPO&INPIT【課題】ガスケットをシリンジに打栓する時のガスケットの傾きを防止すると共にガスケットの密封性を確保する。【解決手段】 薬液側に凸の(円錐面から成る)薬液側斜面を有する傘部と、プランジャの先端のねじ部に対応する雌ねじ部を備え外筒の内周面と接触して少なくとも一つのシール面を形成する胴部とを備え、傘部の薬液側斜面の傾斜角度θ1とその背面側斜面の傾斜角度θ2との関係がθ1-3°≦θ2≦θ1+5°(ただし、θ1>0°,θ2>0°である)であり、前記傘部の厚みが2.5mm~5.0mmの範囲にあることを特徴とするプレフィルドシリンジ用ガスケット。【選択図】図1
