To provide a syringe for a syringe which is not limited in size from a small diameter to a large diameter, is inexpensive and can sufficiently satisfy a sealing property such as sliding property, non-liquid leakage property, water vapor impermeability and the like Providing a piston member.A piston member (10) such as a gasket (10a) or an intermediate piston (10b), which is formed by cutting a PTFE block and pressed into a syringe barrel (1) and used in a sliding state. A sliding contact surface (11) adjacent to at least the liquid contacting surface (14) with the chemical solution (30) among the sliding contact surfaces (11) of the piston member (10) slidably contacting the inner peripheral surface (2) of the syringe barrel (13) in the circumferential direction is formed along the entire circumference of the outer peripheral surface (11a). The pitch P of the ridges (13) during cutting is 50 m or less, and the press fitting allowance T to the syringe barrel (1) is 10 to 150 m.(FIG.【課題】小径から大径まで大きさに限定されることなく、しかも安価であって摺動性や非液漏れ性、水蒸気非透過性などの密封性を十分に満足させることのできるシリンジ用のピストン部材を提供すること。【解決手段】PTFEブロックを切削加工して形成され、シリンジバレル(1)に圧入されて摺動状態で用いられる、ガスケット(10a)や中間ピストン(10b)などのピストン部材(10)である。シリンジバレル(1)の内周面(2)に摺接するピストン部材(10)の摺接面(11)の内、少なくとも薬液(30)との接液面(14)に隣接する摺接面(11a)の全周に亙って周方向の凸条(13)が形成されている。切削加工時の凸条(13)のピッチPが50μm以下、シリンジバレル(1)に対する圧入代Tが10~150μmである。【選択図】図1
