Gasket for prefilled syringe

Abstract

A gasket (10) for a prefilled syringe is provided, which has a generally cylindrical outer shape, and includes a liquid contact portion (13) provided on one of opposite end faces, a thread hole (15) provided in the other end face for attachment of a plunger, and at least two annular projections (17A, 17B) provided on a peripheral surface (16) and spaced from each other by an annular trough (18) in a gasket height direction (gasket axial direction) extending from the one end face to the other end face, wherein a diameter difference (A) (=a1−a2) between a diameter (a1) of the annular projections (17A, 17B) and a diameter (a2) of the annular trough and a diameter difference (B) (=b1−b2) between a thread root diameter (b1) and a thread ridge diameter (b2) of an internal thread portion of the thread hole satisfy a ratio relationship of A:B=1:(2 to 4).

Dependencies are inferred from the claim text.