Paired light shielding flange members, each having: a hollow cylindrical boss section to be inserted into a core around which a photosensitive material has been wound, wherein a plurality of rip sections are formed on the exterior surface of the cylindrical boss section parallel with an axis of the boss section, and an interior surface portion of rib is grooved in parallel with the axis of the hollow cylindrically boss section, and a flange section, integrated concentrically with the hollow cylindrical boss section, to prevent the edge of photosensitive material from being exposed to light.