Patent ID: 8421632

Claim:
A one-piece plastic cap to be fitted to a mouth of a container which contains a water-containing content, and having a top plate and a skirt wall hanging down from a circumferential edge portion of the top plate and, further, having an IC tag storing product information attached to an upper surface of said top plate, wherein: said top plate forms a shielding member that maintains a gap between the water-containing content in the container and said IC tag to such a degree that the transmission and reception of signals to and from the IC tag are not interrupted by the water-containing content; said top plate is formed by an annular flange and a recessed portion continuous to an inner circumferential edge of the annular flange; said recessed portion includes a side wall continuous to the inner circumferential edge of said annular flange, and a bottom continuous to a lower end of said side wall and the bottom is working as said shielding member; and said IC tag is attached to said annular flange to cover said recessed portion, and wherein a gap between said IC tag and the bottom of said recessed portion is maintained to such a degree that transmission and reception of signals to and from said IC tag are not interrupted when a back surface of said bottom comes in contact with the water-containing content.