Patent ID: 6313747
Filing Date: 2001-11-06
Classification: G08B,Y10T

Abstract:
A resonant tag comprising an insulating thin film having a thickness of 10 to 30 .mu.m, and coiled circuits made of a metal foil respectively formed on both sides of the insulating thin film, wherein the coiled circuits are formed in an electrically connected relation to each other with a space at the center of the insulating thin film, said both coils are formed taking turns in reverse directions to each other when viewed from the same direction and almost superimposed on each other except portions that cannot be superimposed on each other because the turning directions of the coils are reversed with the exception of the outermost peripheries when viewed from a direction perpendicular to the thin film, thereby forming a capacitor to constitute an LC circuit, the widths of portions of said both circuits, which correspond to each other, are almost equal except the outermost peripheries, the area of a portion of each side of the thin film, said portion being surrounded by the innermost peripheries of both coils and having no metal foil on both sides, is at least 16% based on the whole area of said one side of the tag, a thin-wall part where the thickness of its corresponding insulating film portion is thinner than that of its remaining portion is formed in part of the portions where said both circuits are superimposed on each other, the resonant tag resonates with a wave of the predetermined radio frequency and undergoes dielectric breakdown at the thin-wall part when applying the prescribed voltage or higher voltage to the tag, whereby the resonant tag can be prevented from resonating with the wave of said radio frequency, and the resonant tag has an area of at most 700 mm.sup.2.