THEFT PREVENTIVE TAG AND METHOD FOR ATTACHING THE SAME

摘要

Even if the surface of an article for theft prevention is made of any material, the resonance frequency of a resonance circuit section does not change. A theft preventive tag (12) attached to an article (11) for theft prevention is provided with a resonance circuit section (14) resonating with the radio wave of a specific frequency transmitted from a transmission antenna. An electromagnetic shielding layer (16) made of insulator is interposed between the attaching surface of the article (11) and the resonance circuit section (14). The electromagnetic shielding layer (16) may be a multilayer comprising a first layer of a composite material consisting of a ferrite powder or soft magnetic powder having a particle diameter of below 10 mu m and plastic or rubber, and a second layer made of plastic or rubber. The soft magnetic powder is preferably of one of an amorphous alloy, permalloy, magnetic soft iron, silicon steel, sendust, and Fe-Al alloy.