The layer contains a maximum of 3% by weight of the second metallic compound, preferably less than 2% and more preferably between 0.5-2%.The binder may be a thermoplastic resin such as an acrylic resin, a thermosetting resin such as an epoxy resin, an electron beam curing resin, or preferably a UV curable resin which may be an acrylate resin of the type disclosed in U.S. Pat. No. 4,557,980, or pre