P. Lippens et H. Lievens, SOFT-MAGNETIC SPUTTERED COATINGS ON PET-SUBSTRATE FOR ELECTRONIC ARTICLE SURVEILLANCE, Surface & coatings technology, 93(1), 1997, pp. 46-50
Thanks to the scaling up to large web widths and the introduction of r
otatable cylindrical magnetron technology, D.C.-magnetron sputtering h
as also entered consumer markets such as electronic article surveillan
ce (EAS). A very widely applied way of protecting goods in shops is th
e use of strip labels. Such labels have a rapidly solidified, cast, so
ft-magnetic strip as the active element. This strip consists of a comp
lex alloy and has a quasi-amorphous microstructure. However, because o
f the finite thickness of the strip (typically 50 mu m), the label is
not perfectly flat and is considerably stiff. As a consequence, printi
ng and fixing the label both have limitations. Therefore, strip labels
are gradually being ruled out by soft-magnetic sputtered thin film la
bels. In order to yield a sufficiently high signal level in the detect
ion gate of the EAS system, a relatively large thickness (up to 1 mu m
) combined with a high degree of amorphicity of the sputter-deposited
soft-magnetic thin film are required. This has, of course, drastic con
sequences for the sputter process itself (cooling conditions, allowed
working pressures, magnetic arrays, etc.). A major factor reducing pro
duction costs is the use of rotatable magnetrons: up to 90% of the mag
netic material of the target can be sputtered. This is even more impor
tant since the magnetic material is an expensive, high-purity, quintar
y Co alloy. A drawback, however, is the fact that such targets are not
readily available on the market. In the following, it will be shown t
hat this problem can successfully be solved if know-how on target prod
uction is integrated in the coating plant. (C) 1997 Elsevier Science S
.A.