EAS tag with magnetically structured control element

A tag 2 for use in an electronic article surveillance system comprises a magnetically structured component 4 in close proximity to a striplike element 6 of magnetically soft material. The component 4 includes magnetic particles 8 orientated into particular directions in regions 10, 12, preferably at .+-.45.degree. relative to the longitudinal axis of the tag. The tag 2 can be deactivated by longitudinal wiping with a deactivator providing a magnetic field corresponding to the angle of orientation of the particles 8. Deactivation is, therefore, straightforward for a check out operator but not for a potential thief. The orientated particles 8 can be used to define an interpretable code enabling product inventory with deactivation.

BACKGROUND OF THE INVENTION 
This invention relates to electromagnetic tagging apparatus and in 
particular to magnetic tags for use with electromagnetic identification 
systems of the kind which can be employed, for example, in electronic 
article surveillance (E.A.S.), primarily for in-store sucurity, or in 
access control. 
Such systems, in either environment, utilise an element, frequently 
referred to a "tag", which influences an electromagnetic field, so causing 
a disturbance in a characteristic of the field as detected by a detector 
device. The tag needs to exhibit a number of characteristics one of which, 
especially relevant for in-store usage, is the capability of being readily 
de-activated by check-out personnel whilst being difficult for a would-be 
thief to de-activate. 
It is usual for the element, or tag, to contain a strip of highly permeable 
magnetic material. Such material is easily influenced by a relatively weak 
interrogating field and caused to generate a number of harmonic 
frequencies which are readily detected by a suitable detection device. 
Unless it is proposed to physically fracture or mechanically strain the 
strip in order to de-activate it, and such activities would place severe 
limitations upon the form which a tage could take, de-activation is 
usually achieved by magnetising hard material disposed in the tag and 
configured so as to produce, when so magnetised, a series of poles along 
the length of the strip of highly permeable material. This series of 
lpoles alters the magnetic "profile" of the tag, as presented to the 
interrogating field, and inhibits th generation of the aforementioned 
harmonics, thus permitting the detection device to distinguish between 
activated and de-activated tags. 
It has been usual hitherto for the magnetically hard material used for 
de-activation of the tag to be provided either in the form of 
discontinuous lengths arranged in close proximity to the strip of 
magnetically soft material, or in continuous lengths similarly disposed. 
In the first case, de-activation is relatively straightforward for 
check-out personnel to accomplish, but the same can be said for would-be 
thieves. In the second case, more care has to be taken by the check-out 
personnel because the continuous length of magnetically hard material has 
to be selectively magnetised to produce a pole pattern sufficient to 
change the electromagnetic profile of the tag, but at the same time 
de-activation is made more difficult for the would-be thief. 
SUMMARY OF THE INVENTION 
The present invention seeks to provide an improved tag which can be 
deactivated easily by check out or access security personnel but for which 
deactivation is difficult for potential thieves or intruders. 
This invention is predicated upon the incorporation into the security tag 
of a magnetically structured component. Such components are well-known in 
the art as being "magnetically watermarked" and are described, for 
example, in British Patent No. 1,331,604. 
Accordingly, there is provided a tag for use in an electromagnetic 
identification system comprising an element of magnetically soft material 
and, in sufficiently close magnetic communmication therewith for 
permitting local magnetic polarisation of the element, a magnetically 
structured component comprising, in a first region thereof, magnetic 
particles having their magnetic axes orientated in a first direction, and 
in a further region thereof, magnetic particles having their magnetic axes 
not generally orientated in any direction or orientated in a further 
direction. 
Preferably, the magnetic particles in the first region are orientated at an 
angle of substantially 90.degree. with respect to the axes of the magnetic 
particles in the further region. 
Advantageously, the magnetically structured component is of strip form and 
the magnetic axes of the magnetic particles in the first and further 
regions are orientated at an angle of substantially 45.degree. to the 
longitudinal axis of the strip. 
In a further embodiment, the magnetic particles in the first and further 
regions are arranged to define an interpretable code.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, a tag 2 comprises a magnetically structured component 
4 and an element 6 of magnetically soft material. The component 4, which 
preferably is in the form of a strip, is arranged in sufficiently close 
proximity to the element 6 to permit the component 4, when magnetised, to 
create in the magnetically soft element 6 a pole pattern sufficient to 
inhibit generation of the aforementioned harmonies when the tag 2 is 
subjected to an interrogating field. As shown in FIG. 1, the component 4 
is arranged to overlie the magnetically soft element 6. However, the tag 2 
may equally be fabricated with the element 6 overlying the structured 
component 4. 
The magnetically structured component 4 comprises a circular magnetic 
particles 8 dispersed in a binder and orientated into particular 
directions in respective regions 10, 12, or orientated in some regions and 
randomly orientated in other regions, as shown in FIG. 2 which also 
illustrates, schematically, how the particles may be so orientated during 
fabrication of the compoent 4. 
The method of manufacturing the component 4 will not be described in the 
context of this application as it will be assumed to be known to those 
skilled in this art. 
In the embodiment shown in FIG. 3 the tag 2, when activated, has the 
magnetic particles 8 orientated at 0.degree. and 90.degree. with respect 
to the longitudinal axis of the component 4 and also, therefore, of the 
tag 2 in which the component 4 is embodied. In this activated condition, 
no pole pattern is induced in the element 6 and hence, the element 6 may 
be sensed when subjected to an interrogating field of, for example, an 
electronic article surveillance system. When the component 4 is 
magnetised, however, such as by a single swipe with a magnet along the 
longitudinal axis of the component, the magnetic particles having 
0.degree. orientations with respect to this axis are aligned to form a 
pole pattern within the component which, in view of the proximity to the 
element 6, creates a pole pattern within the element 6, as shown in FIG. 
3b. In this condition the tag 2 is deactivated as the magnetically soft 
element 6 cannot be detected by the interrogating field. The tag 2 can be 
reactivated readily by subjecting the component 4 to an a.c. magnetic 
field, thereby negating the pole pattern in the component 4, and hence 
also the pole pattern in the element 6, as shown in FIG. 3c, once again 
enabling the element 6 to be detected by the interrogating field. 
It is particularly advantageous to arrange for the magnetic particles 8 in 
the selected regions 10, 12 of the component 4 to be orientated in a 
direction other than longitudinall of the strip. For example, the magnetic 
particles 8 may be orientated at 45.degree. to the longitudinal axis, as 
fabricated, shown in FIG. 4a. In this embodiment, the tag 2 is activated 
by a magnetic swipe along the longitudinal axis of the magnetically 
structured component 4, causing a pole pattern in the component 4 as shown 
in FIG. 4b and enabling the element 6 to be detected by an interrogating 
field. 
The tag 2 may be deactivated by "developing" the component 4 by means of a 
specially constructed deactivator, designed to be swiped along the 
longitudinal axis of the strip but to generate a developing magnetic field 
at an angle corresponding to the angle of orientation of the magnetic 
particles 8 in the regions 10, 12, i.e. at 45.degree. in the embodiment 
shown in FIG. 4a. 
This magnetic swipe causes a reversal of a selection of the magnetic pole 
patterns in regions 10, 12 of the component 4 (alternate regions in the 
embodiment shown in FIG. 4a) to provide a magnetic pole pattern in the 
component 4 as shown in FIG. 4c. This pole pattern, having like magnetic 
poles adjacent to each other, induces a pole pattern in the magnetically 
soft element 6 sufficient to prevent detection of the tag when subjected 
to an interrogating field. This deactivation of the tag by an 
appropriately aligned magnetic field renders deactivation simple for a 
check out operator, but not for the would-be thief who, even if aware of 
the need for an off-set between the developing field and the direction of 
swipe would not be aware of the correct angle, which could be changed for 
different stores and/or batches of product. 
The magnetically structured component 4 can be used to contain coded 
information if desired, as shown in FIG. 5 and, if the coding is matched 
to various products, of product categories, it is possible for product 
inventory to be monitored by providing suitable detection and analysis 
circuitry at the de-activation point and linking such circuitry to the 
store's central computer. 
In any of the above magnetic particle configurations the tag can, of 
course, be re-activated by de-magnetising the magnetically structured 
component. 
It has been determined that the thickness required for the magnetically 
structured component to produce an average longitudinal de-activation 
field of 10 Oe and on the basis of the component bein in strip-like form 
of width 8 mm and with alternate regions of length 2 mm being oriented in 
a chosen direction, with intervening regions either being not orientated 
or orientated perpendicularly to the first-mentioned regions, is 30-35 
microns. This thickness is also dependent on using a magnetically soft 
element 6 in strip-like form, of about the same width as the structured 
component 4. For an element of magnetically soft material 0.026 mm thick, 
1 mm wide and 60 mm long, the required thickness of the magnetically 
structured component 4 would be approximately 125 microns. 
Although the present invention has been described with respect to specific 
embodiments, it should be realised that modifications may be effected 
within the scope of the invention. For example, magnetic particle 
orientations at 0.degree. and 90.degree. or .+-.45.degree. have been 
described. However, magnetic particle orientations at other angles may 
equally be adopted, although it is preferable to maintain an angle in the 
region of 90.degree. between the orientation of the particles in the 
respective elements. Furthermore, the magnetic particles are shown in the 
embodiments as lying flat within the magnetically structured component. It 
should be realised, however, that the magnetic axes of the magnetic 
particles, by suitable known fabrication techniques, can be arranged to 
stand in an upright condition, either at an angle of about 90.degree. or 
at an inclined angle, within the magnetically structured component and the 
present invention is intended to cover also tags incorporating such 
upright magnetic particle configurations.