EP1017033B1 - Security element for electronic article surveillance and production method - Google Patents

Abstract

The present invention relates to a security element for electronic article surveillance, having one lower and one upper conducting track with at least one winding each, the two conducting tracks being wound in opposing directions and overlapping in at least one area of overlap, and a dielectric layer in the area of overlap between the two conducting tracks. In a critical area in which a border edge of the lower and upper conducting tracks overlap, the dielectric layer is thicker than in the remaining area of overlap. The present invention also relates to a method of manufacturing such a security element.

Description

The invention relates to a securing element for electronic article surveillance, consisting of a lower and an upper conductor track, each with at least one winding, the two conductor tracks being wound in opposite directions, overlapping in at least one overlap area and a dielectric layer in the overlap area between the two conductor tracks is provided.

A corresponding securing element has become known, for example, from DE 197 08 180 A1. Such fuse elements are referred to as resonant resonant circuits or as resonant frequency fuse elements, the resonant frequency being determined by the capacitance C, the inductance L and the resistance R of the resonant circuit. Resonance frequency security elements are used in the form of labels or tags to prevent and detect theft in department stores and warehouses and are becoming increasingly popular due to the high detection rate.

The article security itself can be briefly described as follows: The resonance frequency security elements in the surveillance zone of the area to be secured - usually this is the entrance and exit area of the department store or warehouse - are excited by an alternating magnetic field to emit a characteristic detection signal. As soon as the monitoring system registers this detection signal, an alarm is triggered.

It is particularly advantageous if the resonance frequency securing elements are designed to be deactivated. Deactivation takes place as soon as the secured goods have been properly purchased by a customer. The method of generating a short circuit between the two layers of conductor tracks through the dielectric layer by supplying a correspondingly high energy pulse has proven itself, which leads to the destruction of the characteristic resonance properties of the resonant circuit.

A deactivatable securing element and a corresponding manufacturing method have already been disclosed in EP 0 665 705 A2. In the known solution, each of the layers of conductor tracks consists of a large number of turns. The two layers of conductor tracks are connected to each other via a dielectric, very thin resin layer. The resin layer has a substantially constant thickness over the entire area of the layers.

The securing element is also deactivated here by supplying a sufficiently high energy pulse.

Although the resonant circuit described above can be deactivated easily and safely, there is a risk that it will be reactivated by mechanical stress, in particular by bending or twisting - the short circuit can therefore be reversed by the mechanical stress. Reactivation is of course a highly undesirable effect.

In order to counteract the risk of undesired reactivation of a deactivated resonance frequency securing element, it is proposed in the aforementioned DE 197 08 180 A1 to make the strength of the two overlapping conductor tracks so large that, in the event of mechanical stress, the securing element bends in the areas occurs that are essentially free of conductor tracks (→ predetermined bending points). Thanks to this configuration, the reactivation probability of the securing element can be considerably reduced, since reactivation only takes place if the short-circuit point lies in the area of the target bending points. Since this area only makes up a relatively small proportion of the total area of the overlapping conductor tracks, the risk of reactivating a securing element is of course considerably reduced.

Further investigations have shown that areas in which one of the two conductor tracks crosses end areas of the other conductor track (→ critical area) are more susceptible to reactivation than the remaining overlapping areas. In other words, this means that an electrical connection, and thus deactivating the resonant circuit, between the two conductor tracks due to bending or twisting of the securing element is more likely to be broken, if it lies in the critical overlap area than if it occurred in the remaining overlap area of the conductor tracks.

The invention has for its object to propose a security element in which the risk of reactivation after deactivation is reduced or completely eliminated.

With regard to the securing element according to the invention, the object is achieved in that the dielectric adhesive layer either has at least the same thickness in a critical region within the overlap region, in which a boundary edge of the lower conductor path overlaps with the upper conductor path or a boundary edge of the upper conductor path with the lower conductor path as in the remaining overlap area and is coated with an additional dielectric layer (4) or has a greater thickness than in the remaining overlap area.

As already explained above, areas in which a boundary edge of a conductor track is crossed by the other conductor track (→ critical area) are particularly susceptible to reactivation if the preceding deactivation occurred in these areas. Such areas can not be avoided by the way with two conductor tracks that are wound in opposite directions. It has been found that the securing element is particularly resistant to reactivation if the sum of the lengths of the boundary edges in the critical area or in the critical areas or in the strip-shaped area is minimal.

An advantageous development of the securing element according to the invention therefore also proposes that in the critical area or areas, in addition to the dielectric adhesive layer, a dielectric film material, a dielectric lacquer layer or an additional dielectric adhesive layer is provided as an additional dielectric layer. Alternatively, it is proposed that the greater thickness in the critical area or in the critical areas be achieved by applying a lower contact pressure to the two conductor tracks in these areas during the lamination process.

In the event that there are several critical areas in which a boundary edge of the lower conductor track overlaps with the upper conductor track or a boundary edge of the upper conductor track with the lower conductor track, an advantageous embodiment of the securing element according to the invention provides that these areas essentially along one Straight lines are arranged in a strip-shaped area. This strip-shaped area has a width of a few millimeters and preferably extends over the entire length of the securing element. It is of course advantageous if the width of the additional dielectric layer is matched to the width of the strip-shaped region.

According to a preferred embodiment of the fuse element according to the invention, the two conductor tracks are electrically connected to one another in an overlapping end region. The electrical connection can be made in different ways. Alternative options are described in DE 197 08 180. In connection with the present invention, the preferred process for contacting the two conductor tracks is punching through the securing element in the region of the conductor tracks in which the electrical connection is desired.

A particularly favorable production process for the fuse elements according to the invention has the following process steps: a dielectric adhesive layer is applied to the lower conductor track; the critical area or areas are coated with an additional dielectric layer; the upper conductor track is then connected to the lower conductor track in the desired position. Alternatively, it is provided that the lower and the upper conductor tracks are laminated together in the critical area or in the critical areas with a reduced contact pressure. Laminating the two conductor tracks together with reduced contact pressure can also take place in combination with the arrangement of an additional dielectric layer in the critical area or in the critical areas.

In the case of mechanical production, the upper and lower conductor tracks are each arranged on a strip material according to an advantageous development of the method for producing the securing element according to the invention; the conductor tracks are arranged on the strip material in such a way that the critical areas are aligned in the machine direction; the additional dielectric layer is applied in strips to the lower or upper conductor track before the two conductor tracks are laminated together.

An advantageous embodiment of the method for producing the fuse elements according to the invention provides that the additional dielectric layer is sprayed or printed onto the upper or lower conductor track as a dielectric lacquer layer. If there is an additional dielectric adhesive layer, this is preferably applied to the upper or to the lower conductor track by means of extrusion.

• Fig. 1: eine Draufsicht auf die untere Leiterbahn gemäß einer bevorzugten Ausgestaltung des erfindungsgemäßen Sicherungselements,
• Fig. 2: eine Draufsicht auf die obere Leiterbahn gemäß einer bevorzugten Ausgestaltung des erfindungsgemäßen Sicherungselements und
• Fig. 3: eine Draufsicht auf die bevorzugte Ausgestaltung des erfindungsgemäßen Sicherungselements, das sich aus den in den Figuren Fig. 1 und Fig. 2 gezeigten Leiterbahnen zusammensetzt.

The invention is explained in more detail with reference to the following figures. It shows

• 1: a plan view of the lower conductor track according to a preferred embodiment of the fuse element according to the invention,
• 2: a plan view of the upper conductor track according to a preferred embodiment of the securing element according to the invention and
• 3 shows a plan view of the preferred embodiment of the fuse element according to the invention, which is composed of the conductor tracks shown in FIGS. 1 and 2.

FIG. 1 shows a plan view of a lower conductor track 2, on which a dielectric adhesive layer 8 is applied, and FIG. 2 shows a plan view of an upper conductor track 3. The two conductor tracks 2, 3 according to the invention shown in FIG. 3 are used Securing element 1 together. According to a preferred embodiment of the securing element 1 according to the invention, the conductor tracks are punched out of an aluminum foil. The manufacturing method for manufacturing the fuse element 1 according to the invention is relatively inexpensive, since the two conductor tracks 2, 3 are relatively wide and essentially only have one turn. Because of the dimensions, the securing element according to the invention is also characterized by a high degree of stability.

The two conductor tracks 2, 3 each consist of one turn and are wound in opposite directions. One consequence of this configuration is inevitably that boundary edges 5 of the lower conductor track 2 are crossed by the upper conductor track 3. The securing element 1 shown in FIG. 3 has three critical areas 7, in which boundary edges 5 of the lower interconnect 2 are crossed by the upper interconnect 3. The securing element shown in FIG. 3 is now designed in such a way that these three critical areas 7 come to lie essentially along a straight line in a narrowly delimited strip-shaped area. In this strip-shaped area, in addition to the already existing dielectric adhesive layer 8, which insulates the conductor tracks 2, 3 from one another, an additional dielectric layer 4 is inserted, or instead the two conductor tracks 2, 3 are applied in the critical areas with a reduced contact pressure laminated together so that the dielectric adhesive layer 8 has a greater thickness in the critical area than in the remaining overlap area. In the case shown, the additional dielectric layer 4 is a dielectric film material which is preferably made of PET. However, dielectric lacquers or dielectric adhesives can also be used instead.

LIST OF REFERENCE NUMBERS

1

fuse element

2

lower trace

3

upper trace

4

additional dielectric layer

5

boundary edge

6

overlapping end area

7

critical area

8th

dielectric adhesive layer

Claims (12)

1. A security element for electronic article surveillance, comprising one lower and one upper conducting track having at least one winding each, said two conducting tracks being wound in opposing directions, with said two conducting tracks (2, 3) overlapping in at least one area of overlap, and with a dielectric adhesive layer (8), which is provided in the area of overlap between the two conducting tracks (2, 3), connecting the two conducting tracks (2, 3) to one another,
   characterized in that in a critical area (7) within the area of overlap, in which critical area a border edge (5) of the lower conducting track (2) overlaps the upper conducting track (3) or a border edge of the upper conducting track (3) overlaps lower conducting track (2), the dielectric adhesive layer (8) is either at least as thick as in the remaining area of overlap and is coated with an additional dielectric layer (4), or it is thicker than in the remaining area of overlap.
2. The security element as claimed in claim 1,
   characterized in that the additional dielectric layer (4) is a dielectric film material, a dielectric lacquer layer or an additional dielectric adhesive layer.
3. The security element as claimed in claim 2,
      characterized in that the dielectric film material is PET
4. The security element as claimed in any one of claims 1 to 3,
   characterized in that the two conducting tracks have been subjected to a reduced application pressure in the critical area (7) during the production process.
5. The security element as claimed in any one of claims 1 to 4,
   characterized in that in the event of there being several critical areas (7) in which a border edge (5) of the lower conducting track (2) overlaps with the upper conducting track (3) or a border edge of the upper conducting track (3) overlaps with the lower conducting track (2), said critical areas (7) are arranged essentially along a straight line in a strip-shaped area.
6. The security element as claimed in claim 5,
   characterized in that the sum of the lengths of the border-edges (5) is minimal in the strip-shaped area.
7. The security element as claimed in claim 5 or 6,
   characterized in that the width of the additional dielectric adhesive layer (4) is coordinated with the width of the strip-shaped area and extends preferably over the full length of the security element (1).
8. The security element as claimed in any one of claims 1 to 7,
   characterized in that the two conducting tracks (2, 3) are connected electrically to one another in an overlapping end area (6).
9. A method of manufacturing a security element according to any one of claims 1 to 8,
   characterized in that a dielectric adhesive layer (8) is applied to the lower conducting track (2), that the critical area (7) or the critical areas (7) is or are coated with an additional dielectric adhesive layer (4), and/or that the lower conducting track (2) and the upper conducting track (3) are laminated together in the critical area (7) or in the critical areas (7) using a reduced application pressure, with the upper conducting track (3) being laminated together with the lower conducting track (3) in the desired position.
10. The method as claimed in claim 9,
    characterized in that in the event of mechanical production, the upper conducting track (3) and the lower conducting track (2) are positioned each on a web material, that their arrangement on the web material is such that the critical areas (7) are oriented in the running direction of the machine, and that the additional dielectric layer (4) is applied in the strip form to the lower conducting track (2) or to the upper conducting track (3), as applicable, before the two conducting tracks (2, 3) are laminated together.
11. The method as claimed in claim 9 or 10,
    characterized in that the additional dielectric layer (4) is applied as a dielectric lacquer layer to the upper conducting track (3) or to the lower conducting track (2) by spraying or printing.
12. The method as claimed in claim 9 or 10,
    characterized in that the additional dielectric layer (4) is applied as a dielectric adhesive layer to the upper conducting track (3) or to the lower conducting track (2) by means of extrusion.