EP0919050B1 - Electronic anti-theft element - Google Patents

Abstract

An electronic anti-theft element consists of at least one spiral printed circuit, a capacitor and a dielectric layer arranged therebetween, or of two spiral printed circuits which are arranged on respective sides of a dielectric layer in an at least partially overlapping manner (forming resonant circuit). The object of the invention is to provide a resonant circuit which is less liable to be reactivated. For that purpose, in at least one selected area (a rated break point) of the dielectric layer a short-circuit is created between the opposite capacitor plates or spiral printed circuits when a sufficiently high energy is supplied by a magnetic alternating field. The selected area is locally reinforced, preventing the suppression of the short-circuit by mechanical stress and the reactivation of the anti-theft element.

Description

The invention relates to a fuse element for the electronic Article security, consisting of at least one spiral conductor track and a capacitor with a intermediate dielectric layer or existing from two spiral conductor tracks, which are at least partially overlapping on both sides of a dielectric layer are arranged (→ resonant circuit).

Resonance resonant circuits, which at a predetermined resonance frequency, which is usually 8.2 MHz, to resonance vibrations are encouraged to secure goods common against theft in department stores. They are often an integral part of adhesive labels or Cardboard hang tags attached to the items to be secured are attached. Typically, the department store is with one electronic surveillance system in the exit area equipped that recognizes the resonant circuits and one Alarm triggers when a secured item is in an unauthorized manner Way a secured surveillance zone happens. Once a Customer has paid for the goods, the resonant circuit deactivated. The measure prevents a Alarm is triggered as soon as an item is lawfully purchased has been passed and subsequently the surveillance zone.

The deactivation systems, often in the checkout areas placed produce a resonance signal with a larger one Amplitude as it is generated in the surveillance systems. A resonance label is usually in a field strength, which is greater than 1.5 A / m, deactivated. Known are different deactivation mechanisms for Resonant circuits. Either the isolation between opposing interconnects destroyed, whereby a short circuit occurs or a piece of a conductor track becomes overloads and melts, causing an interruption. As a result of the deactivation, the resonant properties of the resonant circuit, i.e. the resonance frequency and / or the "Q" factor is modified so much, that the resonance label is no longer through the surveillance system is detected.

The deactivated resonant circuit can be mechanically Manipulation, for example by kinking, packing and Transporting the goods or by bending the label and thus the resonant circuit, unintentionally again be reactivated. An unintentional reactivation of one Resonant circuit which is based on a lawfully acquired Item attached, can then trigger an alarm perform what is quite a nuisance to both the buyer and also represents for the department store.

To date, no state of the art has become known with the problem of reducing the risk of accidental Reactivation of already deactivated resonance labels deals. Regarding the deactivation of resonance labels different methods have been described.

In US Pat. No. 4,876,555 or in the corresponding EP 0285 559 B1 proposes a hole in the by means of a needle Insulation layer between two opposite To generate capacitor areas. This will be a Deactivation mechanism made that is error free and is permanent.

US Pat. No. 5,187,466 also describes a method for Generation of a deactivatable resonant circuit by means of a short circuit which, under normal circumstances cannot be destroyed.

With regard to the first-mentioned US Pat. No. 4,876,555 and EP 0 285 559 B1 it should be noted that the one disclosed there Resonant circuit has capacitor plates on are arranged on both sides of the dielectric. The between dielectric layer lying between the two capacitor plates has a through hole.

A process is described in the previously mentioned US Pat. No. 5,187,466 described that with a resonant circuit Capacitor plates on both sides of the dielectric is applied, the capacitor plates first be short-circuited and the short-circuit later Electric power is melted.

There are other important techniques in the field of Deactivation of resonance labels has become known however, also does not deal with reducing the risk deal with unintended reactivation. A Patent family that goes in this direction includes the EP 0 181 327 Bl, U.S. Patent 4,567,473 and U.S. Patent 4,498,076. The invention described in these patents The resonance label is composed as follows: Carrier material that serves as a dielectric, capacitor plates on both sides of the planar, dielectric Substrate, a deactivation zone and a resonant circuit, which is arranged on the dielectric. The state of the So far, technology has not mentioned any measures unwanted reactivation after successful deactivation prevent.

The invention has for its object a resonant circuit with a reduced probability of reactivation to propose.

The object is achieved in that in the dielectric Layer at least one selected area (a target breakthrough point) is provided in which at a correspondingly high energy supply through a magnetic Alternating field a short circuit between the opposite Capacitor plates or the spiral conductor tracks is created, and where the selected area is local is so amplified that destruction of the short circuit (= conductive path) due to mechanical stress and thus reactivation of the securing element is prevented.

According to an advantageous development of the invention Fuse element is provided that the dielectric layer essentially a uniform thickness and no additional manufacturing defects (e.g. air pockets) having.

It is further proposed that in the case of two at least partially overlapping traces these in opposite Directions are wound, the selected one Area lies at the outer ends of the conductor tracks. Here namely the highest induction voltage occurs.

An advantageous embodiment of the invention Fuse element suggests the dielectric layer in to make the selected area thinner than in the remaining areas.

According to an alternative, the selected area is thereby excellent that the dielectric layer here is another has chemical or physical properties as in the remaining areas.

According to an advantageous development of the invention Fuse element consists of the dielectric layer from at least two components. In this context it is particularly favorable if the melting point of one component the dielectric layer above the manufacturing temperature for securing elements. Furthermore one sees Design before that the components of the dielectric Layer are such that they can either by Coating or by lamination.

According to an advantageous embodiment of the invention Security element is the selected area, in the deactivation takes place through the application reinforced with additional pressure. By squeezing the liability between the capacitor plates or at least partially overlapping conductor tracks improved. It has proven to be favorable if the Reinforcement by printing the capacitor plates or at least partially overlapping conductor tracks into one three-dimensional shape is achieved. It is special here advantageous if the improved adhesion and the shaping of the Capacitor plates or the conductor tracks in one process can be achieved.

If the resonant circuit is bent or bent in the area of the reinforced zone, in the yes the deactivation takes place, there is still the Risk of warping, shearing, shifting or Replacement of the resonant circuit at the deactivation point. This would cause the resonant circuit in undesirably reactivated. To this danger to prevent, is according to a development of the invention provided weakened on both sides of the reinforced zone Train zones. Attacks a bending moment from the outside, so is the probability that the resonant circuit in the Area of the weakened zones is bent or even breaks, much larger than bending or breaking within the reinforced zone. The weakened zone can therefore also be used as the preferred bending or breaking zone.

The formation of the weakened zones can do this take place that the width of the conductor track is narrowed. A another possibility is that the adhesive layer in these weakened zones is treated in such a way that the Binding between the spiral conductor tracks considerably is reduced. It is also possible to trace the tracks in to perforate the weakened zones.

According to an advantageous development of the invention Resonant circuit designed so that the capacity between the upper and lower conductor tracks at the inner ends the coils are concentrated. In particular is on the inner Ends of the coils a large area of overlap Conductor tracks provided, resulting in a correspondingly large Capacity results while the overlap on the outer Coil ends is very low.

An advantageous development of the invention Device suggests that the overlap areas between the two conductor tracks and thus the capacity between the traces at the inner ends of the Concentrate conductor tracks. In particular, it is provided that the outer ends of the two traces in a small one Area overlap and that is at the outer ends of the Conductors a relatively long area without overlap connects. An advantage of this topology is that deactivation in the overlap area between the outer ones Ends of the upper and lower trace takes place as this the point with the highest voltage potential between the Conductor tracks is.

The deactivation point is therefore very safe in the selected area.

Fig. 1: eine Draufsicht auf eine Ausführungsform des erfindungsgemäßen Resonanzschwingkreises,

Fig. 2: einen Querschnitt gemäß der Kennzeichnung II-II in Fig. 1,

Fig. 3: ein Ersatzschaltbild der bei zwei sich teilweise überlappenden spiralförmigen Leiterbahnen auftretenden Spannungen,

Fig. 4: eine Draufsicht auf den äußeren Endbereich der spiralförmigen Leiterbahnen,

Fig. 5: einen vergrößerten Querschnitt durch die obere Spule und die obere Komponente der dielektrischen Schicht

Fig. 6: einen detaillierten Querschnitt durch den erfindungsgemäßen Resonanzschwingkreis,

Fig. 7: eine Draufsicht auf einen verstärkten Bereich,

Fig. 8a: einen Querschnitt durch ein geeignetes Werkzeug,

Fig. 8b: eine Draufsicht auf das in Fig. 8a dargestellte Werkzeug,

Fig. 9: eine Draufsicht auf eine Leiterbahn mit geschwächter Zone,

Fig. 10: eine Draufsicht auf eine weitere Leiterbahn mit geschwächter Zone,

Fig. 11a: eine Draufsicht auf eine Ausgestaltung der unteren Spule,

Fig. 11b: eine Draufsicht auf eine Ausgestaltung der oberen Spule,

Fig. 11c: der Resonanzschwingkreis, der aus den Spulen zusammengesetzt ist, die in Fig. 11a und Fig. 11b gezeigt sind, und

Fig. 12: ein Ersatzschaltbild für die Spannungsverhältnisse der in Fig. 11c dargestellten Ausführungsform des erfindungsgemäßen Resonanzschwingkreises.

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

1: a plan view of an embodiment of the resonant circuit according to the invention,

2: a cross section according to the marking II-II in Fig. 1,

3: an equivalent circuit diagram of the voltages occurring with two partially overlapping spiral conductor tracks,

4: a plan view of the outer end region of the spiral conductor tracks,

5 shows an enlarged cross section through the upper coil and the upper component of the dielectric layer

6: a detailed cross section through the resonant circuit according to the invention,

7: a plan view of a reinforced area,

8a: a cross section through a suitable tool,

8b: a top view of the tool shown in FIG. 8a,

9: a plan view of a conductor track with a weakened zone,

10: a plan view of a further conductor track with a weakened zone,

11a: a plan view of an embodiment of the lower coil,

11b: a plan view of an embodiment of the upper coil,

FIG. 11c: the resonant circuit composed of the coils shown in FIGS. 11a and 11b, and

FIG. 12: an equivalent circuit diagram for the voltage ratios of the embodiment of the resonant circuit according to the invention shown in FIG. 11c.

Fig. 1 shows an embodiment of the invention Resonant circuit 6 in plan view. 2 is the in Fig. 1 shown resonant circuit 6 in cross section see. Deactivation of the resonant circuit 6 done by shorting between the two spiral Conductor tracks 2, 3, which are preferably made of aluminum are manufactured, through the dielectric layer 4 is produced. An applied alternating magnetic field, like it e.g. is emitted by the monitoring system AC voltages in the two spiral conductor tracks 2, 3 of the resonant circuit 6. The spiral Conductor tracks 2, 3 at least partially overlap and are in opposite directions wrapped. Hence the exterior End of the lower coil 2 has a positive potential relative to inner end of the lower coil 2 when the inner end the upper coil 3 has a positive potential with respect to the has the outer end of the upper coil 3. So it stays to note that the points / areas in which the induced alternating voltages between the two coils 2, 3 are maximum, located in the end regions of the coils 2, 3.

Since in the example shown in FIG. 1 the upper coil 3 has fewer turns than the lower coil 2, the highest voltages between the ends of the upper coil 3 and the positions directly below the lower coil 2 generated.

Fig. 3 illustrates the voltage relationships in different areas of the two themselves at least partially overlapping coils 2, 3 of a resonant circuit 6, according to an advantageous development of the resonant circuit 6 according to the invention used can be.

With the resonant circuit 6 described above with uniform thickness of the dielectric layer 4 between the Coils 2, 3 are deactivated in the end areas of upper coil 3 and lower coil 2, since here the induced Potential is maximum. Because the electric field strength occurs concentrated on a small radius surface, there is a deactivation exactly at the ends of the Conductor tracks 2, 3 - as shown in Fig. 4.

However, if the dielectric layer 4 is not uniform is thick or contains air bubbles 7, which is due to Manufacturing errors is quite possible Deactivation in different areas of coils 2, 3 occur. Such manufacturing defects can be local Cause vulnerabilities and even holes through Air pockets 7 in the dielectric layer 4 cause. As a result, the dielectric layer 4 breaks open these local vulnerabilities together, although the potential for tension here is lower than at the ends of the top Coil 2 and lower coil 3. Since the voltage potential at the local vulnerabilities is less than at the ends of the Conductor tracks 2, 3 are those for generating the deactivation short circuit available electrical energy less than the electrical energy needed to generate one Deactivation short circuit at the ends of the upper coil 3 would be necessary.

Fig. 5 shows a cross section through a dielectric Layer with manufacturing defects, here air bubbles 7 and Irregularities in the surface. To such The dielectric layer is to avoid manufacturing defects 4 trained according to a further training that they in essentially has a uniform thickness and large Part is free from local vulnerabilities 7. Such uniform dielectric layer 4 provides a Deactivation in the end areas of the spiral Conductor tracks 2, 3 safe, since here the induced voltage and Energy are maximum. A short circuit caused by a such deactivation arises, is very robust and little susceptible to inadvertent reactivation.

According to an advantageous development of the invention The resonant circuit 6 consists of the dielectric layer 4 from at least two components 4a, 4b, an upper one Component 4a and a lower component 4b. The lower one Component 4b is stamped onto the lower coil 3 applied. The upper component 4a is on the upper coil 2 applied. The upper component has 4a a relatively low melting point, which allows her to serve as a hot melt adhesive and the two coils 2, 3 during the hot stamping of the upper coil 2 onto the lower one Glue coil 3. The upper component 4a of the dielectric Layer 4 melts during hot stamping of the top coil 2. The lower component 4b of the dielectric layer 4 has a higher melting point and does not melt during the Hot stamping on the top spool 2. The uniformity of the lower component 4b of the dielectric layer 4, which is not melts, improves the uniformity in the thickness of the dielectric layer 4 overall.

Fig. 6 shows a cross section through a resonant circuit 6 with a dielectric layer 4 consisting of two Components 4a, 4b. The lower component 4b can either by coating the lower coil 3 or by Laminating the lower component 4b of the dielectric Layer 4 are produced on the coil 3. Usually is the coil material (A1) in the form of wide Roll material before, so that the uniformity of the surface the dielectric layer 4 can be maintained and other defects, for example, by Air pockets 7 are caused to be minimized.

It can happen that the short circuit by kinking or other mechanical tampering is broken up, even if the dielectric layer 4 is so uniform that Defects 7 are largely reduced and the deactivation short circuit only at the end of the upper conductor track occurs where the induced energy is maximum. (This is of course, only the case if none are otherwise prepared Breakthrough point provided.) Shear or sliding movements of the two layers of metal relative to each other or delamination of the two layers can become an unintended one Lead reactivation.

According to the resonant circuit 6 is local in the Area of the ends of the upper coil 2 or in the area of prepared area reinforced. The reinforced zone 10 is less prone to shear and glide or a Delaminate. With local reinforcement, everyone can Strain on the resonant circuit 6 by buckling or Bends are reduced because the two are spiral Conductor tracks 2, 3 only nearby, but not within the locally reinforced zone 10 shear, slide, kink or delaminate.

According to an advantageous development of the invention Resonant circuit 6 are the areas around the ends one of the two conductor tracks 2, 3, here the upper one Conductor 2, reinforced by the fact that a local zone 10 with an additional pressure is applied, the metal, preferably aluminum, is shaped so that it is a non-plane Takes shape. The local pressurization causes better adhesion between the two conductor tracks 2, 3 and between the lower conductor track 3 and the dielectric layer 4. Is this pressure by means of a shaping tool 11 with a survey with a preset profile (stamp 12), the Traces 2,3 are shaped so that the resistance of the Resonant circuit 6 significantly against reactivation is improved. Incidentally, the tool 11 can also be flat be formed and have predetermined dimensions.

Regarding the structural properties of metals it is well known that a metal sheet with grooves, bulges or other incorporated structures are not so easy bends like a flat sheet. The same principle will applied here to a locally reinforced zone 10 produce. Any large-scale folding or bending of the Resonant circuit 6 leads to the resonant circuit 6 nearby but not within reinforced zone 10 bend, fold, shear or delaminate. So will reduces the risk of unintentional reactivation. The actual shape of the reinforced zone 10 is not crucial to the actual profile of the molded Conductor 2, 3 in the reinforced zone 10 is also not critical.

Fig. 7 shows a plan view of an embodiment of a reinforced zone 10 at one end of the upper conductor track 2.

In Fig. 8a is a cross section and in Fig. 8b is a plan view a tool 11 shown for the manufacture of the reinforced zone 10 can be used.

If the resonant circuit is bent or bent 6 in the area of the reinforced zone 10, that is Zone in which deactivation is known to take place and the. has been deliberately reinforced, still exists here the risk of warping, shearing, shifting or Detachment of the resonant circuit 6. This would result in a unwanted reactivation of the resonant circuit 6 to lead. To prevent this danger, is in one additional development of the invention is provided, weakened zones 13 on both sides of the reinforced zone 10 to train. If a bending moment attacks from the outside, it is it is likely that the resonant circuit 6 in the range the weakened zones 13 fold or even break. The weakened zone 13 can therefore also be considered the preferred bending or fracture zone. Training the weakened zone 13 can be done either by the Width of the conductor track 2, 3 is narrowed, as in FIG. 9 and Fig. 10, or by corresponding Treatment of the adhesive layer in this weakened zone 13, in such a way that the bond between the Conductor tracks 2, 3 is considerably weaker here. Another One way to get weakened zones 13 is to to perforate the conductor tracks 2, 3.

According to an additional development of the invention Conductor tracks 2, 3 and the resonant circuit 6 see above trained that the capacity between upper and lower Conductor 2, 3 at the inner ends of the spiral Conductor tracks 2, 3 is concentrated. 11a, 11b and 11c show a corresponding resonant circuit 6. From the figures it can be seen that the inner ends of the coils 2, 3 a large overlap area the conductor tracks 2, 3 is present, resulting in a gives proportionately large capacity during the overlap at the outer ends of the coils 2, 3 is very low.

The equivalent circuit diagram of this arrangement is shown in FIG. 12 shown. The generated between the two coils 2, 3 Voltage difference is at the outer coil ends is much larger than anywhere else between the coils 2, 3. When looking at the Figures 11c and 12 also show that the outer turn of the lower conductor track 3 from the upper To a large extent, conductor track 2 is not covered at all becomes. Thus, along this overlap-free section 9 there is also no deactivation. If you follow them outer turn of the lower conductor track 3 from the end point back where there is a small overlap area with the upper trace 2 there, it is found that the next Point at which there is an overlap of the conductor tracks 2, 3 and thus there is a possibility of deactivation, one piece back on the outer turn of the lower conductor track 3 lies. This point has a much lower one Voltage potential between upper and lower conductor track 2, 3rd

Even if the dielectric layer 4 is between the two Traces not absolutely uniform in thickness or not is absolutely free of other weaknesses 7, the Deactivation takes place at this outer overlap point at this point a significantly higher potential difference is present between the conductor tracks 2, 3.

Another advantage is that due to the uneven distribution of the potential difference along the Conductor tracks 2, 3 for a deactivation short circuit available energy between the conductor tracks 2, 3 is higher must as with an even distribution of tension and Capacity. However, higher energy means one more reliable short circuit and thus also automatically less risk of unwanted reactivation.

Reference list

1

Backing material

2nd

upper coil

3rd

lower coil

4th

dielectric layer

4a

upper component

4b

lower component

5

Adhesive layer

6

Resonant circuit or
Securing element

7

Trapped air

8th

(prepared) selected area

9

overlap-free area

10th

reinforced zone

11

Tool

12th

stamp

13

weakened zone

Claims (17)

1. A security element for electronic article surveillance, comprising at least one coiled conductive track and a capacitor having a dielectric layer arranged therebetween, or comprising two coiled conductive tracks that are disposed on either side of a dielectric layer so as to overlap at least in part,

   wherein provision is made in the dielectric layer (4) for at least one selected area (8) in which a short circuit is produced between the opposed capacitor plates or the coiled conductive tracks (2, 3) by the supply of energy in sufficiently high amount by an alternating magnetic field,

   and wherein the selected area (8) is strengthened locally such that a destruction of the short circuit by mechanical loads, and hence a reactivation of the security element (6), are prevented.
2. The security element as claimed in claim 1,
   wherein the dielectric layer (4) is of substantially uniform thickness and has no additional manufacturing defects.
3. The security element as claimed in claim 1 or 2,
   wherein in the event of two at least partly overlapping conductive tracks (2, 3) being used these are wound in opposite directions, with the selected area (8) being located in the outer end areas of the conductive tracks (2, 3) where the induced voltage is at its highest level.
4. The security element as claimed in claim 1,
   wherein the selected area (8) is characterized in that the dielectric layer (4) is thinner in said area than in the remaining areas, or that it has a hole.
5. The security element as claimed in claim 1,
   wherein the selected area (8) is characterized in that the dielectric layer (4) has in said area a different chemical or physical property than in the remaining areas.
6. The security element as claimed in claim 1 or 2,
   wherein the dielectric layer (4) is comprised of at least two components (4a, 4b).
7. The security element as claimed in claim 6,
   wherein the melting point of the one component (4a; 4b) of the dielectric layer (4) lies above the production temperature for security elements (6).
8. The security element as claimed in claim 3,
   wherein the components of the dielectric layer (4) are of a nature enabling them to be fabricated by either a coating or a laminating process.
9. The security element as claimed in claim 1, 3, 4 or 5,
   wherein the strengthening in the strong zone (10) is accomplished by the application of additional pressure in order to enhance the bond between the capacitor plates or the at least partly overlapping conductive tracks (2, 3).
10. The security element as claimed in claim 9,
    wherein the strong zone (10) is obtained by pressure forming the capacitor plates or the at least partly overlapping conductive tracks (2, 3) into a three-dimensional shape.
11. The security element as claimed in claim 9 or 10,
    wherein the enhanced bonding and the forming of the capacitor plates or conductive tracks (2, 3) are accomplished in a single operation.
12. The security element as claimed in claim 1, 3, 4 or 5,
    wherein weak zones (13) are provided on either side, or on the other side, of the selected area (8).
13. The security element as claimed in claim 12,
    wherein the weak zones (13) are formed by narrowing down the width of the conductive track (2; 3).
14. The security element as claimed in claim 12 or 13,
    wherein in the weak zones (13) the dielectric layer (4) is less strongly bonded to the capacitor plates or conductive tracks (2, 3) than in the remaining areas.
15. The security element as claimed in claim 12 or 13,
    wherein the weak zones (13) are characterized in that the capacitor plates or the conductive tracks (2, 3) are perforated.
16. The security element as claimed in claim 2,
    wherein the areas of overlap between the two conductive tracks (2, 3) and hence the capacitance between the conductive tracks (2, 3) are concentrated at the inner ends of the conductive tracks (2, 3).
17. The security element as claimed in claim 16,
    wherein the outer ends of the two conductive tracks (2, 3) overlap in a small area and there is a relatively long area with no overlap (9) adjacent to the outer ends of the conductive tracks (2, 3).

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