FR2614109A1 - ELECTRONIC ALARM LABEL - Google Patents

Abstract

Electronic protection circuit with passive elements forming a resonant circuit at a preset frequency. According to the invention, the circuit is formed by printing with the use of a conducting ink on a transparent thin support, so as to be invisible. Applications: improvement of the security against theft of protected objects.

Description

ELECTRONIC ALARM LABEL
The present invention relates to an electronic alarm label intended in particular, but not exclusively, to combat shoplifting, in particular in large areas practicing the so-called self-service distribution.

We already know such labels carrying a resonant electrical circuit housed between two sheets, the lower sheet being coated with glue on its outer surface, so as to be invisible from the outside, the electrical circuit being able to be printed or engraved. This resonant circuit is of the LRC type, that is to say it constitutes a loop
including at least one capacitor and at least one induction coil. On a label the induction coil is a flat coil, that is to say that it is formed by a spiral.

The capacitor (s) consist of metal surfaces arranged on either side of the insulating support.

These labels have the possibility of reacting while passing inside a protected area, under the influence of electromagnetic stimulation. To this end, the protected area includes compulsory passage points for people, on either side of which are mounted on the one hand a transmitter, and on the other hand a receiver, the transmitter emitting high frequency electromagnetic waves. for example from 10 to 27 MHz, and the receiver receiving this broadcast.

When a label, such as the one just mentioned above, passes into the protected area, it absorbs a certain amount of energy, the coupling between the transmitter and the receiver is modified, and the receiver can detect this variation in coupling and emit an audible or other alarm signal. Thus, when a person shows up at the checkout, if they fraudulently try to pass an object over them, an alarm signal is immediately emitted. On the other hand, when all the objects pass through the box, the detection system remains in its standby state, and no alarm is emitted.

When checking out, the cashier can change the electrical characteristics of the resonant circuit, for example by placing a second label on the label, or sticker, which changes the resonance frequency of the circuit, so that the frequency reference becomes inoperative. But, of course, the perpetrators have already found different defenses to these anti-theft means. In particular, they tear off, before going to the cash register, the circuit-holder label, so that the object can pass through the gantry without causing an alarm. In practice, the circuits currently known are opaque and are arranged on a non-magnetic support, and for example on an aluminum foil. All the articles carry a resonant circuit which can be activated at the same frequency. These circuits must also be affixed to the article independently of the label itself, which contains various information relating to the product and in particular its price. This results in a double affixing of the label on the one hand, and of the sticker carrying the resonant circuit on the other hand, which results in a loss of time.

It is also known to mount on the same sticker two resonant circuits responding to two different frequencies. The first resonant circuit responds to the first frequency by triggering an alarm signal. The second resonant circuit responds to a second frequency which has the purpose of deactivating the resonant circuit by causing the interruption of the flow of current through a fusible element. Thus, when the product has undergone the checks and has been paid, the resonant circuit is deactivated, which allows in particular a check after leaving the store.

However, such a circuit, apart from being able to be torn off from the product on which it is affixed, must necessarily be flat, failing which the alarm signal does not occur, the electromagnetic characteristics of the circuit being altered.

The object of the present invention is to remedy these drawbacks and to increase the security obtained with such a resonant circuit.

According to the present invention, the electronic security label, comprising at least one flat resonant circuit, is characterized in that the flat resonant circuit is produced by printing using a conductive ink of thickness less than 40 microns, on a flexible and transparent support. The substrate consists, for example, of a polyethylene film with a high refractive index, so that practically all of the incident light is reflected. Thus, the resonant circuit is invisible to the naked eye and it is therefore not possible to detach it from its support. Of course, a number of false circuits can be placed on the object to further increase the difficulty of fraudulent removal.

In one embodiment of the invention, the label comprises a surface of printed paper or the like bearing the necessary information, and the back of which is coated with a first layer of adhesive on which the substrate of the resonant circuit is disposed, and a second layer of glue.

Advantageously, the first layer of adhesive has less adhesion than the second layer of adhesive. The actual circuit can be coated with a layer of low adhesion silicone material. Thus, even if the label is torn off, the resonant circuit, which is advantageously of dimensions smaller than those of the label, remains adherent, but always invisible, on the object to be protected and the alarm is triggered by passage of this object in a detection area. A thief who has torn off the label is thus trapped, especially since he cannot see on the product that the transparent circuit has remained in place.

Other characteristics and advantages of the present invention will appear during the description which follows of a particular embodiment, given only by way of nonlimiting example, with reference to the single figure which represents, in section, the diagram of a label according to the invention.

In the single figure, it can be seen that a label consists of a printable layer 1 of paper or the like, on the surface of which are printed optically readable indications 2. The underside of the label 1 is coated with a thin layer of a first adhesive 2 against which a face 3 of the circuit is applied.
ésonant 4 which is a double-sided circuit. It comprises, as in the known resonant circuits at least one flat turn 5 and, on the two faces of the substrate 4, plates 6 forming the armatures of a capacitor. The two faces of the substrate 4 can be joined by an eyelet type connection, or by a capacitive coupling.

The underside of the substrate 4 is coated with a second layer of adhesive 7 which is extremely adherent.

 The thickness of the label 1 can be any and, the substrate 4 has a thickness of approximately 1 tenth of a millimeter, the circuit proper having a thickness of less than forty microns and of approximately 30 microns. In fact, the induced currents are of low intensity and the resistance of the circuit intervenes only relatively little in the process. On the other hand, the small thickness of the substrate is favorable for obtaining a large capacity and, preferably, the polyethylene film is bioriented as for the production of traditional capacitors. As mentioned above, it is printed using a virtually invisible conductive ink that dries in the open air. The substrate 4 proper can for example be a polyethylene film. The label-circuit assembly constitutes a multilayer film and it is thus possible to carry out the labeling and product protection in a single operation. The printing of the labels can be done in a labeling machine of known type.

Of course, the circuit itself can be used itself directly, independently of the label which plays the protective role, this can be applied elsewhere, the upper surface of the circuit being protected by a layer of transparent plastic or with a coating.

It goes without saying that many variants can be introduced, in particular by substitution of technically equivalent means without thereby departing from the scope of the invention.

Claims (4)

1. Electronic protection circuit comprising elements  liabilities combined to form a resonant circuit  flat, characterized in that it is produced by printing  using conductive ink on a lower thickness  at 40 microns, on a flexible and transparent support.  2. Circuit according to claim 1, characterized in that the  support consists of a plastic film (4)  flexible whose thickness is less than 0.1 mm. 3. Multilayer label including an electronic circuit  according to one of claims 1 or 2, characterized in that  that it includes a surface of printed paper or the like,  the back of which is coated with a first layer of glue (3)  on which is applied a substrate (4) on its  two sides at least one induction loop (5) ~ and at least  two capacitive surfaces (6), the lower surface of the  substrate being covered with a layer of adhesive (7). 4. Label according to claim 3, characterized in that  the adhesive power of the layer (3) is less than  adhesive power of the layer (7).