WO1998018027A1

WO1998018027A1 - Safety label with resonant circuit

Info

Publication number: WO1998018027A1
Application number: PCT/FR1997/001846
Authority: WO
Inventors: Benoît Thevenot; Alain Larchevesque
Original assignee: Schlumberger Systemes
Priority date: 1996-10-22
Filing date: 1997-10-16
Publication date: 1998-04-30
Also published as: FR2754910A1; FR2754910B1

Abstract

The invention concerns a safety label with resonant circuit, comprising a plastic label body (1) with its faces bearing inductance (6) and capacitance (7, 8) elements forming the resonant circuit (5). The label further comprises an integrated circuit (10) set in the label body (1), said integrated circuit being connected to an inductance element (6) of the resonant circuit (5) for forming a modulating means associated with said resonant circuit.

Description

Resonant circuit security label

The present invention relates to the field of security tags with resonant circuit, of the type which are for example used as anti-theft tags for consumer products, being associated with one or more objects offered for sale.

More particularly, these are safety labels with a resonant circuit, of the type comprising a label body made of plastic material the faces of which carry inductance and capacitive elements forming the resonant circuit. This type of label can be used for theft detection by association with a transmitting antenna generally disposed at a pass door, insofar as the label disturbs the surrounding electromagnetic field. To deactivate these labels, one can for example expose them to a very high electromagnetic field, supplied at the resonance frequency of the resonant circuit in order to cause the breakdown of at least one of the capacitive elements of this resonant circuit.

This type of label inherently has limitations as to the associated detection modes.

It has already been proposed to organize printed circuits comprising a plurality of capacitive elements mounted in parallel, with different capacities, so as to obtain circuits resonating at different frequencies. This makes it possible to organize what specialists call product traceability, with detection carried out at the warehouse level, and then at the level of different stores or departments. The prospects are a priori attractive, but it appears in practice that the applications of such circuits are limited because the breakdown phenomenon is irreversible, and this phenomenon allows only a detection of the presence of product, and in no way an identification.

In the same approach, it has also been proposed, as illustrated in document EP-A-0 142 380, to have on the faces of the label body two conductive windings in opposite directions and connected to each other. The different parts of the facing windings form capacitive and induction elements so that the windings form an association of several circuits resonating at different frequencies.

The technological background of the invention is also illustrated by the arrangements of resonant circuits fitted, no longer to labels, but to contactless type integrated circuit cards. We can for example refer to documents GB-A-2 279 907, US-A-5 337 063 and FR-A-2 679 670.

Document GB-A-2,279,907 thus describes a card of the contactless type comprising, between two sheets of superposed plastic material, an inductive loop and an integrated circuit connected to this loop.

This document mentions that the integrated circuit is used to record banking transactions or to memorize building areas accessible by the intermediary of the card used as an identification card: the integrated circuit therefore has the sole function of allowing card reading via the inductive loop.

Document US-A-5 337 063 also describes a contactless card comprising a resonant circuit forming an antenna connected to an integrated circuit. The resonant circuit comprises a conductive winding, certain portions of which are connected by as many conductive lines to switches which are controlled so as to modify the inductance, and therefore the resonance frequency, of the resonant circuit.

The document FR-A-2 679 670 describes a contactless card comprising two windings and a microprocessor for a FSK type transmission.

Finally, reference may be made to documents OA-93 19993, US-A-5,563,582, OA-88 08592, EP-A-0 556 910 and WO- A-89 07295.

The object of the invention is to propose a security label which implements a technique making it possible to improve the performance of security labels with a resonant circuit while retaining a manufacturing cost comparable to the low cost of basic labels, the structure of which has was recalled above.

The object of the invention is therefore to produce a security label, the structure of which makes it possible to implement different detection modes, in particular in association with transmitter / receiver assemblies or with reading units.

This problem is solved in accordance with the invention thanks to a security label with a resonant circuit, comprising a label body made of plastic material, the faces of which carry inductance and capacitive elements forming the resonant circuit, characterized in that it further comprises an integrated circuit embedded in the label body, said integrated circuit being connected to an inductance element of the resonant circuit to form a modulation means associated with said resonant circuit.

Thanks to the integrated circuit, it becomes possible to organize both a reading of the label and a detection according to various modes, for example according to different frequencies in association with zones of the integrated circuit which are progressively inactivated. In practice, an integrated circuit will be used comprising at the very least a memory, an interface means between the memory and the resonant circuit, as well as a means of reconstituting a time clock, in order to be able to read the label. , and possibly also be able to write particular data sequentially. If a microprocessor integrated circuit is used, the possibilities of modulation and security will be even greater, but the cost of the label will then become high. Preferably, the security label comprises on one face of the label body an inductance element produced in the form of a flat coil, and the integrated circuit is then embedded in this same face of the label body. Such an arrangement considerably facilitates the organization of the connections between the integrated circuit and the resonant circuit of the label.

Advantageously then, and in accordance with a known technique, the inductance element has enlarged zones which cooperate with homologous zones carried by the opposite face of the label body to form capacitive elements of the resonant circuit.

In this case, in accordance with a first embodiment of the invention, the integrated circuit is connected by conductive lines associated with the enlarged zones of the inductance element, or at points adjacent to these enlarged zones.

According to an alternative embodiment of the invention, the circuit can be connected by conductive lines associated with an enlarged area and at an intermediate point of the inductance element.

According to yet another alternative embodiment of the invention, the integrated circuit can be connected by a conductive line associated with an enlarged area of the inductance element and, by another conductive line, via a through conductive hole the label body, to a zone homologous to the other enlarged zone.

Preferably, the aforementioned conductive lines will be produced by depositing a conductive polymer, in particular by screen printing, with possible interposition of an insulating deposit for the overlapped parts of the inductance element.

In some cases, it may be compulsory to use an integrated circuit of considerable thickness, for example by the very fact of its manufacture. This should not necessarily induce the need to use a label body of increased thickness. Indeed, it is then advantageous to provide that the label body, thinner than the integrated circuit, is equipped, on its face opposite to that carrying the inductance element, with a thermoplastic layer in which also comes '' embed the integrated circuit.

Provision may also be made for the face of the label body carrying the inductance element to be fitted with a protective layer of thermoplastic material.

As a variant, the face of the label body carrying the inductance element may comprise a layer of adhesive material covered by a protective sheet having an adhesive coating facing the adhesive material. In this case, it suffices to detach the protective sheet, to allow immediate attachment of the security label to the associated object.

In some cases, finally, it may be advantageous to provide that the integrated circuit itself includes capacitive elements, in order to allow additional types of modulations associated with the resonant circuit.

Other characteristics and advantages of the invention will appear more clearly in the light of the description which follows and of the appended drawings, relating to a particular embodiment, with reference to the figures in which:

- Figure 1 is a perspective view illustrating a security label according to the invention; - Figure 2 is a section on II-II of Figure 1 to better distinguish the connections between the integrated circuit embedded in the label body and the associated resonant circuit;

- Figure 3 is a schematic view illustrating the electrical circuit equivalent to the circuit carried by the aforementioned security label; FIG. 4 is a section illustrating a variant of the previous embodiment in which a connection is provided at an intermediate point of the inductance element, -

- Figure 5 is a diagram illustrating the electrical circuit equivalent to the circuit associated with the safety label of Figure 4;

- Figure 6 is a section illustrating yet another embodiment of the invention, with a connection made via a conductive hole passing through the label body, -

- Figure 7 is a diagram illustrating the electrical circuit equivalent to the circuit associated with the safety label of Figure 6;

- Figure 8 is a section illustrating another embodiment in which the label body is thinner than the integrated circuit, which label body is then equipped with a ther oplastic layer in which is also embedded the integrated circuit;

- Figure 9 is a section illustrating another embodiment in which the label body is equipped with a protective layer of thermoplastic material; - Figure 10 illustrates in section a variant of the embodiment of Figure 9, in which the label body comprises a layer of adhesive material covered by a removable protective sheet.

Figures 1 and 2 illustrate a security label E according to the invention. This label comprises a label body 1 made of dielectric plastic material, having a face 2 (here the upper face) and an opposite face 3 (here the lower face). The label body 1 is equipped with a resonant circuit denoted 5, one embodiment of which is illustrated here by way of example only. The faces of the label body thus carry inductance 6 and capacitive elements 7, 8 forming the resonant circuit 5, in accordance with a technology already well known in the field of security labels with resonant circuit. In this case, the face 2 of the label body 1 carries an inductance element 6 arranged in the form of a spiral pattern which is deposited on this face of the label body. This could for example be a bonding of a printed circuit, or a deposit made by screen printing. This inductance element 6 is thus produced in the form of a flat coil, and it has enlarged zones, which are here provided at the ends of the inductance element. These zones denoted 7.1, 8.1 cooperate with homologous zones 7.2, 8.2 carried by the opposite face 3 of the label body 1 to form capacitive elements 7, 8 of the resonant circuit 5. The electrical connection between the homologous zones 7.2 and 8.2 is for example provided by a connection bar 9 or any other equivalent connection mode. In accordance with an essential characteristic of the invention, the security tag further comprises an integrated circuit denoted 10 which is embedded in the body of the label 1, this integrated circuit being connected to the inductance element 6 of the resonant circuit. 5 to form a modulation means associated with the resonant circuit.

In this case, the integrated circuit 10 is embedded in the face 2 of the label body 1 which carries the inductance element 6 produced in the form of a flat coil. Such an arrangement makes it possible to considerably facilitate the electrical connections between the integrated circuit 10 and the resonant circuit 5.

In the embodiment of FIGS. 1 and 2, the integrated circuit 10 is connected by associated conducting lines 11, 12 to the enlarged zones 7.1, 8.1 of the inductance element 6. The connection can naturally be performed at points adjacent to these enlarged areas (variant not shown). These conductive lines 11, 12 will preferably be produced by depositing a conductive polymer, in particular by screen printing. The conductive line 11 connecting the integrated circuit 10 to the enlarged area 8.1 which is directly adjacent to it can be produced in a simple direct section posing no particular insulation problem. On the other hand, the connection between the integrated circuit 10 and the other enlarged zone 7.1 requires to span several turns (here three turns) of the inductance element 6 in the form of a flat coil. It is then essential to isolate these turns before making the associated conductive line 12: this can be achieved by prior deposition of a local layer of insulating material denoted 13 spanning the zones concerned with the turns of the inductance element. The insulating material may consist of a varnish, preferably deposited by screen printing on the face 2 of the label body 1.

FIG. 3 illustrates the electrical circuit equivalent to the circuit associated with the security label of FIGS. 1 and 2. The inductance element 6 is represented in the form of a coil at the terminals of which the integrated circuit 10 is connected, and we recognize the capacitive elements 7 and 8 shown in the form of conventional capacitors.

The integrated circuit 10 thus makes it possible to manage in multiple ways the reading of the security label and / or the detection either by modulation of the disturbance induced by this label passing through an electromagnetic field, or by responses linked to frequencies. data whose values are previously calculated and stored in the integrated circuit 10.

There is thus a powerful means of modulation associated with the resonant circuit of the security tag, which allows multiple possibilities, without increasing significantly the cost of manufacturing this label, insofar as one can be satisfied with using an unsophisticated integrated circuit, comprising for example only a memory, an interface means between the memory and the resonant circuit, thus as a means of reconstituting a time clock, to allow reading and possibly sequential writing. The integrated circuit 10 provides an electronic switch function which can be in the closed or open state. A reading unit can then easily decode the message sent by the integrated circuit. In the connection between the reading unit and the safety label, the intensity passing through the inductance element can be modulated.

The embodiment illustrated in FIGS. 4 and 5 comprises a large number of components identical to the previous embodiments, which components will be given the same references and will not be described again. This embodiment differs from the previous one in that the integrated circuit 10 is connected, by the conductive line 12, to an intermediate point denoted 6 ′ of the inductance element 6. In this case, the prior insulating deposit 13 will of course have cleared this intermediate point, in order to allow the electrical connection when the conductive line 12 is deposited to ensure the connection to the integrated circuit 10. This makes it possible to insert integrated circuits with low supply voltage, which are vulnerable to overvoltages . By a transformer type assembly, one is content to take a certain number of turns of the inductance element to recover the necessary voltage. The conductive line 11 provides the connection between the integrated circuit 10 and the enlarged area 8.1, as for the previous embodiment.

The embodiment illustrated in FIGS. 6 and 7 differs from the first embodiment described by a link which is provided between the integrated circuit 10 and an area 8.2 homologous to an enlarged zone carried by the face 2 in which the integrated circuit 10 is embedded. A conductive hole, noted 21, is then used, made through the body of dielectric label 1. This hole can be produced by ultrasonic welding between an associated junction tongue 14 and the homologous enlarged zone 8.2, said junction tongue passing through the hole 21. The tongue 14 is connected to the integrated circuit 10 by the conductive line 11, and at its other end to the enlarged zone 8.2 of the capacitive element 8. It can be noted that in the case of ultrasonic welding and of a label body made of thermoplastic material, the prior formation of the hole through the label body is not essential: indeed , the heat from the sonotrode carrying out the welding causes the underlying thermoplastic material to flow, as the junction tongue is lowered until the electrical contact is made with c the homologous area 8.2.

In some cases, moreover, it may prove to be compulsory to use an integrated circuit 10 of substantial thickness. It is then not necessary to use a label body 1 of great thickness, and provision may be made for the association of a thermoplastic layer with this label body. This variant is illustrated in FIG. 8, and a label body 1 which is thinner than the integrated circuit 10 can thus be distinguished, and this label body 1 is equipped, on its face 3 opposite the face 2 carrying the inductance element 6, of a thermoplastic layer 16 in which is also embedded the integrated circuit 10. In practice, a multilayer assembly will be produced consisting of a stack of the label body 1 and of the thermoplastic layer 16 , made by hot gluing under pressure, after which, it suffices to hot press the integrated circuit 10 into the two layers 1, 16, to arrive at the representation of the Figure 8. The conductive connections 11, 12 of the resonant circuit can also be identical or analogous to those already described above.

In addition, FIG. 8 illustrates a sub-assembly denoted 15 which diagrams capacitive elements included in the integrated circuit itself, this to allow additional types of modulations associated with the resonance circuit 5. We can for example obtain modulations associated with multiples of a base frequency. We then manage to further increase the possibilities of modulating the security tag thus equipped.

Depending on the type of use envisaged for the security label thus produced, provision may be made to protect the upper face of the label body 2 in different ways.

In a first way, illustrated in FIG. 9, the face 2 of the label body 1 carrying the inductance element 6 is equipped with a protective layer 17 of thermoplastic material, for example hot glued. This gives a relatively rigid security label reminiscent of security badges, for permanent identification of a product.

In a second way, as illustrated in FIG. 10, the face 2 of the label body 1 carrying the inductance element 6 comprises a layer 18 of adhesive material covered by a protective sheet 19 having opposite the adhesive material a non-stick coating 20. In this case, the security label is much more flexible, insofar as the adhesive material gives no additional rigidity to the label body. It suffices to detach the protective sheet 19, which can be made of plastic or paper, to expose the upper face of the adhesive coating 18, which makes it possible to immediately attach the security label to an object concerned. It goes without saying that the invention is not limited to the embodiments which have just been described, but on the contrary encompasses any variant incorporating, with equivalent means, the essential characteristics set out above.

Claims

1. Safety label with resonant circuit, comprising a label body (1) made of plastic material, the faces of which carry inductance (6) and capacitive elements (7, 8) forming the resonant circuit (5), characterized in what it further comprises an integrated circuit (10) embedded in the label body (1), said integrated circuit being connected to an inductance element (6) of the resonant circuit (5) to form a modulation means associated with said resonant circuit.

2. Security label according to claim

1, comprising on one face (2) of the label body (1) an inductance element (6) produced in the form of a flat coil, characterized in that the integrated circuit (10) is embedded in the same face (2) of the label body.

3. Security label according to claim

2, the inductance element (6) of which has enlarged zones (7.1, 8.1) which cooperate with homologous zones (7.2, 8.2) carried by the opposite face (3) of the label body (1) to form capacitive elements (7, 8) of the resonant circuit (5), characterized in that the integrated circuit (10) is connected by associated conductive lines (11, 12) to the enlarged zones (7.1, 8.1) of the element d 'inductance (6), or at points close to these enlarged zones.

4. Security label according to claim 2, the inductance element (6) of which has enlarged zones (7.1, 8.1) which cooperate with homologous zones (7.2, 8.2) carried by the opposite face (3) of the body label (1) to form capacitive elements (7, 8) of the resonant circuit (5), characterized in that the integrated circuit (10) is connected by associated conductive lines (11, 12) to an enlarged area ( 8.1) and at an intermediate point (6 ') of the inductance element (6).

5. Security label according to claim

2, the inductance element (6) of which has zones widened (7.1, 8.1) which cooperate with homologous zones (7.2, 8.2) carried by the opposite face (3) of the label body (1) to form capacitive elements (7, 8) of the resonant circuit (5), characterized in that the integrated circuit (10) is connected by an associated conductive line (12) to an enlarged area (7.1) of the inductance element (6) and, by another conductive line (11), via a conductive hole (21) passing through the label body (1), to a zone (8.2) homologous to the other enlarged zone (7.2).

6. The security tag according to one of claims 3 to 5, characterized in that the conductive lines (11, 12) are formed by depositing a polymer ^¬ conduc tor, in particular by screen printing, with the possible interposition of a insulating deposit (13) for the overlapped parts of the inductance element (6).

7. Security label according to one of claims 2 to 6, characterized in that the label body (1) is thinner than the integrated circuit (10), and said label body is equipped, on its face (3) opposite to that (2) carrying the inductance element (6), a thermoplastic layer (16) in which is also embedded the integrated circuit (10).

8. Security label according to one of claims 2 to 7, characterized in that the face (2) of the label body (1) carrying the inductance element (6) is equipped with a protective layer (17) in thermoplastic material.

9. Security label according to one of claims 2 to 7, characterized in that the face (2) of the label body (1) carrying the inductance element (6) comprises a layer (18) of material adhesive covered by a protective sheet (19) having a non-stick coating (20) facing the adhesive material.

10. Security label according to one of claims 1 to 9, characterized in that the integrated circuit

(10) itself includes capacitive elements (15), in order to allow additional types of modulations associated with the resonant circuit (5).