WO2003060819A1

WO2003060819A1 - Rfid tag

Info

Publication number: WO2003060819A1
Application number: PCT/FI2003/000031
Authority: WO
Inventors: Karri Palovuori
Original assignee: Karri Palovuori
Priority date: 2002-01-17
Filing date: 2003-01-16
Publication date: 2003-07-24
Also published as: AU2003201431A1; FI114751B; FI20020093A0; FI20020093L

Abstract

An RFID tag (1) arranged attachable to an object of attachment, the tag (1) including an RFID circuit (2) comprising a microcircuit (3) for storing information in the tag (1), and an antenna (4) for transferring the information stored by the microcircuit (3) to a device or system reading the tag (1). The tag (1) further comprises a first substrate (6), in connection with which the RFID circuit (2) is arranged, the first substrate (6) being arranged attachable in connection with the object of attachment for attaching the tag (1) to the object of attachment. The triboelectric characteristics of the material of the first substrate (6) are arranged to differ from those of the material of the object of attachment in such a manner that, when the first substrate (6) is detached from the object of attachment, frictional electricity is generated that is arranged to be used in connection with the tag (1).

Description

RFID TAG

FIELD OF THE INVENTION

[0001] The invention relates to an RFID tag arranged attachable to an object of attachment, the tag including an RFID circuit comprising a micro- circuit for storing information in the tag, and an antenna for transferring the information stored by the microcircuit to a device or system reading the tag.

[0002] The invention further relates to an RFID tag arranged attachable to an object of attachment, the tag including an RFID circuit comprising a microcircuit for storing information in the tag, and an antenna and a ca- pacitor for transferring the information stored by the microcircuit to a device or system reading the tag by action of a magnetic field generated by said device or system.

BACKGROUND OF THE INVENTION

[0003] The use of RFID (Radio Frequency Identification) tags for in- stance in stores in products to be sold is increasing extensively. The identification data included in the RFID tag can be used to automatically read the identification data of the product to be sold at the cashier's desk upon payment, allowing the price of the product to be automatically obtained from the price data system unless the price information is not included in the identification data in- eluded in the tag. An RFID tag can also serve as an antitheft device for preventing shoplifting. An RFID tag includes a microcircuit comprising identification data relating to the product to be sold, for example. The tag further includes an antenna allowing the information included in the microcircuit to be transferred to a reading device or system. The antenna and the microcircuit are typically attached to a substrate made from paper or plastic. The substrate, in turn, is provided with a fixer, typically glue, for fastening the tag to the object of attachment, such as a product to be sold at a store, for example.

[0004] Electric energy is required for reading the identification data included in the microcircuit and forwarding it to for instance the store's cash or billing system or to an antitheft system. As regards the production or source of electric energy, there are two kinds of RFID tags, both active and passive. Active RFID tags use a battery as the source of electric energy, allowing the tag to automatically establish a connection to a billing or antitheft system. However, the problem in active tags is the increased size, weight and production costs of the tag, caused by the battery. Furthermore, the battery ages, and as the battery charge disappears with time, the tag is useless. Passive RFID tags have no energy source providing electric energy; instead, a coil-like antenna and a capacitor included in the tag together constitute an LC circuit, the circuit being used to generate the electric energy required for transferring the identification data from a magnetic field generated by the device or system reading the tag. The use of these passive RFID tags, which thus do not include a source of electric energy and are therefore inexpensive and have a limitless lifetime, can be expected to grow exponentially. An example of passive RFID tags and their method of manufacture is disclosed in WO 01/18749.

[0005] However, particularly regarding passive RFID tags, the lack of a special source of electric energy causes a problem when the aim is to prevent misuse or detachment from the object of attachment. Attempts may be made for instance to detach the tag from the object of attachment for switching the tag from a more inexpensive product to a more expensive one and thus to mislead the store's billing system. Attempts may also be made to detach the tag from the object of attachment to mislead an antitheft system. EP 1 132 859 discloses a solution in association with a passive RFID tag that can be used to prevent the switching of a tag from one product to another. In the solution pre- sented in the publication, the tag is structurally implemented so that the RFID circuit formed by a microcircuit, an antenna and a capacitor is destroyed if attempts are made to remove the tag from the object of attachment. This disables the switching of a tag to another product so that it would still be operative. However, in the solution presented in the publication, the attempt to re- move a tag cannot be detected in any manner, and consequently the product whose tag is detached or destroyed can be conveyed past an antitheft system without the alarm system detecting the product.

DESCRIPTION OF THE INVENTION

[0006] The object of the present invention is to provide a novel solu- tion for generating electric energy in association with an RFID tag.

[0007] The RFID tag of the invention, comprising a microcircuit for storing information in the tag, and an antenna for transferring the information stored by the microcircuit to a device or system reading the tag, is characterized in that the tag further comprises a first substrate, in connection with which the RFID circuit is arranged, the first substrate being arranged attachable in connection with the object of attachment for attaching the tag to the object of attachment, and that the triboelectric characteristics of the material of the first substrate differ from those of the material of the object of attachment in such a manner that, when the first substrate is detached from the object of attachment, frictional electricity is generated that is arranged to be used in connec- tion with the tag.

[0008] The RFID tag of the invention, comprising a microcircuit for storing information in the tag, and an antenna and a capacitor for transferring the information stored by the microcircuit to a device or system reading the tag by action of a magnetic field generated by said device or system, is character- ized in that the tag further comprises a first substrate, in connection with which the RFID circuit is arranged, a charge collector arranged in connection with the first substrate and the RFID circuit, a second substrate arranged with a first fixing material in connection with the first substrate, and a second fixing material arranged in connection with the second substrate for attaching the tag to the object of attachment, and that the characteristics of the first and second fixing materials are arranged such that when the tag is detached from the object of attachment, the first substrate is arranged to be detached from the second substrate, and that the triboelectric characteristics of the material of the first substrate and those of the material of the second substrate are arranged to dif- fer from each other such that when the first substrate is detached from the second substrate, frictional electricity is generated, from which frictional electricity the charge collector is arranged to generate electric energy for use in connection with the tag.

[0009] The essential idea of the invention is that the RFID tag, which is arranged attachable to an object of attachment, the tag including an RFID circuit comprising a microcircuit for storing information in the tag and an antenna for transferring the information stored by the microcircuit to a device or system reading the tag, further comprises a first substrate, in connection with which the RFID circuit is arranged, the first substrate being arranged attach- able in connection with the object of attachment for attaching the tag to the object of attachment. Furthermore, according to the essential idea of the invention, the triboelectric characteristics of the material of the first substrate differ from those of the material of the object of attachment in such a manner that, when the first substrate is detached from the object of attachment, frictional electricity is generated that is arranged to be used in connection with the tag. [0010] According to an embodiment of the invention, the frictional electricity, which is generated when the first substrate is detached from the object of attachment, is arranged to be used as electric driving energy for transmitting the information included in the microcircuit to a device or system reading the tag, based on which transmission the detachment of the tag from the object of attachment is arranged to be detected with the device or system reading the tag. According to a second embodiment of the invention, the tag comprises a charge collector arranged in connection with the first substrate and the RFID circuit, the charge collector being arranged to generate electric driving energy for the RFID circuit of the tag from said frictional electricity. Ac- cording to a third embodiment, the materials of the first substrate and the object of attachment are different plastic qualities, which are as far from each other as possible in a triboelectric series. According to a fourth embodiment, the first substrate is of polytetrafluoroethylene and the object of attachment is of polystyrene. According to a fifth embodiment of the invention, the object of attachment of the tag is a product or another substrate that is attached to or arranged attachable to a product.

[0011] The inventive solution enables the generation of electric energy also in connection with passive tags without a device or system reading the tag. When the frictional electricity, which is generated when the first sub- strate is detached from the object of attachment, is arranged to be used as electric driving energy for the RFID circuit of the tag for transmitting the information included in the microcircuit to the device or system reading the tag, the detachment of the tag from the object of attachment can be easily detected based on said transmission. When the tag comprises a charge collector ar- ranged in connection with the first substrate and the RFID circuit, electric driving energy can be simply and inexpensively be generated for the RFID circuit of the tag from said friction energy. When the materials of the first substrate and the object of attachment are different plastic qualities, which are as far from each other as possible in a triboelectric series, such as polytetrafluoro- ethylene and polystyrene, for example, the higher is the amount of electric energy achieved from the detachment of the tag. Since the object of attachment of the tag can be either a product or a second substrate attached to or arranged attachable to a product, the solution presented for electrifying a tag can be used in connection with products or packages made from various materials.

BRIEF DESCRIPTION OF THE FIGURES

[0012] The invention will be described in detail in the attached draw- ings, wherein

Figure 1 schematically shows a tag of the invention divided into parts and seen obliquely from above,

Figure 2 is a schematic side view of the solution of Figure 1 divided into parts, and

Figure 3 is a schematic side view of a second tag of the invention divided into parts.

DETAILED DESCRIPTION OF THE INVENTION

[0013] Figure 1 schematically shows a passive RFID tag 1 of the in- vention divided into parts and seen obliquely from above. In the present description, the RFID tag 1 is also called a tag 1. The tag 1 can be used for instance in connection with products 11 sold at stores as an antitheft alarm and/or for storing identification data on the products 1 1 associated with the payment of the products 11. The tag 1 of Figure 1 comprises an RFID circuit 2, including a microcircuit 3, a coil-like antenna 4 and a capacitor 5. For instance identification data associated with the product 11 can be stored in the microcircuit 3 and transferred via the antenna 4 to the store's antitheft or billing system reading the tag 1 or to another system or device reading the tag 1. For the sake of clarity, the figures do not show any system or device reading the tag 1. The antenna 4 and the capacitor 5 constitute an electric circuit in a manner known per se, by means of which the magnetic field generated by the system or device reading the tag 1 can be used to generate the necessary electric energy for reading the identification data associated with the product 11 from the microcircuit 3 and for further transfer via the antenna 4 to the system or device reading the tag 1. The tag 1 of Figure 1 further comprises a first substrate 6, the RFID circuit 2 being arranged in connection therewith. The tag 1 further comprises a second substrate 8, arranged in connection with the first substrate 6 by means of a first fixing material 7. The first fixing material 7 is preferably some kind of glue matter. The object of attachment of the tag 1 is the product 11 , to which the tag 1 is attached by means of a second fixing material 9 arranged in connection with the second substrate 8. The second fixing material 9 is also preferably some kind of glue matter, whose fixing characteristics, however, differ from those of the first fixing material 7 such that the adhesion between the second substrate 8 and the product 11 is stronger than the adhesion between the first substrate 6 and the second substrate 8. The tag 1 of Figure 1 further comprises a charge collector 10, or a charge accumulator 10, arranged in connection with the RFID circuit 2 and the first substrate 6 and used for generating electric driving energy for the tag 1 in the manner schematically shown in Figure 2, in which Figure 2 the tag 1 of Figure 1 is shown schematically from the side and divided into parts. [0014] Since a passive RFID tag has no battery or other source of electric energy, such a tag 1 cannot itself communicate with for instance a store's antitheft system when an attempt to remove the tag 1 from the product takes place. To solve this problem, the fixing characteristics of the first fixing material 7 in the tag 1 shown in Figure 1 are selected to be weaker than those of the second fixing material 9 such that when the tag 1 is removed from the product 11 , the first substrate 6 starts to be detached from the second substrate 8, and the second substrate 8 remains attached to the product 11. Furthermore, the triboelectric properties of the first substrate 6 and the second substrate 8 are selected to be different such that the detachment of the first substrate 6 from the second substrate 8 causes frictional electricity, i.e. what is known as triboelectric electricity, which can be accumulated with the charge collector 10. Accordingly, frictional electricity is generated when the first substrate 6 is detached from the second substrate 8. The charge of the frictional electricity generated by the detachment is low, but the voltage is high. Be- cause of the high voltage, the charge accumulated with the charge collector 10 causes a corona discharge 12, which causes an ionic current 13 passing through the air between the tag 1 and the second substrate 8 that remained in the product 11. This ionic current 13 passing through the air generates an electric circuit, where the acting electric energy is used to electrify the RFID circuit 2 such that the RFID circuit 2 itself is automatically able to communicate with the system or device reading or monitoring the tag 1. Automatic communication means for instance that the identification data on the product 11 in the microcircuit 3 are automatically transferred to the system or device reading or monitoring the tag 1. This automatic transfer of the identification data indicates that the tag 1 is detached from the product 11. Consequently, the charge collector 10 enables the frictional electricity generated from the detachment of the tag to be used for electrifying the RFID tag 1 such that the detachment of the tag 1 , either by mistake or as a result of deliberate detachment, can be detected. [0015] In order for the detachment of the first substrate 6 from the second substrate 8 to generate frictional electricity, the triboelectric character- istics of the first substrate 6 and the second substrate 8 have to be selected suitably. In a possible selection the first substrate 6 is of polytetrafluoroethyl- ene PTFE and the second substrate 8 is of polystyrene PS, whereby the polarity of the charge of the frictional electricity is positive (+) on the side of the product 11 and negative (-) on the side of the RFID circuit 2, as shown by broken lines in Figure 2. The materials of the first substrate 6 and the second substrate 8 can also be selected the other way around, whereby the polarity of the charge of the frictional electricity is reverse as compared with Figure 2. Other materials than polytetrafluoroethylene PTFE or polystyrene PS can also be selected as materials for the first substrate 6 and the second substrate 8. In practice, the materials of the first substrate 6 and the second substrate 8 may be almost any plastic. The only prerequisite for material choices is that the materials of the substrates are different, the electric characteristics of the materials are sufficiently dielectric, and that the materials are as far from each other as possible in a triboelectric series.

[0016] The inventive solution enables the generation of electric energy in connection with a passive RFID tag in such a manner that the detachment of the tag 1 can be automatically detected for instance by an antitheft system monitoring products sold in a store. The characteristics of the radio link between the system or the device and the tag determines how far the system or device can be located to enable the detection of the detachment of the tag 1 from the product. When present components are used, this range is several tens of meters. The charge collector 10 can be implemented easily and simply as a charge collector impression printed on the surface of the first substrate 6, for example. When the structure of the charge collector impression is a comb structure of the type shown in Figure 1 , for example, the charge collector 10 does not hinder the operation of the antenna 4. A coil-like antenna 4 can also be used as a charge collector.

[0017] Instead of detecting the detachment of the tag 1 , the fric- tional electricity generated by the detachment of the tag 1 can also be used for destroying the tag 1 in such a manner that the tag 1 is no longer usable in connection with another product. The tag 1 can be destroyed for instance by destroying the identification data associated with the object of attachment of the tag 1 and stored on the microcircuit 3 by means of the electric energy gen- erated from the friction energy.

[0018] Figure 3 is a schematic side view of a second RFID tag 1 of the invention, divided into parts. In the tag 1 of Figure 3, a charge collector 10' is arranged in connection with the second substrate 8. When the tag 1 is detached from the product 11 , a physical connection, schematically denoted by line 14, still exists between the RFID circuit 2 and the charge collector 10' in connection with the second substrate 8. In this case, the electric energy accumulated from the frictional electricity can be led in a usual manner for use as electric driving energy for the RFID circuit 2. Consequently, the frictional electricity generated from the detachment of the tag can be taken directly from between the charge collectors 10 and 10' without a corona discharge 12, leading to a better operating efficiency in the recovery of the electric energy to be generated from the frictional electricity.

[0019] A third inventive solution can also be implemented in such a manner that, provided the triboelectric characteristics of the material of the product 11 are suitable such that the material is sufficiently far away from the material of the first substrate 6 in a triboelectric series, the second substrate 8 and the second fixing material 9 in connection therewith can be left out totally from the tag 1. In this case, when the tag 1 is detached from the product 11 acting as the object of attachment of the tag 1 , frictional electricity is generated, which can be utilized by means of the charge collector 10 for detecting the detachment of the tag 1.

[0020] In a fourth inventive solution, the second substrate 8 and the second fixing material 9 in connection therewith are omitted from the tag 1 ; instead, the second substrate 8 is attached with the second fixing material 9 to the product 11. In this case, the tag 1 is attached to the product 11 such that the first substrate 6 of the tag 1 is arranged in connection with the second substrate 8 in the product 11. In this case, the object of attachment of the tag 1 is the second substrate 8 instead of the product 11. This solution is usable in cases when the frictional electricity generation characteristics of the material of the product 11 are not suitable compared with the first substrate 6 of the tag 1. In this case, a charge collector can also be used in connection with the second substrate 8 to improve the operating efficiency in the recovery of the electric energy to be generated from the frictional electricity.

[0021] The drawings and the related description are only intended to illustrate the inventive idea. The details of the invention may vary within the scope of the claims. Accordingly, it is apparent that the solution presented can naturally also be used in a corresponding manner in connection with active RFID tags, although the examples presented in the figures and the description relate to passive RFID tags. Furthermore, the materials of the first substrate 6 and the second substrate 8 and/or the product 11 can be selected in such a manner that the first fixing material 7 between the first substrate 6 and the second substrate 8 or the product 11 and/or the fixing material 9 between the second substrate 8 and the product 11 are not required at all, but the adhesion between the substrates and/or the product takes place based on the attractive forces between the materials. In addition, the solution presented can naturally also be used in connection with other products than those sold in stores, such as in mail items handled at mail sorting centres, air cargos and suitcases handled at airport terminals, and intermediate products or finished products to be stored at industrial warehouses. The glue matter used as fixing material can be any dielectric glue matter. Furthermore, the first fixing material 7 and the second fixing material 9 may be the same glue matter, but the adhesion between the first substrate 6 and the second substrate 8 is made weaker by the amount of glue matter applied than the adhesion between the second substrate 8 and the product 11 , which can be implemented for instance by applying glue matter only onto part of the area of the substrates between the first substrate 6 and the second substrate 8.

Claims

1. An RFID tag (1) arranged attachable to an object of attachment, the tag (1) including an RFID circuit (2) comprising a microcircuit (3) for storing information in the tag (1), and an antenna (4) for transferring the information stored by the microcircuit (3) to a device or system reading the tag (1), characterized in that the tag (1) further comprises a first substrate (6), in connection with which the RFID circuit (2) is arranged, the first substrate (6) being arranged attachable in connection with the object of attachment for attaching the tag (1 ) to the object of attachment, and that the triboelectric characteristics of the material of the first substrate (6) differ from those of the material of the object of attachment in such a manner that, when the first substrate (6) is detached from the object of attachment, frictional electricity is generated that is arranged to be used in connection with the tag (1).

2. An RFID tag as claimed in claim ^characterized in that the frictional electricity, which is generated when the first substrate (6) is detached from the object of attachment, is arranged to be used as electric driving energy for the RFID circuit (2) of the tag (1) for transmitting the information in- eluded in the microcircuit (3) to a device or system reading the tag (1), based on which transmission the detachment of the tag (1 ) from the object of attachment is arranged to be detected with the device or system reading the tag (1 ).

3. An RFID tag as claimed in claim 1 or 2, characterized in that the tag (1) comprises a charge collector (10) arranged in connection with the first substrate (6) and the RFID circuit (2), the charge collector being arranged to generate electric driving energy for the RFID circuit (2) of the tag (1 ) from said frictional electricity.

4. An RFID tag as claimed in any one of the preceding claims, characterized in that the materials of the first substrate (6) and the ob- ject of attachment are different plastic qualities.

5. An RFID tag as claimed in claim 4, characterized in that the materials of the first substrate (6) and the object of attachment are different plastic qualities, which are as far from each other as possible in a triboelectric series.

6. An RFID tag as claimed in claim 4 or 5, characterized in that the first substrate (6) is of polytetrafluoroethylene and the object of at- tachment is of polystyrene.

7. An RFID tag as claimed in any one of the preceding claims, characterized in that the object of attachment of the tag (1 ) is a second substrate (8) or a product (11 ).

8. An RFID tag as claimed in claim 7, characterized in that the object of attachment of the tag (1) is the second substrate (8), which is arranged attachable to the product (11 ).

9. An RFID tag as claimed in claim 7, characterized in that the object of attachment of the tag (1) is the second substrate (8), which is at- tached to the product (11 ).

10. An RFID tag as claimed in any one of claims 7 to 9, character i z e d in that a charge collector (10') is arranged in connection with the second substrate (8) in such a manner that when the tag (1) is detached, the charge collector (10) arranged in connection with the first substrate (6) and the charge collector (10') arranged in connection with the second substrate (8) are connected with one another in such a manner that as the tag (1) is detached, the energy of the frictional electricity generated is recoverable from between the charge collectors (10, 10').

11. An RFID tag as claimed in any one of claims 3 to 10, c h a r - acterized in that the charge collector (10, 10') is arranged in connection with the first substrate (6) and/or the second substrate (8) as a charge collector impression printed on the substrate (6, 8).

12. An RFID tag as claimed in any one of the preceding claims, characterized in that the tag (1 ) is arranged in connection with the ob- ject of attachment with a first fixing material (7).

13. An RFID tag as claimed in claim 8 or 9, characterized in that the second substrate (8) is arranged in connection with the product (11) with a second fixing material (9).

14. An RFID tag as claimed in claim 12 and 13, character- i z e d in that the fixing characteristics of the first fixing material (7) are weaker than those of the second fixing material (9).

15. An RFID tag as claimed in any one of the preceding claims, characterized in that the RFID circuit (2) of the tag (1 ) further comprises a capacitor (5), and that the antenna (4) is a coil antenna, the tag (1 ) be- ing a passive RFID tag, whereby, when the tag is attached to the object of attachment, the information included in the microcircuit (3) is arranged to be transferred to a device or system reading the tag (1 ) via a magnetic field generated by said device or system.

16. An RFID tag (1 ) arranged attachable to an object of attachment, the tag (1 ) including an RFID circuit (2) comprising a microcircuit (3) for storing information in the tag (1 ), and an antenna (4) and a capacitor (5) for transferring the information stored by the microcircuit (3) to a device or system reading the tag (1 ) by action of a magnetic field generated by said device or system, c h a r a c t e r i z e d in that the tag further comprises a first substrate, in connection with which the RFID circuit (2) is ar- ranged, a charge collector (10) arranged in connection with the first substrate (6) and the RFID circuit (2), a second substrate (8) arranged with a first fixing material (7) in connection with the first substrate, and a second fixing material (9) arranged in connection with the second substrate (8) for attaching the tag (1 ) to the object of attachment, and that the characteristics of the first (7) and second (9) fixing materials are arranged such that when the tag (1 ) is detached from the object of attachment, the first substrate (6) is arranged to be detached from the second substrate (8), and that the triboelectric characteristics of the material of the first substrate (6) and those of the material of the second substrate (8) are arranged to differ from each other such that when the first substrate (6) is detached from the second substrate (8), frictional electricity is generated, from which frictional electricity the charge collector (10) is arranged to generate electric energy for use in connection with the tag (1 ).

17. An RFID tag as claimed in claim 16, c h a r a c t e r i z e d in that a charge collector (10") is arranged in connection with the second substrate (8) in such a manner that when the tag (1 ) is detached, the charge col- lector (10) arranged in connection with the first substrate (6) and the charge collector (10') arranged in connection with the second substrate (8) are connected with one another in such a manner that as the tag (1 ) is detached, the energy of the frictional electricity generated is recoverable from between the charge collectors (10, 10').

18. An RFID tag as claimed in claim 16 or 17, c h a r a c t e r i z e d in that the frictional electricity, which is generated when the first substrate (6) is detached from the second substrate (8), is arranged to be used as electric driving energy for the RFID circuit (2) of the tag (1 ) for transmitting the information included in the microcircuit (3) to a device or system reading the tag (1 ), based on which transmission the detachment of the tag (1 ) from the object of attachment is arranged to be detected with the device or system reading the tag (1 ).