DE102011004674A1 - Adhesive film for deactivating passive radio frequency identification (RFID) transponder of RFID system used in building, has mechanical switch that is closed for deactivation of RFID transponder in non-operated original position - Google Patents

Abstract

The adhesive film (1) has an electromagnetic oscillating circuit (2) that is provided with an electric coil (3) and capacitor (4). A mechanical switch (5) is provided for disrupting the electromagnetic oscillating circuit such that the mechanical switch is closed for deactivation of RFID transponder in non-operated original position.

Description

The invention relates to an adhesive film for attachment to a carrier element with an antenna having a passive RFID transponder. The adhesive film according to the invention is used in particular for deactivating passive RFID transponders with a frequency or operating frequency in the frequency range from 30 kHz to 950 MHz and in particular in the frequency range from 125 kHz to 13.56 MHz.

RFID systems (RFID: Radio Frequency IDentification) have long been known and include a transponder, which is attached for example to a chip having a carrier element and is carried by a person, and a reader for reading a transponder identifier. RFID systems are used, for example, for access control to security-relevant areas in buildings. For communication, the reader generates a high-frequency alternating electromagnetic field which irradiates the antenna of the RFID transponder. In the antenna coil, a voltage is induced by the electromagnetic field. This voltage is rectified and thus charged a capacitor of the transponder as a temporary memory, which provides the power supply of the chip for the reading process. Such a transponder, which does not have its own power supply, is also referred to as a passive RFID transponder.

The activated by means of the electromagnetic field of the reader RFID transponder decodes the commands sent by the reader and sends an encoded and modulated response, for example by antiphase reflection of the field emitted by the reader. The RFID transponder therefore does not emit any field itself, but merely changes the electromagnetic transmission field of the reader. Thus, the RFID transponder transmits its own invariable serial number, other numbers of a designated object or other data requested by the reader to the reader. These are mostly security-related data that can be accessed when decoding the encoding. A disadvantage is that the electromagnetic transmission field modified by the RFID transponder can be received by a third party with a corresponding reading device as soon as the RFID transponder enters a transmission range of the reading device and automatically starts the communication between the transponder and the reading device. This makes it possible for unauthorized third parties to gain access to security-related areas. Such systems pose a security vulnerability.

From the EP 0 946 926 B1 is a chip card with transponder coil and a switch known in such a way that the transponder can be activated by pressing the switch. Such smart cards are more expensive to manufacture and therefore not in use in many RFID systems. A security necessary replacement of a conventional support element without activation switch by a smart card according to the EP 0 946 926 B1 is costly.

From the DE 10 2005 050 099 A1 is a writing and reading protection device for transponder communication devices known. The write and read protection device prevents unwanted wireless communication via the near field antenna of the transponder by another near field antenna by the latter can be brought from the first position with low magnetic coupling to a second position with strong magnetic coupling to the near field antenna of the transponder to be protected and so on an adequate supply of the transponder prevented. For transferring the near-field antenna from the first position to the second position, the latter is arranged in a foldable side of a document or in an insertion or sliding element. The disadvantage of this writing and reading protection device that this is awkward to use.

From the DE 195 42 900 A1 is a contactless data carrier with a coil-shaped antenna for electromagnetic data and energy transmission is known which has an additional coil with a switch. By opening and closing the auxiliary coil, the range of the data carrier can be changed. The antenna coil and the auxiliary coil are fixedly arranged in different levels of the data carrier and separated by insulating spacer layers. Existing data carriers without additional coil can only be completely replaced by this data medium, which is costly.

It is an object of the invention to further develop an existing RFID system in such a way that read-out of security-relevant data by unauthorized third parties is avoided in a simple manner.

This object is achieved by an adhesive film for attachment to a support element with an antenna having a passive RFID transponder with the features specified in claim 1.

According to the invention, it has been recognized that by attaching an adhesive film to an existing carrier element with a passive RFID transponder having an antenna, it can be deactivated. For this purpose, the adhesive film has an electromagnetic resonant circuit with an electrical coil and a capacitor. Furthermore, a mechanical switch for closing and interrupting the resonant circuit is provided on the adhesive film, wherein the switch is closed in a non-actuated starting position for deactivating the RFID transponder. If the carrier element provided with the adhesive film is brought into the transmission range of a reading device of an RFID system, the transmission power of the electromagnetic field of the reading device is picked up by the coil of the oscillating circuit of the adhesive film and stored as energy by the capacitor or oscillating circuit. At the same time, the electromagnetic field of the reading device is so attenuated in relation to the RFID transponder that the passive RFID transponder is not sufficiently supplied with energy. This means that if the mechanical switch of the adhesive film is not actuated, the RFID transponder is deactivated and does not communicate with the reading device, since it is shielded from the oscillating circuit of the adhesive film. Only by pressing the switch of the resonant circuit of the adhesive film is interrupted so that a standard communication between the RFID transponder and the reader can be done, comparable to a carrier element without adhesive film. Thus, a user is allowed to specifically allow the communication between the RFID transponder and the reader by operating the switch. This can reduce the risk that unauthorized third parties read out safety-relevant data of the RFID communication between the transponder and the reader. The security of the RFID system is thereby increased. Surprisingly, it has been found that actuation of the switch not only activates the RFID transponder, but additionally improves the transmission power of the RFID transponder. As a result, in particular the range of the transmission power of the RFID transponder is improved. Due to the fact that the adhesive film can be subsequently attached to the carrier element, in particular by gluing, an existing RFID system can be inexpensively retrofitted so that a read-out of security-relevant data by unauthorized third parties is avoided. The adhesive film according to the invention is used in particular for deactivating passive RFID transponders with a frequency or operating frequency in the frequency range from 30 kHz to 950 MHz and in particular in the frequency range from 125 kHz to 13.56 MHz.

A coil according to claim 2 can be arranged to save space and thus be provided in an adhesive film of small thickness.

A design of the adhesive film according to claim 3 allows utilization of a maximum coil area for the electrical coil of the electromagnetic resonant circuit.

In a design of the coil according to claim 4, this can for example be attached to existing support elements in the form of identification cards and / or key fobs.

A spool according to claim 5 is suitable for mounting on a card-shaped support member according to the format ID-1 for identity documents according to the ISO / IEC 7810 ,

The use of a key switch according to claim 6 guarantees that the activation of the RFID transponder takes place only during the operation of the switch. As a result, unintentional activation of the RFID transponder, which would allow unauthorized reading out of the data of the RFID transponder, be avoided.

A resonant circuit according to claim 7 has a characteristic which is particularly suitable for deactivating the RFID transponder.

An arrangement according to claim 8 serves the intended use of a passive RFID transponder in the environment of a corresponding reader.

In a design of the geometries of the coil of the adhesive film and the antenna of the RFID transponder according to claim 9, the shielding of the RFID transponder and the attenuation of the electromagnetic field of the reader is improved.

In an arrangement of the coil and the antenna according to claim 10, the attenuation of the electromagnetic field of the reader and the shielding of the RFID transponder is ensured.

In a design of the resonant circuit according to claim 11 by appropriate choice of the coil and / or the capacitor, the resonant circuit has a resonant circuit frequency, which is used to deactivate the RFID transponder is suitable. In particular, the resonant circuit frequency is identical to a frequency of the electromagnetic field emitted by the reader. The resonant circuit frequency can also deviate within a permissible range of up to +/- 5% and in particular of up to +/- 10% from the frequency of the field emitted by the reader.

Embodiments of the invention will be explained in more detail with reference to the drawing. In this show:

1 a schematic representation of an adhesive film,

2 a schematic arrangement of the adhesive film to a support member according to a first embodiment and

3 a 2 corresponding representation of a support member according to another embodiment.

An in 1 schematically illustrated adhesive film 1 has an electromagnetic resonant circuit 2 with an electric coil 3 and a capacitor 4 which are connected in series. Furthermore, on the adhesive film 1 a mechanical switch in the form of a pushbutton 5 for closing and interrupting the resonant circuit 2 intended. The push button switch 5 is closed in a non-actuated starting position for deactivating an RFID transponder. Because of the switch as a push button switch 5 is formed, it automatically assumes the starting position after an operation again.

The sink 3 has several turns, which are flat and spiral wound to each other. This limits the coil 3 an inner surface 6 within which the capacitor 4 and the key switch 5 are arranged to save space. The sink 3 , the capacitor 4 and the key switch 5 are from a transparent or printable substrate 7 the adhesive film 1 connected with each other. A transparent carrier material 7 the adhesive film 1 serves a pleasing appearance and thus fulfills the esthetic requirements of a user. For a printable design of the substrate 7 can provide additional information on the adhesive film 1 be provided.

In particular, the coil 3 , the capacitor 4 and the key switch 5 with the carrier material 7 shed. The adhesive film 1 is integrally formed. The sink 3 is essentially along an outer contour of the adhesive film 1 arranged. This will be one of the adhesive film 1 provided surface through the coil 3 best used.

In 2 is a first embodiment of an arrangement of the adhesive film 1 on a support element 8th shown schematically. The carrier element 8th is rectangular in shape and has a width B of 53.98 mm and a length L of 85.6 mm. These dimensions are in accordance with International Identity Documents format ID-1 ISO / IEC 7810 and are thus an internationally very widespread format for identification cards, bank cards, credit cards, driving licenses, etc. As shown in 1 has the adhesive film 1 a maximum length L _{max of} 85.6 mm a maximum width B _max of 53.98 mm. This is the adhesive film 1 on a support element 8th according to the ID-1 format for identity documents. The representation according to 2 shows a plan view of the on the support element 8th glued adhesive film 1 , A transparent carrier material 7 allows the underlying support element 8th through the adhesive film 1 is visible. Thus, for example, graphical information on the support element 8th even after the application of the adhesive film 1 still recognizable.

The carrier element 8th has a passive RFID transponder with a passive RFID chip 9 and an antenna 10 on. Although the antenna 10 in the carrier element 8th is firmly integrated and generally invisible, it is for clarity in 2 shown schematically. The antenna 10 is with the RFID chip 9 connected. For reasons of clarity, the coil and the capacitor are the adhesive film 1 in 2 not shown.

How out 1 shows, is the coil 3 formed substantially rectangular. This applies accordingly to the antenna 10 of the RFID transponder in the carrier element 8th , In the embodiment shown according to 2 cover one from the coil 3 limited area and one from the antenna 10 limited area by at least 85%. It is also possible that the two surfaces of the coil 3 and the antenna 10 cover more than 85%, in particular at least 90% and in particular at least 95%.

In the embodiment shown in FIG 2 is the adhesive film 1 directly on the carrier element 8th glued. It is also possible to use the adhesive film 1 such on the carrier element 8th arrange that coil 3 and the antenna 10 spaced at a vertical distance of at most 2 mm and in particular of at most 3 mm from each other. This makes it possible to use the adhesive film 1 for example, on a protective cover of the support element 8th stick with the protective function for deactivating the RFID transponder through the adhesive film 1 remains guaranteed.

The following is the operation of the adhesive film 1 on the carrier element 8th explained in more detail. In a non-actuated state of the pushbutton 5 is this and thus the resonant circuit 2 closed. At an approximation of the support element 8th to the transmitting region of an electromagnetic field of a reading device is emitted by the reading device with a frequency f _L electromagnetic field from the coil 3 of the resonant circuit 2 absorbed and thus damped. This is done by the electromagnetic field in the coil 3 induces a voltage and in the capacitor 4 saved. The resonant circuit 2 is designed such that it has a resonant circuit frequency f ₁ , which is suitable for deactivating the RFID transponder. This means that the resonant circuit frequency f ₁ coincides with a frequency f _L at least in a deviation range of up to +/- 10%, and thus the electromagnetic field with the frequency f _L emitted by the reading device via the coil 3 can record. In this state, ie when the switch is not actuated 5 , the RFID transponder is deactivated. By pressing the switch 5 becomes the resonant circuit 2 interrupted so that the electromagnetic field emitted by the reader is no longer of the resonant circuit 2 is recorded and directly through the antenna 10 reaches the RFID transponder. In the actuated position of the switch 5 the arrangement works according to 2 analogous to a passive RFID transponder without adhesive film 1 , Once an operator actuates the switch 5 finished, the switch takes 5 automatically its starting position, so that the resonant circuit 2 is closed again and thus a deactivation of the RFID transponder is guaranteed.

The following is with reference to 3 a further embodiment of the invention described. Structurally identical parts receive the same reference numerals as in the first embodiment, to the description of which reference is hereby made. Structurally different but functionally similar parts receive the same reference numerals with a following a. The carrier element 8a is designed essentially round with a tangentially arranged on the round basic shape, triangular attachment lug 11 , The carrier element 8a can be used as a key ring, for example.

On the carrier element 8a is the adhesive film 1a arranged, which is the support element 8a is designed accordingly round. In this case, both are the coil 3a the adhesive film 1a as well as the not shown antenna of the RFID transponder formed around so that both have substantially the same geometries. The capacitor 4a is correspondingly within that of the coil 3a limited inner surface 6a arranged.

The operation of this embodiment is identical to that of the first embodiment, to which reference is hereby made.

The adhesive films 1 . 1a are used to deactivate passive RFID transponders with a frequency or operating frequency in the frequency range from 30 kHz to 950 MHz and in particular in the frequency range from 125 kHz to 13.56 MHz. The capacitors 4 . 4a are preferably formed as ceramic capacitors. The capacitors 4 . 4a preferably have a deviation from a nominal capacity C of at most +/- 15%. Preferably, the capacitors 4 . 4a the quality X7R.

The capacitors 4 . 4a are preferably designed as SMD capacitors. Further, the turns of the spiral coils 3 . 3a preferably around the switch 5 and / or below the switch 5 guided. As a result, plated-through holes can be avoided.

The following are sizing examples for the adhesive film 1 according to the 1 and 2 specified. Dimensioning example 1: Frequency f of the passive transponder f = f _L = 13.56 MHz Number n of turns of the coil 3 n = 7 Length L ₁ and width B _{1 of} the outermost turn of the coil 3 L ₁ = 84.00 mm B ₁ = 52.60 mm Length L ₂ and width B _{2 of} the innermost turn of the coil 3 L ₂ = 59.50 mm B ₂ = 28.20 mm Ohmic resistance R of the coil 3 R = 0.7 Ω Capacitance C of the capacitor 4 C = 153 pF Dimensioning example 2: Frequency f of the passive transponder f = f _L = 125 kHz Capacitance C of the capacitor 4 C = 910 nF

Otherwise, the values are as in the first dimensioning example.

The following is a dimensioning example for the adhesive film 1a according to 3 specified. Dimensioning example 3: Frequency f of the passive transponder f = f _L = 13.56 MHz Number n of turns of the coil 3a n = 12 Diameter D _{1 of} the outermost turn of the coil 3a D ₁ = 26.55 mm Diameter D _{2 of} the inner turn of the coil 3a D ₂ = 18.50 mm Ohmic resistance R of the coil 3a R = 4.5 Ω Capacitance C of the capacitor 4a C = 53 pF

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0946926 B1 [0004, 0004]
• DE 102005050099 A1 [0005]
• DE 19542900 A1 [0006]

Cited non-patent literature

• ISO / IEC 7810 [0013]
• ISO / IEC 7810 [0027]

Claims (11)

Adhesive film for attachment to a carrier element with an antenna having a passive REID transponder comprising a. an electromagnetic resonant circuit ( 2 ) with an electric coil ( 3 ; 3a ) and a capacitor ( 4 ; 4a ) and b. a mechanical switch ( 5 ) for closing and interrupting the resonant circuit ( 2 ), the switch ( 5 ) is closed to deactivate the REID transponder in a non-actuated starting position. Adhesive film according to claim 1, characterized in that the coil ( 3 ; 3a ) is wound evenly and spirally. Adhesive film according to one of the preceding claims, characterized in that the switch ( 5 ) and the capacitor ( 4 ; 4a ) within one of the coil ( 3 ; 3a ) limited inner surface ( 6 ) are arranged. Adhesive film according to one of the preceding claims, characterized in that the coil ( 3 ; 3a ) is substantially rectangular or round. Adhesive film according to claim 4, characterized by a maximum width (B _max ) of 53.98 mm and a maximum length (L _max ) of 85.60 mm. Adhesive film according to one of the preceding claims, characterized in that the switch as a push-button switch ( 5 ) is formed, which automatically assumes the starting position after actuation. Adhesive film according to one of the preceding claims, characterized in that the coil ( 3 ; 3a ) and the capacitor ( 4 ; 4a ) are connected in series. Arrangement of an adhesive film according to one of the preceding claims on a carrier element ( 8th ; 8a ) with an antenna ( 10 ), passive RFID transponder. Arrangement according to claim 8, characterized in that the coil ( 3 ; 3a ) and the antenna ( 10 ) have substantially the same geometries. Arrangement according to claim 8 or 9, characterized in that of the coil ( 3 ; 3a ) and the antenna ( 10 ) limited areas amount to at least 85%, in particular at least 90% and in particular at least 95%. Arrangement according to one of claims 8 to 10, characterized in that the resonant circuit ( 2 ) is designed such that it has a resonant circuit frequency (f ₁ ) which is suitable for deactivating the RFID transponder.

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