Radio frequency identification (rfid) security tag for merchandise and method therefor

This invention relates generally to a Radio Frequency Identification Device (RFID) tag device and, more specifically, to an RFID security device which is small enough to be placed on small items of merchandise and which will be enabled upon attachment and disabled if removed, disassembled or cut.

Various electronic security systems are available for monitoring merchandise and discouraging theft from retail establishments. Present systems generally consist of two dimensional Electronic Article Surveillance (EAS) tags which are coupled to an article of merchandise which is to be monitored.

These types of systems have several drawbacks. In order to achieve sufficient read range for detection of stolen merchandise as it leaves the retailer, a two dimensional tag is rather large and unattractive. Normally, a two inch diameter tag is used in swept RF type systems and a one-half inch by two inch rectangle is used in acoustomagnetic systems. These large tags must hang from even the smallest pieces of merchandise such as jewelry.

Common EAS tags are attached to merchandise, such as jewelry, by a string or a plastic loop. The string or loop may be easily cut by a customer or employee rendering the EAS tag useless since exit monitors are used only to detect the presence of the EAS tag near a surveillance zone. Larger jewelry store chains lose upwards of ten million dollars per year in employee theft alone.

A further problem with current EAS tags is that they do not contain any intelligence that could be used for tracking inventory or sensing the presence of specific jewelry items. Present EAS tags are generally detected by radiating them with radio frequency energy when the tag enters a surveillance zone near an exit of the store, and detecting only that the tag is enabled or disabled.

Therefore, a need existed to provide an improved RFID security tag. The improved RFID security tag must be smaller and less bulky than current EAS tags. The improved RFID security tag must be able to be coupled to small articles of merchandise such that the removal of the RFID security tag can immediately be detected. The improved RFID security must further be able to store information about the item tagged.

Document US-A- 4 973 944 discloses a security tag according to the preamble of claim 1. However, the conductor in the flexible strip is not part of an antenna coil but forms a DC circuit path when the ends of the flexible strip are joined to form a loop. Although it is mentioned in this document that the strip may also act as an antenna, the document is silent on the specific construction of the antenna and on whether the antenna will be rendered inoperable when opening the loop.

In accordance with one embodiment of the present invention, it is an object of this invention to provide an improved RFID security tag.

It is another object of the present invention to provide an improved RFID security tag that is smaller and less bulky than current EAS tags.

It is still another object of the present invention to provide an improved RFID security tag that is smaller and less bulky than current EAS tags and that may be coupled to small articles of merchandise in an unobtrusive manner.

It is still a further object of the present invention to provide an improved RFID security that is able to store information about the item tagged.

In accordance with one embodiment of the present invention, a security tag for attachment to a small article of merchandise is disclosed. The security tag uses a thin flexible strip. A Radio Frequency Identification (RFID) tag device is coupled to the thin flexible strip and is used for storing data related to the small article of merchandise to be monitored. A plurality of conductors are laid on the thin flexible strip. The plurality of conductors are coupled together to form a multiple turn coil for providing energy to the RFID tag device when a first end of the thin flexible strip is coupled to a second end of the thin flexible strip to form a loop.

In accordance with another embodiment of the present invention, a method of providing a security tag for attachment to a small article of merchandise is disclosed. The method comprises the steps of: providing a thin flexible strip; providing a Radio Frequency Identification (RFID) tag device coupled to the thin flexible strip for storing data related to the small article of merchandise to be monitored; and providing a plurality of conductors laid on the thin flexible strip wherein the plurality of conductors are coupled together to form a multiple turn coil for providing energy to the RFID tag device when a first end of said thin flexible strip is coupled to a second end of said thin flexible strip to form a loop.

The foregoing and other objects, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiments of the invention, as illustrated in the accompanying drawing.

Figure 1A shows a front view of a first embodiment of the present invention.

Figure 1B shows a back view of the embodiment depicted in Figure 1A.

Figure 2A shows a front view of another embodiment of the present invention.

Figure 2B shows a back view of the embodiment depicted in Figure 2A.

Figure 3 shows an elevated perspective view of the present invention when the strip is formed into a loop and the ends are coupled together.

Referring to Figure 1A-1B, one embodiment of a Radio Frequency Identification (RFID) security tag 10 for merchandise is shown. While the RFID security tag 10 may be used to monitor any type of merchandise, the RFID security tag 10 was designed to be unobtrusively attached through small items of merchandise like jewelry. The RFID security tag 10 will be enabled upon attachment to a specific piece of jewelry and disabled if removed, disassembled, or cut.

The RFID security tag 10 has a substrate 12. The substrate 12 is generally a thin flexible piece of material in which a conductor may be applied. Some examples of a substrate 12 are, but are not limited to: mylar, polyamide, polyester, paper, or any other type of thin flexible material. An RFID tag device 14 is coupled to the substrate 12. The RFID tag device 14 is used to store information related to the specific piece of merchandise which is tagged. This is important so that a reading mechanism in a display case, point-of-sale terminal, or doorway may detect the specific piece of merchandise being moved or if the RFID security tag 10 is being removed.

A plurality of conductors 16 are formed, etched, deposited or laid on the substrate 12. The conductors 16 are laid such that each conductor 16 does not come in contact with another conductor 16. The conductors 16 are generally laid in a parallel manner to one another along the length of the substrate 12. Each conductor 16 is directly coupled to a directly successive conductor 16 to form a single continuous conductor. When the substrate 12 is coupled together such that a first end 12A is coupled to a second end 12B to form a loop (see Figure 3), the single continuous conductor now becomes a multiple turn coil which will energize the RFID tag device 14 when exposed to a radio frequency field. In a security application, the substrate 12 can be inserted through a ring, a piece of jewelry, or a piece or merchandise before the ends 12A and 12B are coupled together. Once the substrate 12 is cut or removed from the piece of merchandise, the RFID tag device 14 will stop modulating and an RFID reader located nearby can immediately detect that condition.

In the embodiment depicted in Figures 1A-1B, a first conductor and a last conductor are coupled to the RFID tag device 14. The first conductor and the last conductor are generally coupled to the RFID tag device 12 via wirebonding or flip chip techniques which are well understood in the industry.

In the embodiment depicted in Figures 1A-1B, each of the plurality of conductors 16, except for the first conductor, has a surface connector 18 and a through connector 20. The first conductor has a first end coupled to the RFID tag device and a second end coupled to a surface connector 18. When the substrate 12 is coupled together through an item of merchandise such that a first end 12A is coupled to a second end 12 to form a loop (see Figure 3), the surface connector 18 and through connector 20 allow the plurality of conductors 16 to be coupled together to form a single continuous conductor. The single continuous conductor is arranged to form a multiple turn coil which will energize the RFID tag device 14 upon exposure to an RF field. If the RFID security tag 10 is removed, disassembled, or cut, a reader located near the item of merchandise can immediately detect this condition and signal an alarm. The surface connector 18 and through connector 20 are coated with a conductive adhesive or other conductive material so that the circuit is completed when the ends 12A and 12B of tag 10 are coupled together. In the case of a conductive adhesive, the adhesive holds the ends 12A and 12B together. In the case of gold or other conductive material on connectors 18 and 20, a mechanical locking device such as a plastic snap can be molded into the substrate 12 for holding the connectors 18 and 20 in contact with each other.

Referring to Figures 2A-2B, wherein like numerals and symbols represent like elements with the exception of the use of " ' " to indicate a different embodiment, another embodiment of the present invention is shown. The RFID security tag 10' is similar to that shown and described above. The only difference between the two embodiments is that the RFID security tag 10' has an additional bonding pad which allows three conductors 16' to be coupled to the RFID tag device 14'. This additional bonding pad is required for certain RFID tags 14' which have three connections to the resonance coil rather than the more common two connections.

The RFID security tags 10 and 10' are a more attractive and less bulky solution than current EAS tags. The RFID security tags 10 and 10' form a loop connecting through a piece of merchandise so that if the loop is removed or cut, the RFID security tag will stop modulating and an RF reader located near by can immediately detect this condition. The security tags 10 and 10', while smaller in two dimensions than current EAS tags, form an aperture (diameter) in three dimensions as large as current EAS tags, which is necessary for adequate read range. For example, one embodiment may use a 1/8" wide substrate, 6" long to form a 2" diameter loop antenna when the ends of the substrate are coupled together. Those skilled in the art will recognize that he antenna aperture (diameter) is related to the energy coupling the reader to the tag thereby affecting read range. The RFID security tags 10 and 10' will further store information related to the specific piece of merchandise tagged. This is important so that a reader in a display case, point-of-sale terminal, or doorway can detect the specific RFID security tag 10 or 10' being moved, purchased or cut.