Radio frequency identification tags for use on metal or other conductive objects

• US 7,315,248 B2
• Filed: 05/13/2005
• Issued: 01/01/2008
• Est. Priority Date: 05/13/2005
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Egbert, William C.
• Primary Examiner(s): Lee; Benjamin C.
• Assistant Examiner(s): Previl; Daniel
• Application Number:
  US11/128,713
• Publication Number:
  US 20060255945A1
• Time in Patent Office: 963 Days
• Field of Search: 340/572.7, 340/572.8, 340/572.5, 340/551, 340/572.1, 340/10.34, 343/872, 343/873, 235/497, 235/487, 235/492, 235/441, 235/486, 235/488, 235/450, 235/451
• US Class Current: 340/572.7
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07771 the record carrier comprising means for minimising adverse effects on the data communication capability of the record carrier, e.g. minimising Eddy currents induced in a proximate metal or otherwise electromagnetically interfering object

Abstract

A radio frequency identification (“RFID”) tags that are useful on metal or other conductive surface and to methods for manufacturing the same. In one embodiment, the radio frequency identification tag includes: a substrate including a first major surface and a second major surface opposite the first major surface; a radio frequency identification antenna attached to the first major surface of the substrate; an integrated circuit attached to the antenna; and a first composite layer.

Claims

1. A radio frequency identification (“

RFID”

) tag, comprising;

a substrate including a first major surface and a second major surface opposite the first major surface;

an antenna attached to the first major surface of the substrate;

an integrated circuit attached to the antenna; and

a first composite layer including a first major surface and a second major surface opposite the first major surface, wherein the first composite layer is attached to the second major surface of the substrate, wherein the first composite layer comprises;

binder; and

a plurality of multilayered flakes dispersed in the binder, the multilayered flakes comprising two to about 100 layer pairs, each layer pair comprising;

one crystalline ferromagnetic metal layer adjacent to one dielectric layer, wherein the layer pairs form a stack of alternating ferromagnetic metal layers and dielectric layers.

2. The RFID tag of claim 1, wherein the ferromagnetic metal layer is thinner than its skin depth.

3. The RFID tag of claim 1, wherein the dielectric layer has a thickness of about 5 to about 100 nm.

4. The RFID tag of claim 1, wherein the first composite layer includes a thickness of between 0.5 and 5.0 mm.

5. The RFID tag of claim 1, wherein the composite layer includes an areal density of between 0.0001 and 0.1 gm/mm².

6. The RFID tag of claim 1, wherein the composite layer comprises at least two strips of the composite layer attached to the second major surface of the substrate.

7. The RFID tag of claim 1, wherein the composite layer includes an aperture, wherein the aperture corresponds generally to the shape of the antenna.

8. The RFID tag of claim 1, wherein the composite layer includes a first portion and a second portion, wherein the second portion corresponds generally to the shape of the antenna, and wherein the first portion comprises the binder and the plurality of multilayered flakes dispersed in the binder, wherein the second portion comprises only binder.

9. The RFID tag of claim 1, further comprising a first layer of adhesive attached to the second major surface of the composite layer.

10. The RFID tag of claim 9, wherein the first layer of adhesive attaches the radio frequency identification tag to a metal or other conductive surface.

11. The RFID tag of claim 9, further comprising a second layer of adhesive attaching the second major surface of the substrate to the first major surface of the composite layer.

12. The RFID tag of claim 1, further comprising a cover layer attached to the substrate and the composite layer.

13. The RFID tag of claim 12, further comprising a third layer of adhesive between the cover layer and the substrate.

14. The RFID tag of claim 1, further comprising a second composite layer including a first major surface and a second major surface opposite the first major surface, wherein the second composite layer is attached to the second major surface of the first composite layer, wherein the second composite layer comprises:

binder; and

a plurality of multilayered flakes dispersed in the binder, the multilayered flakes comprising two to about 100 layer pairs, each layer pair comprising;

one crystalline ferromagnetic metal layer adjacent to one dielectric layer, wherein the layer pairs form a stack of alternating ferromagnetic metal layers and dielectric layers.

15. The RFID tag of claim 14, further comprising a fourth layer of adhesive attaching the second major surface of the first composite layer to the first major surface of the second composite layer.

16. The RFID tag of claim 15, wherein the fourth layer of adhesive attaches the RFID tag to a metal or other conductive surface.

17. A metal airplane part or tool in combination with the RFID tag of claim 1, wherein the RFID tag is attached to the airplane part or tool, and wherein the RFID tag is readable by an interrogator within a read range of at least 40 mm.

18. A radio frequency identification (“

RFID”

) tag for use on metal or other conductive surfaces, comprising;

a substrate including a first major surface and a second major surface opposite the first major surface;

an antenna attached to the first major surface of the substrate;

an integrated circuit attached to the antenna; and

a first composite layer including a first major surface and a second major surface opposite the first major surface, wherein the first composite layer is attached to the second major surface of the substrate, wherein the first composite layer comprises;

binder; and

a plurality of multilayered flakes dispersed in the binder, the multilayered flakes comprising two to about 100 layer pairs, each layer pair comprising;

one crystalline ferromagnetic metal layer adjacent to one dielectric layer, wherein the layer pairs form a stack of alternating ferromagnetic metal layers and dielectric layers;

wherein the radio-frequency identification tag is attached to the metal or other conductive surface, and

wherein the radio frequency identification tag is readable by an interrogator within a read range of at least 40 mm from the radio frequency identification tag.

19. The method of claim 18, wherein the ferromagnetic metal layer is thinner than its skin depth.

20. The method of claim 18, wherein the dielectric layer has a thickness of about 5 to 100 nm.

21. The RFID tag of claim 18, wherein the first composite layer includes a thickness of 0.5 and 5.0 mm.

22. The RFID tag of claim 18, wherein the composite layer includes an areal density of between 0.0001 and 0.1 gm/mm².

23. The RFID tag of claim 18, wherein the composite layer comprises at least two strips of the composite layer attached to the second major surface of the substrate.

24. The RFID tag of claim 18, wherein the composite layer includes an aperture, wherein the aperture corresponds generally to the shape of the antenna.

25. The RFID tag of claim 18, wherein the composite layer includes a first portion and a second portion, wherein the second portion corresponds generally to the shape of the antenna, and wherein the first portion comprises the binder and the plurality of multilayered flakes dispersed in the binder, wherein the second portion comprises only binder.

26. The RFID tag of claim 18, further comprising a first layer of adhesive attached to the second major surface of the composite layer.

27. The RFID tag of claim 26, wherein the first layer of adhesive attaches the radio frequency identification tag to a metal or other conductive surface.

28. The RFID tag of claim 26, further comprising a second layer of adhesive attaching the second major surface of the substrate to the first major surface of the composite layer.

29. The RFID tag of claim 18, further comprising a cover layer attached to the substrate and the composite layer.

30. The RFID tag of claim 29, further comprising a third layer of adhesive between the cover layer and the substrate.

31. The RFID tag of claim 18, further comprising a second composite layer including a first major surface and a second major surface opposite the first major surface, wherein the second composite layer is attached to the second major surface of the first composite layer, wherein the second composite layer comprises:

binder; and

a plurality of multilayered flakes dispersed in the binder, the multilayered flakes comprising two to about 100 layer pairs, each layer pair comprising;

one crystalline ferromagnetic metal layer adjacent to one dielectric layer, wherein the layer pairs form a stack of alternating ferromagnetic metal layers and dielectric layers.

32. The RFID tag of claim 31, further comprising a fourth layer of adhesive attaching the second major surface of the first composite layer to the first major surface of the second composite layer.

33. The RFID tag of claim 32, wherein the fourth layer of adhesive attaches the RFID tag to a metal or other conductive surface.

34. A metal airplane part or tool in combination with the RFID tag of claim 18, wherein the RFID tag is attached to the airplane part or tool, and wherein an interrogator may read the RFID tag within a read range of at least 40 mm.

35. A method of manufacturing a radio frequency identification (“

RFID”

) tag, comprising the steps of;

providing a substrate containing an antenna on at least one surface of the substrate;

attaching an integrated circuit to the antenna;

providing a first composite layer including a first major surface and a second major surface opposite the first major surface, wherein the first composite layer is attached to the second major surface of the substrate, wherein the first composite layer comprises;

binder; and

a plurality of multilayered flakes dispersed in the binder, the multilayered flakes comprising two to about 100 layer pairs, each layer pair comprising;

one crystalline ferromagnetic metal layer, wherein the ferromagnetic metal layer is thinner than its skin depth, adjacent to one dielectric layer, wherein the dielectric layer has a thickness of about 5 to about 100 nm; and

wherein the layer pairs form a stack of alternating ferromagnetic metal layers and dielectric layers; and

attaching the first composite layer to the substrate opposite the antenna and integrated circuit.