EP0459722A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Multi-layer thin-film EAS marker
Assignee: 3M Co
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Filing: 1991-05-24
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Granted: —
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Expires: 2011-05-24
Abstract
Abstract A marker (10) for use in magnetic-type electronic article surveillance systems, comprising a substrate (12) on which are deposited a plurality of high permeability, low coercive force magnetic thin-films (14, 18, 22, 26, 30, 34), each being separated from an adjacent magnetic thin-film by a non-magnetic thin-film (16, 20, 24, 28, 32). Each of the magnetic films have substantially the same permeability and coercive force, and the non-magnetic films are of a thickness to allow magnetostatic coupling while inhibiting exchange coupling. Accordingly, all of the magnetic thin-films reverse as a single entity and produce a sharp, readily distinguishable response.
Inventors
- 👤 Chester C/O Minnesota Mining And Piotrowski
- 👤 Jerome W. C/O Minnesota Mining And Mcallisteer
- 👤 Charles L. C/O Minnesota Mining And Bruzzone
- 👤 Ching-Long C/O Minnesota Mining And Tsai
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 09:39
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2402; G08B13/2405; G08B13/2408; G08B13/2428; G08B13/2437; G08B13/2442; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
211 words
A marker for use with a magnetic-type electronic article surveillance system which produces in an interrogation zone alternating magnetic fields having average peak intensities of a few oersteds, said marker having a high permeability and a coercive force sufficiently less than the average intensity encountered in said zone that upon exposure to such fields, the magnetization state of the marker is periodically reversed and a remotely detectable characteristic response is produced, said marker (10) characterized by: a) a sheet-like, flexible substrate (12); b) a plurality of magnetic thin-films (14, 18, 22, 26, 30, 34) deposited on said substrate, each of said magnetic thin-films having substantially the same high permeability and low coercive force; and c) a non-magnetic thin-film (16, 20, 24, 28, 32) between each pair of adjacent magnetic thin-films, each said non-magnetic thin-film having a thickness not less than one nm and not more than that of the adjacent magnetic thin-films so as to allow magnetostatic coupling between adjacent magnetic thin-film, and yet sufficiently thick to inhibit exchange coupling between adjacent magnetic films, whereby magnetization states in all of said magnetostatically coupled magnetic thin films may reverse substantially as a single entity upon exposure to said interrogation fields and thus produce a said response which is sharp and readily distinguishable.
Claim 2
Dependent Claim
26 words
A marker according to claim 1, characterized by said substrate and thin-films being substantially rectangular, having a ratio of major to minor length not exceeding three.
Claim 3
Dependent Claim
12 words
A marker according to claim 2, characterized by said ratio being one.
Claim 4
Dependent Claim
14 words
A marker according to claim 1, characterized by said substrate comprising a polymeric material.
Claim 5
Dependent Claim
21 words
A marker according to claim 4, characterized by said polymeric material being selected from the group consisting of polyimides and polyesters.
Claim 6
Dependent Claim
20 words
A marker according to claim 1, characterized by said magnetic thin-films (40, 42, 44, 46) having significantly anisotropic magnetic properties.
Claim 7
Dependent Claim
34 words
A marker according to claim 6, characterized by all said magnetic thin-films havig an easy axis of magnetization which is in substantially the same direction, such that the marker exhibits a substantially undirectional response.
Claim 8
Dependent Claim
42 words
A marker according to claim 6, characterized by an easy axis of magnetization associated with some of the magnetic thin-films (50, 52) being substantially perpendicular to that of other magnetic thin-films (54, 56) such that the marker exhibits a substantially bi-directional response.
Claim 9
Dependent Claim
39 words
A marker according to claim 6, characterized by a first plurality of magnetic thin-films having a first easy axis of magnetization and a second plurality of magnetic thin-films having an easy axis of magnetization different from said first axis.
Claim 10
Dependent Claim
19 words
A marker according to claim 1, characterized by said magnetic thin-films being formed of a nickel and iron alloy.
Claim 11
Dependent Claim
15 words
A marker according to claim 1, characterized by said magnetic thin-films exhibiting substantially zero magnetostriction.
Claim 12
Dependent Claim
15 words
A marker according to claim 1, characterized by said magnetic thin films being substantially amorphous.
Claim 13
Dependent Claim
52 words
A marker according to claim 1, further characterized by at least one remanently magnetizable layer (76, 86), which, when magnetized, magnetically biases the magnetic thin-films and thereby alters said response, thereby causing the marker to alternately have a sensitized and de-sensitized state, depending upon whether the magnetizable layer is magnetized or demagnetized.
Claim 14
Dependent Claim
25 words
A marker according to claim 1, further characterized by an adhesive layer (66) for enabling the marker to be affixed to articles to be protected.
Claim 15
Dependent Claim
25 words
A marker according to claim 14, still further characterized by a release liner (69) for protecting the adhesive layer prior to application to said article.
References Cited (Backward Citations)
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