Patent US4579371A successfully refreshed from Google Patents.
US4579371A
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US
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Document having concealed electrically conductive authenticating layer
Assignee: 3M Co
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Filing: 1983-12-27
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Granted: 1986-04-01
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Expires: 2003-12-27
Abstract
Abstract A standardized document such as a credit card or drivers license contains an electrically conductive authenticating layer which is not visually discernible and has an electrical resistivity of less than 50 megohms per square. The presence of the authenticating layer may be verified by a proximity switch that can be built into mechanisms normally used in processing the document.
Inventors
- 👤 William H. Long
- 👤 Richard M. Fischer, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 17:03
CPC Classifications
B; B42; B42D; B42D25/00; B42D25/20; B42D25/21; G; G06; G06K; G06K19/00; G06K19/06; G06K19/067; G07; G07F; G07F7/00; G07F7/08; G07F7/086; B42D2033/04; B42D2033/20; B42D2033/32; B42D2035/06; B42D2035/08; B42D25/30; B42D25/309
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
79 words
A standardized document including an authenticating layer of electrically conductive material comprising a mixture of ionizable salt and ionizing agent uniformly dispersed in an organic binder, which layer extends over an area of at least 4 mm square and has an electrical resistivity of less than 50 megohms per square, the document being substantially visually indistinguishable from a document which would be identical except for omission of said layer, and a transparent protective plastic film covering said authenticating layer.
Claim 2
Dependent Claim
79 words
A standardized document including an authenticating layer of electrically conductive material comprising a mixture of ionizable salt and ionizing agent uniformly dispersed in an organic binder, which layer extends over an area of at least 4 mm square and has an electrical resistivity of less than 50 megohms per square, the document being substantially visually indistinguishable from a document which would be identical except for omission of said layer, and a transparent protective plastic film covering said authenticating layer.
Claim 3
Dependent Claim
21 words
Document as defined in claim 1 wherein the authenticating layer has an electrical resistivity of less than 500,000 ohms per square.
Claim 4
Dependent Claim
15 words
Document as defined in claim 1 wherein the authenticating layer is coextensive with the document.
Claim 5
Dependent Claim
16 words
Document as defined in claim 3 wherein the authenticating layer covers the face of the document.
Claim 6
Dependent Claim
16 words
Document as defined in claim 1 wherein the electrically conductive material and organic binder are colorless.
Claim 7
Dependent Claim
13 words
Document as defined in claim 1 wherein the conductive material comprises semiconductive salt.
Claim 8
Dependent Claim
27 words
Document as defined in claim 6 wherein the semiconductive salt is colored and a surface of the document which bears said authenticating layer has the same color.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-03-31 | 1989-09-30 | 1990-04-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-03-31 | 1993-09-30 | 1994-04-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-03-31 | 1997-09-30 | 1998-04-01 | $7700.00 | Window Closed / Lapsed |