US4743490A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Counterfeit-resistant magnetic recording tape
Assignee: 3M Co
•
Filing: 1986-02-24
•
Granted: 1988-05-10
•
Expires: 2006-02-24
Abstract
Abstract Some prior magnetic recording tapes have a backside layer of electrically conductive particles and friction-imparting nonmagnetic particles in a nonmagnetic binder. The novel tape differs in that the nonmagnetic particles are replaced by high-H c ferromagnetic particles, onto which may be recorded a distinctive magnetic pattern. This provides a "magnetic watermark" that should protect recordings from being counterfeited, because if one were to copy a recording onto ordinary magnetic recording tape, the copy would lack the "watermark". This should inhibit unauthorized copying of video recordings such as motion pictures.
Inventors
- 👤 Richard E. Fayling
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 16:24
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/74; G11B5/78; G11B23/00; G11B23/28; G11B23/281; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10S428/916; Y10T; Y10T428/00; Y10T428/24; Y10T428/24942; Y10T428/25
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
89 words
Magnetic video recording tape comprising a flexible backing carrying a faceside magnetic recording layer and a backside surface layer comprising electrically conductive particles in a nonmagnetic binder, wherein the improvement comprises: the backside layer includes ferromagnetic particles, the H c of which is sufficiently high that they are not affected by the recording of signals onto the magnetic recording layer, and the B r of which is sufficiently low that when recorded in a distinctive magnetic pattern, their fields do not interfere with signals of the magnetic recording layer.
Claim 2
Dependent Claim
89 words
Magnetic video recording tape comprising a flexible backing carrying a faceside magnetic recording layer and a backside surface layer comprising electrically conductive particles in a nonmagnetic binder, wherein the improvement comprises: the backside layer includes ferromagnetic particles, the H c of which is sufficiently high that they are not affected by the recording of signals onto the magnetic recording layer, and the B r of which is sufficiently low that when recorded in a distinctive magnetic pattern, their fields do not interfere with signals of the magnetic recording layer.
Claim 3
Dependent Claim
26 words
Magnetic recording tape as defined in claim 1 wherein the ferromagnetic particles of the backside layer comprise from 1 to 30 volume percent of that layer.
Claim 4
Dependent Claim
24 words
Magnetic recording tape as defined in claim 2 wherein the ferromagnetic particles of the backside layer an H c of at least 2000 oersteds.
Claim 5
Dependent Claim
26 words
Magnetic recording tape as defined in claim 3 wherein the H c of the ferromagnetic particles of the backside layer is from 3000 to 6000 oersteds.
Claim 6
Dependent Claim
21 words
Magnetic recording tape as defined in claim 3 wherein the ferromagnetic particles of the backside layer have a hexagonal crystal structure.
Claim 7
Dependent Claim
19 words
Magnetic recording tape as defined in claim 5 wherein the ferromagnetic particles of the backside layer comprise barium ferrite.
Claim 8
Dependent Claim
50 words
Magnetic recording tape as defined in claim 6 wherein the magnetic recording layer has an easy axis of magnetization, and the barium ferrite particles are oriented with their easy axes primarily extending at an angle of more than 45° to the easy axis of magnetization of the magnetic recording layer.
Claim 9
Dependent Claim
43 words
Magnetic recording tape as defined in claim 7 wherein the easy axis of magnetization of the magnetic recording layer extends in the longitudinal direction and the easy axes of the ferromagnetic particles of the backside layer are oriented in a substantially transverse direction.
Claim 10
Dependent Claim
19 words
Magnetic recording tape as defined in claim 1 wherein the ferromagnetic particles of the backside layer are substantially equidimensional.
Claim 11
Dependent Claim
24 words
Magnetic recording tape as defined in claim 9 wherein the ferromagnetic particles of the backside layer are from 0.1 to 2 micrometers in size.
Claim 12
Dependent Claim
22 words
Magnetic recording tape as defined in claim 10 wherein the ferromagnetic particles of the backside layer are about 0.3 micrometer in size.
Claim 13
Dependent Claim
32 words
Magnetic recording tape as defined in claim 1 wherein the ferromagnetic particles of the backside layer are magnetized in a distinctive pattern which is reproducible at least in part as digital signals.
Claim 14
Dependent Claim
11 words
Videocassette containing a magnetic recording tape as defined in claim 1.
Claim 15
Dependent Claim
116 words
Method of making a counterfeit-resistant magnetic video recording tape comprising the steps of (1) applying a magnetic recording layer to the faceside of a flexible backing, (2) applying to the flexible backing a backside surface layer comprising electrically conductive particles and ferromagnetic particles in a nonmagnetic binder, the H c of the ferromagnetic particles being sufficiently high that they are not affected by the recording of signals onto the magnetic recording layer, and the B r of which is sufficiently low that when recorded in a distinctive magnetic pattern, their fields do not interfere with signals of the magnetic recording layer, and (3) recording a distinctive magnetic pattern onto the ferromagnetic particles of the backside layer.
Claim 16
Dependent Claim
116 words
Method of making a counterfeit-resistant magnetic video recording tape comprising the steps of (1) applying a magnetic recording layer to the faceside of a flexible backing, (2) applying to the flexible backing a backside surface layer comprising electrically conductive particles and ferromagnetic particles in a nonmagnetic binder, the H c of the ferromagnetic particles being sufficiently high that they are not affected by the recording of signals onto the magnetic recording layer, and the B r of which is sufficiently low that when recorded in a distinctive magnetic pattern, their fields do not interfere with signals of the magnetic recording layer, and (3) recording a distinctive magnetic pattern onto the ferromagnetic particles of the backside layer.
Claim 17
Dependent Claim
22 words
Method as defined in claim 14 wherein the pattern applied in step (3) is reproducible at least in part as digital signals.
Claim 18
Dependent Claim
28 words
Magnetic recording tape as defined in claim 1 wherein the ferromagnetic particles in the backside layer are approximately equidimensional and are between 0.1 and 2 micrometers in size.
References Cited (Backward Citations)
US3219353A
Cited
US3328195A
Cited
US3566356A
Cited
US3617378A
Cited
GB1331604A
Cited
US3878367A
Cited
US4104513A
Cited
US3986205A
Cited
US4090662A
Cited
US4442159A
Cited
US4511617A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-05-10 | 1991-11-09 | 1992-05-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-05-10 | 1995-11-09 | 1996-05-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-05-10 | 1999-11-09 | 2000-05-10 | $7700.00 | Window Closed / Lapsed |