Magnetic recording medium
US4506000A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 9, 1983 |
| Grant date | Mar 19, 1985 |
| Priority date | — |
| Expiry date | Feb 9, 2003 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B5/716
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A magnetic recording medium having a non-magnetic substrate, a first magnetic layer composed mainly of magnetic powder and binder and formed on the non-magnetic substrate, and a second magnetic layer composed mainly of magnetic powder and binder and formed on the first magnetic layer is disclosed. In this case, the magnetic powder of the first magnetic layer is made of ferro-magnetic metal powder which has a specific surface area of 20 to 40 m.sup.2 /g measured according to BET adsorption method, the first magnetic layer has coercive force H.sub.c1 of 800 to 1500 Oe, residual magnetic flux density of 3000 to 5000 Gausses and a thickness of more than 2.mu., while the magnetic powders of the second magnetic layer is made of ferro-magnetic metal powder which has a specific surface area of 40 to 150 m.sup.2 /g measured according to BET adsorption method, the second magnetic layer has coercive force H.sub.c2 of 1000 to 2500 Oe, residual magnetic flux density of 2000 to 3000 Gausses and a thickness 0.1 to 2.mu., and the coercive forces H.sub.c1 and H.sub.c2 are selected to satisfy H.sub.c1 .ltoreq.H.sub.c2 .
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.