Claims
- 1. A magnetic recording medium, comprising a flexible support having provided thereon, at least a lower layer comprising a binder and a non-magnetic powder component dispersed therein and an upper magnetic layer comprising a binder and an acicular ferromagnetic powder dispersed therein which is coated over the lower layer while the lower layer is in a wet state, wherein said upper magnetic layer has an average dry thickness (d) in a range of from 0.05 to 0.8 um and a thickness variation (.sup..DELTA. d) at the interface between said upper magnetic layer and lower layer of not more than d/2, and said non-magnetic powder component comprises an inorganic powder having a Mohs hardness of not less than 3 and an average particle size of not more than 1/3 the major axis length of said acicular ferromagnetic powder in the upper magnetic layer.
- 2. A magnetic recording medium as in claim 1, wherein said non-magnetic powder is an inorganic powder having a Mohs hardness of not less than 3 and an average particle size ranging from 1/2 to 4 times the crystallite size of said acicular ferromagnetic powder.
- 3. A magnetic recording medium as in claim 1, wherein a volume packing of said inorganic powder in the lower layer is from 20 to 60%.
- 4. A magnetic recording medium as in claim 1, wherein said ferromagnetic powder is an acicular ferromagnetic alloy powder containing Fe, Ni or Co.
- 5. A magnetic recording medium as in claim 1, wherein said ferromagnetic powder is a ferromagnetic alloy powder comprising Fe, Ni or Co as a main component and further containing at least one atom selected the group consisting of Al, Si, S, Sc, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta, W, Re, Au, Pb, Bi, La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, Sr and B.
- 6. A magnetic recording medium as in claim 1, wherein said inorganic powder is spherical.
- 7. A magnetic recording medium as in claim 1, wherein said lower layer is coated with a composition which contains a magnetic powder and has physical properties resulting from said magnetic powder imparting: thixotropy to the coating composition for said lower layer.
- 8. A magnetic recording medium as in claim 1, wherein said lower layer has a maximum magnetic flux density (Bm) of not more than 500 gauss.
- 9. A magnetic recording medium as in claim 1, wherein said lower layer contains a magnetic powder component but is of insufficient magnetic power compared to the upper magnetic layer to contribute to magnetic recording.
- 10. A magnetic recording medium as in claim 1, wherein said non-magnetic powder component comprises at least one inorganic powder selected from the group consisting of TiO.sub.2 including rutile and anatase, TiO.sub.x (x=1 to 2), cerium oxide, tin oxide, tungsten oxide, ZnO, ZrO.sub.2, SiO.sub.2, Cr.sub.2 O.sub.3, .alpha.-alumina having an .alpha. ratio of 90% or more, .beta.-alumina, .gamma.-aluimina, .alpha.-iron oxide, geothite, corundum, silicon nitride, titanium carbide, magnesium oxide, boron nitride, molybdenum disulfide, copper oxide, MgCO.sub.3, CaCO.sub.3, Ba CO.sub.3, SrCO.sub.3, BaSO.sub.4, silicon carbide and titanium carbide.
- 11. A magnetic recording medium as in claim 1, wherein said support has a modulus of elasticity of from 100 to 2000 kg/mm.sup.2.
- 12. A magnetic recording medium as in claim 1, wherein said support is a film of polymer selected from the group consisting of polyesters, polyolefins, cellulose triacetate, polycarbonate, polyamide, polyimide, polyamideimide, polysulfone, aramide, and aromatic polyamide.
- 13. A magnetic recording medium as in claim 1, which is a digital audio or video tape, or a digital recording disk.
Priority Claims (6)
Number |
Date |
Country |
Kind |
3-019221 |
Jan 1991 |
JPX |
|
3-121873 |
Apr 1991 |
JPX |
|
3-121875 |
Apr 1991 |
JPX |
|
3-198309 |
Jul 1991 |
JPX |
|
4-18416 |
Jan 1992 |
JPX |
|
4-21782 |
Jan 1992 |
JPX |
|
CROSS-REFERENCE TO RELATED APPLICATION
This is a continuation of appplication No. 07/873,201, filed Apr. 24, 1992, now U.S. Pat. No. 5,645,917, which is a continuation-in-part of application No. 07/822,975, filed Jan. 21, 1991, now U.S. Pat. No. 5,258,223.
US Referenced Citations (60)
Foreign Referenced Citations (61)
Number |
Date |
Country |
0 392 810 A2 |
Oct 1990 |
EPX |
A-54-30002 |
Mar 1979 |
JPX |
55-55438 |
Apr 1980 |
JPX |
A-55-139634 |
Oct 1980 |
JPX |
B-57-6178 |
Feb 1982 |
JPX |
58-85931 |
May 1983 |
JPX |
A-58-139337 |
Aug 1983 |
JPX |
A-58-159228 |
Sep 1983 |
JPX |
58-51327 |
Nov 1983 |
JPX |
59-8124 |
Jan 1984 |
JPX |
59-154646 |
Sep 1984 |
JPX |
60-109020 |
Jun 1985 |
JPX |
60-154327 |
Aug 1985 |
JPX |
A-60-164926 |
Aug 1985 |
JPX |
60-193130 |
Oct 1985 |
JPX |
A-61-172215 |
Aug 1986 |
JPX |
A-61-216116 |
Sep 1986 |
JPX |
61-214127 |
Sep 1986 |
JPX |
61-204827 |
Sep 1986 |
JPX |
61-204829 |
Sep 1986 |
JPX |
61-237623 |
Oct 1986 |
JPX |
A-61-241325 |
Oct 1986 |
JPX |
62-001115A |
Jan 1987 |
JPX |
A-62-22235 |
Jan 1987 |
JPX |
A-62-33337 |
Feb 1987 |
JPX |
62-36727 |
Feb 1987 |
JPX |
A-62-92128 |
Apr 1987 |
JPX |
A-62-159338 |
Jul 1987 |
JPX |
62-188017 |
Aug 1987 |
JPX |
62-222427 |
Sep 1987 |
JPX |
A-62-234231 |
Oct 1987 |
JPX |
A-63-113931 |
May 1988 |
JPX |
63-157313 |
Jun 1988 |
JPX |
63-146210 |
Jun 1988 |
JPX |
63-164022 |
Jul 1988 |
JPX |
63-317926 |
Dec 1988 |
JPX |
1-109518 |
Apr 1989 |
JPX |
A-1-119916 |
May 1989 |
JPX |
1-235211 |
Sep 1989 |
JPX |
1-220120 |
Sep 1989 |
JPX |
1-248318 |
Oct 1989 |
JPX |
A-1-276422 |
Nov 1989 |
JPX |
1-300419 |
Dec 1989 |
JPX |
2-15415 |
Jan 1990 |
JPX |
A-2-58727 |
Feb 1990 |
JPX |
A-2-98816 |
Apr 1990 |
JPX |
2-149916 |
Jun 1990 |
JPX |
A-2-194063 |
Jul 1990 |
JPX |
A-2-208824 |
Aug 1990 |
JPX |
2-257424 |
Oct 1990 |
JPX |
A-2-307806 |
Dec 1990 |
JPX |
3-5913 |
Jan 1991 |
JPX |
3-17817 |
Jan 1991 |
JPX |
3-49032 |
Mar 1991 |
JPX |
3-88118 |
Apr 1991 |
JPX |
3-80422 |
Apr 1991 |
JPX |
A-3-157812 |
Jul 1991 |
JPX |
A-3-219424 |
Sep 1991 |
JPX |
4-271010 |
Sep 1992 |
JPX |
1417442 |
Dec 1975 |
GBX |
1417765 |
Dec 1975 |
GBX |
Non-Patent Literature Citations (3)
Entry |
The Advantages of the Thin Magnetic Layer on a Metal Particulate Tape, IEEE Transactions on Magnetics, vol. 29, No. 6, Nov. 1993. |
Development of Particulate Recording Media with Ultrathin Magnetic Layer, IEICE Trans Electron, vol. E78-C. No. 11, Nov. 1995. |
Enabling technologies for a 100MB 3.5" floppy (ZIP.TM.) disk drive, 220/SPIE vol. 2604 Oct. 1996. |
Continuations (1)
|
Number |
Date |
Country |
Parent |
873201 |
Apr 1992 |
|
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
822975 |
Jan 1992 |
|