Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
1998-07-31
2001-02-27
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S328000, C428S329000, C428S690000, C428S900000
Reexamination Certificate
active
06194058
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to multi-layered magnetic recording media and to a method for preparing multi-layered magnetic recording media.
BACKGROUND OF THE INVENTION
In recent years magnetic recording has become the preferred method of storing information such as sound, video images, and computer data. Magnetic tapes and disks are the most common types of recording media. The trend in magnetic recording is towards higher radio frequency outputs at higher frequencies and larger storage capacities. To achieve these objectives, two approaches have been taken: (1) increasing magnetic power by increasing coercive force and remanent magnetic flux, and (2) decreasing self demagnetization by decreasing magnetic layer thickness and optimizing orientation of the magnetic particles.
Individually, each approach appears insufficient to achieve higher radio frequency outputs and larger storage capacities, however, when used in combination, performance is improved significantly to the level of metal evaporative tape.
However, it has been difficult to form thin layer particulate media using conventional coating methods. To deal with this problem, thin layer particulate recording media coated in combination with a nonmagnetic lower-layer have been manufactured using simultaneous wet-on-wet double coating techniques. Such techniques make it possible to get high density particulate media which performs equivalent to metal evaporated tape.
A conventional nonmagnetic lower layer in a multi-layer recording medium is not capable of magnetic recording, but it may supply a smooth bonding surface for the adjacent upper layer and contribute to durability. The use of a nonmagnetic lower layer, however, can result in poor overwrite characteristics. Typical “hard” magnetic lower layers, on the other hand, containing predominantly particles such as acicular Co—&ggr;—Fe
2
O
3
, &ggr;—Fe
2
O
3
, CrO
2
, Fe
3
O
4
, and Co—Fe
3
O
4
, have high squareness ratios and remanent flux densities. Magnetic media made using such particles in both layers sometimes exhibit unacceptably high levels of demagnetization.
Accordingly, there is a need for an improved multi-layer magnetic medium which exhibits enhanced high frequency output without signal erasure and overwrite problems.
Additionally, there is a need for an improved method for making multi-layer recording media that permits efficient application of successive, multiple layers to a substrate without experiencing significant intermixing of the layers that may be encountered using conventional wet-on-wet techniques.
SUMMARY OF THE INVENTION
The present invention is directed to an improved multi-layer recording medium having enhanced output at higher frequencies and improved overwrite performance. The present invention is further directed to an improved method for making multi-layer magnetic recording media which controls the surface characteristics of the respective layers and substantially eliminates intermixing of the successive layers as they are applied.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the article of manufacture and method particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, the present invention is directed to an improved multi-layer magnetic recording medium comprising a substrate, at least one magnetic inner layer and a magnetic outer layer. In one further aspect of the invention, the magnetic recording medium of the invention is a magnetic recording tape. In another aspect, the multi-layer recording medium of the invention has a magnetic inner layer with a squareness ratio and saturation magnetization (defined by a saturation magnetic flux density (Bm)×thickness of magnetic inner layer) within specific ranges; and the magnetic outer layer of the medium may contain oriented ferromagnetic particles.
The present invention, further, is directed to an improved method for making multi-layer magnetic recording media comprising the steps of applying a plurality of layers, in successive applications, to a nonmagnetic substrate, in which, subsequent to each application, a controlled degree of drying is applied to achieve a partial evaporation of solvent to permit application of the next successive layer while avoiding intermixing with the preceding, applied layer. In a further aspect, at least the last applied layer contains magnetic particles and one or more magnetic layers are subject to magnetic orientation following controlled drying.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 3977985 (1976-08-01), Umeki et al.
patent: 4091158 (1978-05-01), Kasuga et al.
patent: 4101311 (1978-07-01), Aonuma et al.
patent: 4259392 (1981-03-01), Suzuki
patent: 4364988 (1982-12-01), Andoh et al.
patent: 4409281 (1983-10-01), Kitamoto et al.
patent: 4500599 (1985-02-01), Ogawa et al.
patent: 4511617 (1985-04-01), Hideyama et al.
patent: 4550062 (1985-10-01), Takayama et al.
patent: 4603091 (1986-07-01), Mukasa et al.
patent: 4618536 (1986-10-01), Morioka et al.
patent: 4619868 (1986-10-01), Okita et al.
patent: 4621018 (1986-11-01), Yoda et al.
patent: 4624894 (1986-11-01), Kishimoto
patent: 4636433 (1987-01-01), Kubo et al.
patent: 4636448 (1987-01-01), Morita et al.
patent: 4659633 (1987-04-01), Yamaguchi et al.
patent: 4746542 (1988-05-01), Chino et al.
patent: 4844946 (1989-07-01), Komatsu et al.
patent: 4863793 (1989-09-01), Ogawa et al.
patent: 4874633 (1989-10-01), Komatsu et al.
patent: 4982302 (1991-01-01), Kitamoto et al.
patent: 5035948 (1991-07-01), Saito et al.
patent: 5043210 (1991-08-01), Yamakawa et al.
patent: 5089317 (1992-02-01), Noguchi et al.
patent: 5188907 (1993-02-01), Kawhara et al.
patent: 5258223 (1993-11-01), Inaba et al.
patent: 5268206 (1993-12-01), Komatsu et al.
patent: 5324571 (1994-06-01), Koyama et al.
patent: 5370932 (1994-12-01), Inaba et al.
patent: 5445104 (1995-08-01), Moody
patent: 5489466 (1996-02-01), Inaba et al.
patent: 5496607 (1996-03-01), Inaba et al.
patent: 5496622 (1996-03-01), Isobe et al.
patent: 5518804 (1996-05-01), Mizuno et al.
patent: 5527603 (1996-06-01), Isobe et al.
patent: 5637390 (1997-06-01), Isobe et al.
patent: 5645917 (1997-07-01), Ejiri et al.
patent: 5670245 (1997-09-01), Isobe et al.
patent: 5705268 (1998-01-01), Ishikawa et al.
patent: 5712028 (1998-01-01), Seki et al.
Isobe Ryosuke
McQuay Brian
Tadlock Guy M.
Needle & Rosenberg P.C.
Quantegy, Inc.
Resan Stevan A.
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