Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2000-09-05
2003-01-14
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S402000, C428S425900, C428S690000, C428S690000, C428S690000
Reexamination Certificate
active
06506486
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a magnetic recording medium, especially, a particulate magnetic recording medium for broadcasting and computers, which is required to have high reliability and preservability.
2. Description of Related Art
A magnetic recording medium has been widely known as a tape for recording, a video tape, a computer tape, a disc and the like. A recording medium has been subjected to high densification year after year and the recording wavelength becomes shorter, moreover, the recording systems have also spread from analogue systems to digital systems.
Especially, a magnetic recording medium in which a ferromagnetic metal powder containing Fe as a main component is coated on a nonmagnetic support with a binder is mainly used, currently, as a medium for broadcasting, videos and data recording because of its excellent cost performance. These magnetic recording media for broadcasting, videos and date recording are required to have high electromagnetic characteristics as well as recorded images and data are provided to consumers as products. Therefore, they are required to have preservation characteristics that they can survive severe use under various environmental conditions compared with common consumer use, tapes are not degenerated and recorded data can be reproduced without problems even if used for a long time.
When providing a magnetic recording medium having ferromagnetic metal powder, it is known that it is desirable to make the material containing the metal less prone to oxidation. Through techniques such as modifying slow oxidation (Japanese Unexamined Patent Publication (KOKAI) Showa No. 57-89401, Japanese Unexamined Patent Publication (KOKAI) Showa No. 2-54998 and the like), and modifying added elements (U.S. Pat. No. 789,063 and the like), the magnetic material can itself be made more resistant to oxidation, and therefore, more stable In this manner, a sufficient level of resistance to oxidation can be practically achieved
It is also necessary that a magnetic tape have certain running properties so as to avoid problems. For example, where a tape is used after having been stored for a long period of time, or at high temperature an d high humidity, a large amount of adhesive may be deposited on the recording head, in which case dropouts and the error rate may increase and, in extreme cases, head clogging may occur, necessitating cleaning of the head. Such problems following long-term tape storage or storage under adverse conditions may be particularly common in magnetic recording systems which are used for broadcasting, video recording, or data recording, because in such systems the relative speed between the tape and head is large, meaning a large area of tape is used over time.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a magnetic recording medium having excellent preservability, especially, to provide a magnetic recording medium in which head stains generated by a tape are few and a dropout and an error rate are low in recording with a drive after preservation for a long time or after preservation under high temperature and high humidity even if the tape is used for a system in which a relative speed between a tape and a head is large and a large area of a tape is used per unit time.
The object of the present invention is accomplished by the following magnetic recording medium of the present invention.
That is, the present invention relates to a magnetic recording medium comprising a nonmagnetic support having thereon, a magnetic layer containing a ferromagnetic metal powder, a fatty acid, a fatty acid ester and a binder, wherein said ferromagnetic metal powder comprises Fe and 5 to 15% by atom of Al, 1 to 25% by atom of Co, 0.5 to 5% by atom of Y, 0 to 0.1% by atom of Si and 0 to 0.1% by atom of Nd, based on Fe and wherein said fatty acid ester is a fatty acid alkyl ester having an acid-hydrolytic speed equal to or less than 0.03/hour.
As described above, the magnetic recording medium of the present invention has an advantage that head stains resulted from running with a drive after preservation for a certain period are reduced by using a ferromagnetic metal powder having a specific composition and a fatty acid ester having a specific physical property.
MODE FOR CARRYING OUT OF THE INVENTION
Preferred embodiments of the present invention will be explained below.
A ferromagnetic metal powder used in the present invention contains Fe as a main component, and at least Al, Co and Y wherein a ratio of Al to Fe (Al/Fe) ranges from 5 to 15% by atom, a ratio of Co to Fe (Co/Fe) ranges from 1 to 25% by atom and a ratio of Y to Fe (Y/Fe) ranges from 0.5 to 5% by atom. Moreover, the ferromagnetic metal powder used in the present invention should be free from Si and Nd, or if contained, each of Si and Nd could be contained in an amount equal to or less than 0.1% by atom with respect to Fe.
The ferromagnetic metal powders having the above-mentioned composition are those in which the surface characteristics are controlled so as to maintain an excellent absorption of a binder. That is, by giving the above-mentioned composition, a binder is made to adsorb tightly to the ferromagnetic metal powder and a dynamic strength of a magnetic coating film is made tough. As a result, falling or the like of the magnetic layer itself when a head slides at a high speed can be prevented. An amount of a binder absorbed to a ferromagnetic metal powder can be increased and an amount of a binder not absorbed to a ferromagnetic metal powder in a coating film can be reduced. Since the binder not absorbed to the magnetic particles easily appears to a surface of the magnetic layer in a drying process, troubles such as head clog generated in sliding with a head can be reduced by reducing such a binder.
Among the above-mentioned elements contained in the ferromagnetic metal powder, it is considered that Al exists in the relatively neighborhood of the surface of the ferromagnetic metal powder. Therefore, Al easily influences on absorption characteristics between the ferromagnetic metal powder and the binder, in addition, Al also controls the hardness of the ferromagnetic metal powder. If the ratio of Al to Fe (Al/Fe) increases, the binding force between the ferromagnetic metal powder and the binder becomes large, however, it is not preferable that the ratio exceeds 15% by atom because the ferromagnetic metal powder itself becomes excessively hard so that a bead-wear increases. In addition, if the ratio of Al to Fe (Al/Fe) is less than 5% by atom, the binding force between the ferromagnetic metal powder and the binder becomes small and head clog easily occurs. The ratio of Al to Fe (Al/Fe) preferably ranges from 7 to 13% by atom.
It is to be noted that if Si is contained instead of Al or with Al, head stains in running after preservation under high temperature and high humidity remarkably occur. Since SiO
2
and a mixed oxide of SiO
2
and Al
2
O
3
are known as a solid acid catalyst, it is attributed to that if Si is contained in the ferromagnetic metal powder, hydrolyzing of an organic material used in the magnetic recording medium together with the ferromagnetic metal powder is promoted. Therefore, the ferromagnetic metal powder free from Si is used in the present invention or if contained, Si content is to be in an amount equal to or less than 0.1% by atom with respect to Fe. Preferably, the ferromagnetic metal powder not containing Si is used.
Among the above-mentioned elements contained in the ferromagnetic metal powder, Y is important next to Al. A magnetic recording medium using a ferromagnetic metal powder containing IIIa group elements (including Lanthanoids) including Y is already known (referring to, for example, Japanese Unexamined Patent Publication (KOKAI) Heisei No. 6-36265, U.S. Pat. Nos. 5,527,603 and 5,795,645, Japanese Unexamined Patent Publication (KOKAI) Heisei No. 8-306031). The present inventors examined effects of using the ferromagnetic metal powder containing these IIIa group ele
Araki Hiroaki
Ohno Mikio
Bernatz Kevin M
Fuji PhotoFilm Co., Ltd.
Stroock & Stroock & Lavan LLP
Thibodeau Paul
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