Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
2000-01-14
2001-11-06
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S323000, C428S336000, C428S216000, C428S457000, C428S474400, C428S690000, C428S900000
Reexamination Certificate
active
06312785
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P11-010837 filed Jan. 19, 1999, which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic recording medium incorporating a non-magnetic support member on which a thin metal magnetic film is formed, and more particularly to a magnetic recording medium for use as a video tape which is capable of recording data for a long time or a taper streamer having a large capacity.
2. Description of the Related Art
Hitherto, a support member for a thin metal-magnetic-film magnetic recording medium has been mainly composed of polyethylene terephthalate film because of relatively satisfactory strength of its material and dimension stability. In particular, a home video cassette tape, for example, 8 mm-tape has been constituted by a polyethylene terephthalate film having a thickness of about 7 &mgr;m to about 10 &mgr;m. The tape streamer incorporates the polyethylene terephthalate film of a type having a thickness of about 5 &mgr;m to about 7 &mgr;m.
In recent years, the cassette size of each of DVC (Digital Video Cassette) tapes among the video cassette tapes has been reduced. A longer recording operation has been required. Also in the industrial field of the tape streamer tape including D8 (Data 8 mm) and DDS (Digital Data Storage), larger capacity has been required.
To realize the long recording operation and enlargement of the capacity of the magnetic recording medium, the thickness of the base film must be reduced. Reduction in the thickness, however, encounters a problem in that the stiffness of the magnetic recording medium is decreased and the skew characteristic deteriorates.
To realize satisfactorily high stiffness and a sense amplifier skew characteristic, contradictory characteristics, that is, the base film must have high strength and resistance against heat shrinkage, must simultaneously be satisfied. Therefore, the polyethylene terephthalate film has been subjected to a re-orienting process or the like to increase the strength. Moreover, an aging process or the like has been performed to prevent heat shrinkage.
Recently the strength of the polyethylene terephthalate film is limited because the thickness of the film has furthermore been reduced. As a next generation of a base film for a high-density magnetic recording medium, an aromatic polyamide film exhibiting high strength and restrained heat shrinkage has attracted attention.
Since long-time recording and enlargement of the capacity have been realized, the magnetic recording medium must have furthermore improved characteristics. That is, the magnetic recording medium must have a furthermore improved electromagnetic conversion characteristic and a reduced error rate.
From the above-mentioned viewpoints, it is preferable that the surface of the base film is a flat mirror surface which is free from any projection. An evaporated film formed on the foregoing base film, however, suffers from unsatisfactory movement characteristic because the mirror surface of the base film is maintained. Thus, there arises a problem in that a scuff occurs and the error rate is undesirably raised owing to separation of powder from the evaporated film.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a magnetic recording medium which exhibits a satisfactory electromagnetic conversion characteristic and movement characteristic if the magnetic recording medium incorporates a non-magnetic support member constituted by an aromatic polyamide film.
To achieve the above-mentioned object, according to one aspect of the present invention, there is provided a magnetic recording medium comprising: a non-magnetic support member on which a magnetic layer constituted by a thin metal magnetic film is formed, wherein at least either main surface of the non-magnetic support member has small projections, and the either main surface of the non-magnetic support member having the small projections formed thereon has a kurtosis (Ku) which is expressed by the following equation (1) and which is 10.0 to 50.0:
Ku
=
(
1
/
SRq
4
)
·
(
1
/
n
)
∑
i
=
1
n
Yi
4
SRq
=
(
1
/
Lx
·
Ly
)
∫
0
Lx
∫
0
Ly
f
(
x
,
y
)
2
ⅆ
x
ⅆ
y
(
1
)
where f (x) is a roughness curve with respect to the central surface and Lx and Ly are lengths in the directions X and Y on the surface,
average roughness Ra at the central surface of either main surface of the non-magnetic support member is 1.0 nm to 5.0 nm, and average roughness Rz of ten points on either main surface of the non-magnetic support member is 15 nm to 50 nm.
The magnetic recording medium according to the present invention and structured as described above is arranged such that the kurtosis (Ku) of the small projections formed on either main surface of the non-magnetic support member, the average roughness of the central surface of either main surface of the non-magnetic support member and the average roughness of ten points are specified to predetermined values. The thin metal magnetic film is formed on the non-magnetic support member. The magnetic recording medium according to the present invention is characterized in that the main surface of the thin metal magnetic film has required flatness.
Note that the kurtosis Ku, the average roughness of the central surface and the average roughness of ten points are values measured by a so-called atomic force microscope (AFM). Specifically, an atomic force microscope manufactured by Digital Instruments was used to measure the foregoing values.
Other objects, features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.
REFERENCES:
patent: 11-120535 (1999-04-01), None
Resan Stevan A.
Sonnenschein Nath & Rosenthal
Sony Corporation
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