Stock material or miscellaneous articles – Composite – Of fluorinated addition polymer from unsaturated monomers
Reexamination Certificate
2000-01-14
2001-10-16
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of fluorinated addition polymer from unsaturated monomers
C428S422000, C428S690000, C428S690000, C428S900000, C508S421000, C508S459000, C508S496000, C508S564000, C508S582000
Reexamination Certificate
active
06303227
ABSTRACT:
TECHNICAL FIELD
The present invention relates to: a lubricant composition exhibiting an excellent lubricity; a magnetic recording medium having a ferromagnetic metal thin film as a magnetic recording layer, a carbon film thereon, and further a lubricant layer thereon, which is most suitable, for example, for a digital video tape recorder and a highly fine video tape recorder; and a method for producing the same.
BACKGROUND ART
In recent years, in the field of magnetic recording, with the improvement in performance of recording and reproducing equipment such as digitalization, scale reduction, and elongation of time for use, development of a highly dense magnetic recording medium suitable therefor is actively taking place. Recently, a metal thin film type magnetic recording medium, which is extremely advantageous for a short wave length recording, is put into practical use in lieu of an application type magnetic recording medium.
However, since a magnetic layer of a metal thin film type magnetic recording medium has an extremely good surface property, i.e. a small roughness on the surface, it contacts with a magnetic head in broader area, and, as the result, it is liable to be abraded by receiving a great friction force while being in a rapid sliding movement with the magnetic head during a process of recording/reproducing signals. Abrasion of the magnetic layer greatly affects the running durability, the still durability, or the like, so that reduction of the abrasion of the magnetic layer is a great object in the research and development of a metal thin film type magnetic recording medium.
Therefore, an attempt is made to reduce the abrasion by disposing a lubricant layer on a magnetic layer surface to improve the running durability and the still durability. In the case where the lubricant layer is disposed, the lubricant layer on the magnetic layer surface is requested to exhibit a lubricating property with a thickness as small as several nanometers in order to prevent the output reduction caused by a spacing loss between the magnetic recording medium and the magnetic head as much as possible for achieving a high output. Accordingly, use of a fluorine-based compound exhibiting an excellent lubricating property is widely studied and use of various compounds is proposed.
For example, use of a fluorine-containing long chain carboxylic acid ester (See Japanese Laid-open Patent Publication No. 62-46431/1987) represented by the following chemical formula (X):
C
18
H
35
OCOC
9
F
17
(X)
or a fluorine-containing carboxylic acid monoester having a carboxyl group (See Japanese Laid-open Patent Publication No. 61-107529/1986) represented by the following chemical formula (Y):
or the like, is proposed.
However, the request concerning the improvement of the performance of the magnetic recording medium is demanding, and it is difficult to obtain a sufficient lubricity with the aforementioned conventional lubricants, so that a further improvement of the running durability and the still durability for the magnetic recording medium is desired.
DISCLOSURE OF THE INVENTION
In view of the aforementioned problems, the present invention provides a lubricant composition that makes it possible to obtain a magnetic recording medium which is excellent in running durability and still durability and has a high practical reliability without deteriorating the electromagnetic conversion characteristics. Further, the present invention provides a magnetic recording medium using the lubricant composition, and a production method thereof.
A lubricant composition of the present invention, which is the first invention, comprises two or more kinds of specific fluorine-containing compounds as described later. For example, if this lubricant composition is comprised in the lubricant layer of a magnetic recording medium, it allows the magnetic recording medium to exhibit an excellent running durability and an excellent still durability without deteriorating its electromagnetic conversion characteristics, since the adhesion strength of the lubricating layer to a carbon film located thereunder is improved and an excellent lubricating property is imparted to the magnetic recording medium. The present specification discloses various lubricant compositions which provide these effects.
The first lubricant composition of the present invention is characterized by comprising:
at least one compound compounds having a perfluoroalkyl group or a perfluoropolyether group, and an alkyl group or an alkenyl group in a molecule, which compound is selected from a group of consisting of compounds represented by the following general formulae (a) and (b):
wherein R
1
is an alkyl group or an alkenyl group, R
2
is a perfluoroalkyl group or a perfluoropolyether group, “a” is an integer of 0 to 20, and “b” is 0 or 1; and
wherein R
3
is an alkyl group or an alkenyl group, R
4
is a perfluoroalkyl group or a perfluoropolyether group, R
5
is O or S, “c” is an integer of 0 to 20, and “d” is 0 or 1; and
at least one compound having a perfluoropolyether group in a molecule, which compound is selected from a group consisting of compounds represented by the following general formulae (c), (d), and (e):
HOCH
2
CF
2
(OC
2
F
4
)
e
(OCF
2
)
g
OCF
2
CH
2
OH (c)
wherein “e” and “g” each are integers of not less than 1;
HOOCCF
2
(OC
2
F
4
)
i
(OCF
2
)
j
OCF
2
COOH (d)
wherein “i” and “j” each are integers of not less than 1; and
R
6
COOCH
2
CF
2
(OC
2
F
4
)
k
(OCF
2
)
p
OCF
2
CH
2
OCOR
6
(e)
wherein “k” and “p” each are integers of not less than 1, and R
6
is an alkyl group having 4 to 22 carbon atoms.
Each of the compounds represented by the general formulae (a) to (e) is a fluorine-containing compound. This lubricant composition comprises at least one compound selected from a group consisting of fluorine-containing monocarboxylic acids represented by the general formulae (a) and (b), and at least one compound selected from a group consisting of fluorine-containing diols represented by the general formula (c), fluorine-containing dicarboxylic acids represented by the general formula (d), and fluorine-containing diesters represented by the general formula (e). Here, the compounds represented by the general formula (a) may also be referred to as fluorine-containing carboxylic acid monoesters having one carboxyl group.
If this composition is comprised in a lubricant layer of a magnetic recording medium having a ferromagnetic metal thin film, a carbon film, and a lubricant layer formed in this order on a non-magnetic substrate (hereinafter such a magnetic recording medium may be simply referred to as a metal thin film type magnetic recording medium), the adhesion strength of the lubricant layer to the carbon film is improved, and an excellent lubricity is imparted to the magnetic recording medium. Further, a synergistic effect of these makes it possible to obtain a magnetic recording medium having a high practical reliability with improved running durability and still durability without deteriorating the electromagnetic conversion characteristics.
The second lubricant composition of the present invention is characterized by comprising at least one compound selected from compounds represented by the aforementioned general formula (a) and at least one compound selected from compounds represented by the aforementioned general formula (b).
This lubricant composition comprises at least one fluorine-containing monocarboxylic acid (or a fluorine-containing carboxylic acid monoester having one carboxyl group) represented by the general formula (a), and at least one fluorine-containing monocarboxylic acid represented by the general formula (b). This composition also provides an effect similar to that of the aforementioned first lubricant composition.
The third lubricant composition of the present invention is characterized by comprising at least one compound selected from compounds represented by the aforementioned general formula (a) wherein R
2
is a perfluoroalkyl group, and at least one compound selecte
Fuchi Tetuo
Kuwahara Kenji
Murai Mikio
Ohchi Yukikazu
Matsushita Electric - Industrial Co., Ltd.
Resan Stevan A.
Wenderoth , Lind & Ponack, L.L.P.
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