Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
1998-09-28
2001-02-13
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
C508S465000, C508S504000, C508S509000, C508S524000, C560S184000, C428S900000
Reexamination Certificate
active
06187724
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a lubricant composition useful for producing a magnetic recording medium, etc., and a magnetic recording medium obtained by use of said lubricant composition.
In the field of magnetic recording, improvements, such as digitization, miniaturization, long-time running, etc. are in progress, so that there is a growing demand for enhancement of the density of recording media. In particular, thin metal film type recording media having a magnetic recording layer composed of a thin ferromagnetic metal layer have been vigorously investigated in recent years because they are very advantageous for recording at a short wavelength.
In such circumstances, lubricants for magnetic recording medium are also noted and it has turned out that the performance characteristics of a magnetic recording medium itself can be improved by improving the lubricant.
For example, carboxylic acid esters have been known as the lubricants for magnetic recording medium. However, they involve, for example, the following problem: particularly when they are stored at high temperature and humidity, water repellency of the lubricant layer is reduced, and thus water tends to penetrate into the lubricant layer, as a result of which adhesion of the lubricant is weakened and the lubricant itself is coagulated, and hence the original characteristics of the lubricant cannot be maintained any longer.
Fluorocarboxylic acids and esters derived there-from involves, for example, the following problems: the fluorocarboxylic acids damage the surface of a magnetic recording layer or the surface of a protecting layer constituting the magnetic recording medium because they are strong acids; the derived esters are easily hydrolyzable and are not sufficient in weather resistance; synthesis of useful fluorocarboxylic acids having a large number of carbon atoms is difficult; and fluorocarboxylic acids having a relatively small number of carbon atoms and esters derived therefrom are not sufficient in friction-reducing effect, namely, they impart only insufficient running durability.
Ester type lubricants obtained from a mono-carboxylic acid and a perfluoroalkyl alcohol (JP-A 62-256218) have a relatively small cross sectional area of the molecule because of a polar group, a carbonyl group, in its molecule. Therefore, they are advantageous in that they can easily cover the surface of a magnetic layer or the surface of a protective layer constituting a magnetic recording medium. They, however, are disadvantageous in that sufficient exhibition of their lubricating effect is difficult because the alkyl group in the molecule is oriented in such a way as being inclined to the surface of the magnetic layer or protective layer.
Ester type lubricants obtained from a dicarboxylic acid and a fluoroalkyl alcohol (JP-A 5-128498, JP-A 5-282662 and JP-B 6-28717) are advantageous in that since molecules of the lubricant are adsorbed and oriented on the surface by two polar groups per molecule, the alkyl group in the molecule is hardly oriented in such a way as being inclined to the surface, so that the lubricant easily exhibits its lubricating effect. On the other hand, the lubricants are disadvantageous in that the cross sectional area of the lubricant molecule becomes relatively large because of the two polar groups and hence it becomes difficult to cover the surface by the lubricant molecule. In addition, when cooled to room temperature after storage at high temperature and humidity, the lubricants are recrystallized in some cases because of their strong tendency to molecular orientation, which causes deterioration of the weather resistance of the magnetic recording medium. Moreover, the lubricants are disadvantageous also in that the molecular weight of the lubricants is rather high due to their structure, and thus in magnetic recording mediums using these lubricants, still characteristics are lowered at a low temperature range.
BRIEF SUMMARY OF THE INVENTION
The present invention has been accomplished under such circumstances as above, and an object of the present invention is to provide a lubricant composition capable of producing a magnetic recording medium free from the above-mentioned defects and excellent in running durability, still life and weather resistance, and also to provide a magnetic recording medium using said lubricant composition.
The present invention provides a lubricant composition comprising
(A) a compound of the formula:
R
1
—COO—R
2
[1]
wherein R
1
is a higher aliphatic hydrocarbon residue which may have one or more fluorine atoms; and R
2
is an aliphatic hydrocarbon residue which may have one or more fluorine atoms or oxygen atoms or both, and
(B) a compound of the formula:
wherein R
3
is a higher aliphatic hydrocarbon residue which may have one or more fluorine atoms; and R
4
and R
5
are independently a hydrogen atom or an aliphatic hydrocarbon residue which may have one or more fluorine atoms or oxygen atoms or both, provided that at least one of R
4
and R
5
is an aliphatic fluorohydrocarbon residue which may have one or more oxygen atoms.
The present invention also provides a magnetic recording medium using said lubricant composition as a lubricant layer therein.
DETAILED DESCRIPTION OF THE INVENTION
The lubricant composition of the present invention comprises a compound of the formula:
R
1
—COO—R
2
[1]
wherein R
1
is a higher aliphatic hydrocarbon residue which may have one or more fluorine atoms; and R
2
is an aliphatic hydrocarbon residue which may have one or more fluorine atoms or oxygen atoms or both, and a compound of the formula:
wherein R
3
is a higher aliphatic hydrocarbon residue which may have one or more fluorine atoms; and R
4
and R
5
are independently a hydrogen atom or an aliphatic hydrocarbon residue which may have one or more fluorine atoms or oxygen atoms or both, provided that at least one of R
4
and R
5
is an aliphatic fluorohydrocarbon residue which may have one or more oxygen atoms.
The present inventors have earnestly investigated lubricants capable of producing a high-performance magnetic recording medium to reach such finding that the above-mentioned problems in the conventional lubricants can be solved by using a lubricant composition comprising a compound of the formula [1] and a compound of the formula [2], and on the basis of this finding the present invention has been accomplished.
In the formula [1], the higher aliphatic hydrocarbon residue represented by R
1
, i.e., the higher aliphatic hydrocarbon residue which may have one or more fluorine atoms may be either straight-chain or branched, among which the straight-chain is preferable. As the higher aliphatic hydrocarbon residue, there can be exemplified ones having generally 6 to 24 carbon atoms, preferably 8 to 24 carbon atoms, more preferably 11 to 24 carbon atoms. The aliphatic hydrocarbon residue may have 1 to 4 double bonds, preferably one or two double bonds therein. Specific examples of the higher aliphatic hydrocarbon residue are an alkyl group such as an n-hexyl group, an isohexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, an octadecyl group, an icosyl group, a docosyl group, or a tetracosyl group; an aliphatic hydrocarbon residue having 1 to 4 double bonds (i.e. an alkenyl group, an alkadienyl group, an alkatrienyl group or an alkatetraenyl group) such as an oleyl group, or a linoleyl group. As the higher aliphatic fluorohydrocarbon residue containing one or more fluorine atoms, there can be exemplified those obtained by replacing generally 1 to 41, preferably 2 to 18 of the hydrogen atoms of the above-exemplified higher aliphatic hydrocarbon residue by fluorine atoms. In the present specification, each aliphatic fluorohydrocarbon residue exemplified hereinafter is one which has one to a predetermined number of F atoms. But, R
1
does not include a perfluorohydrocarbon group. Specific example
Hayashi Takahiro
Ikarashi Tsunehiko
Iritani Takehiko
Kanazawa Hiromichi
Kobayashi Koji
Medley Margaret
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Toomer Cephia D.
Wako Pure Chemical Industries Ltd.
LandOfFree
Lubricant composition and magnetic recording medium using... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lubricant composition and magnetic recording medium using..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lubricant composition and magnetic recording medium using... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2575612