Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic phosphorus compound – wherein the phosphorus is...
Reexamination Certificate
2000-11-15
2003-05-06
Toomer, Cephia D. (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic phosphorus compound, wherein the phosphorus is...
C508S588000, C428S422000
Reexamination Certificate
active
06559108
ABSTRACT:
FIELD OF INVENTION
This invention relates to a recording medium comprising a phosphorus-containing fluorocarbon compound as lubricant.
BACKGROUND OF THE INVENTION
Magnetic disk drives, magnetic hard disks or magnetic optical disks, are devices well known to one skilled in the art for storing information. The devices can use a rotatable thin film magnetic media with data tracks, a read/write transducer for reading/writing the information on the tracks, a slider for holding the transducer to the tracks, and a flying mode above the media. Ideally, the slider can fly as close as possible to the media leaving small spacing to allow the transducer to distinguish between the magnetic field from the closely spaced regions on the disk. During operation, the transducer head slides against the surface of the disk as the disk begins to rotate. The transducer head, when the disk reaches a predetermined rotational speed, floats in air at a predetermined distance from the surface of the disk. When the operation of the disk drive terminates, the transducer head begins to slide against the surface. Such sliding repeats every time the head and disk assembly is driven.
To maintain the slider as close as possible to the media or the transducer head as close to its recording surface as possible to minimize the flying height of the head, it requires a smooth recording surface. However, excessive stiction (static coefficient of friction) and friction can result if the head surface and the recording surface are too flat. Excessive stiction and friction can cause wear to the head and recording surfaces.
A phosphorus-containing high molecular weight perfluoroalkylpolyether compound has been used as a disk drive lubricant as disclosed in U.S. Pat. No. 5,874,169.
There is a continuing need to lubricate or coat the thin film disks and sliders to ensure the regular transducer fly height. There is also a need to develop a lubricant or coating that is stable at the operating conditions of the disks as well as during the manufacture of magnetic recording media.
SUMMARY OF THE INVENTION
The invention provides a recording medium comprising a phosphorus-containing fluorocarbon compound. The phosphorus-containing fluorocarbon compound can be an esterified phosphorus compound, a salt thereof, or combinations thereof.
DETAILED DESCRIPTION OF THE INVENTION
Generally, a recording medium includes a magnetic medium (hard or flexible), magneto-optical medium, optical medium, or combinations thereof and can include either audio or video tape. A magnetic recording medium can comprise a magnetic layer on a non-magnetic substrate. The magnetic layer can comprise a protective overcoat on the magnetic layer. A lubricant can be present as a lubricant topcoat on the magnetic layer or on the protective overcoat, if present. The lubricant or lubricant topcoat comprises, consists essentially of, or consists of the phosphorus-containing fluorocarbon compound. The non-magnetic substrate, the magnetic layer, and the protective overcoat are well known to one skilled in the art. See, for example, U.S. Pat. No. 5,874,169, disclosure of which is incorporated herein by reference. Therefore the description of the non-magnetic substrate, the magnetic layer, and the protective overcoat is omitted herein for the interest of brevity. The invention disclosed herein is suitable for all recording media.
According to the invention, a magnetic recording medium comprising a phosphorus-containing fluorocarbon compound is provided. The phosphorus-containing fluorocarbon compound can be used as lubricant or as an additive to a lubricant. The phosphorus-containing fluorocarbon compound can be an esterified aryl phosphorus compound, a salt thereof, or combinations thereof.
The esterified aryl phosphorus compound can be a perfluoropolyether- or perfluoroalkyl-containing and phosphorus-containing aryl compound selected from the group consisting of Classes A, B, and C, and combinations of two or more thereof.
The Class A compound can be a perfluoropolyether- or perfluoroalkyl-containing and phosphorus-containing compound selected from the group consisting of partially esterified aryl phosphates, partially esterifled aryl phosphonates, and salts thereof, containing either (i) a mono-alkylene oxide or poly-alkylene oxide or phenylene oxide linking group between the phosphorus and a fluorocarbon group, or (ii) no linking group between the phosphorus and fluorocarbon group, and (iii) combinations of (i) and (ii). Representative compounds within Class A are shown below.
Class A(i) compounds having a mono- or poly-alkylene oxide linking group include those having formulae I, II, III, or combinations of two or more thereof.
[Rf—Y—]
(2−x)
—P(E)—[O
b
C
6
R
5
][OM]
x
(Formula I)
[Rf′—Y—]
(2−x)
—P(E)—[O
b
C
6
R
5
][OM]
x
(Formula II)
[MO]
x
[C
6
R
5
O
b
]
(2−x)
—P(E)—Y—Rf″—Y—P(E)—[O
b
C
6
R
5
]
(2−x)
[OM]
x
(Formula III)
where:
Y is (CH
2
)
z
O(CH
2
CH
2
O)
z′
, wherein z is 1 to 4 and z′ is 0, 1 or 2, or Y is C
6
R
4
,
x is 0.05 to 1,
E is oxygen or sulfur,
b is 0 or 1,
R is the same or different substituent chosen from hydrogen, halogen, alkyl, aryl, nitro, cyano, alkoxy, primary and secondary amino, sulfonyl, carboxyl, or phenoxy, and
M is hydrogen, alkali metal, alkaline earth metal, or ammonium.
Rf is a polyether chain having a molecular weight ranging from 400 to 15,000 and composed of repeating units selected from the group consisting of:
J—O—(CF(CF
3
)CF
2
O)
c
—(CFXO)
d
—CFZ where:
J is a fluoroalkyl group selected from the group consisting of CF
3
, C
2
F
5
, C
3
F
7
, CF
2
Cl, C
2
F
4
Cl, and C
3
F
6
Cl,
X is —F or —CF
3
,
Z is —F, —Cl or —CF
3
, and
c and d are numbers such that the c/d ratio ranges from 0.01 to 0.5, and the molecular weight ranges from 400 to 15,000;
J
1
—O—(CF
2
CF
2
O)
e
—(CF
2
O)
f
—CFZ
1
where:
J
1
is a fluoroalkyl group selected from the group consisting of CF
3
, C
2
F
5
, CF
2
Cl, and C
2
F
4
Cl,
Z
1
is —F or —Cl, and
e and f are numbers such that the e/f ratio ranges from 0.5 to 2 and, the molecular weight ranges from 400 to 15,000;
J
2
—O—(CF(CF
3
)CF
2
O)
j
—CF(CF
3
) where:
J
2
is C
2
F
5
or C
3
F
7
, and
j is a number such that the molecular weight ranges from 400 to 15,000;
J
3
—O—(CQZ
2
—CF
2
CF
2
—O)
k
—CQZ
2
—CF
2
where:
J
3
is selected from the group consisting of CF
3
, C
2
F
5
, and C
3
F
7
,
Q and Z
2
, equal or different, are F, Cl or H, and
k is a number such that the molecular weight ranges from 400 to 15,000;
J
4
—O—(CF
2
CF
2
O)
1
—CF
2
where:
J
4
is CF
3
, or C
2
F
5
and
1 is a number such that the molecular weight ranges from 400 to 15,000;
J
5
—(CF(CF
3
)CF
2
O)
g
—(CF
2
CF
2
O)
h
—(CFX—O)
i
—CFZ— where:
X and Z are as defined above, and
g, h and i are numbers such that (g+h) ranges from 1 to 50, the i/(g+h) ratio ranges from 0.1 to 0.05, and the molecular weight is from 400 to 15,000;
Rf′ is Z
2
—(CF
2
)
m
where:
Z
2
is H, F, or Cl, and
m has a value from 2 to 20; and
Rf″ is a perfluoropolyether chain having a number average molecular weight of 500 to 15,000, selected from the group consisting of:
(i) (CF
2
CF
2
O)
n
—(CF
2
O)
o
—CF
2
wherein the units with formulae C
2
F
4
O and CF
2
O are randomly distributed along the chain, and n and o are integers, whose ratio, n/o, is in the range of from 0.3 to 5;
(ii) (C
3
F
6
O)
p
—(CF
2
CF
2
O)
q
—(CFXO)
r
—CF
2
wherein
X is F or CF
3
and
p, q and r are numbers such that (p+q) ranges from 1 to 50, and the r/(p+q) ratio ranges from 0.1 to 0.05, and the molecular weight is from 400 to 15,000;
(iii) ((CQZ
2
)CF
2
CF
2
O)
s
—CF
2
—CF
2
where
Q and Z
2
, equal or different, are F, Cl or H, and s is a number such that the molecular weight ranges from 400 to 15,000; and
(iv) (CF
2
O)—(CF
2
CF
2
O)
t
—CF
2
where t is a number such that the molecular weight ranges from 400 to 15,000.
Representative compounds within Class A(i) include:
For F
Gao Charles
Gitis Norm V.
Howell Jon Lee
Huffmann Anthony Joseph
Jones David Gareth Vaughan
E.I. du Pont de Nemours and Company
Toomer Cephia D.
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