U.S. patent application number 10/141217 was filed with the patent office on 2003-07-24 for lubricant for thin film storage media.
This patent application is currently assigned to Seagate Technology LLC. Invention is credited to Gui, Jing, Liu, Jianwei, Stirniman, Michael Joseph.
Application Number | 20030138670 10/141217 |
Document ID | / |
Family ID | 26838901 |
Filed Date | 2003-07-24 |
United States Patent
Application |
20030138670 |
Kind Code |
A1 |
Liu, Jianwei ; et
al. |
July 24, 2003 |
Lubricant for thin film storage media
Abstract
Embodiments relate to lubricants disposed over magnetic storage
media, such as rotatable thin film magnetic discs. One embodiment
comprises a lubricant compound of a fluoropolyether chain having
one or more carbonyl-imide pairs. For example, the carbonyl-imide
pair may be located at one end, both ends, and/or in the middle of
the fluoropolyether chain.
Inventors: |
Liu, Jianwei; (Fremont,
CA) ; Stirniman, Michael Joseph; (Fremont, CA)
; Gui, Jing; (Fremont, CA) |
Correspondence
Address: |
Edward P. Heller, III
MOSER, PATTERSON & SHERIDAN, LLP
Suite 250
350 Cambridge Avenue
Palo Alto
CA
94306-1553
US
|
Assignee: |
Seagate Technology LLC
|
Family ID: |
26838901 |
Appl. No.: |
10/141217 |
Filed: |
May 7, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60347161 |
Jan 9, 2002 |
|
|
|
Current U.S.
Class: |
428/835.8 ;
428/841.3; G9B/5.275; G9B/5.28; G9B/5.3 |
Current CPC
Class: |
G11B 5/7257 20200801;
C10N 2040/18 20130101; C10M 2215/2203 20130101; C10N 2030/06
20130101; C10M 105/70 20130101; G11B 5/71 20130101; G11B 5/7266
20200801; C10N 2020/04 20130101; G11B 5/8408 20130101; Y10T 428/265
20150115; Y10T 428/3154 20150401 |
Class at
Publication: |
428/695 ;
428/694.0BP |
International
Class: |
G11B 005/72 |
Claims
1. A lubricant compound, comprising: a fluoropolyether chain; and
one or more carbonyl-imide pairs.
2. The lubricant compound of claim 1, wherein the one or more
carbonyl-imide pairs comprise a nitrogen of an imide group linked
to an alpha position carbon of a carbonyl group.
3. The lubricant compound of claim 2, wherein one carbonyl-imide
pair is located at one end of the fluoropolyether chain.
4. The lubricant compound of claim 3, wherein another
carbonyl-imide pair is located at the other end of the
fluoropolyether chain.
5. The lubricant compound of claim 2, wherein at least one
carbonyl-imide pair is located within the fluoropolyether
chain.
6. The lubricant compound of claim 3, wherein at least one
carbonyl-imide pair is located within the fluoropolyether
chain.
7. The lubricant compound of claim 2, wherein each carbonyl-imide
pairs is represented by the formula selected from the group
including: R.sup.1.dbd.N--(CR.sup.2R.sup.3)--(CO)--, wherein
R.sup.1, R.sup.2, and R.sup.3 are the same or different and may be
an alkyl, alkenyl, alkoxy, aryl, aryloxy, arlyalkyl, arlyalkenyl,
amine, imine, aromatic, or hetero cyclic aromatic group;
R.sup.4.dbd.N--(NR.sup.5)--(CO)--, wherein R.sup.4 and R.sup.5 are
the same or different and may be an alkyl, alkenyl, alkoxy, aryl,
aryloxy, arlyalkyl, arlyalkenyl, amine, imine, aromatic, or hetero
cyclic aromatic group; R.sup.6--N.dbd.(CR.sup.7)--(CO)--, wherein
R.sup.6 and R.sup.7 are the same or different and may be an alkyl,
alkenyl, alkoxy, aryl, aryloxy, arlyalkyl, arlyalkenyl, amine,
imine, aromatic, or hetero cyclic aromatic group;
R.sup.8--N.dbd.N--(CO)--, wherein R.sup.8 may be an alkyl, alkenyl,
alkoxy, aryl, aryloxy, arlyalkyl, arlyalkenyl, amine, imine,
aromatic, or hetero cyclic aromatic group; and
--(C.dbd.O)--R.sup.21.dbd.N--R.sup.22--(C.dbd.O)--, wherein
R.sup.21 and R.sup.22 are the same or different and may be an
alkyl, alkenyl, alkoxy, aryl, aryloxy, arlyalkyl, arlyalkenyl,
amine, imine, aromatic, or hetero cyclic aromatic group.
8. The lubricant compound of claim 7, wherein each carbonyl-imide
pair is selected from the group including 2-pyridinecarbonyl,
2-quinolinecarbonyl, 3-isoquinolinecarbonyl, 2-pyrimidinecarbonyl,
2-quinazolinecarbonyl, 4-quinazolinecarbonyl, 1-pyrazolecarbonyl,
1-benzopyrazolecarbonyl, 2-benzopyrazolecarbonyl,
2-imidazolecarbonyl, 2-benzimidazolecarbonyl,
2,6-pyridine-biscarbonyl, and derivatives thereof.
9. A method of manufacturing a magnetic storage medium, comprising:
forming a protective overcoat over a magnetic layer of the magnetic
storage medium; and applying a lubricant topcoat over the
protective overcoat, the lubricant topcoat comprising
fluoropolyether having one or more carbonyl-imide pairs.
10. The method of claim 9, wherein the fluoropolyether is
fractionated prior to application over the protective overcoat.
11. The method of claim 9, wherein the lubricant topcoat is
post-treated after application over the protective overcoat.
12. The method of claim 9, wherein the protective overcoat
comprises carbon.
13. The method of claim 9, wherein the fluoropolyether is prepared
by reacting a fluoropolyether chain having one or more
functionalized end-groups with a imine compound to form the one or
more carbonyl-imide pairs, wherein the one or more carbonyl-imide
pairs comprise a nitrogen of an imide group linked to an alpha
position carbon of a carbonyl group.
14. A magnetic storage medium, comprising: a carbon-overcoated
magnetic layer; and a lubricant topcoat formed over the
carbon-overcoated magnetic layer, the lubricant topcoat comprising
fluoropolyether having one or more carbonyl-imide pairs.
15. The magnetic storage medium of claim 14, wherein the lubricant
topcoat is formed to a thickness between about 10 angstroms and
about 30 angstroms.
16. The magnetic storage medium of claim 14, wherein the average
molecular weight of the fluoropolyether is between about 2,000 and
about 6,000 Daltons.
17. A magnetic storage medium, comprising: a carbon-overcoated
magnetic disc; and a lubricant means for blocking catalytic metal
sites, the lubricant means formed over the carbon-overcoated
magnetic disc.
18. The magnetic storage medium of claim 17, wherein the lubricant
means comprises a composition of a single class of compounds.
19. The magnetic storage medium of claim 17, wherein the lubricant
means comprising a lubricating polymer backbone and a catalytic
blocking functional group incorporated into the polymer
backbone.
20. The magnetic storage medium of claim 17, wherein the lubricant
means is in a single phase.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. provisional patent
application Ser. No. 60/347,161, filed Jan. 9, 2002, which is
herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention generally relate to
lubricants. More particularly, embodiments relate to lubricants
disposed over magnetic storage media, such as rotatable thin film
magnetic discs.
[0004] 2. Description of the Related Art
[0005] Information storage systems, such as disk drive memory
systems, have been used in computers and other data processing
devices for many years for storage of digital information.
Typically, information is recorded on concentric memory tracks of a
rigid magnetic storage medium, such as a disc, the actual
information being stored in the form of magnetic transitions within
the medium. The disc is typically comprised of a thin rigid
substrate, an underlayer, a magnetic layer, and a protective
overcoat. The discs are rotatably mounted on a spindle, the
information being accessed by means of transducers located on a
pivoting arm which moves radially over the surface of the disc. The
read/write heads or transducers must be accurately aligned with the
storage tracks on the disc to ensure proper reading and writing of
information.
[0006] In the operation of typical disk drives, the read/write head
slides against the surface of the disc as the disc starts to
rotate. Upon reaching a predetermined rotational speed, the head
floats in air at a predetermined distance from the surface of the
disc where the head is maintained during reading and recording
operations. The read/write head floats very close to the surface of
the disc during movement to maximize the signal quality. Due to the
spacing closeness, the head can make intermittent contact with the
disc surface. The head also slides on the disc as the disc rotation
stops.
[0007] To reduce the wear and material interaction on the surface
of the disc, the disc further includes a lubricant topcoat
typically applied over the protective overcoat. The lubricant is
intended to reduce the wear of the interface between the read-write
head and the disc, especially during start/stop cycles in which the
head is in contact with the disc. The lubricant system typically
comprises a mixture of a perfluoropolyether, such as "FOMBLIN .RTM.
Z-DOL" available from Ausimont U.S.A., a subsidiary of Montedison
S.P.A. of Milan, Italy, and a catalytic blocking agent, such as the
hexaphenoxy compound "X-1P" available from The Dow Chemical Company
of Midland, Mich. The perfluoropolyether provides lubrication of
the disc while the catalytic blocking agent prevents catalytic
decomposition of the perfluoropolyether. It is believed that the
catalytic blocking agent prevents exposed metal sites of the head
or of the disc from reacting with the perfluoropolyether.
[0008] One problem with the lubricant system including a mixture of
a lubricant compound, such as a perfluoropolyether, and a catalytic
blocking agent, such as a hexaphenoxy compound, is that the
catalytic blocking agent may be immiscible with the lubricant
compound and may form droplets of the catalytic blocking agent on
the lubricant compound. This "phase separation" between the
lubricant compound and the catalytic blocking agent may cause
reduced protection of the lubricant compound by the catalytic
blocking agent. Moreover, the droplets of the catalytic blocking
agent at the surface of the disc may perturb the head during
operation of the disk drive, thus, causing the head to improperly
read or write to the disc.
[0009] Therefore, there is a continuing need for an improved
lubricant system to be used with magnetic storage media.
SUMMARY OF THE INVENTION
[0010] Embodiments relate to lubricants disposed over magnetic
storage media, such as rotatable thin film magnetic discs. One
embodiment comprises a lubricant compound of a fluoropolyether
chain having one or more carbonyl-imide pairs. In one aspect, the
carbonyl-imide pair may be located at one end, both ends, and/or in
the middle of the fluoropolyether chain. Another embodiment
comprises a method of manufacturing a magnetic storage medium
comprising forming a protective overcoat over a magnetic layer of
the magnetic storage medium. Then, a lubricant topcoat is applied
over the protective overcoat. The lubricant topcoat may comprise a
fluoropolyether having one or more carbonyl-imide pairs. Still
another embodiment comprises a magnetic storage medium including a
carbon-overcoated magnetic layer and a lubricant topcoat formed
over the carbon-overcoated magnetic layer. The lubricant topcoat
may comprise a fluoropolyether having one or more carbonyl-imide
pairs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] So that the manner in which the above recited features of
the present invention are attained and can be understood in detail,
a more particular description of the invention, briefly summarized
above, may be had by reference to the embodiments thereof which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0012] FIG. 1 is a simplified schematic top plan view of one
exemplary embodiment of an information storage system.
[0013] FIG. 2 is a schematic cross-sectional view of one exemplary
embodiment of a magnetic storage medium.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0014] FIG. 1 is a simplified schematic top plan view of one
exemplary embodiment of an information storage system 10. The
information storage system 10 may include a sealed housing 12, a
magnetic storage medium 14 which is usually in the form of a disc
or discs, a read/write head 16, and an actuator assembly 17. The
actuator assembly 17 may include an actuator arm 18 for positioning
the read/write head 16 disposed at the end of the actuator arm 18
over the surface of the storage medium 14. Multiple read/write
heads may also be employed. The read/write head 16 carries a
read/write element, which can be any type of read/write element
known in the art, such as inductive thin film, MIG or MR. The
storage medium 14, such as a disc or discs, may be mounted to a
spindle motor 10 which spins the storage medium 14. The information
storage system 10 may include a header assembly 22 to transfer
electronic signals to and from a motor 24 which positions the
actuator and the read/write head 16 as data is transferred to and
from the storage medium 14. The information storage system 10 may
be employed with a computer, printer or fax machine or other host
system. Other embodiments of an information storage system may also
be used.
[0015] FIG. 2 is a schematic cross-sectional view of one exemplary
embodiment of a magnetic storage medium 102. The magnetic storage
medium 102 includes a substrate 104. The substrate 104 typically
comprises an aluminum (Al) alloy material, such as an
aluminum-magnesium (Al-Mg) alloy, plated with an amorphous
nickel-phosphorus layer. Alternatively, the substrate 104 may
comprise other materials, such as glass, glass-ceramic, graphite
materials, other materials, and combinations thereof. The substrate
104 may be textured or untextured. An underlayer 106, such as a
chromium (Cr) or chromium alloy underlayer, may be formed over each
side of the substrate 104. The underlayer 106 may be applied as a
composite comprising a plurality of sub-layers 106A. A magnetic
layer 108, such as a cobalt alloy magnetic layer, may be formed
over the underlayer 106. A protective overcoat 110, such as a
carbon overcoat, may be formed over the magnetic layer. The carbon
overcoat may also incorporate other elements, such as hydrogen
and/or nitrogen. A lubricant topcoat 112, such as a lubricant
topcoat comprising the lubricant composition described in greater
detail below, may be formed over the protective overcoat 110. The
surface of the magnetic storage medium 112 may be textured or
untextured. Also, separate textured data and landing zones may be
provided on the surface of the disc. As shown in FIG. 2, the
magnetic storage medium 112 includes thin film layers deposited on
each side of the substrate 104. In other embodiments, thin film
layers may be deposited on one side of the substrate 104. Other
embodiments of a magnetic storage medium may also be used.
[0016] The lubricant composition, such as the lubricant composition
of the lubricant topcoat in FIG. 2, includes a lubricant compound
comprising a fluoropolyether chain having at least one
carbonyl-imide pair. Preferably, the carbonyl-imide pair is a
carbonyl-imide pair in which the nitrogen of the imide group is
linked to the alpha position carbon of the carbonyl group. One
embodiment of the lubricant compound comprises a fluoropolyether
chain having a carbonyl-imide pair at one end of the
fluoropolyether chain having the general structure of the
formula:
Cl.sup.1-FPE.sup.1 (1)
[0017] in which Cl.sup.1 represents a carbonyl-imide pair and
FPE.sup.1 represent a fluoropolyether chain. Another embodiment of
the lubricant compound comprises a fluoropolyether chain having a
carbonyl-imide pair at both ends of the fluoropolyether chain
having the general structure of the formula:
Cl.sup.2-FPE.sup.2-Cl.sup.3 (2)
[0018] in which Cl.sup.2 and Cl.sup.3 each represents a
carbonyl-imide pair, which may be the same or different, but are
preferably the same, and in which FPE.sup.2 represent a
fluoropolyether chain.
[0019] In regards to formula (1) and formula (2), Cl.sup.1,
Cl.sup.2, and Cl.sup.3 may each be any carbonyl-imide pair,
preferably any carbon-imide pair having the nitrogen of the imide
group linked to the alpha position carbon of the carbonyl group.
Preferred embodiments of Cl.sup.1, Cl.sup.2, and Cl.sup.3 may each
comprise a carbonyl-imide pair, having the nitrogen of the imide
group linked to the alpha position carbon of the carbonyl group,
represented by the general structure of the formula of
R.sup.1.dbd.N--(CR.sup.2R.sup.3)--(CO)--,
R.sup.4.dbd.N--(NR.sup.5)--(- CO)--,
R.sup.6--N.dbd.(CR.sup.7)--(CO)--, or R.sup.8--N.dbd.N--(CO)-- in
which R.sup.1 to R.sup.8 are the same or different and may be an
alkyl, alkenyl, alkoxy, aryl, aryloxy, arlyalkyl, arlyalkenyl,
amine, imine, aromatic, or hetero cyclic aromatic group. R.sup.1 to
R.sup.8 may be substituted or unsubstituted. Preferably, R.sup.1
and R.sup.2, R.sup.1 and R.sup.3, R.sup.4 and R.sup.5, or R.sup.6
and R.sup.7 together with the atoms binding them form a ring or
rings system. More preferably, R.sup.1 and R.sup.2, R.sup.1 and
R.sup.3, R.sup.4 and R.sup.5, or R.sup.6 and R.sup.7 together with
the atoms binding them form an aromatic ring or rings system.
[0020] Examples of preferred embodiments of the carbonyl-imide
pairs of Cl.sup.1, Cl.sup.2, and/or Cl.sup.3 having the general
structure of the formula of
R.sup.1.dbd.N--(CR.sup.2R.sup.3)--(CO)--,
R.sup.4.dbd.N--(NR.sup.5)--(CO)--,
R.sup.6--N.dbd.(CR.sup.7)--(CO)--, R.sup.8--N.dbd.N--(CO)-- include
the following:
[0021] (A) 2-pyridinecarbonyl 1
[0022] (B) 2-quinolinecarbonyl 2
[0023] (C) 3-isoquinolinecarbonyl 3
[0024] (D) 2-pyrimidinecarbonyl 4
[0025] (E) 2-quinazolinecarbonyl 5
[0026] (F) 4-quinazolinecarbonyl 6
[0027] (G) 1-pyrazolecarbonyl 7
[0028] (H) 1-benzopyrazolecarbonyl 8
[0029] (I) 2-benzopyrazolecarbonyl 9
[0030] (J) 2-imidazolecarbonyl 10
[0031] (K) 2-benzimidazolecarbonyl 11
[0032] in which each R group may be the same or different and may
be a hydrogen atom, halogen atom, alkyl, haloalkyl, alkenyl,
haloalkenyl, alkoxy, haloalkoxy, aryl, haloaryl, arylalky,
haloarylalky group, or other possible substituents.
[0033] In regards to formula (1) and formula (2), the
fluoropolyether chain of FPE.sup.1 and FPE.sup.2 may be any
fluoropolyether chain. In general, the fluoropolyether chain of
FPE.sup.1 and FPE.sup.2 each comprise a chain having a middle
section comprising perfluoroether units and end sections comprising
any functional group. For example, FPE.sup.1 and FPE.sup.2 may each
be represented by the general structure having the formula
--R.sup.11--(OR .sup.12).sub.w--(OR.sup.13).sub.x--(OR.sup.14).su-
b.y--O--R.sup.15 in which R.sup.12, R.sup.13, R.sup.14, are the
same or different and may be a fluoroalkyl or perfluoroalkyl group,
preferably a C.sub.1-4 fluoroalkyl or perfluoroalkyl group. W may
be between 1 and 500. X and Y are the same or different and may be
between 0 and 500. R.sup.11 comprises any functional group, such as
one or more perfluoroether units, one or more partially fluorinated
ether units, one or more non-fluorinated ether units, one or more
hydroxy units, one or more fluoroalkyl units, one or more
fluoroalkenyl units, other suitable functional groups, and
combinations thereof. For FPE.sup.1, R.sup.15 may be a hydrogen,
carboxylate, alkyl, haloalkyl, aryl, haloaryl, arylalky,
haloarylalky, or piperonyl group. For FPE.sup.2, R.sup.15 comprises
any functional group, such as one or more perfluoroether units, one
or more partially fluorinated ether units, one or more
non-fluorinated ether units, one or more hydroxy units, one or more
fluoroalkyl units, one or more fluoroalkenyl units, other suitable
functional groups combinations thereof. Examples of preferred
embodiments of the fluoropolyether chain of FPE.sup.1 and FPE.sup.2
include a fluoropolyether chain having one or more of the following
groups: (--O--CF.sub.2).sub.n; (--O--CF.sub.2--CF.sub.2).sub.n;
(--O--CF.sub.2--CF.sub.2--CF.sub.2).sub.- n;
(--O--CF.sub.2--CF(CF.sub.3)).sub.n. For FPE.sup.1, such
fluoropolyether chains preferably include:
[0034]
--OCH.sub.2CF.sub.2--(O--CF.sub.2).sub.p--(O--CF.sub.2--CF.sub.2).s-
ub.q--OCF.sub.2CH.sub.2--OH; and
[0035]
--OCH.sub.2CF.sub.2--(O--CF.sub.2--CF.sub.2).sub.q--(O--CF.sub.2).s-
ub.p--OCF.sub.2CH.sub.2--OH;
[0036] in which Q and P may be the same or different and may be
between 1 and 500. For FPE.sup.2, such fluoropolyether chains
preferably include:
[0037]
--OCH.sub.2CF.sub.2--(O--CF.sub.2).sub.p--(O--CF.sub.2--CF.sub.2).s-
ub.q--OCF.sub.2CH.sub.2--O--;
[0038] in which Q and P may be the same or different and may be
between 1 and 500. Other fluoropolyethers which may be used for
FPE.sup.1 and FPE.sup.2, include the following and their
derivatives thereof:
[0039]
--(O--CF.sub.2).sub.p--(O--CF.sub.2--CF.sub.2--).sub.q--O--CF.sub.3-
;
[0040]
--(O--CF.sub.2--CF.sub.2).sub.q--(O--CF.sub.2).sub.p--O--CF.sub.3;
[0041]
--(O--CF.sub.2).sub.p--(O--CF.sub.2--CF(CF.sub.3)).sub.q--O--CF.sub-
.3;
[0042]
--(O--CF.sub.2--CF(CF.sub.3)).sub.q--(O--CF.sub.2).sub.p--O--CF.sub-
.3;
[0043]
--(O--CF.sub.2--CF.sub.2--CF.sub.2).sub.p--O--CF.sub.2--CF.sub.3;
[0044]
--(O--CF.sub.2--CF.sub.2--CF.sub.2).sub.p--O--CF.sub.2--CF.sub.2--C-
F.sub.3;
[0045]
--(O--CF.sub.2--CF(CF.sub.3)).sub.q--O--CF.sub.2--CF.sub.3;
[0046]
--(O)--(CF(CF.sub.3)--CF--O).sub.q--CF.sub.2--CF.sub.2--CF.sub.3;
[0047] in which Q and P may be the same or different and may be
between 1 and 500.
[0048] Preferred embodiments of the lubricant compound comprise a
fluoropolyether chain having the carbonyl-imide pair at both ends
of a fluoropolyether chain of formula (2). A particularly preferred
embodiment of the lubricant compound comprises the compound termed
"Pi-Z" of the general structure: 12
[0049] in which P and Q may be the same or different, but are
preferably the same, and may be between 1 and 500. Another
particularly preferred embodiment of the lubricant compound
comprises the compound termed "Py-Z" of the general structure:
13
[0050] in which P and Q may be the same or different, but are
preferably the same, and may be between 1 and 500.
[0051] Another embodiment of the present lubricant compound
comprises a fluoropolyether chain having a carbonyl-imide pair at
the middle of the fluoropolyether chain having the general
structure of the formula:
FPE.sup.3--Cl.sup.4--FPE.sup.4 (3)
[0052] in which Cl.sup.4 represents a carbonyl-imide pair and
FPE.sup.3 and FPE.sup.4 represent a fluoropolyether chain, which
may be the same or different, but are preferably the same.
[0053] In regards to formula (3), Cl.sup.4 may be any
carbonyl-imide pair, preferably any carbon-imide pair having the
nitrogen of the imide group linked to the alpha position carbon of
the carbonyl group. Preferred embodiments of Cl.sup.4 comprise a
carbonyl-imide pair, having the nitrogen of the imide group linked
to the alpha position carbon of the carbonyl group, represented by
the general structure of the formula of
--(C.dbd.O)--R.sup.21.dbd.N--R.sup.22--(C.dbd.O)--, in which
R.sup.21 and R.sup.22 are the same or different and may be an
alkyl, alkenyl, alkoxy, aryl, aryloxy, arlyalkyl, arlyalkenyl,
amine, imine, aromatic, or hetero cyclic aromatic group. R.sup.21
and R.sup.22 may be substituted or unsubstituted. Preferably,
R.sup.21 and R.sup.22 together with the atoms binding them form a
ring or rings system. More preferably, R.sup.21 and R.sup.22
together with the atoms binding them form an aromatic ring or rings
system.
[0054] An example of a preferred embodiment of a carbonyl-imide
pair of Cl.sup.4 having the general structure of the formula of
--(C.dbd.O)--R.sup.21.dbd.N--R.sup.22--(C.dbd.O)-- include the
following:
[0055] (J) 2,6-pyridine-biscarbonyl 14
[0056] in which each R group may be the same or different and may
be a hydrogen atom, halogen atom, alkyl, haloalkyl, alkenyl,
haloalkenyl, alkoxy, haloalkoxy, aryl, haloaryl, arylalky, or
haloarylalky group.
[0057] In regards to formula (3), the fluoropolyether chain of
FPE.sup.3 and FPE.sup.4 may be any fluoropolyether chain. In
general, the fluoropolyether chain of FPE.sup.3 and FPE.sup.4 each
comprise a chain having a middle section comprising
perfluoropolyether units and end sections comprising any functional
group. For example, FPE.sup.3 and FPE.sup.4 may each be represented
by general structure of the formula
--R.sup.31--(OR.sup.32).sub.w--(OR.sup.33).sub.x--(OR.sup.34).sub.y--O--R-
.sup.35, in which R.sup.32, R.sup.33, R.sup.34, are different and
may be a fluoroalkyl or perfluoroalkyl groups, preferably a
C.sub.1-4 fluoroalkyl or perfluoroalkyl group. W may be between 1
and 500. X and Y are the same or different and may be between 0 and
500. R.sup.31 comprises any functional group, such as one or more
perfluoroether units, one or more partially fluorinated ether
units, one or more non-fluorinated ether units, one or more hydroxy
units, one or more fluoroalkyl units, one or more fluoroalkenyl
units, other suitable functional groups, or combinations thereof.
R.sup.35 may be a hydrogen, carboxylate, alkyl, haloalkyl, aryl,
haloaryl, arylalky, haloarylalky, or piperonyl group. Examples of
preferred embodiments of the fluoropolyether chain of FPE.sup.3 and
FPE.sup.4 include a fluoropolyether chain having one or more of the
following groups: (--O--CF.sub.2).sub.n;
(--O--CF.sub.2--CF.sub.2).sub.n;
(--O--CF.sub.2--CF.sub.2--CF.sub.2).sub.- n;
(--O--CF.sub.2--CF(CF.sub.3)).sub.n. Such fluoropolyether chains
preferably include:
[0058]
--OCH.sub.2CF.sub.2--(O--CF.sub.2).sub.p--(O--CF.sub.2--CF.sub.2).s-
ub.q--OCF.sub.2CH.sub.2--OH; and
[0059]
--OCH.sub.2CF.sub.2--(O--CF.sub.2--CF.sub.2).sub.q--(O--CF.sub.2).s-
ub.p--OCF.sub.2CH.sub.2--OH;
[0060] in which Q and P may be the same or different and may be
between 1 and 500. Other fluoropolyethers which may be used for
FPE.sup.3 and FPE.sup.4, include the following and their
derivatives thereof:
[0061]
--(O--CF.sub.2).sub.p--(O--CF.sub.2--CF.sub.2--).sub.q--O--CF.sub.3-
;
[0062]
--(O--CF.sub.2--CF.sub.2).sub.q--(O--CF.sub.2).sub.p--O--CF.sub.3;
[0063]
--(O--CF.sub.2).sub.p--(O--CF.sub.2--CF(CF.sub.3)).sub.q--O--CF.sub-
.3;
[0064]
--(O--CF.sub.2--CF(CF.sub.3)).sub.q--(O--CF.sub.2).sub.p--O--CF.sub-
.3;
[0065]
--(O--CF.sub.2--CF.sub.2--CF.sub.2).sub.p--O--CF.sub.2--CF.sub.3;
[0066]
--(O--CF.sub.2--CF.sub.2--CF.sub.2).sub.p--O--CF.sub.2--CF.sub.2--C-
F.sub.3;
[0067]
--(O--CF.sub.2--CF(CF.sub.3)).sub.q--O--CF.sub.2--CF.sub.3;
[0068]
--(O)--(CF(CF.sub.3)--CF--O).sub.q--CF.sub.2--CF.sub.2--CF.sub.3;
[0069] in which Q and P may be the same or different and may be
between 1 and 500. A particularly preferred embodiment of the
lubricant compound comprises the compound termed "Pi-2Z" of the
general structure: 15
[0070] in which P and Q may be the same or different, but are
preferably the same.
[0071] Other embodiments of the present lubricant compound are
possible such as a fluoropolyether chain having a plurality of
carbonyl-imide pairs. For example, the lubricant compound may
comprise the general structure of the formula:
Cl--FPE--Cl--FPE--Cl; Cl--FPE--Cl--FPE--Cl--FPE- --Cl; and other
possible structures. Embodiments of the present invention include
fluoropolyether homopolymers, copolymers, random polymers, and
block polymers. Different repeat units may be randomly distributed
along the backbone of the fluoropolyether or distributed as a block
of one type of repeat unit and subsequent blocks of different
repeat units along the backbone of the fluoropolyether. The
fluoropolyether can be completely fluorinated or partially
fluorinated and can be linear or branched.
[0072] One example of the synthesis process for preparing Pi-Z
comprises the following general equation: 16
[0073] The process comprises dissolving "Zdeal" (10 g, 5 mmol),
available from Ausimont, in a hydrofluorocarbon "Vertrel XF" (20
mL) available from DuPont Fluoroproducts, a division of E. I. du
Pont de Nemours and Company of Wilmington, Del. Then,
2-pyridinecarboxylic chloride (1.56 g, 11 mmol) and
4-dimethylaminopyridine (0.1 g) in dichloromethane (10 mL) were
added to the solution. Triethylamine was added in drop-wisely to
the solution as an acid acceptor, and the mixture was allowed to
react at room temperature for 4 hours. The solution was poured into
Vertrel XF (100 mL) after it was cooled, and washed with a dilute
HCl aqueous solution. A evaporation step followed by and a
supercritical fluid extraction purification step provided a clear
liquid product of Pi-Z fluoropolyether (8.5 g, 85%). The product
was identified by UV spectra. Other synthesis processes for
preparing Pi-Z are also possible.
[0074] One example of the synthesis process for preparing Py-Z
comprises the following general equation: 17
[0075] The process comprises dissolving Zdeal (10 g, 5 mmol) in a
hydrofluorocarbon Vertrel XF (20 mL). Then, 3,5-dimethylpyrazole
(1.44 g, 15 mmol) in methanol (10 mL) was added to the solution and
the mixture was refluxed for 24 hours. The solution was poured into
Vertrel XF (100 mL) after it was cooled, and washed with a dilute
HCl aqueous solution. A evaporation step followed by a
supercritical fluid extraction purification step gave of a clear
liquid product of Py-Z fluoropolyether (8 g, 80%). The product was
identified by UV spectra. Other synthesis processes for preparing
PyZ are also possible.
[0076] The present lubricant compounds, whether of formula (1),
formula (2), or formula (3), preferably have an average molecular
weight (M.sub.n) of between about 2,000 Daltons and about 6,000
Daltons. The lubricant composition may be unfractionated.
Alternatively, the lubricant composition may be fractioned. For
example, the lubricant composition may be fractionated to remove
certain molecular weight lubricant compounds. Not wishing to be
bound by theory, it is believed that removing low molecular weight
lubricant compounds provides a lubricant composition with improved
stiction and wear properties at a very low topcoat thickness. The
lubricant composition may be prepared by fractionating starting
materials of fluoropolyethers or the end-product may be
fractionated. Fractionating can be achieved by distillation,
solvent extraction, chromatography, e.g. (HPLC), or other molecular
weight separation techniques.
[0077] The lubricant composition may be applied over magnetic media
by any technique known in the art, such as dip, vapor, spray,
solvent, solvent-free, vacuum, and non-vacuum processes. The
lubricant composition may be applied as one layer or as multiple
layers. To provide desirable lubricating properties, the lubricant
composition is preferably applied to a thickness between about 10
angstroms and about 30 angstroms. Thicknesses of less than 10
angstroms and greater than 30 angstroms of the lubricant
composition may also be used. In addition, after application, a
post-treatment of the lubricant topcoat may be performed, such as a
heat, IR, UV, plasma, gas treatment, or other treatment known in
the art.
[0078] Not wishing to be bound by theory, it is believed that the
present lubricant compounds provide good lubrication properties,
such as low stiction and friction properties while also being
resistant to catalytic attack. The present lubricant compound
incorporates the functional group of a catalytic blocking agent
into the fluoropolyether chain. Therefore, it is believed that the
present lubricant composition does not have phase separation
problems of other lubricant mixture systems. In addition, since a
separate catalytic blocking agent compound does not need to be
provided in the lubricant system, the application process of the
lubricant composition is simplified.
EXAMPLE
[0079] The following tests demonstrate the capabilities of the
present invention and such examples are offered by way of
illustration and not by way of limitation.
Example 1
[0080] Thermogravimetric analysis (TGA) tests were performed on
samples comprising various lubricant systems. A first sample
comprised a lubricant system of the mixture of FOMBLIN .RTM. Z-DOL
with Irganox MD 1024 (available from Ciba-Geigy). A first
comparative sample comprised a lubricant system of FOMBLIN .RTM.
Z-DOL. Thermogravimetric analysis spectra showed that the first
sample had a lower mass loss rate over temperature in comparison to
the comparative sample. Not wishing to be bound by theory, it is
believed that the TGA spectra showed that the Irganox MD 1024 of
the first sample is capable of inhibiting catalytic decomposition
of FOMBLIN .RTM. Z-DOL. It is further believed that the
carbonyl-imide functional group, in which the nitrogen of the imide
group is linked to the alpha position carbon of the carbonyl group,
of the Irganox MD 1024 acts in blocking metal catalytic sites and
incorporating this functional group into a fluoropolyether chain
provides protection against catalytic attack.
Example 2
[0081] Potentiostatic corrosion tests were performed on samples
comprising a substrate having a carbon overcoat with various
lubricants formed thereover. A second sample comprised a substrate
lubed with Pi-Z. A third sample comprised a substrate lubed with
Pi-2Z. A second comparative sample comprised a substrate lubed with
the mixture of FOMBLIN .RTM. Z-DOL and X1P. Each sample was
immersed into a sodium chloride solution and was biased at a 900 mV
potential for 10 minutes. The total amount of charge ("total
corrosion charge") passing through each system over this 10 minutes
period of time was measured and calculated. The total corrosion
charge of the second sample and the third sample was less than the
total corrosion charge of the second comparative sample. Therefore,
the second sample and the third sample showed better potentiostatic
corrosion resistance than the second comparative sample. Not
wishing to be bound by theory, it is believed that the
potentiostatic corrosion resistance data shows that the second
sample and third sample is resistance to decomposition.
Example 3
[0082] Contact start-stop (CSS) tests were performed on samples
comprising a disc having a carbon overcoat with various lubricants
formed thereover. A fourth sample comprised a disc lubed with Pi-Z.
A fifth sample comprised a disc lubed with Pi-2Z. A third
comparative sample comprised a disc lubed with a mixture of FOMBLIN
.RTM. Z-DOL and X1P.
[0083] Contact start-stop tests were performed in a conventional
spin stand using 10,000 start/stop cycles in which the discs were
spun to a speed of 7,200 rpm. Stiction and friction data were
obtained at ambient temperature and ambient humidity. None of the
samples "crashed." The fourth sample and the fifth sample showed
low stiction and low friction values similar to the low stiction
and low friction valves of the comparative sample. Not wishing to
be bound by theory, it is believed that the CSS data shows that the
fourth sample and the fifth sample provide good lubrication
properties.
[0084] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *