Hydroxyethyloxymethyl terminated perfluoropolyethers for...

Details Hydroxyethyloxymethyl terminated perfluoropolyethers for... Hydroxyethyloxymethyl terminated perfluoropolyethers for...

1998-12-04

2001-02-20

Resan, Stevan A. (Department: 1773)

Stock material or miscellaneous articles

Circular sheet or circular blank

C428S065100, C428S065800, C428S421000, C428S690000, C428S900000, C428S690000

Reexamination Certificate

active

06190749

ABSTRACT:

FIELD OF THE INVENTION
The field of this invention is lubricants for use in information storage systems. More particularly, the invention pertains to information storage systems employing a lubricant disposed on a disc comprised of a perfluoropolyether having hydroxyethyloxymethyl terminated endgroups.
BACKGROUND OF THE INVENTION
Information storage systems, such as disk drives found in personal computers and other data processing devices, employ a rigid magnetic storage medium which is moved relative to a read/write head to provide information introduction and/or retrieval from the magnetic storage medium. The magnetic storage medium (also referred to as a “disc” or “media” are typically comprised of a thin, rigid substrate, an underlayer, a magnetic layer and a carbon layer atop the magnetic layer. The carbon layer is typically sputtered onto the magnetic layer and is sometimes referred to as an “overcoat.” In the design of such devices, it is most desirable from a magnetic standpoint to have the read/write head fly very close to the surface of the disc during movement to maximize the signal quality. Flying too low, however, can cause wear and material interaction which lead to poor system reliability and performance. To reduce the wear and material interaction on the surface of the disc, a lubricant is commonly disposed on the surface of the disc.
The magnetic thin film discs require a barrier lubricant, typically applied on top of the sputtered carbon protective film, to reduce the wear of the interface between the read-write head and the disc during start stop cycles. The mechanical properties of the sputtered carbon film can be varied by incorporation of other elements during its preparation, such as hydrogen and nitrogen. Thus, the chemical interactions between the lubricant and the chemically modified carbon film are very important for the tribological properties of the carbon/lubricant system.
In particular, the lubricant should adhere strongly to the carbon film, and should wet the film uniformly. Failure to wet the film uniformly could cause droplet formation and result in lubricant transfer to the read-write head during operation. In addition, if the lubricant is too volatile, it may transfer to the read-write head through the vapor phase. If enough lubricant is transferred to the head by these mechanisms, it could flood the head-disc interface when the drive is shut down, and the high value of static friction at the flooded interface could cause a drive failure (fly stiction). For the same reason, the lubricant should adhere strongly enough to the carbon film that it does not migrate and flood the head-disc interface during extended periods of operation. On the other hand, if the lubricant is so strongly bound that it does not replenish itself during drive operation, unacceptably high wear rates could result.
Thus, there is interest in the development of improved lubricants that exhibit good lubricating and tribological properties including wear resistance and low stiction.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an information storage system employing a lubricant exhibiting desirable lubricating properties.
Another object of the present invention is to provide a lubricant having desirable wear resistance properties.
A further object of the present invention is to provide a lubricant that does not flood the head-disc interface when the drive is shut down, such that drive failure is minimized.
More particularly, it is an object of the present invention to provide a lubricant comprised of a perfluoropolyether having hydroxyethyloxymethyl terminated endgroups on the surface of a disc in an information storage system.
These and other objects and advantages are achieved by the invention herein where an information storage system comprising a perfluoropolyether lubricant having hydroxyethyloxymethyl terminated endgroups on the surface of a rigid storage medium is provided. In the subject invention, the perfluoropolyether lubricant has the general formula of: HO
p
(CH
2
—CH
2
O)CH
2
—Z—CH
2
(OCH
2
—CH
2
)
p
OH where Z is —CF
2
—(OC
2
F
4
)
m
—(OCF
2
)
n
—OCF
2
—, p has an average value of 1.5, the ratio of m to n is approximately 1.0 and m and n are selected such that the mean molecular weight of the lubricant is in the range of approximately 2000 to 6000 AMU.
In an alternative embodiment of the invention the perfluoropolyether lubricant having hydroxyethyloxymethyl terminated endgroups is fractionated to remove light and heavy molecular weight components to provide the lubricant with a narrower molecular weight distribution.


REFERENCES:
patent: 5292585 (1994-03-01), Ohnuki et al.
patent: 5593341 (1997-01-01), Gonnella et al.
patent: 5855746 (1999-01-01), Probhakara et al.
patent: 5858182 (1999-01-01), Horng et al.
patent: 5858536 (1999-01-01), Yanagisawa
patent: 5885724 (1999-03-01), Yoshida et al.

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