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Magnetic Recording Head with Lubricant Repellent Surface Disclosure Number: IPCOM000015919D
Original Publication Date: 2002-Jul-11
Included in the Prior Art Database: 2003-Jun-21
Document File: 2 page(s) / 85K

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Background and Introduction

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Magnetic Recording Head with Lubricant Repellent Surface

Background and Introduction

In magnetic hard-disk drive technology, a dramatic increase in the magnetic recording storage density has been achieved by lowering the flying height of the magnetic transducer head relative to the disk's surface, while the rate of disk rotation has also been increased. The resulting close proximity and high rate of air shear between the head/disk interface has accelerated the rate at which bulk lubricant droplets collect at the trailing edge of the transducer head. The aforementioned changes have also accelerated the depletion-rate of the mobile phase of lubricant on the disk's surface (lubricant spin-off). These effects are beginning to impact new disk drive products, especially those under development. This invention significantly reduces the rate of disruption of the uniform lubricant film on the magnetic disk and substantially limits the formation of lubricant droplets on the transducer head. The problem is solved by dip-applying the salt of a perfluoropolyether (PFPE) with acid end groups to the transducer head.

Demonstration of Our Concept

We have discovered that lubricant pick-up by heads can be mitigated by surface treating the heads with an applied coating; that dramatically lowers the surface energy of the heads. Most important is a treatment to the rear, side walls and etch cavity regions of the head, such that, the treatment cannot be worn (removed) by use. Effective, include the following molecular structures: R-(CF2-CF2-O-)m - (CF2-O-)n -R R - (CF2-CF2-CF2-O-)m-R R - [(CF3 )CF-CF2-O-]n -R, where R represents the end group comprising a metal salt of carboxylic acid. A specific example is the sodium salt of Z-Diac.

+ -The definition of ZNa as referred to below is NaOOC-CF2-O-(CF2-O)m-(CF2-CF2-O)n-CF2 --COO Na+. The average molecular weight of the Zdiac starting material, measured by nmr, is 3,300 and m/n is 1.16.

The ZNa is deposited by dip coating from dilute solution. A 2 nm thick ZNa coating prevents spreading of Zdol 2000 onto an aluminum coupon. A thin coating of ZNa remains on the trailing end of the slider. ZNa coatings 3 to 4 nm thick on Si wafers do not rinse off with HFE-7100 or Vertrel XF. ZNa coating increases the Zdol contact angle and decreases the spreading of Zdol 2000 on Si wafers. The withdrawal rate is varied to adjust the film thickness. The best coatings are obtained with a controlled withdrawal rate of 1 mm/sec and 600 ppm of ZNa in HFE 7100, very thick coatings cause head crash.

ZNa dip virtually eliminates lube moguls and transfer between the head and disk. Lubricant transport by the slider on a disk with half of the surface unlubricated is diminished by the ZNa coating. When no ZNa coating is present on the slider (reference experiment), the lubricant is


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quickly transported by the slider from the lubricated region to the unlubricated region, reducing the step height until the lubricant thickness...