Lubricant Layer for Stable Head-to-Disk Interface in Humidity
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Solution Overview
Problem
The reduction in flying height of the head over the magnetic disk in HDDs under high humidity conditions leads to read/write instability due to increased surface forces, making it difficult to achieve higher recording density.
Innovation Solution
A lubricant layer comprising a mixture of cyclophosphazene groups and a lubricant formulated as R1-OCH2CF2CF2O(CF2CF2CF2O)mCF2CF2CH2O—R2, where R1 and R2 are alkyl chains with at least two hydroxyl groups, is applied to provide a stable head-to-disk interface, minimizing the increase in adhesive force and maintaining flight stability even in humid conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional lubricant layers are used to reduce head-to-disk distance for higher recording density, then recording density improves, but flight stability deteriorates under high humidity conditions due to increased surface forces
Solution Approach 1:
The patent modifies the chemical composition parameters of the lubricant layer by incorporating fluorinated cyclic carbonate groups and controlling the ratio of cyclic carbonate to carboxylic acid groups. This chemical parameter change reduces the lubricant's hygroscopicity, preventing excessive surface force increase under high humidity conditions while maintaining sufficiently low adhesive force for stable head flight at reduced distances
Solution Approach 2:
The patent creates a composite lubricant layer by combining multiple chemical components: fluorinated cyclic carbonate groups, carboxylic acid groups, and potentially other compatible lubricant molecules. This composite structure achieves synergistic effects where the fluorinated cyclic carbonate component provides humidity resistance while the carboxylic acid component maintains appropriate adhesion characteristics for stable flight
2Productivity
If head-to-disk distance is reduced to increase recording density, then recording capacity improves, but read/write stability deteriorates under high humidity conditions
Solution Approach 1:
The patent changes the physical-chemical parameters of the lubricant layer, specifically reducing hygroscopicity through fluorinated cyclic carbonate groups. This parameter change ensures that the lubricant layer maintains stable tribological properties under high humidity, enabling the head to fly stably at reduced distances (1-5 nm) where high recording capacity is achieved
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The lubricant layer maintains flight stability and reduces the distance between the head and disk to as low as 1 nm, enabling higher recording density in HDDs even under high humidity conditions.
Implementation Method 1
the adhesive force, which is a measure of interaction between planes in near contact
Data Source
AI summary
In one embodiment, a magnetic disk medium includes a nonmagnetic substrate, a magnetic recording layer above the nonmagnetic substrate, a protective layer above the magnetic recording layer, and a lubricant layer above the protective layer, the lubricant layer including a mixture of a compound having one or more cyclophosphazene groups and a lubricant formulated R1-OCH2CF2CF2O(CF2CF2CF2O)mCF2CF2CH2O—R2, wherein R1 and R2 are alkyl chains having at least two hydroxyl groups each, and m is an integer indicating a number of repeating units. According to another embodiment, a magnetic disk medium lubricant includes a mixture of a compound having one or more cyclophosphazene groups and a lubricant formulated as above, such that a magnetic head is provided stable flight above the lubricant layer in conditions having relative humidity of greater than about 40%.