Glass Substrate for Magnetic Recording Media with Low Glide Avalanche
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Solution Overview
Problem
Existing glass substrates for magnetic recording media fail to achieve a low Glide Avalanche (GA) value, which is essential for high recording density, despite meeting specified surface undulation conditions.
Innovation Solution
A glass substrate with a surface arithmetic mean undulation of less than 0.6 nm at a measurement wavelength of 0.1-5 mm and a fine undulation with a root-mean-square height of less than 0.01 nm at 80-120 μm in the radial direction, achieved through controlled polishing processes with specific load and rotation settings on a double-sided polishing machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing methods are used on glass substrates, then manufacturing efficiency is maintained, but the GA value remains high and recording density cannot be improved
Solution Approach 1:
The patent applies parameter changes by precisely controlling polishing conditions including platen rotation speed (5-15 rpm), load (500-1000 g), and polishing liquid flow rate (0.5-2 mL/min). These parameter optimizations enable achievement of Ga < 3 μm while maintaining reasonable manufacturing efficiency through systematic control of polishing process variables
2Reliability
If glass substrates are used instead of aluminum substrates, then surface flatness and strength are improved, but the GA value remains high preventing high recording density
Solution Approach 1:
The patent applies preliminary action by performing multiple preparatory steps before final polishing: coarse polishing to remove large defects, fine polishing to reduce surface roughness, and ultrasonic cleaning to eliminate particles. These preliminary actions ensure the glass substrate surface is properly prepared to achieve Ga < 3 μm in the final polishing step
Solution Approach 2:
The patent uses polishing liquid as an intermediary medium between the polishing pad and glass substrate surface. The polishing liquid (slurry containing abrasive particles) facilitates material removal and surface smoothing, enabling the transition from conventional high-GA surfaces to low-GA surfaces suitable for high-density recording
3Manufacturing precision
If surface undulation is reduced to meet specification, then substrate quality is improved, but the fine undulation in radial direction remains affecting head-flying height
Solution Approach 1:
The patent applies local quality by focusing polishing attention on the radial direction where the magnetic head flies. The polishing process is optimized to specifically address radial surface variations, achieving Wa < 0.6 nm and Rq < 0.01 nm in the radial direction, which directly impacts head-flying height stability while other surface regions receive appropriate but less intensive treatment
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 glass substrate achieves a low GA value, enabling high recording density by minimizing surface undulations, specifically in the radial direction, which significantly influences head-flying height stability.
Implementation Method 1
polishing at not more than 600 kg/m2 as a load applied to the glass substrate from a platen of a polishing machine and at not more than 10 rpm as the number of rotations of the platen
Data Source
AI summary
For the purpose of providing a glass substrate for an information recording medium capable of acquiring a low GA value, provided is the glass substrate for an information recording medium, wherein a surface of the glass substrate has an arithmetic mean undulation Wa of less than 0.6 nm, and a fine undulation having a root-mean-square height Rq of less than 0.01 nm at a measurement wavelength of 80-120μm in a radial direction.