Magnetic Disk Substrate Waviness Control for High Density Recording
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current magnetic disk substrates face challenges in achieving high recording density due to surface irregularities that cause magnetic head collisions and disrupt electromagnetic conversion, while also being difficult to mass-produce with optimal electromagnetic conversion characteristics.
Innovation Solution
A magnetic disk substrate with a waviness amplitude of 0.1 nm to 0.5 nm and an average microwaviness amplitude of 0.3 nm or less, with a ratio of 0.6 or more, is manufactured using a process involving glass or silicon substrates and specific polishing techniques to ensure compatibility with high recording density and mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surface waviness amplitude is reduced to achieve high recording density, then electromagnetic conversion characteristics improve, but manufacturing difficulty increases and mass production becomes difficult
Solution Approach 1:
The patent applies parameter changes by establishing specific quantitative ranges for surface waviness amplitude (0.3 nm or less) and microwaviness amplitude (0.1 nm or less), along with their ratio (5/3 or more). These parameter specifications enable both high recording density and mass production feasibility by providing clear manufacturing targets that balance performance requirements with production capabilities.
2Reliability
If the surface microwaviness amplitude is reduced to improve electromagnetic conversion, then recording density increases, but production time and effort increase significantly
Solution Approach 1:
The patent uses parameter changes by defining specific amplitude ranges and ratio requirements for surface irregularities. These parameters are optimized to achieve the necessary electromagnetic conversion characteristics while remaining compatible with existing mass production processes, thus avoiding excessive production time and effort.
Solution Approach 2:
The patent applies partial action by specifying that the waviness amplitude should be 0.3 nm or less and micrawaviness amplitude 0.1 nm or less, which are sufficient thresholds to achieve high recording density without requiring excessively tight tolerances that would dramatically increase production complexity and time.
3Productivity
If the waviness amplitude is set to 0.3 nm to enable mass production, then productivity improves, but the ratio of micrawaviness to waviness becomes too low for high recording density
Solution Approach 1:
The patent resolves this contradiction by introducing a ratio parameter (micrawaviness amplitude divided by waviness amplitude should be 5/3 or more) in addition to the absolute amplitude specifications. This ratio requirement ensures that when waviness is controlled at 0.3 nm for mass production, the micrawaviness is appropriately controlled at 0.1 nm or less, maintaining the necessary precision for high recording density.
Data Source
AI summary
The present invention relates to a magnetic disk substrate, in which an amplitude Wa of a waviness on a surface measured by using an interferometer for a versatile disk at a measuring wave-length of 5.0 mm is within the range of 0.1 nm to 0.5 nm, an average amplitude Wb of a microwaviness generated on the waviness measured by using a microscopy for three-dimensional surface-structural analysis at a measuring wave-length of 30 μm to 200 μm is 0.3 nm or less, and a value calculated by dividing the average amplitude Wb of the microwaviness by the amplitude Wa of the waviness is 0.6 or more.