Magnetic Recording Medium Surface Roughness Control for Head Wear Reduction
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Solution Overview
Problem
Magnetic recording media experience deterioration in electromagnetic conversion characteristics due to head wear during repeated running, especially under high temperature environments, leading to reduced performance.
Innovation Solution
A magnetic recording medium with a magnetic layer having an arithmetic average roughness of 2.5 nm or less and a protrusion height difference of 0.7 nm or more, measured using atomic force microscopy and scanning electron microscopy, is developed to minimize head wear and maintain electromagnetic conversion characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the magnetic layer surface is made smoother to reduce head wear, then electromagnetic conversion characteristics are maintained, but the protrusion height difference becomes insufficient leading to increased head wear
Solution Approach 1:
The patent applies parameter changes by precisely controlling the arithmetic average roughness Ra within 0.5 nm to 2.5 nm and the protrusion height difference Δ within 0.7 nm to 3.0 nm. This dual parameter optimization resolves the contradiction by finding the optimal range where both smoothness (for reduced head wear) and sufficient protrusion (for maintaining electromagnetic characteristics) coexist
Solution Approach 2:
The patent applies local quality by creating a specific surface structure with controlled protrusions and valleys. The magnetic layer surface is engineered to have localized protrusion regions with specific height differences, rather than being uniformly smooth or rough. This allows different local areas to contribute to both reducing head wear and maintaining electromagnetic conversion characteristics
2Reliability
If the magnetic recording medium is used under high temperature conditions, then recording performance is maintained initially, but head wear increases leading to deterioration of electromagnetic conversion characteristics after repeated running
Solution Approach 1:
The patent applies beforehand cushioning by pre-engineering the magnetic layer surface with optimal roughness and protrusion characteristics before the recording medium is put into service. This pre-optimized surface structure acts as a cushion against the harsh high temperature operating conditions, reducing the rate of head wear from the outset and maintaining electromagnetic conversion characteristics even after repeated running at temperatures of 40°C or higher
Solution Approach 2:
The patent uses parameter changes by optimizing the arithmetic average roughness Ra to 0.5 nm to 2.5 nm and protrusion height difference Δ to 0.7 nm to 3.0 nm. These specific parameter ranges create a surface structure that is more resistant to thermal-induced wear, allowing the magnetic recording medium to maintain its electromagnetic conversion characteristics under high temperature conditions during repeated running
Data Source
AI summary
Ra measured on a surface of a magnetic layer is 2.5 nm or less, and Δ(HD−HB) between a protrusion height HD with a height of a peripheral base region of 0 nm as a reference, which is measured by AFM, for a region specified as a dark region in a first binarization-processed image of a reflected electron image obtained by imaging the surface of the magnetic layer with SEM and a protrusion height HB with a height of a peripheral base region of 0 nm as a reference, which is measured by AFM, for a region specified as a bright region in a second binarization-processed image of the reflected electron image obtained by imaging the surface of the magnetic layer with SEM, the second binarization processing being performed on a higher gradation side than the first binarization processing, is 0.7 nm or more.