Magnetic Recording Medium Nonmagnetic Layer Void Optimization
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Solution Overview
Problem
Magnetic recording media experience a drop in electromagnetic characteristics due to foreign material accumulation between the magnetic layer and the head during repeated running, leading to spacing loss, which existing abrasive incorporation cannot fully mitigate with increasing recording densities.
Innovation Solution
A magnetic recording medium with a nonmagnetic layer containing nonmagnetic powder and binder on a support, and a magnetic layer with ferromagnetic powder and abrasive, where the nonmagnetic layer's void ratio, void size variation, and thickness are optimized to inhibit head abrasion and maintain electromagnetic characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If abrasive is incorporated into the magnetic layer, then spacing loss due to foreign material adhering to the head is reduced, but the drop in magnetic characteristics with repeated running cannot be sufficiently inhibited for high-density recording
Solution Approach 1:
The patent divides the magnetic recording medium into two functional layers: a magnetic layer containing abrasive particles for head cleaning, and a separate nonmagnetic layer with optimized void structure beneath it. This segmentation allows the nonmagnetic layer to absorb wear debris and prevent head abrasion independently, enabling the magnetic layer to focus on high-density recording without compromising electromagnetic characteristics during repeated running.
Solution Approach 2:
The nonmagnetic layer acts as an intermediary between the magnetic layer and the head. Its controlled void structure (13-25% void ratio with specific size distribution) serves as a buffer zone that captures and contains wear debris, preventing direct contact between foreign material and the head, thereby protecting electromagnetic characteristics while allowing the magnetic layer to achieve high recording density.
2Reliability
If the nonmagnetic layer thickness is increased to prevent head abrasion, then electromagnetic characteristics are maintained, but the overall structure becomes more complex
Solution Approach 1:
The patent optimizes specific parameters of the nonmagnetic layer to achieve the desired protection function with minimal thickness: void ratio controlled at 13-25%, void diameter between 21-58 nm, and layer thickness at 0.20 μm or more. By precisely controlling these parameters, the nonmagnetic layer provides effective head abrasion prevention and electromagnetic characteristic maintenance without excessive thickness or structural complexity.
Data Source
AI summary
The magnetic recording medium has a nonmagnetic layer satisfying: the ratio of the total area accounted for by voids observed to the area of the observed region falls within a range of 13.0% to 25.0% in a sectional image taken by SEM; R+σr is 58.0 nm or less and R−σr is 21.0 nm or greater when denoting the average value of the diameters of corresponding circles for voids observed in the sectional image as R, denoting the standard deviation of the diameters of the corresponding circles as σr; N+σn is 185 voids/μm2 or less and N−σn is 120 voids/μm2 or greater when denoting the average number of voids observed per μm2 unit area of the observed region in the sectional image as N, denoting the standard deviation of this number as σn; and the thickness of the nonmagnetic layer is 0.20 μm or greater.