Magnetic Recording Backcoat Surface Roughness Control
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Solution Overview
Problem
Magnetic recording media face challenges in achieving both good electromagnetic characteristics and running durability, particularly in high-density recording, due to issues like reverse transfer and radial winding defects, which are not adequately addressed by existing technologies.
Innovation Solution
A magnetic recording medium with a backcoat layer having an average surface roughness of 15-25 nm and a protrusion density of 50-150/mm², as measured by specific surface roughness meters, which improves the correlation between backcoat layer properties and magnetic layer defects, thereby reducing dropout and enhancing running durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a backcoat layer having surface protrusions is provided to reduce frictional coefficient and improve running durability, then repeat running durability is improved, but reverse transfer occurs where protrusions transfer to the magnetic layer forming minute indentations that deteriorate electromagnetic characteristics and increase dropout
Solution Approach 1:
The invention changes the physical parameters of the backcoat layer surface by controlling the average surface roughness to 15-25 nm and the protrusion density to 1-50/mm². This parameter optimization allows the surface to maintain sufficient roughness for running durability while reducing protrusion height and density to prevent reverse transfer to the magnetic layer, thereby resolving the contradiction between durability and electromagnetic characteristics.
2Manufacturing precision
If the surface of the backcoat layer is smoothed to eliminate reverse transfer, then electromagnetic characteristics are improved, but the shape of the tape when wound becomes chaotic causing radial winding defects and tape deformation
Solution Approach 1:
The invention optimizes the surface roughness parameter to a specific range (15-25 nm) that maintains tape structural integrity for proper winding while eliminating excessive protrusions that cause reverse transfer. This balanced parameter selection prevents both reverse transfer and winding defects, resolving the contradiction between electromagnetic characteristics and winding shape.
3Measurement precision
If AFM measurement is used to evaluate backcoat layer surface properties, then surface roughness can be measured, but a good correlation does not necessarily exist between AFM measured surface properties and defects in the magnetic layer surface that cause dropout in high-density recording region
Solution Approach 1:
The invention introduces a multi-parameter evaluation system that combines AFM measurement with three-dimensional surface roughness meter measurement as intermediary assessments. By measuring both average surface roughness and protrusion density, this intermediary evaluation method provides a more accurate prediction of magnetic layer defects and dropout in high-density recording, resolving the insufficient correlation problem of single-method AFM measurement.
Data Source
AI summary
The present invention relates to a magnetic recording medium comprising a magnetic layer comprising a ferromagnetic powder and a binder on one surface of a nonmagnetic support and a backcoat layer comprising a granular material and a binder on the other surface of the nonmagnetic support, wherein the backcoat layer has an average surface roughness ranging from 15 to 25 nm, as measured by an atomic force microscope, and a density of protrusions equal to or greater than 50 nm in height ranges from 1 to 50/mm2 on the backcoat layer surface, as measured by a three-dimensional surface roughness meter with a contact needle. The present invention further relates to a method of reproducing magnetic signals and a magnetic signal reproduction system.