Magnetic Recording Glass Substrate With Controlled Expansion and Rigidity
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Solution Overview
Problem
Glass disks for magnetic recording media require high rigidity (Young's modulus) to prevent deformation at high-speed rotation, match thermal expansion with spindle materials, and minimize deflection and flapping to ensure accurate reading and writing, especially in high-capacity drives with multiple disks.
Innovation Solution
The glass substrate is formulated with specific thermal expansion, Young's modulus, and strain point ranges to minimize deformation and flapping, using compositions like 55-65% SiO2, 15-25% Al2O3, and controlled processing methods to achieve a glass disk with 30-70×10−7/°C thermal expansion, 80 GPa Young's modulus, and 700°C strain point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the glass disk is used to increase recording density, then hardness and flatness are improved, but deformation occurs at high-speed rotation
Solution Approach 1:
The patent changes the physical parameters of the glass disk by controlling the coefficient of thermal expansion (30-70×10−7/°C) and Young's modulus (80 GPa or more) through specific glass composition ratios. This resolves the contradiction by adjusting material properties to prevent deformation while maintaining hardness.
Solution Approach 2:
The patent uses composite glass materials with specific compositions (SiO2: 55-65%, Al2O3: 15-25%, B2O3: 2-5.5%, etc.) to achieve both high hardness and low deformation. The composite nature of the glass allows simultaneous optimization of mechanical properties that would be difficult to achieve with single-material systems.
2Productivity
If the rotation speed is increased to 10,000 rpm to increase writing and reading speed, then productivity is improved, but positional displacement occurs
Solution Approach 1:
The patent changes the mechanical parameters of the glass disk by ensuring Young's modulus is 80 GPa or more and the strain point is 700°C or more. These parameter changes enable the disk to maintain dimensional stability at 10,000 rpm rotation speeds, preventing positional displacement of the magnetic head while achieving high productivity.
3Productivity
If the flying height is reduced to 2 nm or less to increase recording density, then recording density is improved, but collision risk increases
Solution Approach 1:
The patent changes the rigidity parameter of the glass disk by ensuring Young's modulus is 80 GPa or more. This increased rigidity reduces flapping and deflection at high rotation speeds, allowing the flying height to be reduced to 2 nm or less without increasing collision risk, thus achieving higher recording density.
4Reliability
If the coefficient of thermal expansion is matched to spindle material to prevent deformation, then reliability is improved, but material selection is restricted
Solution Approach 1:
The patent changes the thermal expansion parameter of the glass disk by controlling the coefficient of thermal expansion to 30-70×10−7/°C. This parameter control enables matching with common spindle materials like stainless steel, improving reliability while maintaining flexibility in material selection through precise compositional control.
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 solution enhances the reliability of magnetic recording media by reducing deformation and flapping, ensuring accurate reading and writing, even at high speeds, and maintaining compatibility with spindle materials.
Implementation Method 1
a average coefficient of linear thermal expansion within a temperature range of from 30° C. to 380° C. of from 30×10−7/° C. to 70×10−7/° C.
Implementation Method 2
a Young's modulus of 80 GPa or more
Implementation Method 3
a base material including the glass disk is subjected to heat treatment at a high temperature of from 600° C. to 800° C.
Implementation Method 4
the base material including the glass disk may be subjected to laser irradiation after the formation of the magnetic layer
Data Source
AI summary
A glass substrate for a magnetic recording medium of the present invention has an average coefficient of linear thermal expansion within a temperature range of from 30° C. to 380° C. of from 30×10−7/° C. to 40×10−7/° C., a Young's modulus of 80 GPa or more, a specific Young's modulus of 30 GPa/g·cm−3 or more, and a strain point of 700° C. or more.