Glass Substrate Composition for Heat-Resistant Magnetic Recording Media
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Solution Overview
Problem
Magnetic recording medium substrates made of aluminum alloys face issues such as deformation, surface smoothness, and thermal expansion coefficient mismatches, leading to reliability problems and increased power consumption due to weight. There is a need for a glass substrate with high heat resistance, rigidity, low specific gravity, and suitable thermal expansion coefficient to address these challenges.
Innovation Solution
A glass composition for magnetic recording medium substrates, comprising specific ranges of SiO2, Al2O3, B2O3, MgO, CaO, BaO, SrO, alkali metal oxides, and optional Sn oxide or Ce oxide, with a glass transition temperature above 625°C, Young's modulus above 83 GPa, specific gravity below 2.85, and thermal expansion coefficient between 48×10−7/°C to 90×10−7/°C, ensuring high heat resistance, rigidity, and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aluminum alloy is used for magnetic recording medium substrate, then ease of manufacture is improved, but deformation occurs and surface smoothness is insufficient
Solution Approach 1:
The patent changes the material parameters by transitioning from aluminum alloy to glass substrate with specific compositional parameters (SiO2: 40-70 wt%, Al2O3: 5-20 wt%, B2O3: 0.1-5 wt%, MgO: 0.1-5 wt%, CaO: 0.1-5 wt%). This material substitution resolves the contradiction by providing both manufacturability and superior surface smoothness (Ra ≤ 0.5 nm) after polishing, eliminating the deformation issues inherent in aluminum alloys.
2Manufacturing precision
If glass substrate is used to improve surface smoothness, then manufacturing precision is improved, but heat resistance requirement becomes more stringent
Solution Approach 1:
The patent adjusts the chemical composition parameters of the glass substrate to achieve a glass transition temperature of 625°C or higher. Specifically, the controlled ranges of SiO2 (40-70 wt%), Al2O3 (5-20 wt%), and other oxides are optimized to simultaneously provide excellent surface smoothness (Ra ≤ 0.5 nm) and high heat resistance, allowing the substrate to withstand high-temperature treatments during magnetic recording layer formation without compromising either surface quality or thermal stability.
3Temperature
If glass transition temperature is increased to improve heat resistance, then temperature resistance is improved, but thermal expansion coefficient must be matched with spindle material
Solution Approach 1:
The patent simultaneously optimizes multiple compositional parameters to achieve a balanced property profile: glass transition temperature of 625°C or higher for heat resistance, while maintaining thermal expansion coefficient between 48-90×10−7/°C to match spindle materials like stainless steel. The specific composition ranges (SiO2: 40-70 wt%, Al2O3: 5-20 wt%, B2O3: 0.1-5 wt%, MgO: 0.1-5 wt%, CaO: 0.1-5 wt%) are carefully controlled to achieve both high heat resistance and compatible thermal expansion characteristics, preventing deformation during operation.
4Productivity
If plate thickness is reduced to increase recording density, then productivity is improved, but warpage and deflection increase
Solution Approach 1:
The patent employs a composite glass formulation combining multiple oxide components (SiO2, Al2O3, B2O3, MgO, CaO) in specific proportions to create a substrate material with inherently high rigidity and low warpage tendency. This composite material approach allows the use of thinner plates (reducing moment of inertia and improving recording density) while the enhanced mechanical properties of the glass composition compensate for the reduced thickness, maintaining dimensional stability and minimizing deflection during spindle rotation.
5Stability of the object's composition
If molding temperature is lowered to improve glass stability, then stability is improved, but crystal precipitation occurs
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass system by incorporating specific oxide combinations (SiO2: 40-70 wt%, Al2O3: 5-20 wt%, B2O3: 0.1-5 wt%, MgO: 0.1-5 wt%, CaO: 0.1-5 wt%) that enhance glass stability and suppress crystal nucleation. This compositional optimization allows molding to be performed at lower temperatures (improving energy efficiency and extending equipment lifespan) while preventing crystal precipitation, as the modified glass composition maintains amorphous structure stability at reduced processing temperatures.
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 glass substrate provides excellent heat resistance, rigidity, and stability, reducing weight and power consumption while maintaining reliability by minimizing thermal expansion mismatches, thus enhancing the performance of magnetic recording media.
Implementation Method 1
a glass transition temperature is equal to or higher than 625° C.
Implementation Method 2
when there is a large difference between respective thermal expansion coefficients of a magnetic recording medium substrate and a spindle material constituting the spindle portion, deviation occurs during use between thermal expansion/thermal contraction of the spindle and thermal expansion/thermal contraction of the magnetic recording medium substrate relative to ambient temperature change
Data Source
AI summary
A glass for magnetic recording medium substrate is an amorphous oxide glass. In terms of mol %, SiO2 content ranges from 45 to 68%, Al2O3 from 5 to 20%, total content of SiO2 and Al2O3 60 to 80%, B2O3 from 0 to 5%, MgO from 3 to 28%, CaO from 0 to 18%, total content of BaO and SrO 0 to 2%, total content of alkali earth metal oxides from 12 to 30%, total content of alkali metal oxides from 3.5 to 15%, and at least one kind selected from the group made of Sn oxide and Ce oxide being included, a total content of Sn oxide and Ce oxide ranges from 0.05 to 2.00%, a glass transition temperature ≥625° C., a Young's modulus ≥83 GPa, a specific gravity ≤2.85, and an average linear expansion coefficient at 100 to 300° C.≥48×10−7/° C.