Glass Substrate for Magnetic Recording Media Bubble Elimination
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Solution Overview
Problem
The increasing demand for high recording density in magnetic recording media requires a glass substrate with extremely few bubbles and excellent chemical durability, as existing alkali-containing glasses face challenges in removing bubbles due to higher melting temperatures and viscosity issues during the clarification process.
Innovation Solution
A glass composition for magnetic recording medium substrates is developed, characterized by specific mass percentages of Si, Al, Li, Na, K, Sn, Ce, and other components, with controlled ratios and additions to achieve low viscosity and effective bubble elimination, ensuring a flat and chemically durable surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alkali-containing glass composition is used to achieve chemical durability, then chemical durability is improved, but melting temperature increases and bubble elimination becomes difficult
Solution Approach 1:
The patent applies parameter changes by carefully controlling the composition ratios of alkali metals (Li, Na, K) and alkaline earth metals (Mg, Ca, Sr, Ba) to achieve an optimal balance. By limiting total alkali content to 15% or less while maintaining specific ranges of individual components, the glass achieves adequate chemical durability without excessive melting temperature, enabling effective bubble elimination during manufacturing.
Solution Approach 2:
The patent uses a composite glass composition combining multiple oxide components (SiO2, Al2O3, B2O3, P2O5) with controlled alkali and alkaline earth metal oxides. This composite approach creates a glass matrix that provides both chemical durability and suitable processing characteristics, resolving the contradiction between durability and manufacturability.
2Quantity of substance
If high recording density is achieved through vertical magnetic recording, then recording density is improved, but substrate surface flatness requirements become more stringent
Solution Approach 1:
The patent applies preliminary action by incorporating specific glass modifiers (Sn, Sb, Ce) during the glass formulation stage that prevent bubble formation and ensure homogeneous structure before the glass is formed into the final substrate. This preliminary control of glass structure eliminates the need for extensive post-processing to achieve the required surface flatness for high-density vertical magnetic recording.
Solution Approach 2:
The patent changes physical parameters of the glass by controlling viscosity through specific composition ratios, particularly using B2O3 and P2O5 in controlled amounts to lower viscosity and improve flow characteristics during forming. This enables the glass to self-level and achieve the extreme surface flatness (Ra < 0.25 nm) required for vertical magnetic recording at 100 Gbit/inch2 or greater densities.
3Ease of operation
If cleaning agents such as acids and alkalis are used to remove foreign matter, then cleaning effectiveness is improved, but surface roughness increases if chemical durability is inadequate
Solution Approach 1:
The patent applies this principle by designing a glass composition that sacrifices some alkali content (limiting to 15% or less) to improve chemical durability and resistance to cleaning agents. This creates a more robust substrate that can withstand aggressive acid and alkali cleaning processes without developing surface roughness, ensuring that cleaning effectiveness is maintained while preserving surface quality.
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 proposed glass substrate achieves a significantly reduced bubble density and enhanced chemical durability, enabling the production of high-density magnetic recording media with improved surface flatness and resistance to acid and alkali etching.
Implementation Method 1
Sn 0.005 to 0.6 percent, and Ce 0 to 1.2 percent; in that the Sb content is 0 to 0.1 percent... effective bubble elimination
Data Source
AI summary
A glass for a magnetic recording medium substrate permitting the realization of a magnetic recording medium substrate affording good chemical durability and having an extremely flat surface, a magnetic recording medium substrate comprised of this glass, a magnetic recording medium equipped with this substrate, and methods of manufacturing the same. The glass is an oxide glass not including As or F.