Glass Composition for Low-Density Recording Substrates

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Solution Overview

Problem

Existing glass compositions for information recording medium substrates have high density, leading to high specific elastic modulus but are not suitable for reducing deflection during rotation, and they require improvements in motor load and breakage resistance, while also being suitable for mass production.

Innovation Solution

A glass composition with specific component ratios of SiO2, Al2O3, MgO, CaO, Li2O, and Na2O, with adjusted [Al2O3] - [R2O] less than −0.5%, optimized for a high specific elastic modulus, low density, and suitable for mass production using a float process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If glass composition is optimized for high Young's modulus, then deflection during rotation is reduced, but density increases leading to higher motor load

Engineering Contradiction:
ImproveYoung's modulusVSAvoiddensity
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

The patent applies parameter changes by precisely adjusting the chemical composition parameters of the glass, specifically setting Al2O3 content to 15-25 mol%, SiO2 to 65-75 mol%, and controlling the difference [Al2O3]-[R2O] to be -3 to -1 mol%. This compositional parameter optimization achieves a balance where the specific elastic modulus is maintained at 30×10-6 m2/kg or higher while density is kept at 2.65 g/cm3 or lower, thereby reducing motor load while preventing substrate deflection during high-speed rotation.

Inventive Principle:
Principle #35Parameter changes

2Weight of moving object

If glass composition is adjusted to reduce density, then motor load is reduced, but specific elastic modulus decreases leading to increased deflection

Engineering Contradiction:
ImprovedensityVSAvoidspecific elastic modulus
Core Design Contradiction:
Weight of moving objectVSStrength

Solution Approach 1:

The patent resolves this contradiction through parameter changes by optimizing the glass composition to contain 15-25 mol% Al2O3, 65-75 mol% SiO2, and controlling the difference between Al2O3 and R2O contents to be -3 to -1 mol%. These specific parameter settings achieve density of 2.65 g/cm3 or lower while maintaining specific elastic modulus of 30×10-6 m2/kg or higher, simultaneously reducing motor load and preventing substrate deflection.

Inventive Principle:
Principle #35Parameter changes

3Strength

If glass composition is optimized for high specific elastic modulus, then deflection is reduced, but shaping temperature and devitrification temperature become unsuitable for mass production

Engineering Contradiction:
Improvespecific elastic modulusVSAvoidshaping temperature and devitrification temperature
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The patent applies parameter changes by optimizing the glass composition parameters: Al2O3 content set to 15-25 mol%, SiO2 to 65-75 mol%, and the difference [Al2O3]-[R2O] controlled to -3 to -1 mol%. This compositional optimization achieves specific elastic modulus of 30×10-6 m2/kg or higher while maintaining shaping temperature at 1000-1150°C and devitrification temperature at 1100-1250°C, which are suitable for mass production by float process.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS12573425B2Glass composition, glass sheet and method for producing same, and substrate for information recording medium
Publication Date: 2026.03.10 NIPPON SHEET GLASS CO LTD

AI summary

The present invention provides a glass composition including, as components, in mol %: 50 to 70% SiO2; 10 to 20% Al2O3; 2 to 5% MgO; 3 to 15% CaO; 3 to 15% Li2O; 3 to 15% Na2O; and 0 to 5% K2O, wherein when a content of a component X in mol % is expressed as [X], [Al2O3]— [R2O] is less than −0.5%, where [R2O] is the sum of [Li2O], [Na2O], and [K2O].