Ion-Exchanged Glass Shallow Depth High Compression
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Solution Overview
Problem
Conventional ion-exchanged glasses with deeper depths of compression do not provide the optimal resistance to radial crack formation from Vickers indentation, as higher compressive stresses and deeper depths of layer do not necessarily enhance performance, and there is a need for glasses with high indentation fracture thresholds at low depths of layer.
Innovation Solution
Development of alkali aluminosilicate glass compositions with high compressive stress and shallow depth of layer, specifically between 600 to 1200 MPa and 10 to 40 μm, which are ion-exchanged to achieve enhanced resistance to indentation fracture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ion-exchanged glass has higher compressive stress and deeper depth of layer, then retained strength is enhanced, but resistance to indentation fracture does not necessarily improve
Solution Approach 1:
The patent applies parameter changes by optimizing the glass composition parameters (specifically achieving a molar volume of 29.0-30.0 cm³/mol) and controlling the ion exchange process parameters to achieve a specific stress profile with compressive stress of 600-1200 MPa at a shallow depth of layer of 10-40 μm. This specific parameter combination resolves the contradiction by demonstrating that higher compressive stress at shallow depth, achieved through controlled parameter changes, provides both enhanced retained strength and superior resistance to indentation fracture.
2Strength
If depth of layer is increased, then retained strength is enhanced, but resistance to radial crack formation from Vickers indentation is reduced
Solution Approach 1:
The patent resolves this contradiction by changing the parameters of compressive stress magnitude and depth of layer simultaneously. Specifically, it achieves compressive stress of 600-1200 MPa at a shallow depth of layer of 10-40 μm, which is shallower than conventional glasses. This parameter change demonstrates that higher compressive stress concentrated at a shallower depth provides superior resistance to radial crack formation while maintaining enhanced retained strength.
Solution Approach 2:
The patent applies local quality by creating a highly concentrated compressive stress zone at the surface and shallow subsurface region (10-40 μm depth). This localized high-quality compressive layer with stress of 600-1200 MPa provides targeted protection against radial crack formation at the critical surface region where indentation cracks initiate, while the deeper regions have reduced compression, achieving optimal balance between crack resistance and strength.
3Strength
If compressive stress is increased, then performance is enhanced, but depth of layer increases
Solution Approach 1:
The patent applies parameter changes by achieving a specific combination of compressive stress (600-1200 MPa) and depth of layer (10-40 μm) through controlled ion exchange of glass compositions with molar volume of 29.0-30.0 cm³/mol. This parameter optimization resolves the contradiction by demonstrating that the glass composition and ion exchange conditions can be tuned to achieve high compressive stress concentrated at a shallow depth, providing enhanced performance without excessive depth of layer.
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 resulting glasses exhibit higher resistance to radial crack formation and improved indentation fracture thresholds, maintaining performance even after impact damage, making them suitable for electronic device cover glasses.
Implementation Method 1
ion-exchanged glass of high surface compression and shallow depth of layer with high resistance to radial crack formation from vickers indentation
Data Source
AI summary
Disclosed are alkali aluminosilicate glasses having unexpected resistance to indentation cracking. The glasses obtain this high resistance as a result of a high level of surface compression accompanied by a shallow depth of layer. The advantaged glasses show greater resistance to radial crack formation from Vickers indentation than glasses with the same compressive stress, but higher depths of layer.