Low-Modifier Cover Glass Composition for Drop Damage Resistance
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Solution Overview
Problem
Portable electronic devices are vulnerable to damage from accidental drops due to flexure and sharp contact failures, and existing strengthening methods do not adequately address both issues while maintaining thinness and formability for cover glasses.
Innovation Solution
A glass composition with specific ranges of SiO2, Al2O3, Li2O, and Na2O, along with controlled compressive stress layers, enhances strength and formability, allowing for thin glass articles with improved resistance to both flexure and sharp contact failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ion-exchange technique is used to make glass more resistant to flexure failure, then flexure resistance is improved, but the glass remains vulnerable to sharp contact failure due to high stress concentration from local indentations
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass, specifically controlling the ratio of Li2O to Na2O and the content of Al2O3, to achieve optimal mechanical properties that balance both flexure and sharp contact resistance. The glass composition is designed with Li2O/Na2O ratio between 0.5-2.0 and Al2O3 content between 10-25 mol% to create a material that can be effectively strengthened while maintaining formability.
Solution Approach 2:
The patent creates a composite glass system combining multiple oxides (SiO2, Al2O3, Li2O, Na2O, B2O3, P2O5) in specific proportions to achieve synergistic effects. This composite composition allows the glass to exhibit both high strength for flexure resistance and appropriate mechanical characteristics for sharp contact resistance, while maintaining compatibility with ion-exchange strengthening processes.
2Strength
If glass composition is optimized for strength and ion-exchange strengthening, then durability is improved, but formability for thin glass article manufacturing may be compromised
Solution Approach 1:
The patent carefully adjusts compositional parameters to achieve a balance between strength and formability. The Li2O content is controlled at 5-20 mol% and Na2O at 5-20 mol% with a specific ratio, which provides sufficient ion-exchange capability for strengthening while maintaining low melting point and good viscosity characteristics for manufacturing thin glass articles by fusion drawing or floating processes.
Solution Approach 2:
The patent applies different functional requirements to different aspects of the glass composition: the SiO2-Al2O3-Li2O-Na2O base composition provides structural integrity and formability, while the controlled addition of B2O3 (0-10 mol%) and P2O5 (0-5 mol%) enhances chemical durability and ion-exchange characteristics. This localized optimization of different compositional elements achieves both manufacturing ease and final product strength.
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 composition achieves high compressive stress, central tension, and depth of compression, resulting in enhanced durability and formability, making it suitable for thin cover glasses in electronic devices.
Implementation Method 1
Glass can be made more resistant to flexure failure by the ion-exchange technique, which involves inducing compressive stress in the glass surface.
Data Source
AI summary
A glass composition includes: from 55.0 mol % to 70.0 mol % SiO2; from 12.0 mol % to 20.0 mol % Al2O3; from 5.0 mol % to 15.0 mol % Li2O; and from 4.0 mol % to 15.0 mol % Na2O. The glass composition has the following relationships −8.00 mol % ≤R2O+RO−Al2O3−B2O3−P2O5≤−1.75 mol %, 9.00≤(SiO2+Al2O3+Li2O)/Na2O, and (Li2O+Al2O3+P2O3)/(Na2O+B2O3)≤3.50. The glass composition may be used in a glass article or a consumer electronic product.