Lithium Oxide Glass Composition for High-Modulus Thin Covers
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Solution Overview
Problem
Existing glasses and glass-based articles used in electronic devices are vulnerable to damage from accidental drops and flexural stresses, particularly when thin, and lack desirable mechanical properties such as high Young's modulus.
Innovation Solution
A glass composition comprising 62.5-68 mol. % SiO2, 9.5-16 mol. % Al2O3, 12-16 mol. % MgO, 8-11.2 mol. % Li2O, and less than 0.6 mol. % ZrO2, with R2O/Al2O3 at least 0.8, and a method of ion-exchanging in a molten salt bath to create a compressive stress layer and central tension region, enhancing mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the glass is made thinner to reduce material costs and device profile, then manufacturing cost and device thickness are improved, but the glass becomes more susceptible to flexural and sharp contact failures
Solution Approach 1:
The patent changes the chemical composition parameters of the glass by incorporating specific amounts of lithium oxide (8-11.2 mol.%), magnesium oxide (12-16 mol.%), and aluminum oxide (9.5-16 mol.%) to achieve a high Young's modulus (at least 82 GPa). This compositional parameter change allows thin glass to maintain high strength and resistance to flexural and contact failures while keeping the device profile thin.
2Strength
If ion-exchange is performed to introduce a compressive stress layer and strengthen the glass against flexural failure, then flexural strength is improved, but the glass remains vulnerable to dynamic sharp contacts
Solution Approach 1:
The patent creates a composite structure within the glass by combining a compressive stress layer (formed through ion-exchange) with a centrally located tension region. This composite stress distribution, achieved by ion-exchanging in a molten salt bath, provides both flexural strength from the compressive layer and resistance to sharp contact failures from the controlled tension region, thereby improving overall reliability.
3Strength
If high Young's modulus is achieved through composition optimization, then mechanical strength and impact resistance are improved, but manufacturing complexity may increase
Solution Approach 1:
The patent optimizes specific compositional parameters (lithium oxide: 8-11.2 mol.%, magnesium oxide: 12-16 mol.%, aluminum oxide: 9.5-16 mol.%, with R2O/Al2O3 ratio at least 0.8) to achieve high Young's modulus (at least 82 GPa). These parameter changes are implemented within standard glass manufacturing processes, including conventional ion-exchange in molten salt baths, thereby improving mechanical strength without significantly increasing manufacturing complexity.
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 Young's modulus and fracture toughness, reducing the likelihood of damage from impacts and maintaining manufacturability, suitable for use in electronic device covers and housings.
Implementation Method 1
ion-exchanging the glass-based substrate in a first molten salt bath to form a glass-based article, wherein the glass-based article comprises a compressive stress layer extending from a surface of the glass-based article to a depth of compression
Data Source
AI summary
A glass comprising 62.5-68 mol. % SiO2; 9.5-16 mol. % Al2O3; 12-16 mol. % MgO; 8-11.2 mol. % Li2O; and less than 0.6 mol. % ZrO2; wherein R2O/Al2O3 is at least 0.8, amounts are in mol. %, and R2O is a total amount of Li2O, Na2O, K2O, Rb2O, and Cs2O in the glass. A glass-based article comprising a compressive stress layer extending from a surface of the glass-based article to a depth of compression; a central tension region; and a composition at a center of the glass-based article comprising the glass. A method for ion-exchanging a glass-based substrate, the method comprising ion-exchanging the glass-based substrate in a first molten salt bath to form a glass-based article wherein the glass-based article comprises a compressive stress layer extending from a surface of the glass-based article to a depth of compression, the glass-based article comprises a central tension region, and the glass-based substrate comprises the glass.