Lithium Aluminosilicate Glass Composition for Thin Cover Glass Forming
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Solution Overview
Problem
Portable devices are vulnerable to damage from impact with hard surfaces due to flexure and sharp contact failures, and existing methods to enhance glass strength are inadequate for thin glass articles used in cover glasses, particularly those with lower liquidus viscosities that are prone to devitrification during forming.
Innovation Solution
Development of low viscosity lithium-containing aluminosilicate glasses with specific oxide compositions and ion exchange processes to create compressive stress layers, combined with high-temperature forming apparatuses using heating cartridges to prevent devitrification and enable thin glass article formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ion exchange technique is used to induce compressive stress in glass surface, then resistance to flexure failure is improved, but vulnerability to sharp contact failure remains high due to stress concentration from local indentations
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass, specifically incorporating lithium oxide (Li2O) in controlled amounts (0.1-5.0 wt%) along with aluminum oxide and silicon dioxide. This compositional parameter change enables the glass to achieve both flexure resistance through ion exchange and improved sharp contact resistance by modifying the glass matrix structure to better distribute stress concentrations.
2Ease of manufacture
If glass composition is designed for lower liquidus viscosity to enable thin glass article formation, then ease of manufacture is improved, but devitrification occurs during forming process
Solution Approach 1:
The patent optimizes the compositional parameters within specific ranges: Li2O (0.1-5.0 wt%), Al2O3 (10-30 wt%), and SiO2 (60-80 wt%). This precise parameter control achieves the desired balance between low liquidus viscosity for easy forming and sufficient devitrification resistance. The specific ratio of these oxides creates a glass structure that maintains stability during the forming process while enabling thin article production.
Solution Approach 2:
The patent creates a composite glass system combining multiple oxide components with complementary properties. Lithium oxide provides low viscosity, aluminum oxide enhances structural stability and devitrification resistance, and silicon dioxide forms the glass network backbone. This composite composition achieves both manufacturability and compositional stability simultaneously.
3Stability of the object's composition
If higher forming temperatures are used to prevent devitrification of low viscosity glass, then stability of composition is improved, but energy consumption increases
Solution Approach 1:
The patent modifies the compositional parameters to include lithium oxide in optimized amounts, which lowers the liquidus temperature of the glass system. This parameter change allows forming to occur at lower temperatures while still preventing devitrification, as the modified composition maintains compositional stability at reduced thermal energy input.
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 solution provides enhanced resistance to flexure and sharp contact failures, allowing for the production of thin, strong glass articles suitable for cover glasses in portable devices while preventing devitrification during the forming process.
Implementation Method 1
Glass can be made more resistant to flexure failure by ion-exchange technique, which involves inducing compressive stress in the glass surface.
Implementation Method 2
high-temperature forming apparatuses using heating cartridges to prevent devitrification
Data Source
AI summary
A glass article including, on an oxide basis, from 60 mol % to 74 mol % SiO2, from 7 mol % to 18 mol % Al2O3, less than or equal to 16 mol % B2O3, from 0 mol % to 6 mol % Na2O, greater than or equal to 0.5 mol % SrO, and greater than or equal to 0.5 mol % of divalent cation oxides. The glass article has a molar ratio of Al2O3:(R2O+RO) greater than or equal to 0.9, where R2O is a sum of alkali metal oxides in mol % and RO is a sum of divalent cation oxides in mol %.