Low-Excess-Modifier Glass Composition for Thin Cover Glasses
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Solution Overview
Problem
Portable electronic devices are vulnerable to damage from accidental drops, particularly 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 impact damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ion-exchange technique is used to strengthen glass, then flexure resistance is improved, but sharp contact resistance remains vulnerable due to high stress concentration
Solution Approach 1:
The patent modifies the glass composition parameters by controlling the ratio of Li2O to Na2O (greater than 0.80) and limiting excess modifiers (R2O+RO−Al2O3−B2O3−P2O5 between -4.00 and -1.00 mol %). These parameter changes optimize the glass structure to reduce stress concentration during sharp contact while maintaining the compressive stress benefits for flexure resistance achieved through ion-exchange strengthening.
Solution Approach 2:
The invention creates a composite glass system combining multiple oxide components (SiO2, Al2O3, Li2O, Na2O, B2O3, P2O5) in specific ratios. This composite composition works synergistically with the ion-exchange process to produce a glass that simultaneously achieves both flexure resistance and sharp contact resistance, overcoming the limitation of conventional single-composition glass strengthening.
2Length of moving object
If glass thickness is reduced to make devices thinner, then device thinness is improved, but strength and damage resistance deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the glass, specifically controlling Li2O content (5-20 mol %), Na2O content (3-15 mol %), and the Li2O/Na2O ratio (>0.80), along with limiting excess modifiers. These parameter changes enable the glass to achieve superior strength characteristics that allow thinning while maintaining or improving impact damage resistance.
Solution Approach 2:
The invention creates a non-uniform stress distribution within the glass thickness through controlled ion-exchange processes. The compressive stress is concentrated in specific regions (surface and subsurface layers) while the core maintains different stress characteristics. This local quality differentiation allows thin glass sections to resist impact damage effectively without requiring uniform thickness increases throughout.
3Strength
If glass composition is optimized for strength, then damage resistance is improved, but formability for thin article production may deteriorate
Solution Approach 1:
The patent carefully balances multiple composition parameters: SiO2 (60-75 mol %), Al2O3 (10-25 mol %), Li2O (5-20 mol %), Na2O (3-15 mol %), B2O3 (0-10 mol %), and P2O5 (0-5 mol %). This balanced parameter optimization ensures that the glass achieves high damage resistance while maintaining adequate formability for thin article production through processes like fusion drawing, avoiding excessive viscosity or melting point issues that would hinder manufacturing.
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, providing enhanced resistance to flexure and sharp contact failures, while maintaining thinness and formability for cover glasses.
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.
Implementation Method 2
a compressive stress layer extending from at least one of the first surface and the second surface into the thickness (t) of the glass article
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+P2O5)/(Na2O+B2O3)≤3.50. The glass composition may be used in a glass article or a consumer electronic product.