Scratch-Resistant Lithium Aluminosilicate Glass via Ion Exchange
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Solution Overview
Problem
Existing ion exchangeable glasses used in electronic devices are susceptible to scratches from harder materials despite enhanced surface strength, and existing methods to improve scratch resistance, such as altering glass composition or applying coatings, have limitations.
Innovation Solution
A lithium aluminosilicate glass composition with a specific ion exchange treatment using a molten salt bath of varying sodium concentration, creating a compressive stress layer with a spike depth of 4 to 8 micrometers and a potassium-to-sodium molar ratio of 0 to 1.8, enhancing scratch resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ion exchange treatment is applied to enhance surface strength, then mechanical strength is improved, but scratch resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the ion exchange treatment conditions, specifically using a molten salt bath with varying sodium concentration to create a controlled stress profile with a spike depth of layer between 4-8 micrometers. This optimized parameter set achieves both enhanced mechanical strength and improved scratch resistance by controlling the depth and distribution of compressive stress in the glass surface layer.
2Object-affected harmful factors
If glass composition is altered to increase hardness, then scratch resistance is improved, but manufacturing complexity increases
Solution Approach 1:
Rather than altering the base glass composition, the patent changes the processing parameters of the ion exchange treatment. By adjusting the molten salt bath composition (sodium concentration) and treatment conditions to achieve a specific spike depth of layer (4-8 micrometers), the method improves scratch resistance while maintaining the simplicity of the original glass manufacturing process.
3Object-affected harmful factors
If hard coatings are applied to the glass surface, then scratch resistance is improved, but device complexity increases
Solution Approach 1:
The patent extracts the scratch resistance function from a separate coating layer and integrates it directly into the glass substrate through ion exchange treatment. By creating a compressed surface layer with optimized spike depth (4-8 micrometers) through chemical modification rather than physical coating, the solution eliminates the need for additional coating layers and associated manufacturing complexity.
4Object-affected harmful factors
If spike depth of layer is increased to improve scratch resistance, then scratch resistance is improved, but risk of lateral cracking increases
Solution Approach 1:
The patent optimizes the spike depth of layer parameter to a specific range (4-8 micrometers) through controlled ion exchange treatment. This optimized parameter achieves sufficient scratch resistance while maintaining reliability by preventing lateral cracking, demonstrating that there is an optimal range rather than a monotonic relationship between spike depth and performance.
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 method results in a glass article with improved scratch resistance and drop performance, maintaining mechanical strength without lateral cracking, achieved through controlled stress profiles.
Implementation Method 1
exposing a glass-based substrate having opposing first and second surfaces defining a substrate thickness (t) and having a lithium aluminosilicate composition to an ion exchange treatment comprising a molten salt bath
Implementation Method 2
creating a compressive stress layer with a spike depth of 4 to 8 micrometers and a potassium-to-sodium molar ratio
Data Source
AI summary
Methods of manufacturing a glass-based article includes exposing a glass-based substrate having a lithium aluminosilicate composition to an ion exchange treatment to form the glass-based article. The ion exchange treatment including a molten salt bath having a concentration of a sodium salt in a range from 8 mol % to 100 mol %. The glass-based article includes sodium having a non-zero varying concentration extending from a surface of the glass-based article to a depth of the glass-based article. The glass-based article has compressive stress layer extending from the surface to a spike depth of layer from 4 micrometers to 8 micrometers. The glass-based article includes a molar ratio of potassium oxide (K2O) to sodium oxide (Na2O) averaged over a distance from the surface to a depth of 0.4 micrometers that is greater than or equal to 0 and less than or equal to 1.8.