Tempered Glass Composition for Warpage Control
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Solution Overview
Problem
Tempered glass used in applications like cellular phones and touch panel displays faces challenges in achieving high mechanical strength, devitrification resistance, and efficient production, particularly due to issues with Al2O3 content affecting liquidus viscosity and KNO3 molten salt degradation, leading to warpage and increased production costs.
Innovation Solution
A tempered glass composition with specific ranges of SiO2, Al2O3, B2O3, Li2O, Na2O, K2O, MgO, CaO, and SrO, along with controlled ion exchange and tempering treatments, to enhance ion exchange performance, devitrification resistance, and reduce warpage, while maintaining mechanical strength and reducing the frequency of KNO3 molten salt exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the content of Al2O3 is increased to enhance compression stress value and mechanical strength, then mechanical strength is improved, but devitrification resistance lowers and liquidus viscosity becomes unsuitable for down-draw and float methods
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Al2O3 content within a specific range (3-13%) rather than simply increasing it. This quantitative parameter control resolves the contradiction by finding the optimal balance point where mechanical strength is sufficiently enhanced while devitrification resistance is maintained at acceptable levels.
Solution Approach 2:
The patent uses composite material principles by combining multiple oxide components (SiO2, Al2O3, B2O3, Li2O, Na2O, K2O, MgO, CaO, SrO) in specific proportions to create a glass composition that achieves both high mechanical strength and good devitrification resistance through synergistic effects of the components.
2Stress or pressure
If the content of Al2O3 is increased to enhance compression stress value, then compression stress value is improved, but liquidus viscosity increases making it difficult to form glass sheets by float method
Solution Approach 1:
The patent applies parameter changes by controlling Al2O3 content within a specific range (3-13%) and balancing it with other components like B2O3 (0-1.5%) and alkali oxides (Na2O: 7-20%, K2O: 0-10%) to achieve optimal compression stress while maintaining suitable liquidus viscosity for float method manufacturing.
Solution Approach 2:
The patent applies local quality by creating a compression stress layer in the surface of the glass through ion exchange treatment, concentrating the stress enhancement effect in the surface region while keeping the bulk glass composition suitable for manufacturing processes.
3Productivity
If KNO3 molten salt is used for continuous ion exchange treatment of large glass sheets, then productivity is improved, but the KNO3 molten salt degrades time-dependently requiring frequent exchange
Solution Approach 1:
The patent applies the principle of using a consumable molten salt bath that can be used until degradation occurs, then replaced. The glass composition is designed to work effectively with KNO3 molten salt during its service life, accepting that the salt will eventually degrade and need replacement, similar to disposable components.
Solution Approach 2:
The patent applies parameter changes by optimizing the glass composition to be more resistant to molten salt degradation through specific component ratios, and by controlling ion exchange treatment parameters (temperature, time, concentration) to maximize the usable life of the KNO3 molten salt.
4Strength
If tempering treatment is applied to large glass sheets, then mechanical strength is improved, but warpage occurs due to difference between front and back surface properties
Solution Approach 1:
The patent applies local quality by creating a compression stress layer in the surface of the glass through ion exchange treatment. This localized stress distribution in the surface region counteracts the warping tendency that occurs during tempering treatment of large glass sheets, allowing the bulk glass to be tempered without excessive warpage.
Solution Approach 2:
The patent applies preliminary anti-action by pre-establishing a compression stress layer through ion exchange treatment before performing tempering treatment. This pre-existing compression stress counteracts the tensile stresses and warpage that would otherwise occur during the subsequent tempering process.
5Strength
If tempering treatment is applied to thin glass sheets, then mechanical strength is improved, but warpage and residual stress problems are particularly remarkable
Solution Approach 1:
The patent applies local quality by creating a compression stress layer in the surface of thin glass sheets through ion exchange treatment. This localized stress enhancement in the surface region provides the necessary mechanical strength while the controlled stress distribution prevents excessive warpage and residual stress problems that are particularly critical in thin glass applications.
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 results in tempered glass with increased mechanical strength, reduced warpage, and efficient production, maintaining high ion exchange performance and devitrification resistance even with degraded KNO3 molten salt, thus lowering production costs and improving the glass's forming capabilities.
Implementation Method 1
A tempered glass of the present invention has a compression stress layer in a surface thereof, and has high ion exchange performance
Implementation Method 2
a tempered glass and a tempered glass sheet, each of which not only has high ion exchange performance and high devitrification resistance and has resistance to degradation of a KNO3 molten salt, but also hardly warps even when produced by applying tempering treatment to a large glass sheet
Data Source
AI summary
A tempered glass has a compression stress layer in a surface thereof, and includes as a glass composition in terms of mol %, 50 to 75% of SiO2, 3 to 13% of Al2O3, 0 to 1.5% of B2O3, 0 to 4% of Li2O, 7 to 20 % of Na2O, 0 to 10 % of K2O, 0.5 to 13% of MgO, 0 to 6% of CaO, and 0 to 4.5% of SrO. The tempered glass is substantially free of As2O3, Sb2O3, PbO, and F. The tempered glass has a molar ratio MgO/(MgO+Al2O3) of 0.05 to 0.30.