Ion-Exchangeable Soft Glass for 3D Vacuum Sagging
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Solution Overview
Problem
Ion-exchangeable alkali aluminosilicate glasses with high softening points react with and degrade molds during the sagging process, limiting the formation of three-dimensional shapes, and lithium-containing glasses require higher temperatures and longer ion exchange times for shallow compressive layers with low stress.
Innovation Solution
Alkali aluminosilicate glasses with compositions containing significant amounts of MgO and ZnO, B2O3, and limited Li2O, achieving a softening point of 790°C or less and high temperature coefficients of thermal expansion, enabling formation into three-dimensional shapes through vacuum sagging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high softening point ion-exchangeable glasses are used, then ion exchange properties are maintained, but the glass reacts with and degrades molds during sagging process
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass, specifically controlling SiO2 (62-70 mol%), Al2O3 (5-11 mol%), B2O3 (0.5-4 mol%), and adding MgO (1-6 mol%) and ZnO (1-7 mol%). This composition adjustment lowers the softening point to 790°C or less, enabling the glass to be formed at lower temperatures that prevent mold degradation while retaining ion exchange capability
2Temperature
If lithium-containing glasses are used to lower softening point, then formation temperature is reduced, but ion exchange properties deteriorate requiring higher temperatures and longer times
Solution Approach 1:
The patent extracts or removes lithium from the glass composition, specifying less than 1 mol% Li2O. Instead, it introduces magnesium oxide (1-6 mol%) and zinc oxide (1-7 mol%) as alternative components that lower the softening point without interfering with ion exchange properties, thereby avoiding the need for high-temperature or prolonged ion exchange processes
3Manufacturing precision
If longer ion exchange times are used to achieve desired depth of layer, then compressive stress decreases and manufacturing efficiency is reduced
Solution Approach 1:
The glass composition is optimized with specific ranges of SiO2, Al2O3, B2O3, MgO, and ZnO to achieve a softening point of 790°C or less. This parameter change enables ion exchange to achieve the desired depth of layer (30-50 μm) within 10-20 hours at temperatures below 420°C, balancing manufacturing precision with productivity by avoiding excessively long treatment times
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 glasses can be formed into complex 3D shapes with enhanced compressive stress and depth of layer, maintaining practical manufacturing conditions and avoiding mold degradation, while maintaining low softening points and high thermal expansion coefficients.
Implementation Method 1
sodium in the glass is exchanged for potassium in the ion exchange medium
Implementation Method 2
the glass is heated and allowed to sag under gravity or vacuum into a mold
Data Source
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AI summary
Ion exchangeable alkali aluminosilicate glasses and glass articles having softening points and high temperature coefficients of thermal expansion that permit the glass to be formed into three-dimensional shapes by the vacuum sagging process are provided. These glasses contain significant amounts of at least one of MgO and ZnO and comprise B?2#191O?3#191 and less than 1 mol% Li?2#191O.