Fictivated Silicate Glass for High Damage Resistance
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Solution Overview
Problem
Post-forming annealing processes in ion exchangeable glass compositions tend to decrease the damage resistance, specifically the Vickers crack initiation threshold, which is a limitation in applications requiring high indentation resistance such as electronic device cover glasses and windows.
Innovation Solution
The development of silicate glasses that are fast cooled or fictivated, with compositions comprising at least 50 mol % SiO2, 10 mol % R2O (where R2O includes Na2O), Al2O3, and B2O3, and a fictive temperature greater than or equal to 1012 Poise, which enhances the Vickers crack initiation threshold to at least 15 kgf when ion exchanged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If post-forming annealing processes are applied to ion exchangeable glass compositions, then the glass manufacturing process is completed, but the damage resistance and Vickers crack initiation threshold decrease
Solution Approach 1:
Instead of annealing the glass after ion exchange (conventional approach), the patent inverts the sequence by fast cooling the glass before ion exchange. This reversal of the thermal treatment timing preserves the glass structure in a state that maintains high crack initiation threshold while still completing the manufacturing process.
Solution Approach 2:
The patent changes the thermal parameter from slow cooling (annealing) to fast cooling. By controlling the cooling rate parameter and maintaining a fictive temperature greater than or equal to the temperature at which the super-cooled liquid has a viscosity of 1012 Poise, the glass achieves both manufacturability and high damage resistance.
2Strength
If fast cooling is applied to silicate glass, then the Vickers crack initiation threshold increases to at least 15 kgf, but the glass requires precise control of fictive temperature
Solution Approach 1:
The patent defines a specific parameter threshold for fictive temperature (greater than or equal to the temperature at which the super-cooled liquid has a viscosity of 1012 Poise). By establishing this quantitative parameter boundary, the patent provides a clear manufacturing target that balances improved strength with achievable manufacturing precision.
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 silicate glasses exhibit significantly improved Vickers crack initiation thresholds, with some embodiments achieving thresholds of at least 25 kgf, demonstrating enhanced intrinsic damage resistance and mechanical durability compared to annealed glasses.
Implementation Method 1
fast cooling the silicate glass from the first temperature to a second temperature, wherein the second temperature is less than a strain point of the silicate glass
Implementation Method 2
The silicate glass has a fictive temperature that is greater than or equal to a temperature at which a super-cooled liquid having the composition of the silicate glass is 1012 Poise
Implementation Method 3
Ion exchangeable glass compositions offer advantages in glass manufacturability and/or final properties compared to previous glass compositions
Data Source
AI summary
Silicate glasses that are fictivated and fast cooled and have high levels of intrinsic or “native” damage resistance. When ion exchanged, the silicate glasses described herein have a Vickers crack initiation threshold of at least 15 kgf and, in some embodiments, at least about 25 kgf.