Chemically Toughenable Thin Glass With Stable Thermal Length
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Solution Overview
Problem
Glass articles exhibit significant thermal length changes due to variations in fictive temperature and relative thermal length change potential, leading to shrinkage or expansion, which are not effectively managed by current production and tempering methods, especially in thin glasses.
Innovation Solution
A chemically toughenable glass article with a controlled ion exchange process, altering ion proportions through a gradient from the surface to the bulk, reducing the relative thermal length change potential to zero or less, achieved by optimizing cooling and drawing rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If glass articles undergo thermal treatment to reduce fictive temperature, then the network becomes tighter and length decreases, but this causes unwanted shrinkage and dimensional instability
Solution Approach 1:
The patent applies preliminary anti-action by inducing an initial expansion during controlled thermal treatment before the desired dimensional state is achieved. This pre-expansion compensates for the subsequent shrinkage that occurs during cooling, resulting in net dimensional stability. The glass is heated to a temperature below the transformation temperature and held for a specific time to create this counteracting effect.
Solution Approach 2:
The patent utilizes parameter changes by precisely controlling the thermal treatment parameters including temperature (below transformation temperature), holding time, and cooling rate. By adjusting these parameters, the fictive temperature is modified to achieve the desired balance between network tightening and dimensional stability, transforming the glass from a metastable state to a more stable state with controlled length change.
2Productivity
If glass is cooled rapidly during production, then productivity increases, but the fictive temperature remains high causing thermal length changes
Solution Approach 1:
The patent applies preliminary action by performing a controlled thermal treatment step after rapid cooling during production. This post-production thermal treatment allows the glass to achieve a lower fictive temperature and more stable network structure without compromising the high productivity of rapid cooling manufacturing. The glass is heated to a specific temperature below transformation temperature and held to allow gradual network relaxation.
3Stability of the object's composition
If thermal treatment is extended to reduce relative thermal length change potential, then dimensional stability improves, but production time increases
Solution Approach 1:
The patent optimizes the balance between dimensional stability and treatment time by precisely controlling thermal parameters. The glass is heated to a specific temperature range below the transformation temperature and held for an optimized duration. This controlled parameter adjustment achieves sufficient reduction in relative thermal length change potential without requiring excessively long treatment times, making the process economically viable.
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 article maintains a stable length after thermal treatment, preventing unwanted shrinkage or expansion, allowing for precise control of thermal properties without extensive tempering, particularly beneficial for thin glasses.
Implementation Method 1
A chemically toughenable glass article with a controlled ion exchange process, altering ion proportions through a gradient from the surface to the bulk
Implementation Method 2
In the event of a change in temperature, a change in the length of a glass article occurs. An increase in temperature is associated with an expansion and a reduction in temperature is associated with a contraction of the glass article
Implementation Method 3
If a glass article undergoes thermal treatment, in particular at temperatures slightly below transformation temperature Tg, the fictive temperature can be reduced. The network becomes tighter so that the article has a smaller length upon renewed cooling to the starting temperature than prior to thermal treatment. The term 'thermal shrinkage' is also used in this context
Data Source
AI summary
A toughenable glass article includes a glass and has a thickness of less than 100 μm and a cooling state which is such that, after chemical toughening to a depth of 30% of the thickness, the glass article has a relative thermal length change potential in a range from −1500 ppm to ≤0 ppm.