Multi-layer Glass Sheet Thermal Expansion Stress
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Solution Overview
Problem
Existing methods for increasing the mechanical strength of glass sheets, such as ion exchange processes, are costly, time-consuming, and generate waste, and require additional production space, while also being limited by the composition and dimensions of the glass.
Innovation Solution
A transparent glass sheet with a surface compressive layer and an inner layer, where the coefficient of thermal expansion difference between the two layers is greater than 50x10^-7 °C^-1, inducing compressive stress of at least 300 MPa without the need for an ion exchange process, achieved through a fusion draw process that allows for precise control of stress and thickness ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ion exchange process is used to increase mechanical strength, then surface compressive stress is achieved, but production cost increases significantly
Solution Approach 1:
The patent uses differential thermal expansion between the core glass layer and surface glass layers to induce compressive stress. The core layer has a higher coefficient of thermal expansion than the surface layers, creating residual compressive stress in the surface layers when the glass transitions from a high-temperature state to room temperature, eliminating the need for ion exchange processes
Solution Approach 2:
The patent creates a composite glass structure with at least three layers: a core glass layer and surface glass layers with different compositions and thermal expansion coefficients. This composite structure inherently generates the desired compressive stress through thermal processing, replacing costly ion exchange methods
2Strength
If ion exchange process is used to increase mechanical strength, then surface compressive stress is achieved, but production time increases significantly
Solution Approach 1:
The compressive stress is built into the glass structure during the manufacturing process through controlled thermal expansion differences, rather than requiring a separate post-processing ion exchange step. The differential thermal expansion is established during the original glass formation and cooling, eliminating additional time-consuming treatment steps
3Strength
If ion exchange process is used to increase mechanical strength, then surface compressive stress is achieved, but production floor space increases
Solution Approach 1:
The patent removes the need for separate ion exchange equipment and facilities by integrating the stress-inducing mechanism directly into the glass manufacturing process. The differential thermal expansion approach eliminates the requirement for large chemical treatment tanks and associated infrastructure
4Strength
If ion exchange process is used to increase mechanical strength, then surface compressive stress is achieved, but waste disposal issues arise
Solution Approach 1:
The patent converts the potentially harmful waste generation of ion exchange processes into a beneficial environmental outcome by using a thermal expansion-based approach. The differential thermal expansion method produces no chemical waste, eliminating the need for waste treatment and disposal infrastructure
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 provides glass sheets with improved mechanical strength and reduced production costs and environmental impact by inducing compressive stress without ion exchange, enabling a wide range of compositions, sizes, and thicknesses.
Implementation Method 1
the coefficient of thermal expansion of the inner layer and the surface compressive layer difference is greater than 50x10^-7 °C^-1
Data Source
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AI summary
Transparent glass sheets having increased mechanical strength include an inner layer surrounded by surface compressive layers wherein the difference of the coefficient of thermal expansion of the inner layer and the surface compressive layer is greater than 50x10-7°C-1 and wherein the surface compressive layer has a compressive stress of at least about 300 MPa.