Alkali-Free Glass Substrate Composition for Flatness and Bubble Removal
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Solution Overview
Problem
Alkali-free glass substrates for large-sized liquid crystal displays face challenges in achieving low viscosity during the melting process, leading to difficulties in homogenizing the glass composition and obtaining flatness, while high viscosity makes it hard to form substrates with few bubbles, and increasing the melting temperature complicates the float forming process and productivity.
Innovation Solution
An alkali-free glass substrate composition with specific ranges of SiO2, Al2O3, B2O3, MgO, CaO, and SrO, along with a float process at lower temperatures, ensures a low viscosity glass melt, reducing sag, and incorporating SnO2 as a fining agent to remove bubbles, resulting in a substrate with high Young's modulus, low linear expansion coefficient, and excellent acid resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the melting temperature is increased to reduce glass viscosity, then the glass melt becomes easier to handle and form, but the float forming process complexity increases and productivity decreases
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass (specific ratios of Al2O3, B2O3, MgO, CaO, and SrO) to fundamentally change the viscosity-temperature relationship of the glass melt, enabling low viscosity at lower temperatures without increasing melting temperature
Solution Approach 2:
The patent creates a composite glass system combining multiple oxide components in specific proportions, where the synergistic interaction between Al2O3, B2O3, and alkaline earth oxides produces a glass composition with optimized melting properties and low-temperature flow characteristics
2Stability of the object's composition
If the glass viscosity is reduced to facilitate homogenization and flatness, then the glass composition becomes more uniform and flatness improves, but bubble removal becomes more difficult
Solution Approach 1:
The patent optimizes the chemical composition parameters to achieve a specific viscosity range that balances homogenization and bubble removal, using precise ratios of B2O3 (6-9%) and alkaline earth oxides to control melt rheology
Solution Approach 2:
The patent introduces SnO2 as a fining agent that acts as an intermediary substance to facilitate bubble coalescence and removal from the glass melt, working synergistically with the optimized base composition
3Weight of moving object
If the glass substrate thickness is reduced to decrease weight, then the display weight is reduced, but the substrate strength and resistance to breaking decrease
Solution Approach 1:
The patent develops a composite glass composition with high Young's modulus through optimized ratios of Al2O3 (10-12%), B2O3 (6-9%), and alkaline earth oxides, creating a material that provides exceptional strength-to-weight ratio enabling thin yet durable substrates
Solution Approach 2:
The patent changes the mechanical property parameters of the glass by optimizing its chemical composition, specifically achieving Young's modulus of 75 GPa or more through controlled ratios of network formers and modifiers
4Area of stationary object
If the glass substrate area is increased to accommodate large displays, then the display size is enlarged, but handling difficulty increases due to sag from own weight
Solution Approach 1:
The patent modifies the mechanical property parameters of the glass (Young's modulus, strength) through compositional optimization, enabling large-area substrates to maintain rigidity and resist sagging under their own weight during handling and installation
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 approach allows for the production of alkali-free glass substrates with high Young's modulus, low density, and low viscosity, enabling the formation of flat, bubble-free glass substrates with improved acid resistance and reduced energy consumption, suitable for large-sized liquid crystal displays.
Implementation Method 1
incorporating SnO2 as a fining agent to remove bubbles
Implementation Method 2
float process at lower temperatures, ensures a low viscosity glass melt, reducing sag
Data Source
AI summary
To provide an alkali-free glass substrate, which has a high Young's modulus, a low linear expansion coefficient, a high strain point and a low density, does not devitrify in the float forming process and is excellent in acid resistance.An alkali-free glass substrate, which contains neither alkali component nor BaO and consists essentially of, as represented by mol % based on oxide, from 57.0 to 65.0% of SiO2, from 10.0 to 12.0% of Al2O3, from 6.0 to 9.0% of B2O3, from 5.0 to 10.0% of MgO, from 5.0 to 10.0% of CaO and from 2.5 to 5.5% of SrO, provided that MgO+CaO+SrO is from 16.0 to 19.0%, MgO/(MgO+CaO+SrO)≧0.40, and B2O3/(SiO2+Al2O3+B2O3)≦0.12; wherein Young's modulus ≧75 GPa; the linear expansion coefficient at from 50 to 350° C. is from 30×10−7/° C. to 40×10−7/° C.; the strain point ≧640° C.; the temperature T2 (the viscosity η satisfies log η=2)≦1,620° C.; the temperature T4 (the viscosity η satisfies log η=4)≦1,245° C.; the devitrification temperature ≦T4; and weight loss per unit area is at most 0.6 mg/cm2, when immersed in 0.1N HCl at 90° C. for 20 hours.