Alkali-Free Glass Bubble Reduction via SnO2 Redox Control
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Solution Overview
Problem
The production of alkali-free glass for display substrates faces challenges with stirring reboil, where sulfur content becomes gas bubbles due to solubility reduction under negative pressure during stirring, leading to defects in the glass.
Innovation Solution
The method involves monitoring S2− content during stirring and adjusting SO3 and SnO2 levels to suppress stirring reboil by controlling the redox state, ensuring a sulfur content of 0.5 to 25 ppm and S2− content of 3 ppm or less, which helps in reducing bubble inclusions in the glass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If stirring is performed during glass production to homogenize the melt, then mixing efficiency is improved, but sulfur solubility decreases causing bubble generation (stirring reboil)
Solution Approach 1:
The invention changes the chemical parameters of the glass composition by adding specific amounts of SnO2 (0.01-1 wt%) as a refining agent and controlling S content (0.1-5 wt%). This parameter adjustment allows the system to tolerate stirring-induced sulfur volatilization while maintaining overall composition homogeneity. The SnO2 content is optimized to balance bubble removal effectiveness against potential discoloration.
Solution Approach 2:
SnO2 acts as an intermediary substance that facilitates bubble removal through redox reactions. During stirring, SnO2 reacts with sulfur compounds to form SnS and other intermediates that can be more easily removed. The SnO2 essentially mediates between the harmful sulfur and the glass matrix, converting it into removable forms while maintaining melt homogeneity.
2Object-generated harmful factors
If SnO2 is added as a refining agent to remove bubbles, then bubble removal is improved, but S content increases leading to stirring reboil
Solution Approach 1:
The invention applies partial action by adding SnO2 in controlled amounts (0.01-1 wt%) rather than excessive quantities. This partial addition is sufficient to promote bubble removal through redox reactions and improve melt homogeneity, while limiting the total sulfur content to acceptable levels (0.1-5 wt%). The controlled dosage prevents over-correction that would lead to excessive sulfur accumulation.
Solution Approach 2:
The invention changes the chemical parameters by establishing specific ranges for SnO2 (0.01-1 wt%) and S (0.1-5 wt%) content. These parameter changes create an optimal balance where SnO2 effectively removes bubbles through redox reactions while the total sulfur content remains controlled. The parameter optimization ensures that bubble removal efficiency is maximized without causing severe stirring reboil.
3Stability of the object's composition
If S content is increased to suppress bubble growth during melting, then bubble stability is improved, but stirring reboil is exacerbated
Solution Approach 1:
The invention optimizes the sulfur content parameter to a specific range (0.1-5 wt%) that balances two competing requirements: sufficient sulfur to suppress bubble growth during high-temperature melting, but not so much that it causes severe stirring reboil. This parameter optimization creates a stable operating window where bubble suppression and stirring reboil are both controlled.
Solution Approach 2:
The invention applies partial action by adding sulfur in controlled amounts (0.1-5 wt%) rather than excessive quantities. This partial addition is sufficient to suppress bubble growth during melting through the formation of stable sulfur compounds, while limiting the total sulfur content to prevent severe stirring reboil. The controlled dosage achieves the minimum necessary effect without over-correction.
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
This approach significantly reduces bubble generation in the alkali-free glass, resulting in a higher quality substrate with improved thermal and mechanical properties suitable for display applications.
Implementation Method 1
SnO2 causes bubbles to grow by releasing O2 at a high temperature such as 1,500° C. or more
Implementation Method 2
A negative pressure produced by stirring may cause a reduction in the solubility of S (sulfur) contained in an oversaturated state and allow S to escape as gas (bubbles)
Implementation Method 3
the melt is stirred with a stirrer
Data Source
AI summary
The present invention relates to an alkali-free glass and a method for producing the same. More specifically, the present invention relates to an alkali-free glass suitable as a glass for substrates of various displays such as liquid crystal display, and a method for producing the same. According to the present invention, an alkali-free glass suitable as a glass for display substrates, in which inclusion of bubbles is greatly reduced by virtue of containing a refining agent and suppressing the stirring reboil, is obtained.