Alkali-free glass substrate bubble removal via composition
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Solution Overview
Problem
The challenge is to efficiently produce large-size alkali-free glass substrates with reduced bubble density, as existing methods require larger vacuum degassing apparatuses and result in lower production yields due to increased bubble defects.
Innovation Solution
An alkali-free glass substrate composition with specific ranges of SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO, along with a bubble growth index of 320 or more, facilitates easy bubble removal in a reduced-pressure atmosphere, preventing excessive bubble growth and maintaining high glass meltability and chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the dimensions of vacuum degassing apparatus are increased to increase the flow rate of molten glass, then the productivity is improved, but the facility investment cost increases
Solution Approach 1:
The patent changes the chemical composition parameters of the glass material by adding specific amounts of chloride (0.1-0.5 mass%) and water (0.03-0.15 mass%), which fundamentally alters the bubble growth characteristics of the molten glass. This parameter change enables efficient vacuum degassing without requiring larger apparatus dimensions, thus maintaining productivity while avoiding increased facility investment costs
2Area of stationary object
If the size of glass substrate is increased to meet display demands, then the area of stationary object is improved, but the production yield decreases due to increased bubble defects
Solution Approach 1:
By modifying the chemical composition parameters (adding chloride and water within specific ranges), the patent changes the physical behavior of bubbles in molten glass during vacuum degassing. This enables larger substrates to be produced with reduced bubble density, thereby maintaining high production yield despite increased substrate area
Solution Approach 2:
The patent performs preliminary action by adding chloride and water to the glass material before melting and vacuum degassing. This preliminary composition adjustment prepares the molten glass to have optimal bubble growth characteristics, ensuring that when vacuum degassing is applied to large substrates, bubbles are effectively removed without compromising production yield
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 allows for the efficient production of large-size glass substrates with reduced bubble density, preventing yield decreases and minimizing facility investment costs, while ensuring high quality and stability of the glass substrates.
Implementation Method 1
there has been known a vacuum degassing method of introducing the molten glass into a reduced pressure atmosphere, allowing bubbles in a continuous flow of molten glass to largely grow under the reduced pressure atmosphere to raise the bubbles contained in the molten glass, breaking and removing the bubbles
Implementation Method 2
allowing bubbles in a continuous flow of molten glass to largely grow under the reduced pressure atmosphere
Data Source
AI summary
An alkali-free glass substrate contains, as represented by mass % based on oxides: 54% to 68% of SiO2; 10% to 25% of Al2O3; 0.1% to 5.5% of B2O3; and 8% to 26% of MgO+CaO+SrO+BaO. The alkali-free glass substrate has β-OH of 0.15 mm−1 to 0.35 mm−1, and a Cl content of 0.15 to 0.3 mass %. A bubble growth index I of the alkali-free glass substrate given by the following formula is 320 or more: I=590.5×[β-OH]+874.1×[Cl]−5.7×[B2O3]−33.3. In the formula, [β-OH] is β-OH of the alkali-free glass substrate in mm−1, [Cl] is the Cl content of the alkali-free glass substrate in mass %, and [B2O3] is a B2O3 content of the alkali-free glass substrate in mass %.