Alkali-free glass panel composition for OLED displays
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Solution Overview
Problem
The challenge is to develop an alkali-free glass sheet with high thermal dimensional stability, high Young's modulus, and reduced cost, suitable for large and thin OLED TV displays, while maintaining productivity and devitrification resistance, as existing glass sheets are prone to deflection and increased manufacturing costs when increased in size and reduced in thickness.
Innovation Solution
The glass sheet composition is restricted to 64-71% SiO2, 12.5-17% Al2O3, 0-4% B2O3, 0-0.5% Li2O+Na2O+K2O, 6-11% MgO, 3-11% CaO, 0-6% SrO, and 14-19% MgO+CaO+SrO+BaO, with specific mole percent ratios to achieve a Young's modulus of 80 GPa or more, a strain point of 700°C or more, and a liquidus temperature of 1350°C or less, allowing for improved thermal stability and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the glass sheet is increased in size and reduced in thickness, then the OLED TV achieves higher resolution and reduced thickness, but the glass sheet becomes liable to deflection and manufacturing cost rises
Solution Approach 1:
The patent applies parameter changes by optimizing the glass composition ratios (SiO2: 64-71%, Al2O3: 12.5-17%, B2O3: 0-4%, MgO: 6-11%, CaO: 3-11%, SrO: 0-6%, BaO: 0-1%) and controlling specific mole percent ratios (Al2O3/CaO × B2O3/(MgO+CaO+SrO+BaO) = 0-0.5, MgO/(CaO+SrO) = 0.5-1.5) to achieve the desired mechanical properties. This resolves the contradiction by changing the chemical parameters of the glass to maintain stability while reducing thickness.
2Stability of the object's composition
If the Young's modulus of the glass sheet is increased to reduce deflection amount, then the glass sheet stability improves, but productivity is reduced and devitrification resistance is remarkably reduced
Solution Approach 1:
The patent uses parameter changes by precisely controlling the glass composition within specific ranges and ratios to achieve the optimal balance between Young's modulus and productivity. The controlled composition ensures high Young's modulus for reduced deflection while maintaining devitrification resistance and productivity through the specified parameter ranges.
Solution Approach 2:
The patent employs composite material principles by combining multiple oxides (SiO2, Al2O3, B2O3, MgO, CaO, SrO, BaO) in specific proportions to create a glass composition that achieves high Young's modulus while maintaining other critical properties. The synergistic combination of these components resolves the contradiction between mechanical strength and manufacturing efficiency.
3Stability of the object's composition
If the strain point of the glass sheet is increased to reduce thermal shrinkage, then the thermal dimensional stability improves, but the liquidus viscosity increases and the glass sheet cannot be formed by overflow down-draw method
Solution Approach 1:
The patent applies parameter changes by controlling the glass composition ratios to achieve the desired strain point while maintaining appropriate liquidus viscosity. The specific composition ranges and ratios (particularly the balance between Al2O3, MgO, CaO, and B2O3) are optimized to simultaneously achieve high strain point for thermal stability and sufficient meltability for overflow down-draw manufacturing.
Data Source
AI summary
The present invention provides an alkali-free glass sheet, including as a glass composition, in terms of mol%, 64% to 71% of SiO2, 12.5% to 17% of Al2O3, 0% to 4% of B2O3, 0% to 0.5% of Li2O+Na2O+K2O, 6% to 11% of MgO, 3% to 11% of CaO, 0% to 6% of SrO, 0% to 1% of BaO, and 14% to 19% of MgO+CaO+SrO+BaO, and having a mole percent ratio (Al2O3/CaO)×{B2O3/(MgO+CaO+SrO+BaO)} of from 0 to 0.5, a mole percent ratio MgO/(CaO+SrO) of from 0.5 to 1.5, a mole percent ratio (MgO+CaO+SrO+BaO-Al2O3)×B2O3 of from 1 to 10, and a mole percent ratio SiO2×CaO/MgO of from 30 to 90.