Alkali-Free Glass Composition for Stiff, Meltable OLED Substrates
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Solution Overview
Problem
Large and thin alkali-free glass sheets used in OLED devices are prone to deflection, leading to defects during handling and conveyance, and increasing the Young's modulus and strain point to address this issue compromises meltability and devitrification resistance, reducing productivity.
Innovation Solution
An alkali-free glass sheet with specific composition ranges for SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO, achieving a Young's modulus of 78 GPa or more and a strain point of 680°C or more, while maintaining high meltability and devitrification resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the Young's modulus and strain point of the glass sheet are increased to reduce deflection and thermal shrinkage, then the deflection resistance and thermal stability are improved, but the meltability and devitrification resistance are reduced, leading to reduced productivity
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the glass sheet. Specifically, it sets SiO2 at 58-68 mol%, Al2O3 at 11-18 mol%, B2O3 at 1.5-6 mol%, and other oxides within specific ranges to achieve the optimal balance between Young's modulus (78 GPa or more) and meltability (liquidus temperature of 1450°C or less).
Solution Approach 2:
The patent uses composite materials by combining multiple glass-forming oxides (SiO2, Al2O3, B2O3) with network modifiers (MgO, CaO, SrO, BaO) in specific proportions. This composite approach allows the glass to achieve both high mechanical strength and good processability, resolving the contradiction between strength and productivity.
2Area of stationary object
If the glass sheet size is increased and thickness is reduced to meet OLED display requirements, then the display area is enlarged, but the glass sheet becomes more liable to deflection and breaking during handling
Solution Approach 1:
The patent changes the material parameters by increasing the Young's modulus to 78 GPa or more through specific composition control, which directly improves the deflection resistance of large-area, thin glass sheets used in OLED displays.
3Manufacturing precision
If alkali metal oxide content is reduced to prevent ion diffusion into semiconductor films, then the purity and device performance are improved, but the meltability and devitrification resistance are reduced
Solution Approach 1:
The patent applies parameter changes by controlling alkali metal oxide content (Li2O+Na2O+K2O) to 0-0.5 mol% while compensating with alkaline earth metal oxides (MgO: 4-10 mol%, CaO: 2-10 mol%, SrO+BaO: 2-13 mol%) to maintain both ion diffusion control and meltability (liquidus temperature ≤1450°C).
Solution Approach 2:
The patent uses composite materials by replacing alkali metal oxides with alkaline earth metal oxides in the glass composition. This substitution maintains the low ion diffusion characteristic required for OLED displays while preserving good meltability and devitrification resistance through the synergistic effect of multiple alkaline earth metals.
Data Source
AI summary
An alkali-free glass sheet, which has a content of Li2O+Na2O+K2O of from 0 mol to 0.5 mol in a glass composition, and has a Young's modulus of 78 GPa or more, a strain point of 680° C. or more, and a liquidus temperature of 1,450° C. or less.