Alkali-Free Glass Composition for OLED Substrates
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Solution Overview
Problem
Alkali-free glass substrates for OLED displays face challenges in balancing devitrification resistance, meltability, strain point, and thermal expansion coefficient, making it difficult to achieve high productivity, heat resistance, and matching thermal expansion with film members.
Innovation Solution
A glass composition with 55% to 80% SiO2, 12% to 30% Al2O3, 0% to 3% B2O3, 0% to 1% Li2O+Na2O+K2O, and 5% to 35% MgO+CaO+SrO+BaO, with specific molar ratios and content restrictions to enhance strain point, devitrification resistance, and reduce thermal expansion coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the strain point of the alkali-free glass is increased, then heat resistance is improved, but devitrification resistance and meltability are reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the glass, specifically setting Al2O3 content at 12-30 mol% and MgO+CaO+SrO+BaO content at 5-35 mol%, while limiting alkali content to 0.5 mol% or less. This compositional parameter optimization enables the glass to achieve a high strain point (improving heat resistance) while maintaining adequate devitrification resistance and meltability for manufacturing.
2Stability of the object's composition
If the thermal expansion coefficient of the alkali-free glass is reduced, then matching with film members is improved, but devitrification resistance and meltability are reduced
Solution Approach 1:
The patent resolves this contradiction through parameter changes in glass composition, specifically optimizing the ratio of Al2O3 (12-30 mol%) to alkaline earth metal oxides (MgO+CaO+SrO+BaO at 5-35 mol%). This compositional parameter control enables the glass to achieve a low thermal expansion coefficient that matches semiconductor films while maintaining sufficient devitrification resistance and meltability for practical manufacturing.
3Productivity
If the devitrification resistance and meltability of the alkali-free glass are increased, then productivity is improved, but strain point is reduced
Solution Approach 1:
The patent applies parameter changes by optimizing the glass composition within specific ranges: Al2O3 at 12-30 mol% provides adequate devitrification resistance, while MgO+CaO+SrO+BaO at 5-35 mol% improves meltability. The alkali content is strictly limited to 0.5 mol% or less to maintain high strain point. This balanced compositional parameter selection achieves all three requirements simultaneously.
4Productivity
If the chemical etching rate in HF is increased, then production efficiency is improved, but glass composition control becomes more difficult
Solution Approach 1:
The patent applies parameter changes by selecting specific glass composition parameters that inherently provide high etching rate in HF. The composition ranges (Al2O3: 12-30 mol%, MgO+CaO+SrO+BaO: 5-35 mol%, alkali: ≤0.5 mol%) are optimized to achieve rapid HF etching for thickness reduction while maintaining compositional simplicity and manufacturing control, avoiding the need for complex additional components.
Data Source
AI summary
Devised is a glass which has high heat resistance and a low thermal expansion coefficient, and is excellent in productivity. A glass of the present invention includes as a glass composition, in terms of mol %, 55% to 80% of SiO2, 12% to 30% of Al2O3, 0% to 3% of B2O3, 0% to 1% of Li2O+Na2O+K2O, and 5% to 35% of MgO+CaO+SrO+BaO, and has a thermal expansion coefficient within a temperature range of from 30° C. to 380° C. of less than 40×10−7/° C.