High-Strain-Point, High-Modulus Glasses for AMLCD Stability
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Solution Overview
Problem
Existing glass substrates for active matrix liquid crystal displays (AMLCDs) face challenges in maintaining high dimensional stability and minimizing compaction during high-temperature TFT manufacturing, which can lead to misalignment and defects in the display, while also being cost-effective and resistant to devitrification and corrosion.
Innovation Solution
Development of glass compositions with high strain points, high Young's modulus, and high liquidus viscosities, manufactured through processes like fusion drawing, to minimize compaction and devitrification, ensuring high dimensional stability and reduced stress relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass substrates are used for high-temperature TFT manufacturing, then transistor mobility and display performance are improved, but glass compaction and dimensional instability occur
Solution Approach 1:
The patent modifies the glass composition parameters by adjusting the ratios of Al2O3, SiO2, and alkaline earth metal oxides to achieve a strain point above 760°C, which prevents compaction during high-temperature TFT manufacturing while maintaining dimensional stability
Solution Approach 2:
The patent creates a composite glass system combining multiple oxides (Al2O3, SiO2, MgO, CaO, SrO, BaO) in specific proportions to achieve both high strain point for thermal stability and appropriate viscosity for manufacturability, resolving the contradiction between thermal resistance and dimensional stability
2Productivity
If fusion drawing process is used to manufacture glass, then production efficiency is improved, but glass devitrification occurs
Solution Approach 1:
The patent optimizes the glass composition parameters to achieve high liquidus viscosity (>20,000 Poise) and appropriate melting characteristics, allowing rapid cooling in the fusion drawing process without devitrification while maintaining high production efficiency
Solution Approach 2:
The patent enables rapid cooling through the fusion drawing process by designing glass composition with high liquidus viscosity, allowing the glass to skip through the critical temperature range where devitrification could occur, thus maintaining productivity while preventing crystallization
3Stability of the object's composition
If high strain point glass is used to minimize compaction, then dimensional stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent achieves high dimensional stability through controlled composition parameters (strain point >760°C, specific oxide ratios) that are compatible with standard fusion drawing processes, avoiding the need for complex post-manufacturing treatments like lapping and polishing
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
The proposed glass compositions exhibit low compaction and stress relaxation, reducing variability in TFT manufacturing, extending asset lifetime, and minimizing devitrification, thus enhancing display quality and production efficiency.
Implementation Method 1
high liquidus viscosities
Implementation Method 2
high strain points
Implementation Method 3
compaction. Compaction, also referred to as thermal stability or dimensional change, is an irreversible dimensional change (shrinkage) in the glass substrate due to changes in the glass fictive temperature
Implementation Method 4
stress relaxation
Implementation Method 5
The fusion process, by contrast, results in very rapid quenching of the glass sheet from the melt, and freezes in a comparatively high temperature structure
Data Source
AI summary
Substantially alkali free glasses are disclosed with can be used to produce substrates for flat panel display devices, e.g., active-matrix liquid crystal displays (AMLCDs). The glasses have high annealing temperatures and Young's modulus. Methods for producing substantially alkali free glasses using a downdraw process (e.g., a fusion process) are also disclosed.