Flat Panel Display Glass Substrate Heat Shrinkage Reduction
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Solution Overview
Problem
Conventional glass substrates for flat panel displays undergo significant heat shrinkage during the high-temperature processing of polysilicon thin-film transistors (p-Si TFTs), leading to non-uniform pixel pitches and challenges in achieving high resolution, due to their insufficient strain point and devitrification resistance.
Innovation Solution
A glass substrate composition comprising 55-80% SiO2, 3-20% Al2O3, 3-15% B2O3, and 3-25% RO (MgO, CaO, SrO, BaO) with a devitrification temperature of 1250°C or less and a heat shrinkage rate of 75 ppm or less, which reduces heat shrinkage while maintaining devitrification resistance, allowing for the formation of p-Si TFTs without pixel pitch non-uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the composition of glass is modified to increase the Tg and strain point, then the heat shrinkage is reduced, but the devitrification resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely adjusting the chemical composition parameters of the glass, specifically setting SiO2 at 55-80%, Al2O3 at 3-20%, B2O3 at 3-15%, and RO at 3-25%, while controlling As2O3 and Sb2O3 to substantially 0%. This compositional parameter optimization simultaneously achieves low heat shrinkage (75 ppm or less) and maintains devitrification resistance (devitrification temperature of 1250°C or less), resolving the contradiction between heat shrinkage reduction and devitrification resistance preservation.
Solution Approach 2:
The patent employs composite materials by combining multiple glass-forming oxides (SiO2, Al2O3, B2O3, and RO) in specific proportions to create a glass composition that exhibits both low heat shrinkage and high devitrification resistance. This composite approach allows the material to inherit beneficial properties from each component while achieving a balanced performance that satisfies both requirements.
2Temperature
If the devitrification temperature is increased, then the liquidus viscosity decreases, but the flexibility of the production method decreases
Solution Approach 1:
The patent applies parameter changes by controlling the devitrification temperature within a specific range (1250°C or less) through compositional adjustment. This parameter control ensures that the glass maintains appropriate liquidus viscosity for manufacturing while preventing excessive devitrification resistance that would reduce production flexibility. The balanced composition achieves both goals simultaneously.
3Ease of manufacture
If conventional glass substrates are used for p-Si TFT production, then the production process is simple, but significant heat shrinkage occurs leading to non-uniform pixel pitch
Solution Approach 1:
The patent applies parameter changes by modifying the glass composition parameters to achieve low heat shrinkage (75 ppm or less) while maintaining ease of manufacture. The specific composition ranges (SiO2: 55-80%, Al2O3: 3-20%, B2O3: 3-15%, RO: 3-25%) are optimized to balance manufacturing simplicity with high pixel pitch uniformity, resolving the contradiction between process simplicity and precision.
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 substrate effectively reduces heat shrinkage and maintains devitrification resistance, enabling the production of p-Si TFTs with uniform pixel pitches and high resolution, facilitating the use of polysilicon in flat panel displays without increasing manufacturing costs or environmental impact.
Implementation Method 1
the glass substrate undergoes heat shrinkage and heat shock during production of the p-Si TFT
Implementation Method 2
the glass substrate undergoes heat shrinkage and heat shock during production of the p-Si TFT
Implementation Method 3
the devitrification resistance of the glass is likely to deteriorate. If the devitrification resistance deteriorates, i.e., the devitrification temperature increases
Data Source
AI summary
A flat panel display glass substrate according to the present invention includes a glass comprising, as expressed in mol %, 55-80% SiO2, 3-20% Al2O3, 3-15% B2O3, 3-25% RO (the total amount of MgO, CaO, SrO, and BaO), and substantially no As2O3, and Sb2O3. The devitrification temperature of the glass is 1250° C. or less. The glass substrate has a heat shrinkage rate of 75 ppm or less. The heat shrinkage rate is calculated from the amount of shrinkage of the glass substrate measured after a heat treatment which is performed at a temperature rising and falling rate of 10° C./min and at 550° C. for 2 hours by the heat shrinkage rate (ppm)={the amount of shrinkage of the glass substrate after the heat treatment/the length of the glass substrate before the heat treatment}×106.