Glass Substrate Composition for p-Si TFT Displays
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Solution Overview
Problem
Conventional glass substrates for polysilicon thin-film transistor (p-Si TFT) flat panel displays experience heat shrinkage issues due to high-temperature manufacturing processes, leading to uneven pixel pitch, and the increased specific resistance of molten glass during direct electrical heating can cause erosion of melting tanks.
Innovation Solution
A glass substrate composition with 52-78% SiO2, 3-25% Al2O3, 3-15% B2O3, 3-20% RO (MgO, CaO, SrO, BaO), 0.01-0.8% R2O (Li2O, Na2O, K2O), and 0-0.3% Sb2O3, with specific mass ratios to achieve a high strain point and inhibit heat shrinkage, while minimizing the specific resistance of molten glass to prevent tank erosion during direct electrical heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the strain point and Tg of the glass substrate are increased to inhibit heat shrinkage, then the low-temperature-viscosity characteristic temperatures are improved, but the specific resistance of molten glass increases causing current to pass through refractory materials and erode the melting tank
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition ratios of glass components (SiO2: 58-75 mass%, Al2O3: 15-19 mass%, B2O3: 3-7 mass%, RO: 8-15 mass%, R2O: 0.1-1.0 mass%) to achieve an optimal balance between strain point (680°C or higher) and specific resistance of molten glass, preventing both heat shrinkage and tank erosion
Solution Approach 2:
The patent uses composite materials by combining multiple glass-forming oxides and modifiers in specific proportions, creating a glass composition that simultaneously achieves high strain point for heat shrinkage inhibition and appropriate specific resistance for direct electrical heating without tank erosion
2Ease of manufacture
If conventional glass compositions are used to maintain ease of manufacture, then the manufacturing process is simple, but the glass substrate experiences significant heat shrinkage during high-temperature heat treatment causing uneven pixel pitch
Solution Approach 1:
The patent changes the compositional parameters of the glass by increasing SiO2 content to 58-75 mass% and Al2O3 to 15-19 mass%, which raises the strain point to 680°C or higher, thereby reducing heat shrinkage during heat treatment and improving pixel pitch uniformity while maintaining manufacturability
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 solution effectively increases the strain point of the glass substrate, reduces heat shrinkage, and prevents melting tank erosion, enabling the production of high-quality glass substrates for p-Si TFT flat panel displays with improved manufacturing efficiency and productivity.
Implementation Method 1
the glass having a strain point of 680° C. or higher... significant heat shrinkage occurs due to the heat treatment at the time of manufacturing p-Si TFT flat panel displays
Implementation Method 2
direct electrical heating is often employed for the efficient melting of glass... an increase in the specific resistance of molten glass may cause a current to pass through refractory materials
Data Source
AI summary
A substrate for p-Si TFT flat panel displays made of a glass having a high low-temperature-viscosity characteristic temperature and manufactured while avoiding erosion/wear of a melting tank during melting through direct electrical heating. The glass substrate comprises 52-78 mass % of SiO2, 3-25 mass % of Al2O3, 3-15 mass % of B2O3, 3-20 mass % of RO, wherein RO is total amount of MgO, CaO, SrO, and BaO, 0.01-0.8 mass % of R2O, wherein R2O is total amount of Li2O, Na2O, and K2O, and 0-0.3 mass % of Sb2O3, and substantially does not comprise As2O3, wherein the mass ratio CaO/RO is equal to or greater than 0.65, the mass ratio (SiO2+Al2O3)/B2O3 is in a range of 7-30, and the mass ratio (SiO2+Al2O3)/RO is equal to or greater than 5. A related method involves melting glass raw materials blended to provide the glass composition; a forming step of forming the molten glass into a flat-plate glass; and an annealing step of annealing the flat-plate glass.