Glass Substrate Composition for Display Panels with Low Heat Shrinkage
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Solution Overview
Problem
Current glass substrates for high-definition displays face challenges with heat shrinkage, productivity, and devitrification issues, particularly when using low-temperature polysilicon (LTPS-TFT) or oxide-semiconductor (OS-TFT) thin-film transistors, as they require high strain points and low devitrification temperatures, which can lead to increased specific resistance and erosion of melting tanks during direct electrical heating.
Innovation Solution
A glass substrate composition comprising SiO2, Al2O3, B2O3, MgO, BaO, and controlled ratios of other oxides, with a devitrification temperature of 1235°C or lower and a strain point of 700°C or higher, optimized for reduced heat shrinkage and improved etching rates, produced using direct electrical heating and overflow down-draw processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the strain point of glass is increased to reduce heat shrinkage, then heat shrinkage rate is reduced, but specific resistance of molten glass increases causing erosion of melting tank
Solution Approach 1:
The patent changes the chemical composition parameters of the glass, specifically limiting B2O3 to less than 4% and controlling the ratio of alkaline earth metal oxides (CaO+SrO+BaO)/(SiO2+Al2O3) to 0.25 or less. These parameter changes achieve a strain point of 700°C or higher while keeping specific resistance manageable through the controlled presence of alkali metal oxides (Na2O+K2O) at 0.01-1.0%
Solution Approach 2:
The patent creates a composite glass material with a specific multi-component composition including SiO2 (40-70%), Al2O3 (10-30%), B2O3 (0-4%), and controlled amounts of alkaline earth metal oxides and alkali metal oxides. This composite composition achieves both high strain point (700°C or higher) and controlled specific resistance to prevent melting tank erosion during direct electrical heating
2Use of energy by moving object
If direct electrical heating is used for efficient glass melting, then energy efficiency is improved, but high specific resistance causes current to pass through refractory materials causing erosion
Solution Approach 1:
The patent optimizes the electrical conductivity parameters of the molten glass by controlling the content of alkali metal oxides (Na2O+K2O) at 0.01-1.0% and alkaline earth metal oxides. This parameter optimization maintains sufficiently low specific resistance to allow efficient direct electrical heating while preventing excessive current leakage to the refractory lining
Solution Approach 2:
The patent develops a composite glass composition that inherently balances conductivity and stability: SiO2 (40-70%) + Al2O3 (10-30%) + B2O3 (0-4%) + controlled alkaline earth metals (0.1-5% each) + alkali metals (0.01-1.0% total). This composite achieves the dual goal of enabling direct electrical heating efficiency while protecting the melting tank from erosion
3Manufacturing precision
If glass composition is optimized for high strain point, then heat shrinkage is reduced, but devitrification temperature increases causing production issues
Solution Approach 1:
The patent carefully balances composition parameters to achieve strain point ≥700°C while maintaining devitrification temperature ≤1235°C. The key is limiting B2O3 to less than 4% (which would otherwise lower devitrification temperature too much) while still using it as a flux, and controlling the alkaline earth to silica-alumina ratio at 0.25 or less to prevent excessive network modification that would raise devitrification temperature
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 glass substrate achieves low devitrification temperature while maintaining high strain point, reducing heat shrinkage and enhancing productivity, and prevents erosion of melting tanks by controlling specific resistance, making it suitable for high-definition displays with LTPS-TFT or OS-TFT.
Implementation Method 1
a melting step of melting glass raw materials blended according to a predetermined composition by employing at least direct electrical heating
Implementation Method 2
heat shrinkage of glass substrates during production of display panels, which is a cause of unevenness in pixel pitch
Implementation Method 3
having a devitrification temperature of 1235° C. or lower
Data Source
AI summary
A glass substrate that achieves a high strain point while having a low devitrification temperature; and a method for producing the glass substrate. This glass substrate for a display is made of a glass comprising SiO2 and Al2O3, comprising 0% or more to less than 4% B2O3 in mass %, and substantially devoiding Sb2O3, wherein 3×BaO/(MgO+CaO+SrO) is 5 or less, MgO/(CaO+SrO) is 0.36 or greater, the devitrification temperature is 1235° C. or lower, and the strain point is 700° C. or higher. The method comprises: melting, by using at least direct electrical heating, a glass material prepared to have a predetermined composition; forming, into a flat glass sheet, the molten glass that has been melted in the melting step; and annealing the flat glass sheet, wherein a condition for cooling the flat glass sheet is controlled so as to reduce the heat shrinkage rate of the flat glass sheet.