Low-Alkali Glass for OLED Substrates with High Strain Point
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Solution Overview
Problem
The production process for p-Si TFTs in OLED displays faces challenges with thermal shrinkage of glass substrates during heat treatment, leading to display defects, and existing methods to reduce shrinkage either increase production costs or compromise productivity.
Innovation Solution
A glass composition with specific ranges of SiO2, Al2O3, B2O3, and other oxides, along with a strain point above 715°C, is developed to minimize thermal shrinkage while maintaining high productivity and devitrification resistance, using a composition of 55% to 70% SiO2, 15% to 25% Al2O3, and controlled amounts of other oxides, and forming the glass through an overflow down-draw method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If annealing treatment is performed to reduce thermal shrinkage, then thermal shrinkage is reduced, but production time is increased and cost is increased
Solution Approach 1:
The patent changes the chemical composition parameters of the glass, specifically controlling alkali metal oxide content to 0.3 mass% or less and adjusting the ratios of Al2O3 (15-25 mass%), B2O3 (1-5 mass%), and other oxides, to achieve a strain point of 715°C or higher. This compositional parameter change enables the glass to inherently resist thermal shrinkage without requiring prolonged annealing treatment, thus reducing production time while maintaining dimensional stability.
2Manufacturing precision
If strain point is increased to reduce thermal shrinkage, then thermal shrinkage is reduced, but productivity is reduced
Solution Approach 1:
The patent optimizes the glass composition parameters to achieve a strain point of 715°C or higher through specific ratios of Al2O3 (15-25 mass%), B2O3 (1-5 mass%), and controlled alkali metal oxide content (0.3 mass% or less), while maintaining meltability and devitrification resistance. This balanced compositional design enables high strain point without sacrificing productivity, as the glass can be processed efficiently despite the elevated strain point requirement.
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 composition achieves reduced thermal shrinkage, high strain point, and improved productivity, enabling the production of glass substrates suitable for OLED displays with minimal defects and cost-effective manufacturing.
Implementation Method 1
the glass sheet causes a minute dimensional change called thermal shrinkage. When the thermal shrinkage is large, a TFT pixel pitch shift occurs. As a heat treatment temperature of the glass sheet becomes higher, the thermal shrinkage is increased more.
Implementation Method 2
To have a high strain point in order to reduce thermal shrinkage in a production process for a p-Si TFT. having a strain point of more than 715°C. As the strain point becomes higher, the thermal shrinkage is less liable to occur
Implementation Method 3
To have small contents of alkali metal oxides in order to prevent a situation in which alkali ions are diffused into a semiconductor substance having been formed into a film in a heat treatment step.
Data Source
AI summary
A glass of the present invention includes as a glass composition, in terms of mass %, 55% to 70% of SiO2, 15% to 25% of Al2O3, 1% to 5% of B2O3, 0% to 0.5% of Li2O+Na2O+K2O, 0% to 4% of MgO, 3% to 11% of CaO, 0% to 4% of SrO, and 0% to 11% of BaO, and has a strain point of more than 715° C.