Chemically Tempered Glass Composition for Display Cover
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Solution Overview
Problem
Conventional chemically tempered glass used in display devices, such as mobile devices and large-sized flat screen televisions, is prone to breakage due to reduced strength when indentations are formed, especially under shock or static loads, as the thickness of the cover glass is compromised for weight reduction.
Innovation Solution
A chemically tempered glass composition comprising 62-68% SiO2, 6-12% Al2O3, 7-13% MgO, 9-17% Na2O, with a content difference of R2O—Al2O3 less than 10%, and up to 0.8% ZrO2, which maintains a compressive stress layer thickness of at least 30 μm and surface compressive stress of at least 550 MPa, enhancing flexural strength and resistance to indentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of the cover glass is reduced for weight reduction and flat design, then the weight and thickness are improved, but the strength is lowered making the glass prone to breakage under shock or static loads
Solution Approach 1:
The patent changes the chemical composition parameters of the glass by specifying precise ranges of SiO2 (62-68%), Al2O3 (6-12%), MgO (7-13%), Na2O (9-17%), and limiting ZrO2 (0-0.8%). This compositional parameter change enables the glass to achieve both thinness and high strength through optimized chemical structure that resists breakage while maintaining reduced thickness of 0.1-2.0mm
Solution Approach 2:
The patent creates a composite glass material by combining multiple oxide components in specific proportions. The synergistic combination of SiO2, Al2O3, MgO, and Na2O forms a composite structure that provides both the desired thin profile and enhanced mechanical strength, resolving the contradiction between weight reduction and strength maintenance
2Stress or pressure
If conventional soda lime glass is chemically tempered, then the surface compressive stress can be made to be at least 550 MPa, but it has been difficult to make the thickness of the compressive stress layer to be at least 30 μm
Solution Approach 1:
The patent modifies the glass composition parameters by adjusting the ratio of Na2O (9-17%) to Al2O3 (6-12%) and limiting ZrO2 to 0-0.8%, which changes the chemical reactivity and ion exchange characteristics. This enables the chemical tempering process to form a sufficiently thick compressive stress layer (t≥30μm) while achieving the required surface compressive stress (S≥550 MPa)
Solution Approach 2:
The patent creates local quality differentiation within the glass structure by forming a compressive stress layer with specific thickness and stress characteristics at the surface, while the bulk glass composition remains different. The controlled ion exchange process creates a gradient structure where the surface layer has enhanced compressive properties distinct from the interior glass matrix
3Stress or pressure
If SiO2-Al2O3-Na2O type glass is chemically tempered, then both the surface compressive stress can be made to be at least 550 MPa and the thickness of the compressive stress layer can be made to be at least 30 μm, but the strength is likely to be lowered once an indentation is imparted to the cover glass
Solution Approach 1:
The patent optimizes the glass composition parameters by precisely controlling SiO2 (62-68%), Al2O3 (6-12%), and Na2O (9-17%) content, which changes the glass network structure and defect characteristics. This compositional optimization enables the glass to maintain high strength even after indentation by reducing the formation and propagation of cracks from stress concentration points
Solution Approach 2:
The patent applies beforehand cushioning by incorporating MgO (7-13%) and controlling the Al2O3 content to create a glass structure that is pre-conditioned to resist crack propagation. The optimized composition creates a more tolerant glass matrix that cushions against the initiation and growth of cracks from indentations, maintaining strength even after surface damage occurs
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 significantly reduces the likelihood of breakage under load conditions, maintaining strength even with indentations, and is suitable for use as a cover glass in display devices, offering improved durability and resistance to scratches and shocks.
Implementation Method 1
a chemical tempering method wherein alkali metal ions having a small ion radius (typically Li ions or Na ions) at a glass plate surface are exchanged with alkali ions having a larger ion radius (typically K ions) by ion exchange at a temperature lower than the glass transition point
Data Source
AI summary
To provide glass to be used for chemically tempered glass, of which the strength is less likely to be reduced even when indentations are formed thereon. Glass for chemical tempering, which comprises, as represented by mole percentage based on oxides, from 62 to 68% of SiO2, from 6 to 12% of Al2O3, from 7 to 13% of MgO, from 9 to 17% of Na2O, and from 0 to 7% of K2O, wherein the difference obtained by subtracting the content of Al2O3 from the total content of Na2O and K2O is less than 10%, and when ZrO2 is contained, its content is at most 0.8%. Chemically tempered glass obtained by chemically tempering such glass for chemical tempering. Such chemically tempered glass has a compressive stress layer formed on the glass surface, which has a thickness of at least 30 μm and a surface compressive stress of at least 550 MPa.