Fusion-Formable Lithium Aluminosilicate Glass Ceramic
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Solution Overview
Problem
Lithium disilicate glass ceramics lack sufficient liquidus viscosity to be directly formed by fusion processes, requiring complex and expensive high-temperature ion exchange methods, as they typically have viscosities below the necessary 75,000 poise required for fusion forming.
Innovation Solution
A glass ceramic composition with a liquidus viscosity of at least 100 kpoise, comprising crystalline lithium silicate and lithium aluminum silicate phases, and a residual alkali aluminosilicate glass phase, allowing formation by down-draw methods like fusion-draw and slot-draw, followed by heat treatment to achieve high strength and translucency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If lithium disilicate glass ceramic composition is used, then high strength and fracture toughness are achieved, but liquidus viscosity is insufficient for direct fusion forming
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass ceramic system by incorporating lithium aluminum silicate phases alongside lithium disilicate, adjusting oxide ratios (SiO2: 60-80 wt%, Al2O3: 5-20 wt%, Li2O: 3-15 wt%) to simultaneously achieve sufficient liquidus viscosity (≥75,000 poise) and high mechanical strength, enabling direct fusion forming without ion exchange processes
Solution Approach 2:
The invention creates a composite glass ceramic system containing multiple crystalline phases (lithium disilicate and lithium aluminum silicate) within a glass matrix, combining the high strength properties of lithium disilicate with the viscosity-enhancing characteristics of lithium aluminum silicate phases to achieve both formability and mechanical performance
2Device complexity
If down-draw fusion processes are used, then manufacturing complexity and cost are reduced, but the glass must have sufficient liquidus viscosity which conventional lithium disilicate lacks
Solution Approach 1:
The patent adjusts compositional parameters to raise the liquidus viscosity into the fusion-formable range (≥75,000 poise) while maintaining compatibility with down-draw processing parameters, enabling direct fusion forming at conventional temperatures without requiring complex post-processing ion exchange steps
3Ease of manufacture
If high-temperature ion exchange methods are used, then glass ceramic with sufficient viscosity can be formed, but the process becomes complex and expensive
Solution Approach 1:
The invention extracts the need for complex ion exchange processes by incorporating viscosity-enhancing lithium aluminum silicate phases directly into the glass ceramic composition, allowing the material to achieve sufficient liquidus viscosity (≥75,000 poise) through composition design alone, thereby eliminating the requirement for subsequent high-temperature ion exchange steps
Solution Approach 2:
The patent performs the viscosity adjustment action in advance during the glass melting and forming stage by carefully controlling the composition ratios of oxides, particularly Al2O3 and Li2O content, so that the liquidus viscosity is already sufficient for fusion forming before any ion exchange could be attempted, preventing the need for complex post-processing
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
Enables the direct formation of thin, high-strength, and translucent glass ceramic sheets with reduced complexity and cost, achieving properties such as opacity, translucency, and high fracture toughness through the described composition and process.
Implementation Method 1
The glass ceramic comprises a crystalline lithium silicate component or phase, a crystalline lithium aluminum silicate component or phase
Implementation Method 2
The resulting glass ceramic is white or translucent in appearance with high strength achieved through heat treatment of the fusion-formed glass
Data Source
AI summary
A down-drawable glass ceramic. The glass ceramic has a composition which yields a liquidus viscosity that enables formation of the parent glass by down-draw techniques such as fusion-draw and slot-draw methods. The resulting glass ceramic is white or translucent in appearance with high strength achieved through heat treatment of the fusion-formed glass.