Chemically Strengthened Glass-Ceramics With Controlled Ion-Exchange Stress
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Solution Overview
Problem
Existing aluminosilicate and microcrystalline glasses face limitations in compressive stress enhancement, leading to unsatisfactory fall resistance and optical performance, particularly during rough ground tests and high humidity conditions.
Innovation Solution
A chemically toughened microcrystalline glass with controlled crystalline phases and ion exchange layers, including a Na/Li exchange and a K/Na exchange, achieving a specific depth and intensity of compressive stress, along with a high Young's modulus, to enhance piercing and impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the compressive stress intensity of lithium aluminosilicate glass is increased, then the piercing resistance is improved, but the internal tensile stress becomes excessively high causing glass shards to be too small or spontaneous explosion
Solution Approach 1:
The patent changes the chemical composition parameters by replacing lithium aluminosilicate glass with microcrystalline glass containing specific crystalline phases (beta-quartz solid solution, lithium metasilicate, or lithium disilicate). This composition change enables achieving higher compressive stress (CS50≥230 MPa) while maintaining safety by controlling the stress distribution through the unique crystalline structure and ion exchange characteristics of microcrystalline glass.
Solution Approach 2:
The patent creates a composite structure within the glass material by incorporating microcrystalline phases (35-75 wt%) into the glass matrix. This composite microcrystalline glass combines the benefits of crystalline phases (which can accommodate stress) with the glass matrix, enabling high compressive stress while preventing spontaneous explosion through the stress-absorbing capability of the crystalline network.
2Illumination intensity
If the crystallinity of microcrystalline glass is increased to ensure excellent optical performance, then the transmittance and chromatic aberration are improved, but the crystalline phase becomes susceptible to heat during 3D hot bending forming causing optical performance to deteriorate
Solution Approach 1:
The patent applies local quality by creating a dual-phase structure where microcrystalline phases are distributed within the glass matrix. The crystalline phases (beta-quartz solid solution, lithium metasilicate, or lithium disilicate) have different thermal and optical properties than the glass matrix, allowing the material to maintain optical performance while the crystalline phases provide thermal stability during 3D hot bending forming processes.
3Strength
If the ion exchange path is extended to achieve higher compressive stress in microcrystalline glass, then the fall resistance is improved, but the processing time and complexity increase
Solution Approach 1:
The patent optimizes the ion exchange parameters by controlling the exchange temperature (400-450°C), time (2-6 hours), and salt bath composition (NaNO3-KNO3 mixture). The specific composition ratios and processing conditions are tuned to achieve adequate compressive stress (CS50≥230 MPa) within reasonable timeframes, balancing fall resistance improvement with production efficiency.
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 chemically toughened microcrystalline glass exhibits improved piercing resistance, increased fall height, enhanced optical performance, and stability under heat and humidity, with larger shard sizes and reduced risk of spontaneous explosion.
Implementation Method 1
a secondary-toughened glass body uses lithium aluminosilicate glass... a K/Na exchange and a Na/Li exchange... a Na/Li exchange layer and a compressive stress layer
Data Source
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AI summary
Embodiments of this application disclose chemically toughened microcrystalline glass and a preparation method and application thereof. The chemically toughened microcrystalline glass has a Na/Li exchange layer, and has a compressive stress layer. A depth of the compressive stress layer and a total thickness t of the chemically toughened microcrystalline glass meet the following: the depth of the compressive stress layer is 0.15 t to 0.22 t. In addition, a compressive stress intensity CS50 at a toughening depth of 50 µm in a surface layer of the chemically toughened microcrystalline glass and the total thickness t of the chemically toughened microcrystalline glass meet the following: CS50 is 130 + (20 t - 13) × 15 Mpa to 230 + (20 t - 13) ×15 MPa. In addition, CS50 and the depth of the compressive stress layer meet the following: CS50/(Doc - 50) is 1.4 to 6. The chemically toughened microcrystalline glass has strong piercing resistance to a rough ground, and a chemical toughening condition for the preparation method of the chemically toughened microcrystalline glass is easy to control, so that prepared chemically toughened microcrystalline glass has stable performance, high efficiency, and reduced preparation costs.