Glass Ceramic Surface Microstructure for Strength and Transparency
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Solution Overview
Problem
Existing materials used for protective covers in mobile devices, such as glass, plastic, and crystalline substances, suffer from drawbacks like brittleness, weight, susceptibility to scratches, and reduced transparency due to crystallites, making them unsuitable for thin, high-strength applications.
Innovation Solution
A sheet-like glass ceramic article with a specific microstructure design, featuring distinct first and second microstructures on its surfaces and core, with controlled thermal expansion coefficients, allowing for compressive stress toughening without chemical or thermal treatment, enhancing mechanical strength and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If glass ceramic material is used for protective covers, then mechanical strength is improved, but transparency is worsened due to light scattering from crystallites
Solution Approach 1:
The patent applies local quality by creating a surface microstructure with controlled crystallites only in a superficial layer (first microstructure), while the bulk material (second microstructure) remains substantially free of crystallites. This localized approach allows the surface to gain mechanical strength through controlled crystallization, while the transparent bulk maintains optical clarity, thus resolving the contradiction between strength and transparency.
2Illumination intensity
If glass is used for protective covers, then transparency is improved, but mechanical strength is worsened due to brittleness
Solution Approach 1:
The invention creates a differentiated microstructure where only the surface layer contains controlled crystallites for strength enhancement, while the bulk glass remains amorphous and transparent. This selective crystallization approach allows the material to simultaneously achieve both transparency (in the bulk) and mechanical strength (at the surface), resolving the contradiction between these two properties.
3Strength
If chemical toughening is applied to glass, then mechanical strength is improved, but process complexity and inability to cut the glass worsen
Solution Approach 1:
The patent replaces chemical toughening processes with a physical/thermal approach: controlled crystallization through heat treatment. Instead of using chemical ion exchange methods that complicate manufacturing and prevent cutting, the invention uses thermal processing to create a crystalline surface layer, achieving strength enhancement through a simpler, more versatile process that maintains post-manufacturing flexibility.
4Strength
If glass ceramic with crystallites is used, then mechanical strength is improved, but manufacturing thin articles becomes difficult
Solution Approach 1:
The invention solves the manufacturing challenge by applying crystallites locally only to the surface layer rather than throughout the entire thickness. This allows thin articles to be manufactured because the bulk material remains as transparent, easily processable glass, while still achieving mechanical strength through the crystalline surface layer. The controlled superficial crystallization enables thin article production that would be difficult with bulk glass ceramic.
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 ceramic article achieves high mechanical strength, resistance to sharp impacts, and excellent transparency, enabling effective protection for mobile devices while maintaining flexibility and low weight, with crack deflection at the microstructure boundary.
Implementation Method 1
a first microstructure is provided on each of the surfaces (11, 12), which extends inwardly from the surface towards the core (3) and has a thickness d1, and wherein the core (3) defines a second microstructure with a thickness d2
Implementation Method 2
with the coefficient of linear thermal expansion of the first microstructure being smaller than the coefficient of linear thermal expansion of the second microstructure
Data Source
AI summary
Sheet-like glass ceramic article are provided that include surfaces with a thickness between the surfaces between 0.5 mm and 1.9 mm and a core. The articles have a first microstructure provided on each of the surfaces and have a second microstructure in the core with a second thickness (d2). The first microstructures extend inwardly from the surfaces towards the core and has a first thickness (d1). The first microstructure has a difference from the second microstructure selected from a group consisting of: a crystalline phase type, a crystalline phase amount, crystalline phase size distribution, crystalline phase orientation, crystalline phases composition, crystalline inclusion, an amorphous phase type, an amorphous phase percentage amount, an amorphous phase composition, and any combinations thereof. The difference results in a first coefficient of linear thermal expansion of the first microstructure that is smaller than a second coefficient of linear thermal expansion of the second microstructure.