Low-Temperature PVD Scratch-Resistant Glass Coating
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Solution Overview
Problem
Current glass substrates in handheld devices and displays face challenges with microductile scratches, which are shallow and narrow but still affect optical properties and are difficult to prevent through modification of glass chemistry, while existing scratch-resistant solutions do not effectively address these issues without compromising the glass's chemical strengthening.
Innovation Solution
A method is developed to form a scratch-resistant glass article by applying an inorganic, optically-transparent layer with a hardness greater than 9 GPa over a chemically-strengthened glass substrate, using processes like reactive or non-reactive sputtering, while maintaining the substrate's temperature below 500°C to preserve stress distribution and avoid adverse effects on chemical strengthening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard surface layer is formed on oxide glass to increase scratch resistance, then microductile scratch resistance is improved, but the chemical strengthening of the glass substrate may be compromised due to high processing temperatures
Solution Approach 1:
The patent applies parameter changes by controlling the substrate temperature during inorganic layer formation to be below 500°C. This temperature parameter control allows the glass substrate to maintain its chemical strengthening properties while still enabling the deposition of a hard scratch-resistant coating layer on the surface.
Solution Approach 2:
The patent creates a composite structure consisting of a chemically-strengthened glass substrate combined with an inorganic coating layer. This composite material approach allows the bulk glass to provide chemical strengthening while the surface layer provides scratch resistance, combining the benefits of both materials without compromising either property.
2Reliability
If the glass substrate temperature is kept below 500°C during inorganic layer formation, then chemical strengthening is preserved, but the deposition process may be more time-consuming or require more complex process control
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature deposition to low-temperature deposition (below 500°C). This parameter modification enables the use of physical vapor deposition techniques like sputtering that can form hard inorganic layers at lower temperatures, thus preserving chemical strengthening while achieving scratch resistance.
Solution Approach 2:
The patent substitutes thermal energy with physical vapor deposition mechanisms (such as sputtering) to form the inorganic layer. Instead of relying on high temperature to drive the deposition process, the method uses physical ejection and deposition of material, allowing layer formation at lower temperatures that preserve the glass's chemical strengthening.
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 solution significantly reduces scratch depth and width, maintaining the glass's optical clarity and chemical strengthening, with the inorganic layer being substantially free of microductile scratches and enhancing the glass's scratch resistance by at least 20% compared to uncoated substrates.
Implementation Method 1
The inorganic layer can be formed using reactive or non-reactive sputtering, though other physical vapor deposition or chemical vapor deposition processes can be used.
Implementation Method 2
The inorganic layer can be formed using reactive or non-reactive sputtering
Data Source
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AI summary
A scratch-resistant glass substrate is prepared by forming a hard, scratch-resistant layer over a major surface of the substrate. The layer is formed from an inorganic material such as a metal oxide, metal nitride, metal carbide, or metal boride using, for example, physical vapor deposition such as reactive or non-reactive sputtering at a process temperature of less than 500°C. The inorganic layer is resistant to micro-ductile scratching, which can safeguard the visible appearance of the glass substrate in use. The glass substrate can include chemically-strengthened glass.