Hard Coated Glass Substrate for Scratch Resistance
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Solution Overview
Problem
Glass substrates in handheld devices and displays face challenges with microductile scratches that are not effectively prevented by modifying glass chemistry, affecting optical properties and requiring a harder surface layer for improved scratch resistance.
Innovation Solution
A chemically-strengthened glass substrate with an inorganic layer having a Berkovich indenter hardness of at least 10 GPa and an x-ray amorphous structure is applied over a majority of the glass surface, enhancing scratch resistance while maintaining optical clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If glass chemistry is optimized to improve scratch resistance, then deep and wide scratches are reduced, but microductile scratches (shallow and narrow) are not effectively prevented
Solution Approach 1:
The patent applies a hard coating layer composed of silicon oxynitride (SiO2-xNx) over the glass substrate. This composite structure combines the scratch resistance of the hard coating with the optical properties of the glass, effectively preventing microductile scratches while maintaining optical clarity. The coating layer has a hardness of at least 10 GPa, significantly higher than the glass substrate.
Solution Approach 2:
The patent changes the surface hardness parameter by depositing a hard coating layer with a hardness of at least 10 GPa on the glass substrate. This parameter change from the base glass hardness (6-9 GPa) to the coated surface hardness (≥10 GPa) provides enhanced resistance against microductile scratching while maintaining optical properties.
2Object-affected harmful factors
If a harder surface layer is formed to reduce microductile scratches, then scratch resistance is improved, but optical transparency may be compromised
Solution Approach 1:
The patent controls the thickness and composition parameters of the hard coating layer to achieve optimal performance. The coating is designed to be sufficiently thin to maintain optical transparency while being thick enough to provide scratch resistance. The silicon oxynitride composition and controlled thickness ensure the layer is transparent to visible light while providing the necessary mechanical hardness.
Solution Approach 2:
The silicon oxynitride coating layer is specifically designed to combine hardness with optical transparency. This composite material approach allows the surface layer to provide scratch resistance while maintaining the optical clarity needed for display applications, as the coating is transparent to visible light.
3Strength
If a hard coating layer is applied to enhance scratch resistance, then surface hardness is improved, but adhesion compatibility with underlying glass may be compromised
Solution Approach 1:
The patent carefully controls the deposition parameters of the silicon oxynitride coating, including deposition temperature, pressure, and composition ratios, to ensure proper adhesion to the glass substrate. The coating is formed under controlled conditions that promote strong bonding while maintaining the desired hardness and optical properties.
Solution Approach 2:
The silicon oxynitride coating is designed to be chemically compatible with glass substrates, forming a stable interface that ensures good adhesion. The coating material and its deposition conditions are optimized to create a strong bond between the coating and glass while maintaining the composite's overall performance characteristics.
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, improving the durability and optical quality of glass substrates by forming a harder, optically-transparent layer that is economically viable and compatible with the underlying glass.
Implementation Method 1
The layer has a Berkovich indenter hardness of at least 10 GPa... the propensity of microductile scratch formation can be dramatically decreased by forming a harder surface layer on the oxide glass
Implementation Method 2
The glass substrate includes a chemically-strengthened glass main body... a compressive stress of at least 10 MPa
Data Source
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AI summary
Scratch-resistant glass substrates including a hard, scratch-resistant layer over a major surface of the substrate are disclosed. The layer may exhibit a hardness, as measured using a Berkovich indenter, of at least 10 GPa and an x-ray amorphous structure along at least a portion of the thickness of the layer. The layer may optionally exhibit an optical transparency of at least 70% and/or a compressive stress of at least 10 MPa.