Transparent Wear-Resistant Coating for Glass Ceramic Substrates
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Solution Overview
Problem
Conventional wear protection layers for glass or glass ceramic substrates face challenges in achieving high scratch resistance, transparency, and thermal stability while maintaining optical properties, particularly due to differences in thermal expansion coefficients and surface roughness, which limits the suitability of coatings like aluminum nitride or boron nitride.
Innovation Solution
A semi-transparent or transparent wear protection layer with a chroma of less than 14 in the CIELAB color system, having a high transmission of at least 60% in the visible wavelength spectrum, and a modulus of elasticity of at least 100 GPa, applied using a sputtering process with controlled nitrogen content and oxygen levels to ensure adhesion and chemical inertness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard material layer based on aluminum nitride or boron nitride is applied to glass ceramic substrates, then scratch resistance is improved, but thermal expansion compatibility deteriorates due to high thermal expansion coefficients
Solution Approach 1:
The patent applies a composite coating system consisting of multiple layers: a base layer of aluminum nitride or boron nitride providing hardness and scratch resistance, combined with intermediate and top layers of silicon nitride, silicon oxynitride, or silicon oxide that provide thermal expansion compatibility with glass ceramic substrates. This multi-layer composite structure allows each layer to fulfill its specific function while working together to resolve the contradiction between hardness and thermal compatibility.
Solution Approach 2:
The patent modifies the chemical composition parameters of the coating layers by controlling the nitrogen and oxygen content. Specifically, it uses silicon nitride layers with controlled nitrogen content and silicon oxide layers with controlled oxygen content to adjust the thermal expansion coefficient of the overall coating system, making it compatible with glass ceramic substrates while maintaining the protective hardness of the aluminum nitride/boron nitride base layer.
2Illumination intensity
If a transparent wear protection layer is applied to glass or glass ceramic substrates, then optical properties are improved, but wear resistance deteriorates
Solution Approach 1:
The patent creates a multi-layer composite coating where transparent layers of silicon oxide or silicon oxynitride provide optical clarity and low chroma, while the underlying aluminum nitride or boron nitride base layer provides wear resistance. The intermediate silicon nitride layer serves as a transition zone, ensuring adhesion between the transparent top layer and the hard base layer, thus achieving both transparency and wear resistance simultaneously.
3Stability of the object's composition
If the thermal expansion coefficient of the coating is reduced to match glass ceramic substrates, then thermal stability is improved, but the selection of suitable coating materials is limited
Solution Approach 1:
The patent overcomes material selection limitations by using composite coating systems. The base layer can use aluminum nitride or boron nitride for hardness, while the intermediate and top layers use silicon nitride, silicon oxynitride, or silicon oxide to adjust the overall thermal expansion coefficient to match glass ceramic substrates. This composite approach provides versatility in material selection while achieving thermal stability.
Solution Approach 2:
The patent changes the chemical composition parameters of the coating layers, specifically controlling the nitrogen-to-oxygen ratio in silicon-based compounds. By adjusting these compositional parameters, the thermal expansion coefficient of the overall coating system can be tuned to match glass ceramic substrates, expanding the range of suitable coating materials beyond those with naturally matching thermal properties.
4Illumination intensity
If the surface roughness of the wear protection layer is reduced, then optical clarity is improved, but adhesion to the substrate deteriorates
Solution Approach 1:
The patent uses a multi-layer composite structure where the intermediate silicon nitride layer provides a rougher surface that enhances adhesion to the aluminum nitride or boron nitride base layer, while the top silicon oxide or silicon oxynitride layer provides a smooth, optically clear surface. This composite structure resolves the contradiction by distributing the surface properties across different layers.
Solution Approach 2:
The patent applies different surface qualities to different layers of the coating system. The intermediate layer has higher surface roughness optimized for adhesion, while the top layer has low surface roughness optimized for optical clarity. This local differentiation of surface properties allows each layer to fulfill its specific function without compromising the other.
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 provides a wear protection layer that is both scratch-resistant and transparent, maintaining high light transmittance and optical clarity while being chemically inert and thermally stable, suitable for applications like cooking surfaces and glass ceramics, with improved adhesion and resistance to mechanical and thermal stresses.
Implementation Method 1
The object of the invention is solved surprisingly simply by the subject matter of the independent claims... applied using a sputtering process with controlled nitrogen content and oxygen levels
Data Source
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AI summary
The present invention relates to a semi-transparent or transparent wear-resistant coating for substrates. The invention further relates to a substrate with such a semi-transparent or transparent wear-resistant coating and a method for its production. The wear-resistant coating is formed at least partially on at least one surface of the substrate and exhibits a chromaticity in the CIELAB color system of C* less than 14, preferably less than 7, and particularly preferably less than 4 when illuminated, as measured by reflectance under standard illuminant A or standard illuminant C, or under blackbody radiation with a temperature between 2,500 K and 10,000 K. The wear-resistant coating further exhibits a light transmittance in the visible wavelength spectrum between 380 nm and 780 nm of at least 60%, preferably at least 75%, and particularly preferably at least 80%.