Crystalline Aluminum Nitride Coating for Scratch Resistance
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Solution Overview
Problem
Existing scratch-resistant coatings for glass ceramics face limitations due to thermal expansion coefficient mismatches, restricting the use of hard materials like aluminum nitride, and require enhanced resistance to wear, polishing, and environmental stresses.
Innovation Solution
A transparent, high-refractive hard material layer based on crystalline aluminum nitride with a hexagonal crystal structure and a preferred (001) orientation, exceeding 50% AlN by weight, is applied using sputtering, providing high scratch resistance, chemical resistance, and mechanical durability while maintaining transparency and optical inconspicuousness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If aluminum nitride coating is applied to increase scratch resistance, then hardness is improved, but thermal expansion coefficient mismatch causes layer stresses and reduced reliability
Solution Approach 1:
The patent changes the crystal structure parameter of aluminum nitride from amorphous to crystalline hexagonal phase, which fundamentally alters the thermal expansion coefficient to match glass ceramic substrates, thereby reducing layer stresses while maintaining high scratch resistance
Solution Approach 2:
The patent creates a composite coating system where crystalline aluminum nitride is combined with specific crystal orientation (c-axis perpendicular to substrate) to achieve both high hardness and thermal compatibility, effectively combining properties that were previously mutually exclusive
2Strength
If crystalline structure is used to improve mechanical resistance, then hardness and elasticity are improved, but surface roughness increases leading to more defects
Solution Approach 1:
The patent optimizes crystallite size parameter to the nanometer range (5-50 nm), which is sufficient to provide mechanical strength through crystalline structure while small enough to minimize surface roughness and defect formation
Solution Approach 2:
The patent controls the orientation dimension of crystallites by ensuring c-axis perpendicularity to the substrate surface, which provides mechanical strength in the relevant direction while maintaining smooth surface topology in the lateral dimensions
3Strength
If high AlN content is used to improve scratch resistance, then hardness is improved, but transparency decreases
Solution Approach 1:
The patent changes the crystalline phase and orientation parameters of aluminum nitride, which modifies the optical properties to reduce light scattering while maintaining high hardness, allowing >80% transparency even with high AlN content
Solution Approach 2:
The patent exploits the anisotropic optical properties of hexagonal crystalline AlN by orienting crystals with c-axis perpendicular to substrate, which minimizes light scattering in the visible spectrum while maintaining mechanical strength
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 coating achieves superior scratch resistance, wear resistance, and environmental durability with enhanced mechanical properties, including high transparency and resistance to cleaning agents, making it suitable for optical and cooking surfaces.
Implementation Method 1
The coating according to the invention and the correspondingly coated substrate can in particular be produced by sputtering
Data Source
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AI summary
The invention relates to a substrate with a coating for increasing scratch resistance, wherein the coating comprises at least one high-refractive-index, transparent hard layer. The hard layer contains crystalline aluminum nitride, which has a hexagonal crystal structure with a predominant (001) preferred orientation of the hexagonal symmetry. The invention further relates to a method for producing a correspondingly coated substrate and its use.