Multi-Layer Anti-Reflective Coating Hardness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional glass substrates used in consumer electronics, such as Gorilla® Glass, exhibit insufficient hardness for many applications, leading to inadequate scratch resistance and optical performance issues like increased reflectivity and reduced clarity.
Innovation Solution
A multi-layer coating structure is applied to the glass substrate, comprising layers with specific chemical compositions and thicknesses, including silicon nitride and silicon oxynitride, to enhance hardness and maintain desirable optical characteristics like anti-reflectivity and clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer coating is applied to increase hardness, then scratch resistance is improved, but optical performance (anti-reflectivity and clarity) deteriorates
Solution Approach 1:
The patent divides the coating into multiple layers with different compositions and functions. The first layer (higher nitrogen content) provides hardness and scratch resistance, while the second layer (lower nitrogen content) optimizes optical performance by reducing reflectivity and improving clarity. This segmentation allows each layer to specialize in one function rather than trying to achieve all properties in a single layer.
Solution Approach 2:
Different regions of the coating have different compositions tailored to local requirements. The first layer near the glass substrate has higher nitrogen content for maximum hardness where scratch resistance is most needed, while the outer second layer has lower nitrogen content for optimal optical performance where light interaction occurs. This local quality variation resolves the contradiction between hardness and optical properties.
2Strength
If the nitrogen content in silicon oxynitride coating is increased to improve hardness, then scratch resistance is enhanced, but reflectivity increases and optical clarity deteriorates
Solution Approach 1:
The coating is segmented into two layers with different nitrogen contents. The first layer has higher nitrogen content (30-40 at%) to provide hardness without excessive reflectivity, while the second layer has lower nitrogen content (15-30 at%) to minimize reflectivity and maximize optical clarity. This segmentation prevents the harmful effect of high reflectivity that would result from uniformly high nitrogen content throughout the coating.
Solution Approach 2:
The patent changes the nitrogen content parameter across different layers of the coating. By varying the nitrogen concentration from the first layer to the second layer, the coating achieves a gradient of properties that balances hardness and optical performance. This parameter change allows optimization of both scratch resistance and anti-reflective properties simultaneously.
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 multi-layer coating structure achieves a hardness of over 15 GPa, significantly improving scratch resistance while maintaining low total reflectance, thus addressing the limitations of single-layer coatings in achieving both high hardness and optimal optical performance.
Implementation Method 1
The intermediate layer and the first and second outer layers are formed from materials having respective refractive indices... formed by physical vapor deposition
Implementation Method 2
A desirable scratch resistant coating... is thin, of high hardness... anti-reflective... The multi-layer coating structure achieves a hardness of over 15 GPa, significantly improving scratch resistance while maintaining low total reflectance
Data Source
AI summary
Methods and articles are provide for: a substrate having first and second opposing surfaces; an intermediate layer substantially covering the first surface of the substrate, the intermediate layer being between about 1-5 microns in thickness and having a hardness of at least 15 GPa; a first outer layer substantially covering the intermediate layer; and a second outer layer substantially covering the first outer layer, and having a hardness of at least 15 GPa.