Anti-Reflective Optical Coating for Durable Curved Cover Surfaces
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Solution Overview
Problem
Existing anti-reflective coatings on non-planar substrates, such as those found in curved or faceted surfaces, are susceptible to wear, abrasion, and scratch damage, compromising their optical performance and durability.
Innovation Solution
A coated article with an optical coating that exhibits a hardness of 8 GPa or greater at an indentation depth of 100 nm or greater, and a single side maximum light reflectance of 3% or less, applied to both planar and non-planar surfaces, using a substrate with varying normal directions and deposition techniques that account for substrate curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional anti-reflective coatings are applied to non-planar substrates, then optical performance is improved, but the coatings become susceptible to wear, abrasion, and scratch damage
Solution Approach 1:
The patent applies a composite optical coating structure consisting of multiple layers with different refractive indices and mechanical properties. The coating includes at least two layers: a first layer with higher hardness applied to the curved or faceted portion, and a second layer with optimized optical properties applied to the planar portion. This composite structure combines the scratch resistance of hard materials with the optical performance of multi-layer dielectric coatings, resolving the contradiction between optical performance and durability.
Solution Approach 2:
The patent implements different coating configurations for different portions of the substrate. The curved or faceted portion receives a coating optimized for hardness and scratch resistance, while the planar portion receives a coating optimized for anti-reflective optical performance. This local differentiation allows each region to have the specific properties needed for its function, maintaining both optical performance and durability across the entire non-planar surface.
2Illumination intensity
If the optical coating thickness is increased to improve optical performance on curved surfaces, then reflectance control improves, but the coating becomes more susceptible to wear and damage
Solution Approach 1:
The patent specifies that the first layer applied to the curved or faceted portion has a thickness optimized for both optical performance and mechanical durability in that specific region. The second layer applied to the planar portion has a different thickness optimized for anti-reflective performance. This localized thickness optimization ensures that no single region compromises overall durability while maintaining optical performance.
Solution Approach 2:
The multi-layer composite structure allows the first layer to provide mechanical protection and scratch resistance on the curved portion, while the second layer provides optimized optical performance on the planar portion. The composite design distributes the functional requirements across layers, preventing the need for excessive thickness in any single layer that would compromise wear resistance.
3Ease of manufacture
If a single coating layer is applied to the entire substrate, then manufacturing is simplified, but optical performance varies across different portions of the non-planar surface
Solution Approach 1:
The patent divides the coating into at least two distinct layers applied to different portions of the substrate. The first layer is applied to the curved or faceted portion with properties optimized for that geometry, while the second layer is applied to the planar portion with properties optimized for flat surfaces. This local differentiation ensures consistent optical performance across the entire non-planar surface, addressing the variation problem while maintaining manufacturing feasibility through a systematic multi-layer approach.
4Reliability
If hard materials like nitrides are used to improve scratch resistance, then hardness increases, but light transmittance decreases
Solution Approach 1:
The patent employs a composite multi-layer structure where the first layer applied to the curved or faceted portion uses harder materials with appropriate refractive indices to provide scratch resistance. The second layer applied to the planar portion uses materials optimized for high light transmittance and anti-reflective performance. This composite approach allows hard materials to be used where mechanically critical without sacrificing overall optical transmittance, as the second layer compensates for optical losses while maintaining the protective function of the first layer.
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 maintains high optical performance and durability by providing consistent reflectance and color stability across different viewing angles, enhancing scratch resistance and abrasion resistance on non-planar substrates.
Implementation Method 1
The optical coating forms an anti-reflective surface, wherein: (b) the coated article exhibits a single side maximum light reflectance of about 3% or less as measured at the anti-reflective surface
Implementation Method 2
There is also a need for optical coating configurations with these properties that are suitable for non-planar cover articles and the various line-of-sight processes for forming such coatings
Data Source
AI summary
A coated article is described herein with a substrate having a major surface that comprises a first portion and a second portion that is curved or faceted; and an optical coating on the major surface that forms an anti-reflective surface. A first direction is normal to the first portion and is not equal to a plurality of second directions that are normal to the second portion, and the angle between the first direction and each of the second directions is from about 10 degrees to 60 degrees. Further, the coated article exhibits at the first and second portion a hardness of about 8 GPa or greater at an indentation depth of about 100 nm or greater. Further, the coated article exhibits a single side maximum reflectance of about 3% or less as the first and second portion, wherein the reflectance is measured in a range from about 425 nm to about 950 nm.