Durable Multilayer Anti-Reflective Coatings for Cover Articles
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Solution Overview
Problem
Existing anti-reflective coatings on cover articles are susceptible to abrasion, leading to compromised optical performance and durability issues, particularly in applications requiring scratch-resistance and strong optical performance characteristics.
Innovation Solution
Development of a multi-layer anti-reflective coating with a thickness of 1 μm or less, comprising alternating layers of low and high refractive index materials, which exhibits abrasion resistance through a Taber Test, with haze of 1% or less, average roughness of 12 nm or less, and scattered light intensity of 0.05 or less, and includes additional coatings like diamond-like carbon for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional anti-reflective coatings are used to improve optical performance, then light transmittance and reflectance are improved, but abrasion resistance deteriorates
Solution Approach 1:
The coating system is divided into multiple functional layers: a base anti-reflective coating layer for optical performance and a separate overcoat layer for abrasion resistance. This segmentation allows each layer to be optimized for its specific function without compromising the other.
Solution Approach 2:
The patent uses composite material structures combining different coating materials with complementary properties. The base layer uses materials optimized for optical performance while the overcoat uses materials optimized for durability and scratch resistance, creating a composite system that achieves both goals.
2Illumination intensity
If coating thickness is reduced to improve optical performance, then angular color shift is minimized, but abrasion resistance deteriorates
Solution Approach 1:
The protective function is separated from the optical function by placing a thin anti-reflective base layer (for minimal angular color shift) and a separate overcoat layer (for abrasion resistance). This allows the base layer to remain thin for optimal optics while the overcoat provides the necessary protective thickness.
Solution Approach 2:
Different regions of the coating system have different properties: the base layer is optimized for optical quality with minimal thickness to reduce angular color shift, while the overcoat is optimized for mechanical durability and scratch resistance, providing local quality enhancement where needed.
3Reliability
If hard materials like nitrides are used to improve abrasion resistance, then scratch resistance is improved, but light transmittance deteriorates
Solution Approach 1:
The functional separation places hard, scratch-resistant materials in the overcoat layer while keeping the base anti-reflective layer thin and optimized for light transmittance. This segmentation prevents the transmittance-damaging hard materials from being in the primary optical path while still providing scratch resistance through the overcoat.
Solution Approach 2:
Hard materials with superior scratch resistance are applied locally in the overcoat layer rather than throughout the entire coating system. This allows scratch resistance to be enhanced at the surface level without compromising the light transmittance properties of the underlying base 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 superior optical performance with minimal angular color shift and improved abrasion resistance, ensuring consistent light transmittance and reflectance across varying angles, with haze and roughness maintained at low levels even after 500 cycles of abrasion.
Implementation Method 1
The optical performance of cover articles can be improved by using various anti-reflective coatings
Implementation Method 2
Nitrides and diamond-like coatings may exhibit high hardness values
Data Source
AI summary
Embodiments of durable, anti-reflective articles are described. In one or more embodiments, the article includes a substrate and an anti-reflective coating disposed on the major surface. The article exhibits an average light transmittance of about 94% or greater over an optical wavelength regime and/or an average light reflectance of about 2% or less over the optical wavelength regime, as measured from an anti-reflective surface. In some embodiments, the article exhibits a maximum hardness of about 8 GPa or greater as measured by a Berkovich Indenter Hardness Test along an indentation depth of about 50 nm or greater and a b* value, in reflectance, in the range from about −5 to about 1 as measured on the anti-reflective surface only at all incidence illumination angles in the range from about 0 degrees to about 60 degrees under an International Commission on Illumination illuminant.