Thin Anti-Reflection Coatings with High Hardness and IR Transmission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing anti-reflective coatings for cover articles are susceptible to abrasion, leading to degradation in optical performance and durability, particularly in applications requiring high visible light transmission and infrared transmission, and are often thick, increasing manufacturing costs.
Innovation Solution
A thin, multi-layer anti-reflective coating structure comprising alternating high refractive index and low refractive index layers with a capping low refractive index layer, made of silicon-containing materials, providing a maximum hardness of 8 GPa or greater and maintaining high infrared transmission and abrasion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If known anti-reflective coatings are used to improve optical performance, then light transmittance is improved, but abrasion resistance deteriorates
Solution Approach 1:
The patent employs a multi-layer composite structure consisting of alternating high refractive index layers (silicon-containing nitride or oxynitride) and low refractive index layers (silicon-containing oxide). This composite material approach allows the coating to simultaneously achieve high light transmittance through optical interference effects and superior abrasion resistance through the hardness of the nitride/oxynitride layers, directly resolving the contradiction between optical performance and durability
Solution Approach 2:
Different layers in the coating structure are assigned different local properties: high refractive index layers provide hardness and abrasion resistance, while low refractive index layers provide optical performance. The capping layer with specific hardness ≥8 GPa is applied at the surface to provide localized protection against abrasion. This spatial differentiation of material properties allows simultaneous optimization of both transmittance and abrasion resistance
2Illumination intensity
If anti-reflective coating thickness is increased to improve optical performance, then light transmittance is improved, but manufacturing cost increases
Solution Approach 1:
The patent optimizes the thickness parameters of individual layers to achieve high optical performance at reduced total thickness. The high refractive index layers have thicknesses of 5-20 nm and low refractive index layers have thicknesses of 10-30 nm, with the total coating thickness controlled at 50-500 nm. By precisely controlling these dimensional parameters, the coating achieves superior light transmittance while minimizing material consumption and manufacturing cost
3Ease of manufacture
If anti-reflective coating thickness is reduced to lower manufacturing cost, then manufacturing cost is reduced, but abrasion resistance deteriorates
Solution Approach 1:
The multi-layer composite structure with alternating high and low refractive index layers provides enhanced abrasion resistance despite reduced total thickness. The high refractive index silicon-containing nitride/oxynitride layers inherently possess high hardness, and the capping layer is specifically designed with hardness ≥8 GPa to provide superior surface protection. This composite approach maintains durability while reducing overall coating thickness and cost
Solution Approach 2:
The capping layer is specifically engineered with high hardness (≥8 GPa) and applied at the surface location where abrasion resistance is most critical. This localized concentration of protective properties ensures that even though the total coating thickness is reduced, the surface maintains superior abrasion resistance, resolving the contradiction between thinness and durability
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 achieves high infrared transmission and abrasion resistance while maintaining optical performance and reducing thickness, thereby addressing the issues of durability and manufacturing costs.
Implementation Method 1
a plurality of alternating high refractive index (RI) and low RI layers with a first low RI layer directly on and in contact with the first major surface
Implementation Method 2
an optical film structure in direct contact with the first major surface of the substrate, the optical film structure comprising a physical thickness from about 50 nm to less than 500 nm
Data Source
AI summary
An article is described that includes: a substrate having opposing major surfaces; and an optical film structure in direct contact with a first major surface and comprising a physical thickness from ˜50 nm to less than 500 nm, high refractive index (RI) and low RI layers with a first low RI layer directly on the first major surface, and a capping low RI layer. The high and low RI layers total three (3) layers to nine (9) layers, wherein each low RI layer and the capping low RI layer comprises a silicon-containing oxide and each high RI layer comprises a silicon-containing nitride or oxynitride. The article exhibits a Berkovich maximum hardness of 8 GPa or greater measured over an indentation depth ≥˜50 nm. The article exhibits a two-side average transmittance >85% at infrared wavelengths from 840 to 860 nm and from 930 to 950 nm at 0° incidence.