Interferential Optical Coating for Abrasion and Thermal Stability
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Solution Overview
Problem
Existing optical articles, such as ophthalmic lenses, face challenges in achieving improved abrasion resistance and thermal stability without compromising optical and mechanical performance, as conventional coatings often lead to delamination or decreased durability.
Innovation Solution
A multilayer interferential coating with a specific ratio of outermost low refractive index layer thickness to outermost high refractive index layer thickness, combined with a thick sub-layer and ionic assistance deposition, enhances abrasion resistance and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the total thickness of the anti-reflection coating is increased to improve abrasion resistance, then abrasion resistance is improved, but the coating becomes more prone to delamination and thermal instability
Solution Approach 1:
The coating is divided into multiple functional layers with different thicknesses and material compositions. The outermost layer has low refractive index and specific thickness to provide abrasion resistance, while inner layers have progressively different optical and mechanical properties to manage stress distribution and prevent delamination, resolving the contradiction between thickness for abrasion resistance and layer structure for adhesion stability
Solution Approach 2:
The patent specifies precise parameter ranges for each layer including refractive index, physical thickness, and optical thickness ratios. By controlling the ratio of physical thickness of outermost low refractive index layer to outermost high refractive index layer within specific ranges, and controlling total optical thickness, the coating achieves optimal balance between abrasion resistance and thermal/adhesion stability
2Strength
If ion-assisted vapor deposition is used to increase compressive stress and improve durability, then abrasion resistance is improved, but delamination occurs due to excessive stress
Solution Approach 1:
The patent controls the deposition parameters including ion assistance level, deposition temperature, and layer thickness to achieve specific compressive stress ranges. By managing stress accumulation through controlled ion assistance and layer design, the coating achieves durability without exceeding adhesion limits that would cause delamination
3Illumination intensity
If high refractive index materials are used to improve optical performance, then antireflection properties are improved, but thermal resistance decreases
Solution Approach 1:
Different layers are assigned different material compositions with locally optimized properties. Outer layers use materials with lower refractive index and higher thermal stability, while inner layers may use higher refractive index materials where thermal exposure is less critical, achieving both optical performance and thermal resistance through spatial differentiation of material properties
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 higher abrasion resistance, better adhesion, and improved thermal stability, maintaining optical performance and mechanical integrity.
Implementation Method 1
a multilayer transparent interferential coating, typically an antireflection coating
Implementation Method 2
a method of manufacturing such optical article
Data Source
AI summary
The invention relates to an optical article having a Bayer value determined in accordance with the ASTM F735-81 standard higher than or equal to 7, comprising a substrate having at least one main face successively coated with a monolayer sub-layer having a thickness higher than or equal to 250 nm and a multilayer interferential coating comprising a stack of at least one high refractive index layer having a refractive index higher than 1.55 and at least one low refractive index layer having a refractive index of 1.55 or less. The ratio: (I) is higher than or equal to 1.5, and/or the deposition of the high refractive index layer of the interferential coating having a refractive index higher than 1.55 and a thickness higher than or equal to 15 nm that is the furthest from the substrate has been carried out under ionic assistance.RD=thickness of the outermost low refractive indexlayer(s) of the interferential coatingthickness of the outermost high refractive indexlayer(s) of the interferential coating(I)