Multilayer Interferential Coating for Abrasion-Resistant Optical Lenses
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Solution Overview
Problem
Existing optical articles, such as ophthalmic lenses, face challenges in achieving improved abrasion and heat resistance while maintaining low UV reflection properties and optical clarity, with existing coatings often leading to delamination or degradation issues.
Innovation Solution
A multilayer interferential coating system is applied, comprising at least 6 layers with specific refractive index and thickness ratios, including a sub-layer and sheets with precise thicknesses, to enhance abrasion resistance and adhesion, while maintaining low UV reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of high-refractive-index layers in the interferential coating is increased to improve UV reflection control, then optical performance improves, but abrasion resistance deteriorates
Solution Approach 1:
The patent precisely controls the thickness of the outermost high-refractive-index layer to be less than 40 nm, which is a critical parameter change. This thin layer maintains the necessary optical interference effect for UV reflection control while minimizing the layer's contribution to coating brittleness and delamination risk, thereby preserving abrasion resistance.
Solution Approach 2:
The patent uses a composite multilayer structure combining low-refractive-index materials (SiO2, MgF2) and high-refractive-index materials (TiO2, Ta2O5, ZrO2) in specific configurations. This composite approach allows optimization of both optical properties (through refractive index contrast) and mechanical properties (through material selection and layer thickness control).
2Reliability
If ion-assisted vapor deposition is used to increase compressive stress and improve coating density, then coating durability improves, but delamination risk increases
Solution Approach 1:
The patent controls the compressive stress parameter by limiting the thickness of high-refractive-index layers and optimizing the overall coating structure. This parameter control prevents excessive stress accumulation that would lead to delamination, while still achieving adequate coating density and durability through optimized deposition parameters.
Solution Approach 2:
The patent applies different material compositions and thicknesses to different layers within the coating system. Each layer is locally optimized for its specific function, with low-refractive-index layers providing structural stability and high-refractive-index layers providing optical functionality, while the overall structure maintains stress balance.
3Strength
If the ratio of SiO2 layer thickness to TiO2 layer thickness is increased to improve abrasion resistance, then coating hardness improves, but UV reflection control deteriorates
Solution Approach 1:
The patent optimizes the thickness ratio parameter between SiO2 and TiO2 layers, specifically limiting the TiO2 layer thickness to less than 40 nm for the outermost layer. This parameter optimization achieves a balance where sufficient SiO2 provides abrasion resistance while adequate TiO2 maintains UV reflection control through optical interference.
Solution Approach 2:
The patent employs a composite layer structure where SiO2 layers provide mechanical protection and TiO2 layers provide optical functionality. The composite design allows each material to contribute its optimal properties while working together to achieve both abrasion resistance and UV reflection control.
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 provides enhanced abrasion and heat resistance with improved adhesion to the substrate, maintaining optical clarity and low UV reflection, suitable for ophthalmic lenses and other optical articles.
Implementation Method 1
a multilayer interferential coating comprising a stack of at least 6 layers with at least one high refractive index layer and at least one low refractive index layer
Implementation Method 2
These coatings are designated in general as functional coatings
Data Source
AI summary
The invention relates to an optical lens comprising a substrate having a front main face and a rear main face, said rear main face of which being successively coated with: —(A) a first high refractive index sheet having a refractive index higher than 1.55, which does not comprise any TaaOs layer, —(B) a second low refractive index sheet having a refractive index of 1.55 or less in direct contact with the former sheet, —(C) a third high refractive index sheet having a refractive index higher than 1.55 in direct contact with the former sheet, —a monolayer sub-layer having a thickness higher than or equal to 100 nm in direct contact with the former sheet (C), —a multilayer interferential coating comprising a stack of at least 6 layers with at least one high refractive index layer and at least one low refractive index layer, wherein the outermost high refractive index layer of the multilayer interferential coating has a thickness lower than 40 nm, and the mean reflection factor RUV on said rear main face between 280 nm and 380 nm, weighted by the function W(λ) defined in the ISO 13666:1998 standard, is lower than 10%, for an angle of incidence of 35°.