Thin Antireflective Coating for Ophthalmic Lenses
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Solution Overview
Problem
Existing antireflective coatings for ophthalmic lenses are either too thick, leading to thermomechanical weakness and optical performance issues, or too thin, resulting in inadequate reflection reduction, especially in the visible and UV regions, while also being difficult to implement and reproduce effectively.
Innovation Solution
A thin antireflective coating comprising a metal layer with a thickness of at least 6 nm, combined with a wetting layer and a protective layer, which avoids plasmonic effects and ensures a continuous metal layer, eliminating the need for silicon nitride and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional multilayer antireflective coating is used, then good optical properties are achieved, but the coating becomes too thick (200-250 nm) causing thermomechanical weakness and robustness issues
Solution Approach 1:
The patent changes the material composition parameters by introducing a metal layer (silver, aluminum, or tin) with specific thickness (5-15 nm) into the antireflective coating structure. This parameter change enables achieving good optical properties with a thinner overall coating structure, resolving the contradiction between optical performance and coating thickness.
Solution Approach 2:
The patent uses composite materials by combining metal layers with dielectric materials (such as silicon nitride, silicon oxide, or titanium oxide) to create a multilayer antireflective coating. This composite structure achieves both thin profile and good optical properties, resolving the contradiction between thickness and optical performance.
2Length of stationary object
If the antireflective coating is made thinner to improve robustness, then manufacturing robustness improves, but optical performance deteriorates with insufficient reflection reduction
Solution Approach 1:
The patent optimizes the thickness parameters of individual layers, particularly the metal layer (5-15 nm) and dielectric layers, to achieve the desired optical performance with reduced overall thickness. This parameter optimization ensures sufficient reflection reduction while maintaining manufacturing robustness.
Solution Approach 2:
The patent applies local quality by using different materials with specific properties in different layers of the coating. The metal layer provides specific optical properties, while dielectric layers provide structural support and additional optical functionality, enabling thin overall thickness with maintained optical performance.
3Length of stationary object
If very thin metal layers (less than 5 nm) are used to reduce thickness, then coating thickness is reduced, but continuous metal layer formation becomes difficult and optical performances deteriorate due to plasmonic effects
Solution Approach 1:
The patent sets the metal layer thickness parameter within the optimal range of 5-15 nm, which is thick enough to ensure continuous layer formation and avoid plasmonic effects, yet thin enough to maintain overall coating thinness and good optical performance. This parameter optimization resolves the contradiction between thickness reduction and continuous layer formation.
4Reliability
If multiple dielectric layers are used to achieve good antireflection, then optical performance is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent uses a composite structure with a metal layer combined with one or more dielectric layers, which achieves good antireflection performance with a simplified structure compared to traditional multilayer dielectric coatings. This composite approach reduces manufacturing complexity while maintaining optical performance.
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 excellent antireflective performance in both the visible and UV regions, enhancing robustness and aesthetic appearance while maintaining economic and industrial feasibility, with improved reproducibility and optical clarity.
Implementation Method 1
An antireflection coating usually consists of a multilayer comprising interferential thin layers... the function of such a coating is to reduce its light reflection
Implementation Method 2
combined with a wetting layer and a protective layer
Implementation Method 3
the metal layer has a physical thickness equal to or higher than 6 nm... combined with a wetting layer and a protective layer
Data Source
Figure 1~2
Figure 3~4
Figure 5~6(b)
AI summary
This invention relates to an ophthalmic lens comprising a transparent substrate with a front main face and with a rear main face, at least one of the main faces being coated with a multilayered antireflective coating comprising a stack composed of at least: (i) a wetting layer; (ii) a metal layer, wherein the metal is selected from silver, gold or copper or mixtures thereof; (iii) a protective layer which is able to avoid oxidation of said metal layer, characterized in that wetting layer (i) is in direct contact with metal layer (ii), with the proviso that said multilayered antireflective coating does not comprise silicon nitride and wherein (ii) the metal layer has a physical thickness equal to or higher than 6 nm.