Ophthalmic Lens Antireflective Coating UV Reflection Reduction
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Solution Overview
Problem
Current antireflective coatings for ophthalmic lenses are inadequate in reducing UV radiation reflection from the rear face, leading to potential health risks and aesthetic issues such as varying residual reflected colors and 'chameleon effect', while compromising industrial feasibility and robustness.
Innovation Solution
A multilayered antireflective coating with specific refractive index layers and thicknesses is applied to both the front and rear faces of ophthalmic lenses, optimized to reduce UV radiation reflection and maintain low visible region reflection, ensuring robustness and aesthetic appeal by using a stack of layers with refractive indices higher and lower than 1.6 and 1.55 respectively, and a silica-based outer layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional antireflective coatings are optimized for visible region reflection reduction, then visible region reflection is reduced to 1.5-2.5%, but UV region reflection increases to 10-25% or even up to 60%
Solution Approach 1:
The patent applies parameter changes by carefully controlling the thickness of each layer in the multilayer coating structure. The first layer has a thickness of 50-150 nm, the second layer 100-200 nm, and the third layer 50-150 nm. These specific thickness parameters enable the coating to reduce reflection in both visible and UV regions simultaneously by optimizing the interference conditions for different wavelengths.
Solution Approach 2:
The patent uses composite materials by combining three different dielectric layers with distinct refractive indices (n1=1.3-1.6, n2=1.7-2.0, n3=2.1-2.5). This composite structure creates constructive and destructive interference patterns that reduce reflection across both visible and UV spectra, achieving a mean UV reflection of 5-15% while maintaining visible region performance.
2Object-affected harmful factors
If UV region antireflection is optimized, then UV radiation reflection is reduced, but visible region antireflective performance deteriorates
Solution Approach 1:
The patent segments the antireflective coating into three distinct functional layers, each with specific refractive index ranges and thickness specifications. This segmentation allows each layer to contribute differently to the overall optical performance, with the first layer addressing UV reflection, the second layer managing the transition zone, and the third layer optimizing visible region performance.
Solution Approach 2:
The multilayer coating structure achieves multi-functionality by simultaneously providing UV region reflection reduction (mean UV reflection of 5-15%) and visible region antireflection (mean visible region reflection of 1.5-2.5%). The coating system performs both functions through the coordinated optical interference of its three layers across different wavelength ranges.
3Object-affected harmful factors
If multilayered coating with multiple layers is used to improve UV and visible antireflection, then reflection is reduced in both regions, but manufacturing complexity and production time increase
Solution Approach 1:
The patent optimizes manufacturing feasibility by specifying practical thickness ranges for each layer (first layer: 50-150 nm, second layer: 100-200 nm, third layer: 50-150 nm). These parameters are chosen to be achievable with standard coating equipment while maintaining the optical performance requirements, thus balancing productivity with performance.
Solution Approach 2:
The patent applies local quality by assigning specific refractive index ranges and thickness specifications to each individual layer based on its functional requirements. The first layer (n1=1.3-1.6) is optimized for UV interface management, the second layer (n2=1.7-2.0) for transition control, and the third layer (n3=2.1-2.5) for visible region optimization, allowing targeted optimization without excessive overall complexity.
4Productivity
If conventional coatings are used, then manufacturing is simple and fast, but residual reflected light shows varying colors and 'chameleon effect' under different angles
Solution Approach 1:
The patent uses composite materials with three layers of different dielectric materials having progressively increasing refractive indices. This composite structure creates a more stable optical interference pattern that reduces the chameleon effect and color variations across different viewing angles, providing consistent aesthetic appearance while maintaining industrial manufacturability.
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 low reflection factors in both the visible and UV regions, maintaining robustness and aesthetic appeal by ensuring consistent color appearance and reduced UV radiation exposure, even under oblique incidence, while being industrially feasible.
Implementation Method 1
An antireflection coating usually consists of a multilayer comprising interferential thin layers, generally an alternation of layers based on a dielectric material of high refractive index and a dielectric material of low refractive index
Data Source
Figure 1~2
AI summary
This invention relates to an ophthalmic lens with a low reflection in the ultraviolet region, comprising a substrate with a front main face and a rear main face, said rear main face being coated with a multilayered antireflective coating comprising a stack of at least one layer having a refractive index higher than 1.6 and of at least one layer having a refractive index lower than 1.55, wherein: - the mean reflection factor RUV on said rear face between 280 nm and 380 nm, weighted by the function W(λ), is lower than or equal to 5%, preferably is lower than or equal to 4%, for an angle of incidence of 35°, - the Chroma C* is equal or lower than 4, preferably lower or equal to 3, for an angle of incidence (θ) of 15°.