Interferential Ophthalmic Lens Coating for IR Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ophthalmic lenses face challenges in achieving high visible transmittance while effectively filtering infrared radiation and minimizing angular dispersion in residual reflection, often requiring complex solutions that result in high thickness and mechanical issues such as residual stress and delamination, especially in organic-based lenses.
Innovation Solution
A multi-layer coating structure with specific thickness ranges and refractive index layers, including interphase and intermediate layers, is applied to ophthalmic lenses, achieving infrared radiation filtering and anti-reflective properties with limited angular dispersion and maintaining low visible reflection, all within a total thickness of less than 600 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If metal layers are applied to filter IRA radiation, then infrared filtering is improved, but visible light absorption increases causing loss of visible transmittance
Solution Approach 1:
The patent uses a composite multi-layer structure combining materials with different refractive indices (high index layers like TiO2, ZrO2, Nb2O5 with n>1.8 and low index layers like SiO2, MgF2, Al2O3 with n<1.65) to create interferential filtering. This composite approach replaces metal layers with dielectric materials that can selectively reflect infrared radiation while maintaining high visible light transmittance through constructive and destructive interference patterns.
Solution Approach 2:
The patent optimizes specific parameters including layer thicknesses (total thickness 200-1000 nm with individual layers ranging from 20-300 nm), refractive index contrasts (nD > 1.8 vs nD < 1.65), and spectral characteristics to achieve wavelength-selective filtering. By precisely controlling these parameters, the coating reflects IRA radiation (780-1400 nm) while maintaining high transmission in the visible range (380-780 nm).
2Object-affected harmful factors
If heat mirror type interferential filters with 40-100 layers are used, then infrared radiation transmittance is reduced, but the lens displays iridescence and residual colouring reducing aesthetic appeal
Solution Approach 1:
The patent reduces the number of layers from 40-100 down to just 2-6 layers by optimizing the refractive index contrast between adjacent layers and precisely controlling layer thicknesses. This parameter optimization allows achieving the same infrared filtering effect with far fewer layers, thereby eliminating iridescence and residual colouring while maintaining aesthetic appearance.
Solution Approach 2:
The patent applies different refractive index materials strategically at different positions in the coating structure. High index materials (TiO2, ZrO2, Nb2O5) are positioned to maximize infrared reflection, while low index materials (SiO2, MgF2, Al2O3) are positioned to control visible light transmission. This localized material assignment achieves spectral selectivity without aesthetic degradation.
3Object-affected harmful factors
If complex multi-layer structures with many layers are applied, then infrared filtering performance is improved, but mechanical stress and delamination increase
Solution Approach 1:
The patent uses a composite structure with alternating high and low refractive index dielectric layers that are chemically compatible and have matched thermal expansion coefficients. This composite design reduces internal mechanical stress compared to metal layers or excessive dielectric layers, preventing delamination while maintaining infrared filtering performance.
Solution Approach 2:
The patent optimizes the total coating thickness to 200-1000 nm and individual layer thicknesses to specific ranges (20-300 nm) to achieve the required optical performance with minimal layers. This parameter control reduces the cumulative mechanical stress that would accumulate in thicker, multi-layer structures, thereby improving mechanical stability and preventing delamination.
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 effectively filters infrared radiation, maintains anti-reflective properties in the visible spectrum with low angular dispersion, and reduces blue light transmission, providing enhanced protection and aesthetic appeal while minimizing mechanical stress in ophthalmic lenses.
Implementation Method 1
The technology of multiple layer structures is known for creating interferential effects on optical surfaces
Implementation Method 2
a first high refraction index layer, of a material from the group made up of oxides, nitrides or oxynitrides of Zr, Ti, Sb, In, Sn, Ta, Nb, Hf and mixtures thereof, with a refraction index nD higher than 1.8, a second low refraction index layer, of a material from the group made up of SiO2, MgF2, Al2O3, LaF3 and mixtures thereof, with a refraction index nD lower than 1.65
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Ophthalmic lens comprising a base of polymeric material with a coating having an interferential, anti-reflective, anti-iridescent and IR filter multiple layer structure. Ophthalmic lens with a multiple layer structure comprising an interphase, a first layer (of 91-169nm) with a refraction index higher than 1.8, a second layer (of 128-248nm) with a refraction index lower than 1.65, a third layer (of 73-159nm) with a refraction index higher than 1.8 and a fourth layer (of 40-138nm) with a refraction index lower than 1.8. The total thickness of the multiple layer structure is less than 600nm. The structure can have intermediate layers with intermediate refraction indices, in which case the doublet made up of two adjacent layers that fulfil the thicknesses above is replaced by a triplet so that the thickness and the optical thickness of the triplet differ from those of the doublet by less than 5%, respectively.