Plastic Spectacle Lens Coating for Inconspicuous Reflected Light
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Solution Overview
Problem
Plastic lenses with antireflection films exhibit conspicuous green-colored reflection due to high luminous reflectance, making them noticeable, especially when used as spectacle lenses.
Innovation Solution
A plastic optical product with an optical multilayer film composed of alternating SiO2 and ZrO2 layers, specifically structured to have a total thickness of 480-530 nm, with ZrO2 layers closest to the base and SiO2 layers at specific thicknesses, achieving a luminous reflectance of ≤0.8% and a bluish-white reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an optical multilayer film with alternating low and high refractive index layers is formed to achieve low reflectance, then the reflectance is reduced, but the reflected light appears green and conspicuous due to high luminous reflectance
Solution Approach 1:
The patent changes the optical parameters of the multilayer film by adjusting the refractive indices of the constituent materials. Specifically, it uses a low refractive index material (n1=1.30-1.50) and a high refractive index material (n2=2.00-2.50), and optimizes the film thicknesses to control the spectral reflectance distribution, thereby reducing luminous reflectance and making reflected light inconspicuous
Solution Approach 2:
The patent directly addresses the color problem by designing the optical multilayer film to produce a spectral reflectance distribution where the reflectance in the green region (500-570 nm) is suppressed. This shifts the reflected light color from conspicuous green to inconspicuous blue or purple, achieving the goal of reducing visual conspicuousness
2Object-affected harmful factors
If the optical multilayer film is designed to reduce reflectance across all wavelengths, then the overall reflectance is reduced, but the green color remains conspicuous due to human eye sensitivity
Solution Approach 1:
The patent specifies precise parameter ranges for the optical multilayer film: the low refractive index material has n1=1.30-1.50, the high refractive index material has n2=2.00-2.50, and the film thicknesses are controlled within specific ranges (first layer: 5-15 nm, second layer: 80-150 nm, third layer: 10-20 nm). These controlled parameters enable suppression of green reflectance while maintaining manufacturability
Solution Approach 2:
Instead of attempting to reduce reflectance uniformly across all wavelengths, the patent applies partial action by specifically targeting the reduction of reflectance in the green wavelength region (500-570 nm) where human eye sensitivity is highest. This selective approach reduces conspicuousness without requiring extreme precision across the entire spectrum
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 reduces the conspicuousness of reflected light, making it inconspicuous and maintaining excellent adherence and durability.
Implementation Method 1
an optical multilayer film as an antireflection film is formed on a surface of a base. The optical multilayer film is formed by stacking eight layers in total such that low refractive index layers and high refractive index layers alternate
Data Source
AI summary
A plastic optical product 1 includes optical multilayer films 6 formed via intermediate films 4 on both surfaces of a plastic base 2. In each optical multilayer film 6, SiO2 layers 10 made of SiO2 and ZrO2 layers 12 made of ZrO2 alternate such that a total number of the SiO2 layers 10 and the ZrO2 layers 12 is eight and a layer closest to the base 2 is the ZrO2 layer. The optical multilayer film 6 has a physical film thickness of not less than 480 nm and not greater than 530 nm. A total of physical film thicknesses of all the SiO2 layers 10 is not less than 350 nm and not greater than 440 nm. The ZrO2 layer 12 that is a first layer L1 closest to the base 2 has a physical film thickness of not less than 5 nm and not greater than 12 nm.