Plastic Spectacle Lens Multilayer Coating to Reduce Green Reflection
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Solution Overview
Problem
Plastic lenses with antireflection films exhibit conspicuous green-colored reflection due to their 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, where the layer closest to the base is ZrO2, and specific film thicknesses are optimized to reduce luminous reflectance to less than 0.8%, resulting in inconspicuous white or bluish-white reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an optical multilayer film is formed on a plastic lens to reduce reflectance, then the reflectance is reduced, but the reflected light appears conspicuous green color due to high luminous reflectance
Solution Approach 1:
The patent changes the physical film thickness parameters of the optical multilayer film to a specific range (480-530 nm total thickness with controlled SiO2 layer thickness) to shift the spectral reflectance distribution. This parameter optimization reduces luminous reflectance by controlling the interference pattern of reflected light waves, thereby minimizing the conspicuous green reflection while maintaining low overall reflectance
Solution Approach 2:
The patent uses a composite optical multilayer film structure with alternating layers of SiO2 and ZrO2 materials. This composite structure exploits the different refractive indices of the materials to create destructive interference for green light wavelengths, converting the harmful green reflection into beneficial reduced luminous reflectance
2Object-generated harmful factors
If the optical multilayer film is designed with specific thickness to reduce luminous reflectance, then the reflected light becomes less conspicuous, but the manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for film thickness (total thickness 480-530 nm, SiO2 layer thickness controlled within specific bounds) that provide an optimal balance between reducing conspicuous reflection and maintaining manufacturability. These parameter specifications ensure sufficient tolerance for manufacturing variations while achieving the desired optical effect
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 minimizes the visibility of reflected light, providing a more inconspicuous appearance and enhancing the aesthetic appeal of plastic lenses.
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
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AI summary
Provided is a plastic optical product that allows reflected light to be more inconspicuous. 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.