Photochromic Lens Hardness Gradient for Fading Rate and Scratch Resistance
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Solution Overview
Problem
Conventional photochromic films struggle to achieve both high optical responsivity and lens strength, as methods to improve responsivity by making the film soft result in low scratch resistance and adhesion.
Innovation Solution
A photochromic layer with controlled three-dimensional hardness, combined with a protective film, where the hardness ratio between the two is within a specific range, ensuring high strength and optical responsivity while maintaining sufficient adhesion and scratch resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the photochromic film is made soft to improve optical responsivity and fading rate, then the fading rate and optical responsivity are improved, but the scratch resistance and adhesion are reduced
Solution Approach 1:
The invention divides the lens structure into multiple functional layers: a photochromic layer containing the dye and a separate protective layer. This segmentation allows the photochromic layer to remain soft for high fading rate while the protective layer provides the necessary hardness for scratch resistance and adhesion.
Solution Approach 2:
Different regions of the lens structure are assigned different properties: the photochromic layer has low hardness (0.1-10 mgf/μm²) to enable fast fading, while the protective layer has high hardness (10-100 mgf/μm²) to provide durability. This local differentiation of material properties resolves the contradiction between softness for responsivity and hardness for strength.
2Speed
If the photochromic film is made soft to improve optical responsivity, then the fading rate is improved, but the adhesion is reduced
Solution Approach 1:
The invention separates the adhesion function from the photochromic function by introducing a protective layer. The photochromic layer maintains softness for fast fading while the protective layer provides the necessary adhesion to the substrate, preventing peeling.
Solution Approach 2:
The protective layer acts as an intermediary between the soft photochromic layer and the substrate. It mediates the adhesion requirement, allowing the photochromic layer to remain soft while the protective layer ensures strong bonding to the substrate through its higher hardness and adhesive properties.
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 a spectacle lens with high strength and high optical responsivity, particularly a high fading rate, while maintaining adequate adhesion and scratch resistance.
Implementation Method 1
organic photochromic dyes develop color in response to light including ultraviolet rays, such as sunlight, in bright outdoor environments and return their original color (colorless state) in the absence of ultraviolet rays
Data Source
AI summary
An optical article, such as a spectacle lens, includes, on a substrate, a photochromic layer containing a photochromic dye and a resin component, and a protective film. The indentation hardness of the photochromic layer in the thickness direction is less than or equal to the indentation hardness of the surface of the substrate. The result of multiplying the indentation hardness of the protective film in the thickness direction and the thickness of the protective film is five-hundredths or more times and one or less times the result of multiplying the indentation hardness of the photochromic layer in the thickness direction and the thickness of the photochromic layer.