Plastic Spectacle Lens with UV-Absorbing Hard Coating
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Solution Overview
Problem
Plastic spectacle lenses that absorb light below 400 nm alter the perceived color, making them unsuitable for applications where color accuracy is crucial, and glass lenses offer high transmittance but are heavy and prone to breakage, compromising handleability and comfort.
Innovation Solution
A plastic spectacle lens with a high transmittance across the visible range, achieved by a plastic base with a hard coating layer containing metal oxide particles and an antireflection film, ensuring minimal color shift when viewed through the lens compared to naked eyes, while maintaining excellent handleability and comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plastic spectacle lens absorbs light having a wavelength of not less than 300 nm and less than 400 nm, then eye protection and lens degradation prevention are improved, but color accuracy deteriorates
Solution Approach 1:
The patent changes the absorption wavelength parameter from absorbing light below 400 nm to absorbing light below 380 nm. This parameter adjustment allows the lens to maintain eye protection functionality while improving color accuracy, as the absorption edge is shifted to a shorter wavelength that has less impact on the visible spectrum
Solution Approach 2:
The patent applies different properties to different parts of the spectrum by using a UV absorber that specifically targets the 380 nm boundary. The absorption characteristic is localized to the ultraviolet region below 380 nm, while allowing full transmission in the visible region above 380 nm, thus achieving both protection and color accuracy
2Measurement precision
If a glass spectacle lens is used to achieve high transmittance of about 80% for light having a wavelength of 380 nm, then color accuracy is improved, but weight and breakability worsen
Solution Approach 1:
The patent creates a plastic lens that copies the optical properties of glass lenses by achieving similar transmittance characteristics in the visible range (80% or more at 380 nm). The plastic lens replicates the color transmission performance of glass without inheriting its weight and fragility issues
Solution Approach 2:
The patent changes the material parameter from glass to plastic polymer, which fundamentally alters the weight and mechanical properties while maintaining or improving optical transmission parameters. The plastic material enables high transmittance with significantly reduced weight and improved impact resistance
3Reliability
If a plastic spectacle lens absorbs light having a wavelength of not less than 300 nm and less than 400 nm, then eye protection is improved, but handleability and comfortability worsen due to color distortion
Solution Approach 1:
The patent changes the absorption wavelength parameter from below 400 nm to below 380 nm, which reduces color distortion and improves the natural appearance when wearing the lens. This parameter change enhances user comfort and acceptance while maintaining the essential UV protection function
Solution Approach 2:
The patent converts the potential harm of UV absorption (color distortion) into a benefit by precisely targeting the absorption edge at 380 nm. This precise positioning ensures that protection against harmful UV radiation is achieved while minimizing negative impacts on visible light transmission and color perception
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 plastic spectacle lens with high transmittance across the visible range, ensuring color accuracy similar to naked eye viewing with minimal color change, and offers improved handleability and comfort by preventing breakage and reducing weight.
Implementation Method 1
a plastic spectacle lens has been formed by an ultraviolet absorber described in Japanese Patent No. 3477723 being added to a polymerizable composition such that light having a wavelength of not less than 300 nm (nanometer) and less than 400 nm is absorbed
Implementation Method 2
a hard coating layer is formed on at least one surface of the base. particles of a metal oxide are added to the hard coating layer
Implementation Method 3
an antireflection film is formed on at least one surface of the base
Data Source
AI summary
A plastic spectacle lens includes at least a plastic base. In the plastic spectacle lens, a difference between a highest transmittance and a lowest transmittance for light in a range of wavelengths of not less than 400 nm and not greater than 780 nm, is not greater than 10 points, and an internal transmittance of the base for light in a range (visible range) of wavelengths of not less than 380 nm and not greater than 780 nm is not less than 80% over the entirety of the range of the wavelengths.