Polymerizable Composition UV Absorber Segmentation
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Solution Overview
Problem
Optical materials made from plastics, such as polythiourethane-based polymers, lack light resistance and exhibit color defects like yellowing when exposed to sunlight, despite the addition of ultraviolet absorbers which are intended to enhance their light resistance.
Innovation Solution
A polymerizable composition comprising a polythiol compound, a polyisocyanate compound, a first ultraviolet absorber with a primary absorption wavelength between 320 nm to 350 nm, and a second ultraviolet absorber with a primary absorption wavelength between 250 nm to 300 nm, which are combined and thermally cured to form an optical material with improved light resistance and minimized color defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an ultraviolet absorber is added to enhance light resistance, then light resistance is improved, but the plastic optical material becomes yellow resulting in poor aesthetics
Solution Approach 1:
The ultraviolet absorption function is segmented into two distinct absorbers with different absorption characteristics. The first ultraviolet absorber (λmax 320-350 nm) handles longer wavelength UV, while the second ultraviolet absorber (λmax 250-300 nm) handles shorter wavelength UV. This segmentation allows comprehensive UV protection without relying on a single absorber that causes yellowing.
Solution Approach 2:
The patent uses a composite approach by combining two different ultraviolet absorbers in the polymerizable composition. This composite material strategy enables synergistic effects where the combination of absorbers provides broader spectral coverage and superior light resistance while minimizing the yellowing effect associated with individual absorbers.
2Device complexity
If a single ultraviolet absorber is used, then the composition is simple, but light resistance is insufficient in the entire ultraviolet region
Solution Approach 1:
The ultraviolet spectrum is segmented into two regions (320-350 nm and 250-300 nm), and each region is addressed by a specialized absorber. This segmentation enables comprehensive coverage of the entire UV spectrum while maintaining reasonable composition complexity through the use of two well-defined absorber types.
3Ease of manufacture
If conventional ultraviolet absorbers are used, then manufacturing is straightforward, but color defects occur and light resistance is poor
Solution Approach 1:
The patent changes the key parameter of absorption wavelength by selecting specific λmax ranges for the ultraviolet absorbers (320-350 nm and 250-300 nm). This parameter optimization enables simultaneous improvement of light resistance and color stability while maintaining ease of manufacture through the use of readily available absorbers within these wavelength ranges.
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 resulting optical material exhibits excellent light resistance and minimized color defects, maintaining high total light transmittance and low yellow index even after exposure to ultraviolet light, thereby addressing the issues of poor light resistance and color defects in previous plastic optical materials.
Implementation Method 1
one or more types of a first ultraviolet absorber having a primary absorption wavelength (λ1) in a wavelength range of 320 nm to 350 nm
Implementation Method 2
one or more types of a second ultraviolet absorber having a primary absorption wavelength (λ1') in a wavelength range of 250 nm to 300 nm
Implementation Method 3
optical materials prepared from a polythiourethane-based polymer obtained by polymerizing a polythiol compound and a polyisocyanate compound
Data Source
Figure 1~2
AI summary
One embodiment relates to a polymerizable composition and an optical material produced therefrom which has excellent lightfastness and minimized color defects, and more specifically, the polymerizable composition according to one embodiment includes UV absorbers having, as the main absorption wavelength, either a long-wavelength region or a short-Wavelength region Within the UV region, wherein the UV absorbers do not absorb in the Visible light region. Accordingly, the polymerizable composition may be used to provide an optical material having excellent lightfastness and minimized color defects.