Polymerizable Composition for Optical Materials with Low Defect Rates
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Solution Overview
Problem
Polythiourethane-based optical materials often exhibit appearance defects such as striae and bubbles due to varying reactivity of polyisocyanate and polythiol compounds and catalysts, leading to low production yield and insufficient improvement in these defects.
Innovation Solution
A polymerizable composition comprising specific types of polyisocyanate and polythiol compounds, along with a catalyst, is formulated to achieve a viscosity of 1000 mPa·s or more after 24 hours, with a calculated parameter R ranging from 9.5 to 19.5, which balances reactivity and minimizes striae and bubble generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polythiol compound and polyisocyanate compound are reacted to prepare polythiourethane-based optical material, then the material can be produced with various properties (high transparency, high refractive index, high Abbe number), but appearance defects such as striae and bubbles occur due to varying reactivity
Solution Approach 1:
The patent applies parameter changes by carefully controlling the NCO content (20-40 wt%) and the ratio of polyisocyanate to polythiol (0.95-1.05 molar ratio), as well as selecting specific catalyst amounts (0.01-0.1 wt% based on total monomer weight). These parameter optimizations ensure complete reaction without excessive reactivity, preventing striae and bubbles while maintaining high production yield.
2Productivity
If reactivity is increased to improve production efficiency, then productivity increases, but appearance defects such as striae and bubbles increase
Solution Approach 1:
The patent optimizes reactivity parameters by controlling NCO content within 20-40 wt% and maintaining catalyst content at 0.01-0.1 wt% based on total monomer weight. This controlled reactivity ensures complete polymerization for high productivity while preventing excessive reaction that causes striae and bubbles, thus maintaining appearance quality.
Solution Approach 2:
The patent uses specific catalysts (such as organometallic compounds) as intermediaries to mediate the reaction between polyisocyanate and polythiol. The catalyst enables the reaction to proceed at optimal rates, ensuring complete conversion without runaway reactivity that would cause appearance defects.
3Productivity
If NCO content is increased to improve reaction completeness, then production yield increases, but viscosity increases and workability decreases
Solution Approach 1:
The patent optimizes NCO content within the range of 20-40 wt%, avoiding excessive NCO content that would cause high viscosity. This parameter control ensures complete reaction for high production yield while maintaining viscosity at levels that preserve workability and ease of handling the polymerizable composition.
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 composition produces plastic lenses with excellent appearance, improved workability, and enhanced dimensional stability, reducing striae and bubble generation rates while maximizing production yield.
Implementation Method 1
a catalyst, wherein the polymerizable composition has a viscosity of 1000 mPa·s (1000 cps (centipoise)) or more after it stands at 10°C for 24 hours
Implementation Method 2
polymerizable composition for a polythiourethane-based compound prepared therefrom
Data Source
AI summary
An embodiment relates to a polymerizable composition for an optical material and a polythiourethane-based compound prepared therefrom. The polythiourethane-based compound is excellent in appearance with low generation rates of striae and bubbles.