Optical Polymer Composition Preventing Yellowing via Thiourethane Oligomer
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Solution Overview
Problem
The development of optical materials with high refractive index and Abbe number is hindered by issues such as non-uniform refractive index generation, distortion, white turbidity, and yellowing, particularly when using compositions involving thiol and isocyanate compounds with episulfide compounds, which also face challenges with heat resistance and adhesive elution during the polymerization process.
Innovation Solution
A polymerizable composition is developed that includes a thiourethane oligomer formed through a preliminary reaction using a specific catalyst, which preferentially progresses the thiourethanation reaction over the polymerization of episulfide compounds, thereby suppressing distortion, white turbidity, and yellowing, and preventing adhesive elution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thiol compound and an isocyanate compound are added to an episulfide compound to improve strength, then tensile strength and impact resistance are improved, but non-uniform refractive index is generated causing distortion or white turbidity
Solution Approach 1:
The patent applies preliminary action by conducting a prepolymerization reaction between the thiol compound and isocyanate compound before adding the episulfide compound. This preliminary reaction forms a prepolymer that controls the subsequent polymerization process, preventing non-uniform refractive index while maintaining improved strength properties.
Solution Approach 2:
The patent uses a specific catalyst (compound with formula (2)) as an intermediary to control the reaction process. This catalyst enables selective thiourethanation reaction between thiol and isocyanate groups, mediating the reaction to proceed uniformly and prevent distortion and white turbidity in the cured product.
2Productivity
If a polymerization catalyst is added and thermal polymerization is performed to produce optical materials, then the polymerization reaction proceeds, but adhesive tape components are eluted causing white turbidity
Solution Approach 1:
The patent changes the reaction parameters by conducting prepolymerization at controlled temperatures (0-50°C) before the main polymerization step. This parameter control prevents adhesive elution while maintaining polymerization efficiency, as the lower initial temperature reduces adhesive softening and elution.
Solution Approach 2:
The patent uses a specific catalyst compound (formula (2)) as an intermediary that enables the polymerization reaction to proceed without requiring high temperatures that would cause adhesive elution. This catalyst mediates the reaction at lower temperatures, preserving optical clarity.
3Temperature
If heating treatment is performed for surface treatment or long-term storage acceleration test, then surface properties are improved or aging is accelerated, but yellowing occurs
Solution Approach 1:
The patent uses a specific catalyst (compound with formula (2)) as an intermediary that controls the polymerization reaction to proceed without generating byproducts that cause yellowing. This catalyst enables heating treatment and long-term storage without significant yellowing by maintaining reaction uniformity and preventing degradation.
Solution Approach 2:
The patent changes the chemical composition parameters by incorporating specific compounds (thiol, isocyanate, and catalyst of formula (2)) that are resistant to yellowing under thermal stress. This parameter change in composition enables high temperature treatment and long-term storage without yellowing.
4Reliability
If tetrabutylphosphonium bromide is used as a prepolymerization catalyst to react thiol and isocyanate compounds, then the thiourethanation reaction proceeds, but viscosity increases to 3000 cP or more making cast molding extremely difficult
Solution Approach 1:
The patent replaces tetrabutylphosphonium bromide with a different catalyst compound (formula (2)) as an intermediary that achieves the same thiourethanation reaction but with different physical properties. This new catalyst produces lower viscosity (below 3000 cP) while maintaining reliable reaction completion, enabling cast molding.
Solution Approach 2:
The patent changes the catalyst parameter from tetrabutylphosphonium bromide to a compound with formula (2), which has different molecular structure and solubility characteristics. This parameter change reduces the viscosity of the reaction mixture to below 3000 cP, making the composition suitable for cast molding while maintaining reaction reliability.
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
This approach allows for the production of optical materials with improved heat resistance, optical clarity, and surface quality, while maintaining industrial feasibility by controlling the reaction conditions to achieve high refractive index and Abbe number without significant yellowing or turbidity.
Implementation Method 1
a reaction solution containing a thiourethane oligomer obtained by preliminarily reacting a compound (b) and a compound (c) using a compound (d) as a catalyst for preliminary reaction
Implementation Method 2
polymerizing and curing the polymerizable composition
Data Source
AI summary
The present invention addresses the problem of providing: a catalyst for preliminary reaction and a preliminary reaction method, which are suitable for a composition that is obtained by adding a thiol compound and an isocyanate compound to an episulfide compound; and a polymerizable composition for optical materials, which is capable of preventing yellowing of an optical material which contains a composition that is obtained by adding a thiol compound and an isocyanate compound to an episulfide compound. The above-mentioned problem can be solved by a polymerizable composition for optical materials, which contains a thiourethane oligomer that is obtained by preliminarily reacting the whole or a part of a thiol compound and an isocyanate compound in a composition that contains an episulfide compound, the thiol compound and the isocyanate compound, while using a compound represented by formula (2) below as a catalyst for preliminary reactionIn formula (2), R represents an alkyl group having 1 to 4 carbon atoms; and X represents an organic group which has 2 to 11 carbon atoms and contains a vinyl group, a vinylidene group or a vinylene group.