Polythiol Composition for Optical Lenses Preventing Striae
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Solution Overview
Problem
The generation of striae and bubbles in polythiourethane-based optical lenses due to rapid viscosity increase during polymerization, which is not effectively controlled by existing compositions containing hydrogen-bondable functional groups.
Innovation Solution
A polythiol composition comprising a first polythiol compound with an ester group and mercapto group, and a second polythiol compound with an ester group and another hydrogen-bondable functional group, used in specific weight ratios to control viscosity and reaction rate during polymerization, preventing striae and bubble formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a compound containing hydrogen-bondable functional groups is used to increase viscosity at the initial stage of polymerization, then the generation of striae and bubbles is prevented, but if used in excessive amount, the viscosity increases too rapidly which expedites striae formation
Solution Approach 1:
The invention changes the chemical structure parameters of the polythiol compound by introducing specific functional groups (carboxyl, hydroxyl, or amino groups) with defined hydrogen bonding capabilities. This allows precise control over the rate of viscosity increase during polymerization, preventing both striae formation and excessive thickening by optimizing the hydrogen bonding strength and kinetics.
Solution Approach 2:
The invention creates a composite polythiol compound containing multiple functional groups (mercapto groups for polymerization and carboxyl/hydroxyl/amino groups for controlled hydrogen bonding). This composite structure enables simultaneous achievement of appropriate initial viscosity control and moderated viscosity increase rate during the polymerization process.
2Ease of operation
If the viscosity of the polymerizable composition is kept low at the initial stage, then the composition is easy to handle and fill molds, but striae and bubbles are generated due to convection during polymerization
Solution Approach 1:
The invention optimizes the viscosity parameter of the polymerizable composition by controlling the molecular weight and functional group content of the polythiol compound. This achieves an optimal viscosity range that allows easy handling and complete mold filling while suppressing convection currents during polymerization that cause striae and bubble formation.
Solution Approach 2:
The carboxyl, hydroxyl, or amino groups in the polythiol compound act as intermediary hydrogen bonding sites that moderate the polymerization process. These groups create controlled intermolecular interactions that reduce rapid convection and bubble formation while maintaining adequate fluidity for mold filling.
3Productivity
If a polythiol compound that forms crosslinked structure at low temperature is used, then the polymerization reaction proceeds rapidly, but the viscosity increases excessively which causes striae
Solution Approach 1:
The invention changes the polymerization kinetics parameters by selecting polythiol compounds with specific molecular weights and functional group densities. This controls the crosslinking rate to proceed rapidly enough for high productivity while preventing excessive viscosity increase that would cause striae formation.
Solution Approach 2:
The invention introduces local hydrogen bonding sites (carboxyl, hydroxyl, or amino groups) distributed throughout the polythiol compound structure. These local sites provide controlled intermolecular interactions that moderate the overall viscosity increase during crosslinking, allowing rapid polymerization without striae formation.
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 controlled viscosity and reaction rate result in high-quality polythiourethane-based lenses with excellent appearance and optical characteristics, free from striae and bubbles, and improved heat resistance.
Implementation Method 1
a first polythiol compound having an ester group and a mercapto group only as a hydrogen-bondable functional group; and a second polythiol compound having an ester group and a hydrogen-bondable functional group other than a mercapto group
Data Source
AI summary
The embodiments relate to a polythiol composition for a plastic optical lens and a polythiourethane-based plastic optical lens prepared therefrom. In the embodiments, a first polythiol compound having an ester group and a mercapto group only as a hydrogen-bondable functional group and a second polythiol compound having an ester group and a hydrogen-bondable functional group other than a mercapto group are used in an appropriate amount. Thus, it is possible to control the viscosity of a polymerizable composition at the initial stage of polymerization at a low temperature of 5 to 15°C and to stabilize the rate of increase in the viscosity of the composition and the reaction rate thereof, thereby preventing the generation of striae, bubbles, and the like. Further, various plastic lenses such as eyeglass lenses, camera lenses, and the like having excellent appearance characteristics (without striae and bubbles) and excellent optical characteristics can be obtained from the composition.