Curable Optical Composition for Low Shrinkage Lenses
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Solution Overview
Problem
Current polymeric materials used in optical articles face challenges such as high shrinkage, extended curing times, energy consumption, thermal stress, birefringence, and moisture sensitivity, which hinder the production of precision optics and coatings with desired properties like low polymerization shrinkage, low viscosity, and low birefringence.
Innovation Solution
A curable composition comprising oligomers with pendent ethylenically unsaturated functional groups, a free-radically polymerizable crosslinking agent, and a photoinitiator, which exhibits low shrinkage, low birefringence, and resistance to moisture, allowing for rapid curing and use in optical applications like lenses, fibers, and coatings without the need for solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal polymerization of monomers is used to form polymers, then polymerization can be achieved, but high shrinkage (11-20%) occurs during cure
Solution Approach 1:
The patent changes the fundamental parameter of polymerization mechanism from thermal to photopolymerization. This enables curing at room temperature without the high shrinkage associated with thermal processes, while achieving complete polymerization through UV light activation of photoinitiators in the composition
Solution Approach 2:
The patent employs a composite oligomeric system combining multiple components: oligomers with pendent ethylenically unsaturated groups, crosslinking agents, and photoinitiators. This composite approach achieves both complete polymerization and low shrinkage by distributing functions across different molecular components
2Reliability
If thermal polymerization is used, then polymerization can proceed, but extended curing time (5-16 hours or more) is required
Solution Approach 1:
The patent replaces thermal energy with photonic energy (UV light) to drive polymerization. Photoinitiators absorb UV radiation and generate radicals that initiate rapid chain reaction, reducing curing time from hours to minutes or seconds while ensuring complete polymerization
Solution Approach 2:
The patent uses intermittent or continuous UV irradiation to drive polymerization. The photopolymerization process can be controlled by light exposure duration and intensity, enabling rapid curing cycles that significantly reduce production time compared to thermal methods
3Reliability
If thermal cure cycle is used to polymerize monomer, then polymerization can be achieved, but large amounts of energy are consumed
Solution Approach 1:
The patent substitutes thermal heating with photopolymerization using UV light sources. This eliminates the need for energy-intensive thermal cycling equipment and reduces overall energy consumption, as UV curing occurs at room temperature without requiring sustained high-temperature maintenance
Solution Approach 2:
The patent incorporates photoinitiators into the composition beforehand, which remain dormant until UV exposure. This preliminary preparation allows the system to store chemical potential energy that is rapidly released upon light activation, avoiding continuous energy input required by thermal processes
4Reliability
If thermal cure cycle is used, then polymerization can be achieved, but thermal stress on dies occurs
Solution Approach 1:
The patent replaces thermal curing with photopolymerization, eliminating thermal stress on molding dies. UV light curing occurs at ambient temperature, preventing thermal expansion, warping, and stress-related damage to expensive tooling while ensuring complete polymerization of the optical composition
5Ease of manufacture
If injection molding is used to prepare optical products, then molding can be achieved, but high birefringence is induced in the resulting article
Solution Approach 1:
The patent replaces injection molding with cast-and-cure processing. The liquid oligomeric composition is cast into molds and cured in place via photopolymerization, eliminating the high-shear injection process that causes molecular orientation and birefringence. This yields optically uniform articles suitable for precision optical applications
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 enables the production of precision optics with reduced shrinkage and birefringence, improving manufacturing efficiency and optical performance, and is suitable for applications in electronic displays, cameras, and optical communication devices.
Implementation Method 1
a photoinitiator. The composition, when cured, is non-yellowing, exhibits low shrinkage and low birefringence
Data Source
AI summary
A curable composition is provided which includes an oligomer having a plurality of pendent and/or terminal ethylenically unsaturated, free-radically polymerizable functional groups, a free-radically polymerizable crosslinking agent, and/or a diluent monomer, and a photoinitiator. The composition, when cured, is non-yellowing, exhibits low shrinkage and low birefringence making it suitable for many optical applications such as optical lenses, optical fibers, prisms, light guides, optical adhesives, and optical films.