UV Blocking Silicone Hydrogel Lens Polymerization
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Solution Overview
Problem
Existing ophthalmic devices face challenges in achieving complete polymerization and maintaining wettability while providing sufficient UV blocking, particularly with the use of benzotriazole UV blockers, which can result in incomplete cure and compromised surface properties.
Innovation Solution
A method involving the polymerization of a monomer mixture containing NVP, other comonomers, and Bis o-hydroxy benzophenone to create a substantially fully polymerized UV blocking hydrogel lens with a wettable surface, meeting Class II UV blocking specifications, by ensuring complete co-cure and optimal water content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If benzotriazole UV blockers are used in the monomer mix, then UV blocking capability is improved, but polymerization completeness deteriorates due to incomplete cure
Solution Approach 1:
The patent removes benzotriazole UV blockers from the monomer mix and instead incorporates them into the finished lens through post-polymerization soaking. This extraction approach eliminates the interference with polymerization while still achieving UV blocking functionality, resolving the contradiction between UV protection and complete cure.
Solution Approach 2:
The patent performs UV blocking incorporation after polymerization rather than before. By soaking the cured lens in UV blocker solutions, the UV protective function is added as a separate preliminary treatment that does not interfere with the polymerization process, thereby maintaining both complete cure and UV blocking capability.
2Ease of operation
If traditional surfacing methods are used to improve wettability, then surface wettability is improved, but manufacturing complexity and cost increase due to additional post-cure steps
Solution Approach 1:
The patent combines the wettability enhancement function with the UV blocking function by using the same post-polymerization soaking process for both purposes. The multifunctional approach eliminates separate surfacing steps, reducing manufacturing complexity while achieving both wettable surface and UV blocking properties.
Solution Approach 2:
The post-polymerization soaking treatment serves multiple functions simultaneously: it provides UV blocking capability and enhances surface wettability. This multi-functional approach consolidates what would traditionally require separate processing steps, thereby reducing overall device complexity.
3Ease of operation
If high molecular weight PVP is incorporated into the monomer mix, then surface wettability is improved, but material cost and processing complexity increase
Solution Approach 1:
The patent uses relatively low molecular weight PVP (10-300 kDa) rather than high molecular weight PVP, which is sufficient for achieving the desired wettability effect. This substitution with a lower molecular weight analog reduces material cost and improves processing characteristics while maintaining the essential function.
Solution Approach 2:
The patent optimizes the PVP molecular weight parameter to the range of 10-300 kDa, which balances wettability performance with processing ease and cost. This parameter optimization avoids the complexities associated with high molecular weight PVP while achieving sufficient surface modification.
4Adaptability or versatility
If mixtures of fast and slow reacting monomers are used, then material functionality is improved, but polymerization uniformity deteriorates due to differential reaction kinetics
Solution Approach 1:
The patent performs complete polymerization first to achieve uniform curing throughout the lens, then adds functional properties (UV blocking and wettability enhancement) through post-polymerization soaking. This preliminary completion of the polymerization process eliminates kinetic conflicts while preserving the benefits of using diverse monomer components.
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 method achieves a fully polymerized hydrogel lens with enhanced wettability and effective UV blocking, reducing variability in contact angles and improving the water content, thus addressing the issues of incomplete cure and surface properties.
Implementation Method 1
polymerizing a monomer mixture of at least one monomer selected from the group consisting of NVP, O-vinyl carbonates such as 2-hydroxyethyl vinyl carbonate, O-vinyl esters such as vinylacetate, O-allyl esters such as allyl acetate, O-allyl carbonates such as allyl (2-(dimethylamino)ethyl) carbonate, N-vinyl carbamates such as 2-methoxyethyl vinylcarbamate, O-vinyl carbamates such as Vinal acid also known as 3-(((vinyloxy)carbonyl)amino)propanoic acid, N-vinyl ureas such as 1-(2-hydroxyethyl)-3-vinylurea and 1-allyl-3-(2-hydroxyethyl)urea, N-allyl carbamates such as 2-hydroxyethyl allylcarbamate, O-allyl carbamates such as allyl (2-hydroxyethyl)carbamate and mixtures thereof and at least one other comonomer and a free-radical polymerizable, substituted or unsubstituted, Bis o-hydroxy benzophenone
Implementation Method 2
sufficient blocking of UV light to meet at least Class II specifications for UV blocking
Data Source
Figure 1A~2B
Figure 3~4
AI summary
A substantially fully copolymerized UV blocking hydrogel lens demonstrating sufficient blocking of UV light to meet at least FDA Class II specifications for UV blocking formed from a reaction mixture comprising at least NVP and one other comonomer and a free-radical polymerizable, substituted or unsubstituted, Bis Ο-hydroxy benzophenone is provided herein.