UV Blocking Silicone Hydrogel Lens Polymerization
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Solution Overview
Problem
Traditional silicone hydrogel contact lenses face challenges in achieving a fully polymerized state with UV blocking capabilities and a wettable surface, often resulting in incomplete cure and compromised surface properties due to the use of benzotriazole UV blockers, which lead to unreacted or partially oligomerized NVP and lower water content.
Innovation Solution
A method of polymerizing a monomer mixture comprising NVP, other comonomers, and free-radical polymerizable Bis o-hydroxy benzophenone to create a hydrogel ophthalmic device with a wettable surface and sufficient UV blocking, meeting at least Class II specifications, by forming large chains of hydrophilic polymer polyvinylpyrrolidone (PVP) in situ during cure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If benzotriazole UV blockers are used in silicone hydrogel contact lenses, then UV blocking capability is improved, but polymerization completeness deteriorates leading to unreacted or partially oligomerized NVP
Solution Approach 1:
The patent removes benzotriazole UV blockers from the monomer mix and instead incorporates water-soluble UV blockers that can be added after polymerization or incorporated in a way that does not interfere with the polymerization reaction, thereby eliminating the negative impact on cure completeness while maintaining UV blocking capability
Solution Approach 2:
The patent uses a composite approach by combining silicone hydrogel with water-soluble UV blockers, creating a multi-component system where each component performs its specific function without interfering with the others, achieving both complete polymerization and effective UV blocking
2Object-affected harmful factors
If benzotriazole UV blockers are used, then UV blocking is improved, but surface wettability deteriorates due to lower water content
Solution Approach 1:
The patent extracts benzotriazole UV blockers from the system and replaces them with water-soluble alternatives that do not compromise the hydrophilic nature of the lens, thereby maintaining both UV blocking and surface wettability
Solution Approach 2:
The patent changes the chemical parameters of the UV blocker from lipophilic benzotriazole to hydrophilic water-soluble compounds, which alters the overall hydrophilicity of the lens material and improves surface wettability while maintaining UV blocking performance
3Ease of operation
If post cure treatment is applied to enhance wettability, then surface wettability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent incorporates hydrophilic components and water-soluble UV blockers into the monomer mix before polymerization, ensuring that the lens achieves adequate wettability during the manufacturing process itself, eliminating the need for separate post-cure wettability enhancement steps
Solution Approach 2:
The lens material itself provides the wettability function through its inherent hydrophilic components and water-soluble UV blockers, making the material self-sufficient and eliminating the need for additional post-processing treatments
4Ease of operation
If high molecular weight PVP is incorporated into the device, then surface wettability is improved, but PVP may leach out due to incomplete polymerization
Solution Approach 1:
The patent removes benzotriazole UV blockers that interfere with polymerization, thereby enabling complete curing that locks PVP into the polymer matrix and prevents leaching
Solution Approach 2:
The patent creates a composite structure where PVP is integrated into a fully polymerized silicone hydrogel matrix with water-soluble UV blockers, forming a stable multi-component system where PVP remains entrained due to complete crosslinking
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 ensures a fully polymerized UV blocking hydrogel lens with improved wettability and UV protection, maintaining high water content and reducing variability in contact angles, thus enhancing the performance and biocompatibility of the lenses.
Implementation Method 1
polymerizing a monomer mixture of at least NVP and 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
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 O-hydroxy benzophenone is provided herein.