Silicone Hydrogel Contact Lens Surface Modification via UV-Curing
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Solution Overview
Problem
There is a need for a cost-effective method to produce silicone hydrogel contact lenses with a durable and wettable surface that maintains hydrophilicity without post-curing surface treatment, addressing the limitations of existing methods such as plasma treatment, layer-by-layer deposition, and incorporation of wetting agents which may be costly or result in haziness.
Innovation Solution
A class of actinically crosslinkable silicone-containing prepolymers with pendant ethylenically unsaturated groups and latent UV-activated free radical generating moieties is used, allowing for one-step UV-curing to create silicone hydrogel contact lenses with high oxygen permeability and hydrophilic surfaces by crosslinking in the presence of hydrophilic vinylic monomers, eliminating the need for post-curing treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plasma treatment is used to modify surface hydrophilicity, then durability and hydrophilicity are improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent incorporates hydrophilic monomers and crosslinking agents directly into the lens formulation before casting, so that the hydrophilic surface layer is formed during the initial curing process rather than requiring a separate post-treatment step. This preliminary action eliminates the need for expensive plasma treatment equipment and additional processing steps.
Solution Approach 2:
The patent combines the hydrophilic surface modification function with the lens fabrication process itself by using a two-stage curing mechanism. The first stage forms the bulk lens structure, while the second UV irradiation stage simultaneously creates the hydrophilic surface layer through crosslinking of pendant unsaturated groups, merging multiple functions into a single integrated process.
2Reliability
If wetting agents are incorporated into lens formulation, then surface hydrophilicity is improved, but optical clarity deteriorates due to haziness
Solution Approach 1:
The patent creates a spatially differentiated structure where hydrophilic functional groups are concentrated at the surface region while the bulk lens material maintains its optical clarity. The pendant unsaturated groups and hydrophilic monomers are positioned preferentially at the surface, providing localized hydrophilicity without compromising the overall optical properties of the lens.
Solution Approach 2:
The patent uses UV irradiation to induce crosslinking reactions that transform the physical and chemical parameters of the surface layer. The UV light activates the latent crosslinking agents and hydrophilic monomers, causing them to crosslink and form a dense hydrophilic network at the surface, while the bulk material remains unaffected and maintains its optical clarity.
3Ease of manufacture
If layer-by-layer polyionic material deposition is used, then manufacturing cost is reduced, but coating durability deteriorates
Solution Approach 1:
The patent incorporates crosslinking agents and hydrophilic monomers into the lens formulation before casting, so that the hydrophilic surface layer is formed during the initial curing process rather than requiring a separate post-treatment step. This preliminary action creates a durable, integrated surface layer that becomes part of the lens matrix.
Solution Approach 2:
The patent creates a composite structure consisting of the silicone hydrogel bulk material and a crosslinked hydrophilic surface layer. The surface layer is formed by the interaction of multiple components (hydrophilic monomers, crosslinking agents, and pendant unsaturated groups) that work together to create a durable, integrated coating that is chemically bonded to the bulk material.
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 eliminates haziness issues, provides durable hydrophilic surfaces, and reduces the need for additional processing steps, enhancing the processing ease and quality of silicone hydrogel contact lenses while maintaining high oxygen permeability.
Implementation Method 1
latent UV-activated free radical generating moieties
Implementation Method 2
crosslinking in the presence of hydrophilic vinylic monomers
Implementation Method 3
crosslinking in the presence of hydrophilic vinylic monomers
Data Source
AI summary
The invention provides vinylic monomers having a structure of formula (II) or (III): in which R is H, C1-C12 alkyl, C1-C12alkoxy, C1-C12 alkyl-NH- or -NR3R4 wherein R3 and R4 independent of each other are C1-C8 alkyl; R1 and R2 independent of each other are hydrogen, C1-C8 alkyl, C1-C8 cycloalkyl, or C1-C8 aryl, or R1 and R2 together are -(CH2)n-where n is an integer from 2 to 6; X is a linkage selected from the group consisting of -O-, where R5 is H or C1-C8 alkyl; Y is bivalent -NR5- or -O-; L is a divalent radical selected from the group consisting of C1-C12 alkylene, C1-C12 substituted alkylene, C1-C12 cycloalkylene and C8-C16 arylalkylene radical; and R6 is H or CH3. The invention also provides actinically crosslinkable prepolymers containing chain-extending units having latent UV-activated free radical generating (UV-AFRG) moieties derived from these vinylic monomers.