Actinically Crosslinkable Siloxane Copolymers for Contact Lens Molding
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Solution Overview
Problem
Conventional cast molding techniques for producing silicone hydrogel contact lenses suffer from dimensional variations in plastic molds, leading to inconsistencies in lens parameters and low fidelity in duplicating complex designs, which can be overcome by using reusable molds and actinic radiation curing, but require new actinically-crosslinkable prepolymers suitable for the Lightstream Technology.
Innovation Solution
Development of an actinically crosslinkable prepolymer through RAFT polymerization of a reactive mixture comprising a polysiloxane crosslinker with terminal vinyl-groups, a hydrophilic vinylic monomer, and a RAFT agent, allowing for actinic crosslinking in the absence of monomers to form silicone hydrogel materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cast molding technique with disposable plastic molds is used, then production cost is reduced, but manufacturing precision and consistency of lens parameters deteriorate
Solution Approach 1:
The patent applies the disposable mold concept but improves it by using injection-molded plastic molds that are discarded after a single use. These disposable molds eliminate the need for expensive, precision-machined reusable molds while maintaining acceptable manufacturing precision for mass production of contact lenses.
2Manufacturing precision
If reusable high precision molds are used, then manufacturing precision and fidelity to design are improved, but production cost increases
Solution Approach 1:
The patent uses injection-molded plastic molds that are inexpensive copies or replicas of the master lens design. These disposable molds capture the essential geometric features needed for mass production without requiring the same level of precision as reusable molds, thereby reducing cost while maintaining adequate manufacturing precision.
3Productivity
If actinic radiation curing is used, then productivity and curing speed are improved, but device complexity increases
Solution Approach 1:
The patent replaces traditional thermal or chemical curing processes with actinic radiation (UV light) curing. This substitution enables rapid, spatially controlled crosslinking of the hydrogel material directly in the mold cavity, significantly improving curing speed and productivity while the process complexity is managed through integration into the existing molding operation.
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 solution enables the production of silicone hydrogel contact lenses with high consistency and fidelity to the original design at a lower cost, utilizing reusable molds and rapid curing times, thereby addressing the dimensional issues and cost inefficiencies of conventional methods.
Implementation Method 1
The prepolymer is capable of being actinically crosslinked, in the absence of one or more vinylic monomers, to form a silicone hydrogel material
Implementation Method 2
The prepolymer of the invention is a RAFT polymerization product of a reactive mixture comprising a polysiloxane crosslinker with two terminal vinyl-groups, a hydrophilic vinylic monomer, a RAFT agent, and a free-radical initiator
Data Source
AI summary
The invention provide a class of actinically-crosslinkable silicone-containing prepolymers which comprise dangling polysiloxane chains each having a terminal ethylenically-unsaturated group and are obtained in a one-step of RAFT polymerization of a reactive mixture comprising a polysiloxane crosslinker, a hydrophilic vinylic monomer, a RAFT agent, and a free-radical initiator. The present invention is also related to silicone hydrogel contact lenses made from a prepolymer of the invention and methods for making the contact lenses in a cost-effective way and with high consistency and high fidelity to the original lens design.