Contact Lens Cast-Molding Process Using Visible Light Photoinitiators
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Solution Overview
Problem
The conventional cast-molding process for contact lenses faces challenges such as the use of organic solvents, dimensional variations in plastic molds, and the inability to produce UV-absorbing contact lenses using visible light due to the lack of water-soluble photoinitiators that can efficiently initiate curing.
Innovation Solution
A process involving a lens-forming composition with a photoinitiator and a thiol-containing compound or polymer, which reduces curing time and allows for the production of contact lenses using visible light, specifically within the wavelength range of 380 to 460 nm, utilizing reusable high-precision molds and spatial limitation of actinic radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cast-molding technique is used with disposable plastic molds, then production cost is reduced, but manufacturing precision deteriorates due to unavoidable dimensional variations
Solution Approach 1:
The patent applies disposable molds for certain lens types (e.g., daily disposable lenses) where cost-effectiveness is prioritized over high precision, while using reusable precision molds for other applications. This selective application resolves the contradiction by matching mold type to product requirements.
2Ease of manufacture
If conventional cast-molding with organic solvents is used, then lens extraction is enabled, but environmental harm increases and production cost increases
Solution Approach 1:
The patent changes the chemical parameter of the solvent from organic to water-based, eliminating environmental harm while maintaining lens extraction capability. The water-soluble photoinitiator system enables this green chemistry approach without sacrificing manufacturing effectiveness.
3Adaptability or versatility
If visible light with wavelength 380-460 nm is used for curing, then UV-absorbing lenses can be produced, but curing time increases due to lack of efficient water-soluble photoinitiators
Solution Approach 1:
The patent introduces a water-soluble photoinitiator as an intermediary substance that enables efficient visible light curing (380-460 nm) in aqueous lens formulations. This photoinitiator acts as a mediator between the visible light source and the lens-forming composition, allowing UV-absorbing lens production with reduced curing time.
4Manufacturing precision
If reusable high-precision molds are used, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the mold system into reusable precision molds for high-value lenses and disposable molds for standard lenses. This segmentation allows the complex precision mold system to be used only where necessary, reducing overall system complexity while maintaining high manufacturing precision for premium products.
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 enables the production of contact lenses with high consistency and fidelity to the original design, reduces production costs, and eliminates the need for organic solvents, while also allowing for the creation of UV-absorbing lenses with a shorter curing time and improved comfort due to softer material properties.
Implementation Method 1
irradiating, with a UV or visible light, the lens-forming composition in the mold for a time period of about 15 seconds or less, so as to crosslink and/or polymerize said at least one lens-forming material
Implementation Method 2
obtaining a lens-forming composition comprising at least one lens-forming material, at least one photoinitiator, and at least one thiol-containing compound or polymer in an amount for reducing the curing time of the lens-forming composition by at least 20%
Data Source
AI summary
Described herein is a cast-molding process for producing contact lenses in a relatively short curing time. The short curing time has been achieved by adding a chain transfer agent into a lens-forming composition.