Room-Temperature Lathing of Silicone Hydrogel Contact Lenses
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Solution Overview
Problem
Silicone hydrogel contact lenses are typically manufactured at low temperatures due to their softness and stickiness, leading to high manufacturing costs and limitations in producing complex surface designs, which are necessary for correcting astigmatism, presbyopia, and high-order monochromatic aberrations, as well as issues with oxygen and ion permeability.
Innovation Solution
A method for directly lathing silicone hydrogel contact lenses at room temperature, involving the use of a lens-forming material with silicone-containing vinylic monomers and hydrophilic vinylic monomers, slow curing, stripping, post-curing, and drying to increase lathability, resulting in lenses with high oxygen transmissibility and ion permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicone hydrogel contact lenses are manufactured at low temperature, then the material softness and stickiness are controlled, but manufacturing cost increases
Solution Approach 1:
The patent changes the temperature parameter from low temperature to room temperature for lathing operations. This is achieved by modifying the material composition (using specific silicone-containing vinylic monomers and hydrophilic vinylic monomers) and controlling the curing process (slow curing followed by post-curing), which allows the material to maintain stability while being processable at higher temperatures, thereby reducing manufacturing costs.
2Reliability
If silicone hydrogel contact lenses are manufactured at low temperature, then material stability is maintained, but the ability to produce complex surface designs is limited
Solution Approach 1:
The patent enables lathing at room temperature by changing the material formulation and curing parameters. This temperature parameter change allows the use of precision lathing equipment to create complex surface designs (such as toric surfaces for astigmatism and multifocal surfaces for presbyopia) that require rotational and orientational stability, which cannot be achieved with traditional low-temperature molding processes.
3Productivity
If full molding process is used, then mass production is economical, but fidelity in reproducing complex lens design features is reduced
Solution Approach 1:
The patent segments the manufacturing process into two stages: first, economical mass production of lens blanks using the full molding process; second, precision lathing of the lens blanks at room temperature to create complex surface designs. This segmentation allows each process to optimize for its strength - molding for efficiency and lathing for precision - thereby resolving the contradiction between mass production efficiency and design feature fidelity.
4Ease of manufacture
If silicone hydrogel material is lathed at room temperature, then manufacturing cost is reduced, but material stickiness and softness cause processing difficulties
Solution Approach 1:
The patent changes multiple parameters to enable room temperature lathing: (1) material composition parameters - using specific ratios of silicone-containing vinylic monomers and hydrophilic vinylic monomers; (2) curing parameters - implementing slow curing followed by post-curing to achieve optimal crosslinking density. These parameter changes modify the material's viscoelastic properties, reducing stickiness and increasing firmness at room temperature, thereby improving lathability while maintaining cost advantages.
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
Enables the production of silicone hydrogel contact lenses with improved oxygen transmissibility and ion permeability, allowing for more complex designs and reduced manufacturing costs, while maintaining the necessary properties for corneal health and comfort.
Implementation Method 1
obtain a lens-forming fluid material capable of forming a polymer or copolymer having high oxygen permeability
Implementation Method 2
drying the polymer for a time sufficiently long to increase the lathability at room temperature of the polymer
Implementation Method 3
allow oxygen to diffuse through the lens to reach the cornea, namely having a relatively high oxygen transmissibility
Data Source
AI summary
The present invention provides methods for lathing at room temperature a silicone hydrogel material, in particular silicone hydrogel material having a high oxygen permeability and made of a polymerizable composition containing a relative large amount of oxyperm component, into contact lenses.