Hydrogel Contact Lens Coating for Lubricity and Cost Reduction
Solution Overview
Problem
Conventional cast-molding techniques for producing non-silicone hydrogel contact lenses face issues such as the use of costly and environmentally unfriendly organic solvents for unpolymerized monomer removal, dimensional variations in disposable plastic molds leading to inconsistent lens production, and a lack of surface lubricity for enhanced wearing comfort.
Innovation Solution
The development of a method involving a lens-forming composition with a purified, water-soluble polyvinylalcohol prepolymer, reusable high-precision molds, and actinic radiation curing, along with a soft and lubricious hydrogel coating applied using a water-based process to enhance surface lubricity and maintain the benefits of the preformed lens material.
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 lens parameter consistency deteriorate
Solution Approach 1:
The patent uses disposable plastic molds for cast-molding production, which are inexpensive and easy to manufacture. Although disposable molds have dimensional variations, the patent resolves this by using a preformed lens body approach where the mold serves only for coating application, not for defining the final lens geometry. The actual lens shape is determined by the preformed body, allowing disposable molds to be used without compromising precision.
2Reliability
If conventional cast-molding technique with organic solvent extraction is used, then monomer removal is achieved, but environmental harm and production cost increase
Solution Approach 1:
The patent extracts and eliminates the harmful organic solvent extraction step from the conventional process. Instead of using organic solvents to remove unpolymerized monomers, the invention uses a preformed lens body made from purified polyvinyl alcohol prepolymer that is substantially free of residual monomers, thereby removing the need for solvent extraction entirely.
Solution Approach 2:
The patent converts the potential harm of residual monomers into a benefit by using a prepolymer system that polymerizes completely under actinic radiation, leaving no harmful residual monomers. The purified polyvinyl alcohol prepolymer with ethylenically-unsaturated groups undergoes complete crosslinking, transforming the monomer removal problem into a complete polymerization solution.
3Reliability
If DAILIES AquaComfort Plus lenses are produced with high water content and surface wettability, then optical quality is improved, but surface lubricity for wearing comfort deteriorates
Solution Approach 1:
The patent applies local quality by differentiating the properties of different parts of the lens system. The preformed lens body maintains high water content (about 69%) and surface wettability for optical quality, while a separate hydrogel coating layer is applied to the surface to provide enhanced lubricity for wearing comfort. This allows different regions/layers to have optimized properties for their specific functions.
Solution Approach 2:
The patent uses composite materials by combining the preformed lens body made from purified polyvinyl alcohol prepolymer with a hydrogel coating layer. The composite structure integrates the optical properties of the high-water-content lens body with the lubricious properties of the hydrogel coating, achieving both optical quality and wearing comfort.
4Manufacturing precision
If reusable high precision molds are used, then lens parameter consistency is improved, but production cost increases
Solution Approach 1:
The patent applies universality by making the preformed lens body serve multiple functions: it provides the final lens geometry, acts as the substrate for the hydrogel coating, and eliminates the need for precision disposable molds. The preformed body is manufactured with high precision using conventional techniques, and then reused as a universal substrate for the coating process, reducing overall system cost while maintaining precision.
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 results in contact lenses with high consistency, optical quality, and reduced production costs, while providing superior wearing comfort through enhanced surface lubricity and maintaining the softness and water content of the lens material.
Implementation Method 1
curing under a spatial limitation of actinic radiation (e.g., UV)
Implementation Method 2
a soft and lubricious hydrogel coating thereon
Data Source
AI summary
The invention is generally related to soft contact lenses which comprise a non-silicone hydrogel lens body and a hydrogel coating thereon. The non-silicone hydrogel lens body is composed of a hydrogel material which is free of silicone and comprises at least 50% by mole of repeating units of at least one hydroxyl-containing vinylic monomer. The hydrogel coating comprises a first polymeric material having first reactive functional groups and a hydrogel layer derived from a second polymeric material having second reactive functional groups, and the hydrogel layer is covalently attached onto the anchor layer through linkages each formed between one first reactive functional group and one second reactive functional group. The soft contact lens has a surface lubricity better than the lubricity of the non-silicone hydrogel lens body and has a friction rating of about 2 or lower after 7 cycles of manual rubbing, a water content of from about 10% to about 85% by weight and an elastic modulus of from about 0.2 MPa to about 1.5 MPa when being fully hydrated at room temperature.