Silicone Hydrogel Lens Crosslinked Coating
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Solution Overview
Problem
Current methods for modifying the hydrophilicity of silicone hydrogel contact lenses, such as plasma treatment and layer-by-layer deposition, are either costly, time-consuming, or result in coatings that are not durable or compatible with cleaning solutions, necessitating a cost-effective and time-efficient method for producing lenses with a durable, wettable surface.
Innovation Solution
A method involving the application of a carboxyl-containing polymeric material onto silicone hydrogel contact lenses, followed by autoclaving in a packaging solution containing crosslinkable hydrophilic polymeric materials with epoxide groups, forming a crosslinked non-silicone hydrogel coating that enhances surface hydrophilicity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plasma treatment is used to modify the hydrophilicity of silicone hydrogel contact lenses, then the surface hydrophilicity and wettability are improved, but the manufacturing cost increases due to high capital investment in plasma treatment equipment
Solution Approach 1:
The patent replaces expensive plasma treatment equipment with a cost-effective chemical crosslinking process using readily available reagents. The method uses a two-step approach: first applying a polymeric material containing carboxyl groups, then crosslinking with a polyepoxide compound during autoclave sterilization, eliminating the need for costly plasma equipment while achieving comparable surface hydrophilicity
Solution Approach 2:
The patent changes the chemical parameters of the lens surface by introducing carboxyl groups through polymeric material application and subsequent crosslinking with polyepoxide. This chemical modification transforms the hydrophobic silicone hydrogel surface into a hydrophilic surface, achieving plasma-like effects through chemical parameter changes rather than physical plasma treatment
2Reliability
If wetting agents are incorporated into the lens formulation to modify surface hydrophilicity, then the surface wettability is improved, but the lens may exhibit haziness due to incompatibility with silicone components
Solution Approach 1:
The patent separates the hydrophilicity modification from the lens bulk material by applying polymeric material only to the lens surface. This segmentation ensures that the bulk lens material maintains its optical clarity while the surface gains hydrophilic properties, avoiding the haziness problem that occurs when wetting agents are mixed throughout the entire lens formulation
Solution Approach 2:
The patent applies hydrophilic polymeric material locally to the lens surface rather than incorporating it throughout the bulk material. This local application ensures that the surface has the desired wettability while the bulk material remains optically clear and compatible with silicone components, resolving the conflict between surface modification and overall lens clarity
3Reliability
If layer-by-layer polyionic material deposition is used to render silicone hydrogel material wettable, then the surface hydrophilicity is improved, but the coating durability is insufficient for extended wear purposes
Solution Approach 1:
The patent applies polymeric material containing carboxyl groups to the lens surface before the final autoclave sterilization step. This preliminary action allows the polymeric material to be incorporated into the lens structure and crosslinked during the subsequent autoclave process, ensuring the hydrophilic coating is durable and integrated into the lens before it reaches the user
Solution Approach 2:
The patent creates a composite structure by combining the polymeric material containing carboxyl groups with a polyepoxide crosslinking agent. This composite approach forms a crosslinked network on the lens surface that integrates the hydrophilic polymeric material with the lens substrate, significantly improving coating durability compared to simple layer-by-layer deposition
4Reliability
If the lens is dried before plasma treatment to modify hydrophilicity, then the surface hydrophilicity is improved, but the processing time increases
Solution Approach 1:
The patent merges the hydrophilicity modification process with the autoclave sterilization process. By applying polymeric material to the lens surface and then performing autoclave treatment, the patent achieves both sterilization and surface hydrophilicity modification in a single step, eliminating the need for separate drying and treatment steps required by plasma methods
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 method achieves high surface hydrophilicity, durability, and compatibility with ophthalmic use, allowing for direct use of the lenses without rinsing, while maintaining oxygen permeability and resistance to lipid and protein deposition.
Implementation Method 1
autoclaving the sealed package with the silicone hydrogel contact lens therein at a temperature from about 115° C. to about 125° C. for at least about twenty minutes, thereby forming a non-silicone hydrogel coating on the silicone hydrogel contact lens, wherein the non-silicone hydrogel coating is a crosslinked polymeric material composed of the carboxyl-containing polymeric material crosslinked with the one or more crosslinkable material
Implementation Method 2
autoclaving the sealed package with the silicone hydrogel contact lens therein at a temperature from about 115° C. to about 125° C. for at least about twenty minutes
Data Source
AI summary
The invention is related to a cost-effective method for making a silicone hydrogel contact lens having a crosslinked hydrophilic coating thereon. A method of the invention involves autoclaving, in a sealed lens package, a silicone hydrogel contact lens having a base coating of polyacrylic acid thereon in an aqueous solution in the presence of a water-soluble, crosslinkable hydrophilic polymeric material having epoxide groups, for a period of time sufficient to covalently attach the crosslinkable hydrophilic polymeric material onto the surface of the silicone hydrogel contact lens through covalent linkages each formed between one epoxide group and one of the carboxyl groups on and/or near the surface of the silicone hydrogel contact lens.