In-package Coating for Silicone Hydrogel Contact Lenses
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Solution Overview
Problem
Existing methods for applying hydrophilic coatings to silicone hydrogel contact lenses are not cost-effective and time-efficient, particularly in a mass production environment, as they often require multiple steps and extended time periods.
Innovation Solution
A method involving a packaging solution with a polyanionic polymer, a water-soluble thermally-crosslinkable polymeric material with azetidinium groups, and a decomposable-at-autoclave material, which is autoclaved to form a crosslinked hydrophilic coating, enhancing the lens's hydrophilicity and lubricity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple-step coating methods are used to improve hydrophilicity, then coating quality is improved, but production time and complexity increase
Solution Approach 1:
The patent combines multiple coating steps into a single in-package coating process. The coating solution containing polyanionic polymer and crosslinking agents is applied directly in the final package, and all coating and crosslinking operations are completed in one autoclaving cycle, eliminating the need for separate coating, drying, and crosslinking steps.
Solution Approach 2:
The autoclaving process serves multiple functions simultaneously: it sterilizes the lens, applies the coating through heat-activated crosslinking, and completes the hydrophilization process. This multi-functional approach consolidates several operations into a single step that achieves both sterilization and coating application.
2Reliability
If multiple-step coating methods are used to improve hydrophilicity, then coating quality is improved, but process complexity increases
Solution Approach 1:
The patent merges coating application, crosslinking activation, and sterilization into a single integrated process. The coating solution is prepared with all necessary components (polyanionic polymer, crosslinking agents, and buffers), and the entire coating process is completed within the final package during autoclaving, eliminating multiple handling steps and reducing process complexity.
Solution Approach 2:
The coating solution is formulated to automatically crosslink when exposed to autoclaving conditions. The polyanionic polymer and crosslinking agents react spontaneously at autoclave temperatures without requiring additional catalysts or complex control systems, allowing the coating process to be self-regulating and simple to implement.
3Reliability
If conventional coating methods are used, then hydrophilicity is improved, but cost-effectiveness decreases
Solution Approach 1:
The patent extracts the coating application step from the manufacturing process and moves it to the packaging stage. By applying the coating solution directly in the final package rather than during lens production, the method eliminates the need for specialized coating equipment and complex manufacturing line modifications, significantly reducing implementation costs.
Solution Approach 2:
The coating solution is formulated as a disposable in-package solution that is discarded after use. The polyanionic polymer and crosslinking agents are provided in the package at low concentrations, and the solution is consumed during the autoclaving process, eliminating the need for expensive reusable coating equipment and complex recovery systems.
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 results in a cost-effective and time-efficient process that produces silicone hydrogel contact lenses with improved hydrophilicity and lubricity, characterized by a water contact angle of 80 degrees or less, allowing for direct use from the package without rinsing.
Implementation Method 1
autoclaving said package with the contact lens and the in-package-coating solution therein, thereby inducing crosslinking reaction between azetidinium groups of the water-soluble polymeric material and the carboxyl groups of the polyanionic polymer
Implementation Method 2
crosslinking reaction between azetidinium groups of the water-soluble polymeric material and the carboxyl groups of the polyanionic polymer to form a crosslinked hydrophilic coating
Implementation Method 3
wherein the decomposable-at-autoclave material is hydrolyzed to increase the pH to 6.5 to 7.5
Implementation Method 4
autoclaving said package with the contact lens and the in-package-coating solution therein
Data Source
AI summary
The present invention generally relates to a method for applying a coating of hydrophilic polymers onto silicone hydrogel contact lenses to improve hydrophilicity and lubricity. In particular, the present invention is directed to a method for forming a coating on a contact lens, preferably a silicone hydrogel contact lens, directly in the primary package and maintaining the coated contact lens within said primary package until insertion of the coated contact lens in the eye of the contact lens user. The resultant silicone hydrogel contact lens has a coating with good hydrophilicity, improved lubricity and good durability and also can be used directly from the lens package by a patient without washing and/or rising.