Low-Temperature Hydrogel Coating for Electro-Optic Contact Lenses
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Solution Overview
Problem
Existing coating processes for contact lenses, particularly those with electro-optic elements, are unsuitable for low temperatures due to potential damage from high temperatures, necessitating a need for a durable coating process at relatively-low temperatures.
Innovation Solution
A method involving a solution-based coating process at temperatures between 20°C to 65°C, followed by rinsing and forming a hydrogel coating at 40°C to 65°C with a pH-adjusted reactive coating solution containing azetidinium groups, ensuring a durable hydrogel coating without damaging electro-optic elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-temperature autoclave process (about 121°C) is used to form a durable coating on silicone contact lenses, then the coating durability is improved, but electro-optic elements embedded in the lenses are damaged
Solution Approach 1:
The patent changes the temperature parameter from high-temperature autoclave (121°C) to low-temperature processing (below 50°C, preferably 20-40°C). This is achieved by modifying the coating chemistry to use a two-layer system with a polyanionic polymer anchoring layer followed by a hydrophilic polymeric material crosslinked at low temperatures, thereby protecting temperature-sensitive electro-optic elements while maintaining coating durability
Solution Approach 2:
The patent employs a composite coating structure consisting of two distinct layers: (1) an anchoring layer made of polyanionic polymer that provides strong adhesion to the silicone lens surface, and (2) a hydrophilic polymeric material layer that crosslinks with the anchoring layer to form a durable, lubricious surface. This composite approach enables durable coating formation at low temperatures without damaging electro-optic elements
2Object-affected harmful factors
If a low-temperature coating process (below 50°C) is used to protect electro-optic elements, then the integrity of electro-optic elements is preserved, but coating durability may be compromised
Solution Approach 1:
The patent uses a composite two-layer coating system where the polyanionic polymer anchoring layer provides strong chemical adhesion to the silicone lens, and the hydrophilic polymeric material layer crosslinks with it to form a durable network. This composite structure achieves coating durability comparable to or exceeding traditional high-temperature methods, even at low processing temperatures
Solution Approach 2:
The patent optimizes several parameters including pH (adjusting to enhance crosslinking efficiency at low temperatures), concentration ratios of coating materials, and reaction time to ensure complete crosslinking and maximum coating durability under low-temperature conditions, thereby matching or surpassing the performance of high-temperature processes
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 produces a durable hydrogel coating on contact lenses that withstands simulated abrasion cycling, maintaining lubricity and wettability, while preserving the integrity of electro-optic elements.
Implementation Method 1
forming a base coating on the preformed contact lens according to a solution-based coating process to form a treated contact lens having the base coating thereon, wherein the solution-based coating process comprises contacting the preformed contact lens with a coating solution
Implementation Method 2
the coating solution has a first pH and the first temperature and comprises from about 0.001% to about 5.0% by weight of a polyanionic polymer, wherein the polyanionic polymer is a homo- or copolymer of acrylic acid or C1-C3 alkylacrylic acid, wherein the first pH is from 0 to about 4.5
Implementation Method 3
forming a coated contact lens have a hydrogel coating thereon by contacting the treated contact lens obtained in step (3) with an aqueous reactive coating solution at a third temperature of from about 40°C to about 65°C for a third period of time, wherein the aqueous has a third temperature of about 30°C or lower, a third pH of about 8.0 or less, and at least one ophthalmic salt at a concentration of at least 20 mM, wherein the aqueous reactive coating solution has a third pH of at least about 9.5 and comprises a water-soluble, thermally-crosslinkable hydrophilic polymeric material having azetidinium groups
Data Source
Figure 1A~1E
AI summary
The invention is generally related to a method for producing, in a consistent manner, contact lenses each having an intact durable coating thereon, wherein the coating is a hydrogel coating formed by covalently attached a hydrophilic polymeric material having azetidinium groups onto a base coating of a polyanionic polymer on a contact lens at a relatively low temperature (e.g., from about 40ºC to about 60ºC). The coating temperature for forming a durable hydrogel coating on top of the base coating of a contact lens can be significantly lowered by raising, in situ, the pH (to about 9.5 or higher) of a reactive coating solution which contains the hydrophilic polymeric material having azetidinium groups.