Actinically Curable Silicone Hydrogel Copolymers for Colored Contact Lenses
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Solution Overview
Problem
Existing methods for producing colored silicone hydrogel contact lenses using a print-on-mold process face challenges due to the fragility of cured inks when exposed to silicone hydrogel lens formulations, leading to potential damage and compromised image quality, as well as issues with dimensional changes during extraction in organic solvents.
Innovation Solution
The use of an actinically-curable fluorine-containing binder copolymer in the ink, which includes ethylenically unsaturated groups, hydrophilic, fluorine-containing, and silicone-containing segments, forms a durable colorant-entrapping polymer network that withstands solvation and maintains image quality during lens extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional inks are used in the print-on-mold process for colored silicone hydrogel contact lenses, then the manufacturing process can be completed, but the cured inks become fragile when exposed to lens formulation and may be damaged during mold closing
Solution Approach 1:
The patent uses a composite binder polymer system comprising both silicone-containing segments and hydrophilic segments. The silicone-containing segments provide compatibility with the silicone hydrogel lens formulation and prevent solvation, while the hydrophilic segments maintain the ink's processing properties. This composite structure resolves the contradiction by creating a cured ink that is both durable and strong when exposed to lens formulation.
Solution Approach 2:
The patent modifies the chemical composition parameters of the binder polymer by incorporating specific ratios of silicone-containing monomers (e.g., trimethylsilyl groups) and hydrophilic monomers (e.g., polyethylene oxide segments). By adjusting these compositional parameters, the cured ink achieves optimal balance between durability against solvation and mechanical strength to withstand mold closing forces.
2Productivity
If the cured ink is exposed to lens formulation for a long period during manufacturing, then the lens can be properly formed, but the cured ink becomes fragile and susceptible to damage
Solution Approach 1:
The patent extracts the problematic solvating components from the binder polymer structure by using silicone-containing segments that are chemically incompatible with the lens formulation monomers and solvents. This extraction of solvating capability prevents the cured ink from degrading during the manufacturing cycle, allowing longer exposure times without compromising reliability.
Solution Approach 2:
The patent changes the chemical parameters of the binder polymer by incorporating fluorine-containing segments and silicone-containing segments with specific molecular weights and functional groups. These parameter changes create a cured ink network that is chemically resistant to lens formulation, enabling stable performance throughout the entire manufacturing process including line stoppage and staging operations.
3Ease of manufacture
If the binder polymer has high solvating capability, then it can dissolve well in the ink formulation, but the cured ink becomes fragile when exposed to lens formulation
Solution Approach 1:
The patent segments the binder polymer into distinct functional segments: hydrophilic segments for ink processability and solubility, and silicone-containing segments for resistance to lens formulation solvation. This segmentation allows each segment to perform its specific function independently, resolving the contradiction between ease of manufacture and durability.
Solution Approach 2:
The patent applies local quality by giving different regions of the binder polymer different properties. The hydrophilic segments provide local solubility for ink formulation, while the silicone-containing segments provide local resistance to lens formulation solvation. This local differentiation of properties allows the single polymer to satisfy both contradictory requirements.
4Ease of manufacture
If the lens is extracted in organic solvent, then the lens can be cleaned and processed, but the lens dimensions increase substantially causing potential damage to the printed image
Solution Approach 1:
The patent changes the dimensional parameters of the cured ink by incorporating crosslinkable functional groups and adjusting the polymer network density. This creates a cured ink structure that maintains dimensional stability during organic solvent extraction, preventing image damage while allowing the extraction process to proceed.
Solution Approach 2:
The patent uses a composite polymer network combining silicone-containing crosslinking segments with hydrophilic matrix segments. This composite structure provides dimensional stability during extraction while maintaining the necessary porosity and flexibility for the lens to undergo reversible dimensional changes without damaging the printed image.
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 fluorine-containing binder copolymer ensures the durability and adhesion of the ink, preventing damage during mold closure and maintaining image quality even in solvated states, while allowing for substantial reversible dimensional changes, thus enhancing the production of high-quality colored silicone hydrogel contact lenses.
Implementation Method 1
the amount of the ethylenically unsaturated groups in the fluorine-containing binder polymer is high enough to ensure that the fluorine-containing binder copolymer can be crosslinked actinically or thermally to form the colorant-entrapping polymer network
Implementation Method 2
the amount of the ethylenically unsaturated groups in the fluorine-containing binder polymer is high enough to ensure that the fluorine-containing binder copolymer can be crosslinked actinically or thermally to form the colorant-entrapping polymer network
Data Source
AI summary
The present invention provides inks and methods for making colored silicone hydrogel contact lenses. The ink of the invention comprises an actinically-curable binder copolymer comprising fluorine-containing segments and is characterized by having capability to be cured actinically or thermally to form a colored film on a molding surface of a mold or a silicone hydrogel contact lens and by having an increased durability in a solvated state in a silicone-hydrogel lens formulation in relation to a control colored film obtained from a control ink including an actinically-curable fluorine-free binder copolymer. The invention also provides methods for making colored silicone hydrogel contact lenses based on print-on-mold processes for producing colored contact lenses.