Curable Silicone Hydrogel Lens Ink Formulation
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Solution Overview
Problem
Existing methods for creating colored contact lenses are not compatible with silicone hydrogel lenses, as they are designed for conventional hydrogels and can have adverse effects on silicone hydrogel properties such as surface energy, oxygen permeability, and water content.
Innovation Solution
Development of an ink suitable for silicone hydrogel contact lenses using a pad-printing system, comprising a pigment, polymeric dispersant, solvent, and an actinically or thermally curable binder polymer with ethylenically unsaturated groups derived from silicone-containing vinylic monomers or macromers, which adheres to the lens surface upon curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional hydrogel ink formulations are used on silicone hydrogel lenses, then the ink can be applied to the lens surface, but the ink has adverse effects on lens properties such as surface energy, oxygen permeability, and water content
Solution Approach 1:
The ink formulation parameters are specifically changed to be compatible with silicone hydrogel lenses. The binder polymer is selected to have appropriate molecular weight, functional groups, and crosslinking characteristics that match the silicone hydrogel substrate, thereby maintaining lens properties while enabling successful ink application and adhesion.
Solution Approach 2:
The ink is formulated as a composite system containing pigment, solvent, polymeric dispersant, and binder polymer in specific proportions. This composite structure allows the ink to simultaneously achieve proper flow characteristics for application, strong adhesion to silicone hydrogel, and compatibility with lens properties like oxygen permeability and water content.
2Productivity
If existing ink formulations designed for conventional hydrogels are used, then the printing process can proceed, but the print life is short and adhesion is poor
Solution Approach 1:
The ink formulation replaces mechanical adhesion mechanisms with chemical bonding mechanisms. The binder polymer contains functional groups that form strong chemical bonds with the silicone hydrogel lens surface, replacing weak mechanical interlocking and thereby extending print life significantly.
Solution Approach 2:
The crosslinking density and functional group composition of the binder polymer are optimized to achieve the right balance between initial adhesion strength and long-term durability. This parameter optimization extends the functional life of the printed lens while maintaining good initial adhesion.
3Reliability
If inks compatible with silicone hydrogel are developed, then lens property stability is improved, but the ink formulation becomes more complex
Solution Approach 1:
The binder polymer is designed to perform multiple functions simultaneously: providing adhesion to silicone hydrogel, ensuring proper ink flow and drying characteristics, maintaining lens oxygen permeability, and enabling crosslinking for durable attachment. This multi-functionality reduces the need for multiple separate additives, thereby limiting formulation complexity.
4Manufacturing precision
If the ink adheres strongly to the lens surface, then color image quality is improved, but the lens properties such as surface energy and oxygen permeability may be compromised
Solution Approach 1:
The ink formulation creates a localized color layer on the lens surface with controlled thickness and composition. The binder polymer and pigment are distributed to provide sufficient adhesion and color quality only where needed on the lens surface, while the bulk lens properties including oxygen permeability and water content remain unaffected.
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 ink provides a high-quality color image with a longer print life and improved compatibility with silicone hydrogel lenses, ensuring stable adhesion and maintaining the lens's properties.
Implementation Method 1
an actinically or thermally curable binder polymer which comprises ethylenically unsaturated groups
Implementation Method 2
segments derived from at least one silicone-containing vinylic monomer or macromer
Data Source
AI summary
The present invention provides an actinically or thermally curable ink for making colored silicone hydrogel contact lenses. The ink of the invention comprises at least a pigment, a polymeric dispersant, a solvent and an actinically or thermally curable silicone- containing binder polymer including ethylenically unsaturated groups and segments derived from at least one silicone-containing vinylic monomer or macromere. The ink of the invention is characterized by having capability to be cured actinically or thermally to form a colored coat on a silicone hydrogel contact lens, wherein the ink is characterized by having an longer print life using a pad-printing system by at least 30% comparing to the ink which has the same composition except of no polymeric dispersant, wherein ink life is a number of printed parts that can be achieved in a print cycle.