Catanionic Vesicle Coating for Contact Lens Mold Release
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Solution Overview
Problem
The existing methods for producing contact lenses using cast-molding processes face challenges in mold separation and lens removal, leading to defects such as cracks, flaws, and tears, which reduce the production yield and quality due to strong adhesion between the lens and the mold.
Innovation Solution
A method involving the application of an aqueous catanionic solution containing a cationic and anionic surfactant on the mold surfaces, forming a coat of catanionic vesicles that significantly reduces the mold separation force and adhesion, allowing for easier and more efficient lens removal with minimal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional cast-molding process is used with disposable or reusable molds, then mass production of contact lenses can be achieved, but strong adhesion between the polymerized lens and mold occurs causing cracks, flaws, and tears during mold separation
Solution Approach 1:
The patent applies a mold releasing agent coating to the mold surfaces before introducing the lens-forming composition. This preliminary action creates a protective layer that prevents strong adhesion between the polymerizing lens and mold, enabling successful mold separation without lens damage while maintaining mass production capability
Solution Approach 2:
The mold releasing agent acts as an intermediary substance between the lens-forming composition and the mold surface. This intermediary layer reduces the adhesion force, allowing the lens to be released from the mold without suffering cracks, flaws, or tears during the separation process
2Reliability
If surfactants are added to the hydration bath to facilitate lens release, then lens adhesion to mold is reduced, but mold separation becomes more difficult and lens damage cannot be minimized
Solution Approach 1:
Instead of adding surfactants to the hydration bath after molding, the patent applies the mold releasing agent coating to the mold surfaces before the lens-forming composition is introduced. This preliminary application ensures the releasing agent is present during polymerization, facilitating both lens release and mold separation without requiring additional surfactant treatment
Solution Approach 2:
The mold releasing agent coating serves as an intermediary layer between the lens and mold surface, reducing adhesion forces during both the molding and separation processes. This intermediary action eliminates the need for post-molding surfactant addition and makes mold separation easier without compromising lens release effectiveness
3Reliability
If internal mold releasing agents are incorporated into the lens-forming composition, then adhesion between mold and lens is reduced, but the migration speed of the agent to the interface is not fast enough to effectively reduce adhesion
Solution Approach 1:
The patent applies the mold releasing agent coating to the mold surfaces before introducing the lens-forming composition, ensuring the agent is already positioned at the interface where it is needed. This eliminates the slow migration process required when incorporating agents into the composition, as the agent is immediately available to prevent adhesion during polymerization
Solution Approach 2:
By applying the releasing agent as a coating on the mold surface, the patent creates an intermediary layer that is immediately present at the lens-mold interface. This approach bypasses the limitation of slow migration speed associated with internal agents, as the agent is pre-positioned to effectively reduce adhesion from the start of the polymerization process
4Force
If external mold releasing agents are applied as coating onto mold surfaces, then mold separation force is reduced, but portion of the agents migrate to the surface and interior of the polymerized lens
Solution Approach 1:
The patent applies the mold releasing agent coating to the mold surfaces before introducing the lens-forming composition. This preliminary application allows the agent to function during molding while minimizing post-molding migration into the lens, as the agent is already in place and the lens is removed before significant migration can occur
Solution Approach 2:
The mold releasing agent coating serves as an intermediary layer that reduces mold separation force while being applied in a controlled manner. By applying the coating before molding and removing the lens after curing, the patent minimizes the amount of agent that migrates into the lens interior, balancing the need for easy separation with lens purity requirements
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 a substantial reduction in mold separation force by at least 50% and minimizes lens defects like star tears, thereby enhancing the quality and yield of produced contact lenses.
Implementation Method 1
applying a coating of an aqueous catanionic solution containing a cationic surfactant and an anionic surfactant onto the first molding surface and/or the second molding surface... drying the coating of the aqueous catanionic solution to form a coat of catanionic vesicles
Implementation Method 2
the formation of the coat of the catanionic vesicles on the first and/or second molding surfaces is characterized by having a percentage of reduction in mold separation force of at least about 50%
Data Source
AI summary
The invention provides a method for producing ophthalmic lenses, preferably contact lenses, more preferably silicone hydrogel contact lenses. This method involves applying a coat of catanionic vesicles onto the molding surfaces of a mold. By having a coat of catanionic vesicles on the molding surfaces of a mold, mold separation force and lens defects generated during mold opening and de-molding process can be substantially reduced.