Temporary Coating for Ophthalmic Lens Mold Adhesion Control
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Solution Overview
Problem
The high adhesive forces between ophthalmic lens forming surfaces and the lenses, particularly with silicone hydrogel materials, result in damage during mold opening and removal, leading to unacceptable quality standards in mass production of contact lenses.
Innovation Solution
Applying a temporary coating to at least a portion of the lens forming surfaces of the mold halves reduces adhesive forces, facilitating mold separation and lens removal without damaging the lenses, and this process can be integrated into automated mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reusable molds with highly finished glass lens forming surfaces are used, then manufacturing precision is improved, but adhesive forces between the lens forming surfaces and contact lenses increase causing damage during removal
Solution Approach 1:
A temporary coating layer is applied to the lens forming surfaces of the mold halves, serving as an intermediary between the glass surface and the contact lens material. This coating layer reduces adhesive forces during polymerization and enables easy removal of the cured lens without damage, while maintaining the high surface quality needed for precision manufacturing.
Solution Approach 2:
The surface properties of the lens forming surfaces are temporarily modified by applying a coating layer with different adhesive characteristics. This changes the surface energy and wettability parameters, reducing the adhesive forces between the mold and lens material during curing, while allowing easy detachment after polymerization.
2Ease of operation
If high forces are applied to open the molds and remove contact lenses, then removal is achieved, but lens damage occurs reducing productivity
Solution Approach 1:
The temporary coating acts as a mediator that reduces the force required for mold opening and lens removal. By lowering the adhesive bonding strength between the mold surface and lens material, the coating enables easy detachment with minimal force, preventing lens damage and maintaining high production rates.
Solution Approach 2:
The temporary coating is applied to the lens forming surfaces before the contact lens material is introduced into the mold. This preliminary action prepares the surface to minimize adhesive forces during subsequent polymerization, ensuring that when the mold needs to be opened, the lens can be removed easily without requiring high forces that would cause damage.
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 temporary coating significantly reduces the forces required to open the molds and detach the lenses, minimizing damage and ensuring higher quality standards by reducing adhesive forces between the lenses and the mold surfaces.
Implementation Method 1
adhesive forces between the lens forming surfaces and the formed contact lens may require considerably high forces to allow the opening of the molds
Implementation Method 2
polymers formed by photochemical polymerization and/or cross-linking include polymers based on polyvinyl alcohols (PVA) or silicone hydrogels (SiHy)
Data Source
Figure 1~2
AI summary
There are described a method for applying a coating to a surface of an ophthalmic lens mold. The mold comprises male and female (20) mold halves, with each of the mold halves being provided with a lens forming surface (21). The method includes - applying a temporary coating to at least a portion of at least one of the male and female mold halves (20), the temporary coating being capable of reducing adhesive forces between a lens forming material and the lens forming surface (21); and - drying the temporary coating applied to the portion of the lens forming surface (21). Also described is a device (1) for applying such temporary coating to the portion of the lens forming surface (21) of the ophthalmic lens mold.