Ophthalmic Lens Mold Surface Energy for Dry Demolding
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Solution Overview
Problem
Current contact lens molds made from highly polar thermoplastics like EVOH are expensive, brittle, and require costly organic solvent-based washing processes, and often necessitate wet demolding, which complicates the production of ophthalmically acceptably wettable silicone hydrogel lenses without surface treatments or interpenetrating networks.
Innovation Solution
The use of contact lens molds with thermoplastic polymer surfaces having a percent polarity from 3% to 20% and a total surface energy from 25 mN/m to 40 mN/m, allowing for dry demolding and delensing of silicone hydrogel lenses without surface treatments or interpenetrating networks, using a polymerizable composition with a surface tension from 20 mN/m to 25 mN/m and a surface energy differential less than or equal to zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If highly polar thermoplastic polymers (e.g., EVOH) are used to manufacture contact lens molds, then ophthalmically acceptably wettable lens surfaces are achieved, but production costs increase due to expensive materials and organic solvent-based washing processes
Solution Approach 1:
The patent changes the surface energy parameter of the mold from high (EVOH) to a specific range (25-40 mN/m) using different thermoplastic polymers. This parameter change maintains the wetting capability during molding while enabling dry demolding and eliminating the need for expensive organic solvent washing processes, thus reducing production costs while preserving surface wettability
Solution Approach 2:
The patent employs conventional thermoplastic polymers that are less expensive than EVOH to create mold surfaces. These molds can be used multiple times (not truly disposable) but represent a cost-effective alternative to expensive EVOH molds, achieving the desired wettability without requiring costly material substitutions
2Reliability
If highly polar thermoplastic polymers (e.g., EVOH) are used to manufacture contact lens molds, then wettable lens surfaces are achieved, but production complexity increases due to wet demolding and solvent-based washing processes
Solution Approach 1:
By adjusting the surface energy parameter to the specific range of 25-40 mN/m using conventional thermoplastic polymers, the patent transforms the demolding process from wet to dry, and eliminates the washing step entirely. This parameter optimization simplifies the manufacturing process while maintaining ophthalmically acceptable wettability
3Ease of manufacture
If non-polar thermoplastic polymers are used to manufacture contact lens molds, then production costs are reduced, but additional surface treatments or interpenetrating networks are required to achieve wettable lens surfaces
Solution Approach 1:
The patent identifies and applies the optimal surface energy parameter range (25-40 mN/m) that conventional thermoplastic polymers can achieve. This parameter optimization allows these lower-cost materials to produce wettable lenses directly without requiring additional surface treatments or interpenetrating networks, thus reducing both cost and process complexity
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
This approach enables the production of ophthalmically acceptably wettable silicone hydrogel lenses with reduced production costs and improved process efficiency, eliminating the need for expensive materials and solvent-based washing, while allowing for dry demolding and delensing, thus simplifying the manufacturing process.
Implementation Method 1
the molding surface having a percent polarity from 3% to 20% and a total surface energy from 25 mN/m to 40 mN/m
Implementation Method 2
the polymerizable composition having a surface tension from 20 mN/m to 25 mN/m and a surface energy differential of the surface tension of the polymerizable composition less the surface energy of the molding surface is less than or equal to zero
Implementation Method 3
curing the polymerizable composition in the mold assembly to form a cast-molded polymerized reaction product in the lens-shaped cavity of the mold assembly
Data Source
Figure 1~2
AI summary
Methods of manufacturing contact lenses using ophthalmic lens molds having a molding surface comprising a thermoplastic polymer, the molding surface having a percent polarity from 3% to 20% and a surface energy from about 25 mN/m to about 40 mN/m to cast mold a polymerizable composition having a surface tension from about 20 mN/m to about 25 mN/m, wherein a surface energy differential of the surface tension of the polymerizable composition less the surface energy of the molding surface less than or equal to zero (0); and silicone hydrogel contact lens bodies so manufactured are described.