Polar Ophthalmic Lens Molds with Low Flexural Modulus
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Solution Overview
Problem
Existing ophthalmic lens molding technologies require surface treatments or interpenetrating polymer networks (IPNs) for silicone hydrogel contact lenses to achieve ophthalmically acceptable surface wettabilities, and they often necessitate contact point coupling methods, which are inefficient and costly.
Innovation Solution
Development of polar ophthalmic lens molds with a flexural modulus less than 3800 MPa, allowing for interference fitting and eliminating the need for surface treatments or IPNs, enabling the production of silicone hydrogel contact lenses with ophthalmically acceptable surface wettabilities through the use of polar polymeric materials like ethylene-vinyl alcohol (EVOH) and plasticizers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid polar resin mold members (e.g., SOARLITE S) are used to produce silicone hydrogel contact lenses with ophthalmically acceptable wettabilities, then the lenses achieve good surface wettability without surface treatment, but the mold members require point contact coupling which adds device complexity and manufacturing cost
Solution Approach 1:
The patent changes the physical parameter of flexural modulus of the mold member material from high (rigid SOARLITE S at 3800 MPa) to low (flexible polar resin less than 3800 MPa). This parameter change enables the mold member to achieve both good surface wettability for silicone hydrogel lenses and interference fit coupling capability, eliminating the need for complex point contact coupling mechanisms while maintaining ophthalmically acceptable surface wettabilities
2Device complexity
If flexible non-polar resin mold members are used to enable interference fit coupling, then the device complexity is reduced, but the produced lenses require surface treatment or IPN to achieve ophthalmically acceptable wettabilities
Solution Approach 1:
The patent employs composite material design by creating polar resin mold members with specific flexural modulus characteristics. The material combines the flexibility needed for interference fit coupling with the polar surface chemistry required to impart ophthalmically acceptable wettability to silicone hydrogel lenses. This composite approach integrates both coupling and wettability functions into a single material system, eliminating the need for separate surface treatment steps
Solution Approach 2:
The patent changes the chemical parameter of the mold member material from non-polar to polar resin composition, while simultaneously controlling the physical parameter of flexural modulus to be less than 3800 MPa. This dual parameter change enables the mold member to provide both mechanical coupling capability through interference fit and surface wettability enhancement for the produced lenses, resolving the contradiction between simplified coupling and lens wettability
3Ease of manufacture
If rigid polar resin molds are used, then additional processing steps (surface treatment or IPN) are eliminated, but point contact coupling increases manufacturing time and reduces productivity
Solution Approach 1:
The patent changes the flexural modulus parameter of the mold member material to less than 3800 MPa, transforming it from rigid to flexible. This enables interference fit coupling which is simpler and faster to implement than point contact coupling methods. Combined with the polar resin composition that eliminates surface treatment requirements, this parameter change streamlines the manufacturing process and improves productivity by reducing both the number of processing steps and the time required for mold assembly
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 new molds facilitate efficient and cost-effective production of silicone hydrogel contact lenses with improved surface wettabilities, enhancing manufacturing efficiency and reducing the need for additional processing steps, while ensuring ophthalmic compatibility.
Implementation Method 1
polar ophthalmic lens molds with a flexural modulus less than 3800 MPa, allowing for interference fitting and eliminating the need for surface treatments or IPNs, enabling the production of silicone hydrogel contact lenses with ophthalmically acceptable surface wettabilities
Implementation Method 2
An interference fit can be understood to be a fastening between first and second mold members that is achieved by friction between a portion of the first mold member and a portion of the second mold members after the mold members are pushed or pressed together
Data Source
AI summary
Ophthalmic lens molds include first and second mold members sized and adapted to be assembled, for example interference fitted, together to define a lens-shaped cavity therebetween. At least one of the mold members includes a polar polymeric material and has a flexural modulus less than 3800 MPa.