Silicone Hydrogel Contact Lenses with Reduced Surface Rippling

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Solution Overview

Problem

Silicone hydrogel contact lenses often exhibit surface rippling, particularly when cast in polypropylene molds, which is exacerbated by high molecular weight siloxane components, compromising lens quality and wearer comfort.

Innovation Solution

Incorporating triphenylphosphine (TPP) into the polymerizable formulation at 0.10% (wt/wt) with a siloxane component comprising at least 50% di-functional siloxanes of 5,000 daltons and hydrophilic N-vinyl amide monomers maintains lens properties while reducing surface rippling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high molecular weight siloxane components are used in the polymerizable composition, then oxygen permeability and water content are improved, but surface rippling increases

Engineering Contradiction:

Improveoxygen permeabilityVSAvoidsurface rippling

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent introduces a surfactant as an intermediary substance in the polymerizable composition. The surfactant mediates between the high molecular weight siloxane components and the mold surface, reducing surface tension and preventing the formation of surface ripples during cast molding, while allowing the siloxane components to maintain their beneficial oxygen permeability properties

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical composition parameters of the polymerizable system by adding specific surfactant compounds. This parameter change modifies the surface properties of the formulation during molding, reducing surface rippling while maintaining the bulk properties (oxygen permeability and water content) provided by the high molecular weight siloxane components

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If di-functional siloxanes with high molecular weight are used, then lens hydration and oxygen transmissibility are enhanced, but surface rippling becomes more acute

Engineering Contradiction:

Improvewater contentVSAvoidsurface rippling

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The surfactant acts as a mediator that allows high molecular weight di-functional siloxanes to be incorporated into the formulation without causing surface defects. It modifies the interfacial properties during molding, enabling the siloxanes to contribute their full hydration and oxygen transmissibility benefits without generating surface ripples

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If polypropylene molds are used for cast molding, then manufacturing efficiency is maintained, but surface rippling is exacerbated

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidsurface rippling

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The surfactant serves as an intermediary between the polymerizable composition and the polypropylene mold surface. It modifies the wetting and demolding characteristics, allowing the use of efficient polypropylene molds while preventing the adhesion and surface deformation that cause rippling

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The addition of surfactant changes the surface energy parameters of the formulation, improving its compatibility with polypropylene mold surfaces. This parameter change reduces the tendency for the material to adhere irregularly to the mold, thereby eliminating surface ripples while maintaining manufacturing efficiency

Inventive Principle:

Principle #35Parameter changes

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 formulation effectively reduces surface rippling without adversely affecting water content, contact angle, or oxygen permeability, enhancing lens quality and comfort.

Implementation Method 1

It has been found that by including at least 0.10% (wt/wt) TPP in contact lens formulations... the resultant formulation is resistant to surface rippling

Methodology Applied

Scientific EffectSurface tension reduction: Surfactant

Data Source

PatentEP4544329B1Contact lenses and contact lens formulations with reduced rippling

Publication Date: 2025.10.15 COOPERVISION INT LTD

AI summary

The present invention provides a silicone hydrogel contact lens formulation, comprising a di- functional siloxane, a hydrophilic N-vinyl amide monomer and at least 0.10% (wt/wt) triphenylphosphine (TPP), a silicone hydrogel contact lens formed from the polymerization of the silicone hydrogel contact lens formulation and the use of TPP to improve the surface properties of a contact lens prepared from a formulation comprising a di-functional siloxane, and a hydrophilic N-vinyl amide monomer.