Silicone Hydrogel Contact Lens Oxygen Permeability Transparency
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Solution Overview
Problem
Contact lenses with high oxygen permeability and softness are challenging to produce due to issues with devitrification and mechanical properties, leading to inferior user experience and potential corneal lesions.
Innovation Solution
A silicone hydro-gel contact lens is developed using a copolymer with a well-developed intermediate region, formed from a combination of terminal-polymerizable silicone oligomers, hydrophilic components, and hydrophobic monomers, requiring specific stirring conditions to ensure uniform mixing and prevent polymerization initiation during stirring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicone hydro-gel is formed as a copolymer to achieve high oxygen permeability, then oxygen permeability is improved, but the copolymer becomes opaque and develops devitrification, causing inferior transparency
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular weight of the silicone oligomer component within 1000-100000 range and adjusting its content to 1-40% in the copolymer. These specific parameter ranges optimize the balance between oxygen permeability and transparency, preventing devitrification while maintaining high oxygen transmission capability.
Solution Approach 2:
The patent creates a composite material system combining silicone oligomer, hydrophilic component, and hydrophobic monomer in specific proportions. This composite approach allows the material to simultaneously achieve high oxygen permeability from the silicone component and transparency through proper phase distribution and composition control, resolving the contradiction between these two properties.
2Use of energy by moving object
If silicone copolymer is used to achieve high oxygen permeability, then oxygen permeability is improved, but the polymer exhibits higher elasticity and inferior feeling in daily use compared to conventional hydro-gel lens
Solution Approach 1:
The patent controls the elastic properties by adjusting the silicone oligomer molecular weight and content parameters. By limiting silicone content to 1-40% and molecular weight to 1000-100000, the material achieves sufficient oxygen permeability while maintaining elasticity comparable to conventional hydro-gel lenses, thereby improving wear comfort.
Solution Approach 2:
The patent creates local quality differentiation through phase separation, where hydrophilic regions provide softness and comfort similar to conventional lenses, while hydrophobic silicone regions provide oxygen permeability. This local distribution of properties allows the lens to simultaneously deliver high oxygen transmission and comfortable wear feeling.
3Use of energy by moving object
If silicone copolymer is used to achieve high oxygen permeability, then oxygen permeability is improved, but the lens can result in lesions of anterior epithelium of cornea known as SEALs
Solution Approach 1:
The patent controls the silicone oligomer content within 1-40% and molecular weight within 1000-100000 to optimize material properties. These parameter constraints ensure sufficient oxygen permeability while preventing excessive elasticity and surface irregularities that could cause SEALs, thereby reducing corneal lesion risk.
Solution Approach 2:
The patent promotes homogeneous distribution of the silicone oligomer and other components during mixing to ensure uniform material properties throughout the lens. This homogeneity prevents localized areas of excessive hardness or surface irregularities that could contribute to corneal epithelium lesions.
4Stability of the object's composition
If ingredient materials are mixed uniformly in a step of mixing them, then mixing uniformity is improved, but the resultant mixture can result in an opaque copolymer with devitrification after polymerization
Solution Approach 1:
The patent addresses this contradiction by controlling the molecular weight parameter of the silicone oligomer within 1000-100000 and its content within 1-40%. These parameter controls ensure that even with uniform mixing, the copolymer remains transparent and free from devitrification, as the controlled parameters prevent excessive phase separation during polymerization.
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 solution achieves a balance of high oxygen permeability, pliability, and kinetic properties while maintaining transparency, reducing the risk of corneal lesions and enhancing user comfort.
Implementation Method 1
terminal-polymerizable silicone oligomer component, which forms a hydrophobic region (A) in the copolymer
Implementation Method 2
hydrophilic component and (III) a hydrophobic monomer component... which form a hydrophilic region (C) in the copolymer
Implementation Method 3
intermediate region (B) which comprises constituents similar to those of the hydrophilic region but is not easily swollen with hydrophilic solvents... owing to the influence of the hydrophobic region
Implementation Method 4
requiring specific stirring conditions to ensure uniform mixing and prevent polymerization initiation during stirring
Data Source
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AI summary
A contact lens is provided as a hydrate of a copolymer of at least three components including (I) a both terminal-polymerizable silicone oligomer component that forms a hydrophobic region (A) in the copolymer, (II) a hydrophilic component that forms a hydrophilic region (C) in the copolymer, and (III) a hydrophobic monomer component having a molecular weight of at most 700 that forms the hydrophilic region (C) together with the component (II) and also contributes to form an intermediate region (B) which does not solvate with a hydrophilic solvent between said hydrophobic region (A) and hydrophilic region (C), wherein the intermediate region (B) shows a volume rate of 5 to 40% with respect to the region (A) in the copolymer, and the contact lens is transparent and free from bubbles therein. The contact lens is not only transparent but also is characterized by a combination of a high oxygen permeability, and a balance between softness and mechanical properties. The lens is produced through a process including steps of stirring a material liquid comprising at least three components of the above-mentioned components (I), (II) and (III) under a stirring power of 5 - 10000 W/m3 per unit volume of the material liquid for at least 10 minutes, and the injecting the stirred material liquid into a lens mold to polymerize the material liquid.