Low Refractive Index Optical Fiber Coating via Crosslinked Fluorinated Monomers
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Solution Overview
Problem
Existing fluorinated low refractive index coatings for optical fibers, such as those using perfluorinated polyether (PFPE) oligomers, face issues like softness, low thermo-oxidative stability, polydispersity, and lot-to-lot variability, as well as environmental concerns due to the use of restricted chemical components like PFOA and its precursors.
Innovation Solution
A composition comprising 65 to 95 weight percent of a fluorinated monofunctional monomer, 5 to 35 weight percent of a fluorinated multifunctional monomer, and 0.5 to 3 weight percent of a silane coupling agent, devoid of trifunctional fluorocarbon moieties, which forms a crosslinked coating with a shore D hardness of 56 to 85 and a refractive index meeting the equation RI≤1.368+10.8/X, where X denotes wavelength in nanometers, providing improved hardness, stability, and consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PFPE oligomers are used to achieve low refractive index coating, then the refractive index is reduced, but the coating becomes soft and lacks hardness
Solution Approach 1:
The patent uses a composite approach by combining fluorinated monomers with silane coupling agents to create a crosslinked polymer network. This composite structure provides both the low refractive index property from the fluorinated chains and the hardness from the crosslinked gel structure, resolving the contradiction between optical property and mechanical property.
Solution Approach 2:
The patent changes the molecular architecture parameters by using monomers with specific fluorine content and chain lengths, and by controlling the crosslinking density through silane coupling agent concentration. This allows independent optimization of refractive index (through fluorine content) and hardness (through crosslinking density), resolving the trade-off between these properties.
2Illumination intensity
If PFPE derivatives are used to achieve low refractive index, then the refractive index is reduced, but thermo-oxidative stability deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters by selecting fluorinated monomers with specific structures that resist oxidation, and by controlling the crosslinking density to protect the polymer chains from thermal and oxidative degradation. This resolves the contradiction between achieving low refractive index and maintaining thermo-oxidative stability.
3Quantity of substance
If PFPE oligomers with high molecular weight are used to achieve desirable viscosity, then the viscosity is improved, but polydispersity increases causing lot-to-lot variability
Solution Approach 1:
The patent segments the polymer structure into discrete monomer units with defined chemical structures, rather than using high molecular weight oligomers with broad molecular weight distributions. This segmentation approach allows precise control over the chemical composition and crosslinking behavior, eliminating polydispersity-related variability while maintaining desirable viscosity through controlled crosslinking.
Solution Approach 2:
The patent changes the molecular weight approach from using high molecular weight oligomers to using low molecular weight monomers that can be precisely controlled. This parameter change eliminates the polydispersity problem inherent in oligomer synthesis while allowing viscosity to be controlled through crosslinking density, thereby improving manufacturing precision.
4Illumination intensity
If conventional fluorinated coatings are used to achieve low refractive index, then the refractive index is reduced, but environmental friendliness deteriorates due to restricted chemicals
Solution Approach 1:
The patent changes the chemical composition parameters by selecting fluorinated monomers that do not contain restricted substances like PFOA or its precursors, while maintaining the low refractive index property through appropriate fluorine content. This resolves the contradiction between optical performance and environmental compatibility.
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 hardness and low refractive index, enhancing the thermal and environmental resistance of optical fibers, while avoiding the use of restricted chemicals, resulting in a more consistent and environmentally friendly coating.
Implementation Method 1
a crosslinked composition has a shore D hardness of 56 to 85
Implementation Method 2
a crosslinked composition has a refractive index (RI) that meets the limitation of the equation RI≤1.368+10.8/X
Data Source
AI summary
Disclosed herein is a composition comprising 65 to 95 weight percent of a fluorinated monofunctional monomer; 5 to 35 weight percent of a fluorinated multifunctional monomer; and 0.5 to 3 weight percent of a silane coupling agent; where all weight percents are based on the total weight of the composition; where the fluorinated monofunctional monomer and the fluorinated multifunctional monomer are devoid of any trifunctional fluorocarbon moieties when they have 6 or more fluorocarbon repeat units; where the fluorocarbon repeat units are CF2 or CF moieties; and where a crosslinked composition has a shore D hardness of 56 to 85 and has a refractive index (RI) that meets the limitation of the equation RI≤1.368+10.8/X, where X denotes wavelength in nanometers.