Optical Fiber Coating Curing with Norrish Type I Photoinitiators
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Solution Overview
Problem
The challenge in the optical fiber coating industry is to develop coatings that can effectively cure using LED light sources, which typically provide lower irradiance and a narrower wavelength distribution compared to traditional mercury lamps, while also maintaining performance at higher draw speeds and temperatures, where the coatings may experience reduced curing efficiency and increased microbend-induced attenuation.
Innovation Solution
A radiation curable composition comprising a urethane acrylate oligomer, a reactive diluent monomer, and a Norrish Type I photoinitiator with specific ionization potential and polymerization rate characteristics, optimized for use with LED light sources, is applied to optical fibers. This composition ensures superior curing efficiency and adhesion, even at elevated temperatures and high draw speeds, by utilizing a photoinitiator with a normalized rate of polymerization greater than 0.5 at 150°C and an ionization potential between 3.0 and 3.75 eV, enhancing the cure performance of both primary and secondary coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional mercury lamps are used for curing coatings, then higher irradiance and broader wavelength distribution are achieved, but LED light sources are preferred for energy efficiency and environmental reasons
Solution Approach 1:
The patent modifies the chemical parameters of the coating composition by selecting photoinitiators with specific absorption characteristics that match LED wavelength outputs. The composition is formulated with photoinitiators that have maximum absorption in the 380-420nm range, enabling effective curing with LED sources while maintaining energy efficiency benefits
Solution Approach 2:
The patent introduces a specially formulated coating composition as an intermediary between the LED light source and the curing process. This composition contains photoinitiators that act as mediators to convert the LED's narrow wavelength output into effective polymerization initiation, bridging the gap between LED energy efficiency and adequate curing performance
2Productivity
If draw speed is increased to improve productivity, then output increases, but curing efficiency decreases and microbend-induced attenuation increases
Solution Approach 1:
The patent applies the coating composition with pre-selected photoinitiators before the curing stage, optimizing the formulation in advance to respond rapidly to LED irradiation. This preliminary optimization of the coating's chemical composition enables fast curing kinetics that can keep pace with high draw speeds
Solution Approach 2:
The patent changes the chemical parameters of the coating by incorporating photoinitiators with high molar extinction coefficients and high quantum yields. These parameter changes in the coating's photoreactive components enable rapid polymerization rates that maintain curing efficiency even at elevated draw speeds where exposure time is reduced
3Productivity
If draw speed is increased to improve productivity, then output increases, but microbend-induced attenuation increases
Solution Approach 1:
The patent formulates the coating composition in advance with photoinitiators optimized for LED sources, ensuring that the coating is primed for rapid and complete curing. This preliminary optimization prevents incomplete curing that would otherwise occur at high draw speeds and lead to microbends
Solution Approach 2:
The patent modifies the coating's chemical composition parameters to include photoinitiators with high reactivity and efficiency under LED irradiation. These parameter changes ensure complete and uniform curing even with reduced exposure time at high draw speeds, preventing the formation of microbends that cause signal attenuation
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 improved surface and through-cure of optical fiber coatings, maintaining or exceeding existing performance standards, even under conditions of high-speed drawing and elevated temperatures, thereby reducing microbend-induced attenuation and ensuring the integrity and reliability of the coated optical fibers.
Implementation Method 1
A radiation curable composition comprising a urethane acrylate oligomer, a reactive diluent monomer, and a Norrish Type I photoinitiator... is applied to optical fibers. This composition ensures superior curing efficiency... by utilizing a photoinitiator with a normalized rate of polymerization greater than 0.5 at 150°C
Data Source
AI summary
Described herein are methods of producing a coated optical fiber from a primary and/or secondary coating composition that contain a reactive oligomer having an average of at least one polymerizable group, a monomer having an average of at least one polymerizable group, and a photoinitiator, wherein the photoinitiator possesses specified normalized rates of polymerization at (150) degrees Celsius and/or a potential excited triplet state with certain ionization potential values. Also described and claimed are the compositions for use therewith, including primary coating compositions and secondary coating compositions. Yet further described and claimed are the coated optical fibers produced from the methods and/or compositions elsewhere described.