Radiation-curable fiber optic materials having reduced moisture content

Abstract

A method of making radiation-curable, fiber optic materials having extended shelf-life and reduced water content which when suitably cured provide reliable and consistent adhesion characteristics to optical glass fibers.

Description

FIELD OF THE INVENTION.[0001] This invention provides a method for making radiation-curable fiber optic materials having an extended shelf-life, and in particular, materials which comprise hydrolyzable glass coupling agent and which have reduced moisture content.DESCRIPTION OF RELATED ART[0002] Optical glass fibers are frequently coated with two or more superposed radiation-curable coatings, which together form a primary coating. The coating which contacts the optical glass fiber is called the "inner primary" coating and the overlaying coating is called the "outer primary" coating. Alternatively, the inner primary coating may simply be called the "primary" coating and the outer primary coating the "secondary" coating. Other optical fiber materials include matrix materials, inks, and bundling materials. All of these fiber optic materials are preferably radiation-curable and are within the scope of the present invention. Coated optical fibers can be incorporated into ribbon and cable ...

AI Technical Summary

Benefits of technology

[0010] An objective of the present invention is to provide a process of making radiation-curable fiber optic materials having extended shelf-life and which when suitably cured provide materials having reliable and consistent characteristics, and in particular, adhesion characteristics.

[0011] Another objective of the present invention is to provide a radiation-curable, inner primary, optical glass fiber coating composition having extended-shelf life, which when suitably cured provides consistent and reliable adhesion and delamination characteristics to optical glass fibers.

[0013] The present invention is therefore based on the discovery that the amount of water can be carefully controlled when making the radiation-curable, inner primary, optical glass fiber coating composition to provide an extended shelf-life for the uncured composition and to provide a cured inner primary coating having reliable and predictable adhesion characteristics.

[0014] In particular, the present invention provides a process for extending the useful shelf-life of radiation-curable resin coating compositions, adapted for use in forming inner primary coatings on optical glass fibers for signal transmission, and which contain a coupling agent having a functionally-effective glass binding group for promoting adhesion to glass fibers and which group is susceptible to hydrolysis under normal shelf storage conditions for the coating composition. The cured coating provides reliable and consistent resistance to delamination from the optical glass fiber.

[0016] The invention also provides a process for extending the shelf-life of radiation-curable coating compositions adapted for use in forming inner primary coatings on optical glass fibers for signal transmission and containing a coupling agent having a functional group which bonds with the glass fiber and which is susceptible to hydrolysis under normal shelf storage conditions for the coating composition. The cured coating provides reliable and consistent adhesion to the optical glass fiber. The process consists essentially in the steps of formulating the coating composition from components having sufficiently low respective water contents such that after formulation the ratio of total molar equivalent water content of the formulated coating composition to the total molar equivalent content of the functional groups is less than one.

[0018] The invention further provides a radiation-curable, inner primary, optical glass fiber coating composition having extended shelf-life and when suitably cured exhibits reliable and consistent resistance to delamination from the optical glass fiber. The coating composition comprises a radiation-curable oligomer or monomer and a coupling agent containing at least one functionally-effective glass binding group capable of bonding to said glass fiber and which is susceptible to hydrolysis under normal shelf storage conditions for said coating composition. The coating composition has a controlled stoichiometric water content less than the stoichiometric amount of the said functional groups present in the coupling agent.

Problems solved by technology

Microbending is associated with attenuation of the signal transmission capability of the coated optical glass fiber and is therefore undesirable.

In general, optical glass fibers are weakened upon exposure to water.

For example, moisture in air can cause weakening and the eventual breakage of optical glass fibers.

In addition to causing the weakening of the optical glass fibers, moisture can also cause the inner primary coating layer to delaminate from the optical glass fiber.

The delamination of the inner primary coating from the optical glass fiber further results in a weakened optical glass fiber, because the inner primary coating can no longer protect the optical glass fiber from attack from moisture.

Delamination may also cause attenuation of the signal transmission capability of the coated optical glass fiber.

However, for certain applications, conventional radiation-curable, optical glass fiber coating compositions may not provide cured inner primary coatings having sufficient reliability and consistency in resistance to delamination caused by moisture.

Moreover, when suitable compositions have been formulated, erratic and inconsistent performance on the glass fiber has been observed.

It has also been found that the resistance to delamination of the cured inner primary coating from an optical fiber decreases with the age or shelf-life of the radiation-curable, optical glass fiber coating composition, and this decrease may be erratic from one batch of composition to another.

Such inconsistency can have severe repercussions in optical fiber technology.

Materials with insufficient shelf life may need to be discarded.

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