Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Utility Patent
1999-07-15
2001-01-02
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S090000, C522S157000, C522S158000, C522S150000, C428S378000, C428S380000, C428S383000
Utility Patent
active
06169126
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to radiation-curable, optical fiber coating systems comprising an inner and an outer primary coating compositions. The invention also relates to coated optical fibers and optical fiber assemblies. More particularly, the invention relates to a radiation- curable, optical fiber coating system that provides improved strip cleanliness and optical fibers coated with the coating system, ribbon assemblies comprising such coated optical fibers and methods of making and forming the same.
BACKGROUND OF THE INVENTION
Optical fiber coating systems commonly comprise two coating compositions. The first coating composition contacts the glass surface and is called the inner primary coating. The second coating composition is designed to overlay the inner primary coating and is called the outer primary coating.
The inner primary coating is usually a soft coating having a low glass transition temperature (hereinafter “Tg”), to provide resistance to microbending. Microbending can lead to attenuation of the signal transmission capability of the coated optical glass fiber and is therefore undesirable. The outer primary coating is typically a harder coating providing desired resistance to handling forces, such as those encountered when the coated fiber is cabled.
For the purpose of multi-channel transmission, optical fiber assemblies containing a plurality of coated optical fibers have been used. Examples of optical fiber assemblies include ribbon assemblies and cables. A typical optical fiber assembly is made of a plurality of coated optical fibers which are bonded together in a matrix material. For example, the matrix material can encase the optical fibers, or the matrix material can edge-bond the optical fibers together.
Optical fiber assemblies provide a modular design which simplifies the installation and maintenance of optical fibers by eliminating the need to handle individual optical fibers.
Coated optical fibers for use in optical fiber assemblies are usually coated with an outer colored layer, called an ink coating, or alternatively a colorant is added to the outer primary coating to facilitate identification of the individual coated optical glass fibers. Such ink coatings and colored outer primary coatings are well known in the art. Thus, the matrix material which binds the coated optical fibers together contacts the outer ink layer if present, or the colored outer primary coating.
When a single optical fiber of the assembly is to be fusion connected with another optical fiber, or with a connector, an end part of the matrix layer is required to be stripped away from the optical fiber. A common method for practicing ribbon stripping at a terminus of the ribbon assembly is to use a heated stripping tool. Such a tool consists of two plates provided with heating means for heating the plates to about 90 to about 120 C. An end section of the ribbon assembly is pinched between the two heated plates and the heat of the tool softens the matrix material and the primary coatings prior to and during the stripping procedure.
Ideally, the primary coatings on the coated optical fibers, and the ink coating if present, are removed simultaneously with the matrix material to provide bare portions on the surface of the optical fibers (hereinafter referred to as “ribbon stripping”). In ribbon stripping, the matrix material, primary coatings, and ink coating, are desirably removed as a cohesive unit to provide a clean, bare optical glass fiber which is substantially free of residue. Any residue can interfere with the optical glass fiber ribbon mass fusion splicing operation, and therefore is presently removed by wiping with a solvent prior to splicing. However, the solvent wipe can cause abrasion sites on the bare optical fiber, thus compromising the integrity of the connection. Many attempts have been made to increase the strip cleanliness of the ribbon assemblies by adding adhesion reducing additives to the inner primary coating which results in systems with little improvement in the strip cleanliness or system with insufficient adhesion. The ability to produce ribbon assemblies that can be stripped to provide clean, residue-free, bare optical glass fibers without unduly sacrificing other desirable or required properties of the primary coatings continues to challenge the industry.
There are many test methods which may be used to determine the performance of a ribbon assembly during ribbon stripping. An example of a suitable test method for determining the stripping performance of a ribbon is disclosed in the article by Mills, G., “Testing of 4- and 8-fiber ribbon strippability”, 472 International Wire & Cable Symposium Proceedings (1992), the complete disclosure of which is incorporated herein by reference.
Many attempts have been made to understand the problems associated with ribbon stripping and to find a solution to increase ribbon stripping performance. The following publications attempt to explain and solve the problems associated with ribbon stripping: K. W. Jackson, et. al., “The Effect of Fiber Ribbon Component Materials on Mechanical and Environmental Performance”, 28 International Wire & Symposium Proceedings (1993); H. C. Chandon, et. al., “Fiber Protective Design for Evolving Telecommunication Applications”, International Wire & Symposium Proceedings (1992); J. R. Toler, et. al., “Factors Affecting Mechanical Stripping of Polymer Coatings From Optical Fibers”, International Wire & Cable Symposium Proceedings (1989); and W. Griffioen, “Strippability of Optical Fibers”, EFOC & N, Eleventh Annual Conference, Hague (1993).
The ability of a ribbon assembly to ribbon strip cleanly so as to provide bare optical glass fibers that are substantially free of residue was heretofore unpredictable and the factors affecting ribbon stripping not fully understood. Accordingly, there is a need for an optical fiber, radiation-curable coating composition system that improves the strippability of optical fiber ribbons.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide a radiation-curable, optical fiber primary coating system comprising an inner primary coating composition and a, colored or non-colored, outer primary coating composition that imparts improved ribbon stripping to a ribbon assembly, when incorporated therein.
It is another objective of the present invention to provide a coated optical fiber having a coating such that when it is incorporated into a ribbon assembly the ribbon assembly achieves better strip cleanliness.
It is another objective of the present invention to provide a ribbon assembly having improved ribbon stripping capabilities.
It is still a further objective of the present invention to provide a method of preparing a radiation-curable, optical fiber coating system comprising an inner primary coating composition and an outer primary coating composition that imparts improved ribbon stripping to a ribbon assembly, when incorporated therein.
Surprisingly, the above objects and other objects are and have been obtained by the following. The present invention provides a radiation-curable, optical fiber primary coating system having; i) a radiation-curable inner primary coating composition comprising at least strip enhancing component wherein said composition, after cure, is capable of sufficiently adhering to an optical fiber so as to prevent delamination in the presence of moisture and during handling, and ii) a radiation-curable outer primary coating composition that, upon cure, has a secant modulus of at least 1000 MPa (when measured on Mylar). Suitable strip enhancing components including, for example:
a. an oligomer comprising at least one strip agent moiety and/or a composite oligomer comprising at least one glass coupling moiety, at least one slip agent moiety, and at least one radiation-curable moiety capable of polymerizing under the influence of radiation;
b. a soluble wax that is soluble in said inner primary coating composition and/or a solid lubricant;
c. a radiation-curable silicone oligomer and/or a silicone
Bishop Timothy E.
Chawla Chander P.
Pasternack George
Petisce James R.
Snowwhite Paul E.
DSM N.V.
McClendon Sanza L.
Pillsbury Madison & Sutro
Seidleck James J.
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