Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1998-09-04
2002-03-26
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...
C522S181000, C522S120000, C522S121000, C522S090000, C522S116000, C522S167000, C522S096000, C522S173000, C522S174000, C522S178000, C522S179000, C522S183000
Reexamination Certificate
active
06362249
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to radiation-curable, optical fiber coating compositions, which are adaptable for forming coatings such as inner primary coatings, outer primary coatings, colored secondary coatings, ink coatings, bundling materials, ribbon matrix materials and colored matrix materials on optical fibers. The compositions comprise acrylated acrylic oligomers. The present invention also relates to a coated optical fiber.
BACKGROUND OF RELATED ART
Radiation-curable compositions are vital to the optical fiber industry. Materials used in the manufacture of optical fibers are typically sensitive to environmental and handling stresses and can be made of glass, for example. Radiation-curable compositions have been formulated to provide protective coatings for sensitive optical fibers. Such compositions include, among others, inner primary coatings, outer primary coatings, colored outer primary coatings, single coatings, matrix materials, colored matrix materials, bundling materials, inks, adhesives, and upjacketting coatings. Optical fiber cable manufacturers increasingly demand better performance from these coating compositions in order to allow the optical fiber to function in a wider array of environments and have better transmission performance In addition, compositions are demanded which deliver high performance at reduced cost.
Optical fiber assemblies provide a modular design which simplifies the construction, installation and maintenance of optical fibers by eliminating the need to handle individual optical fibers. 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. Such optical fiber assemblies containing a plurality of coated optical fibers have been used for the purpose of multi-channel transmission. The matrix material can encase the optical fibers, or the matrix material can edge-bond the optical fibers together.
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 fibers. Thus, the matrix material which binds the coated optical fibers together contacts the outer ink coating 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 can be removed to separate each of the optical fibers.
Desirably, 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 fiber which is substantially free of residue.
The production of and useful characteristics for coated optical fibers are discussed in, for example, U.S. Pat. No. 5,104,433, which is hereby incorporated by reference. Single mode or multimode fiber can be prepared. Step index and graded index fibers can be prepared. In the coated fiber, loss due to absorption, scattering, macrobending and microbending should be minimized. Avoiding microbending loss is particularly important. Optical fiber typically is about 125 microns in diameter, and coating layers of approximately 30 microns are applied thereto.
Optical fiber ribbons are described in, for example, U.S. Pat. No. 4,900,126 to Jackson et al.; U.S. Pat. No. 5,373,578 to Parker et al., U.S. Pat. No. 5,379,363 to Bonicel et al.; the complete disclosures of which are hereby incorporated by reference. Ribbon stripping is discussed in, for example: “Testing of 4- and 8-Fiber Ribbon Strippability”, G. A. Mills, Int. Wire & Cable Symp. Proc., 1992, pgs. 472-474; “The Effect of Fiber Ribbon Component Materials on Mechanical and Environmental Performance”, K. W. Jackson et al., Int. Wire & Cable Symp. Proc., 1993, pgs. 28-34; which are hereby incorporated by reference.
In addition to ribbon packaging, fiber designs can include tight buffer, loose tube, filled loose tube, and mini-bundle. Cables can be packaged by conventional buffering, stranding, and jacketing steps. Optical fiber fabrication is disclosed in, for example, the article “Fiber Optics” Encyclopedia of Chemical Technology, Vol. 10, 4th Ed., pg. 514-538, (John Wiley & Sons, 1993), which is hereby incorporated by reference.
Inner primary coatings, outer primary coatings and matrix materials are usually formed from radiation-curable systems. Ink coatings usually are formed from a pigment dispersed within a radiation-curable system. The UV curable systems contain a UV curable oligomer or monomer that is liquid before curing to facilitate application of the composition, and then a solid after being exposed to UV radiation.
Modern high speed optical fiber drawing towers and ribbon forming towers operate at a very high speed. Thus, the radiation-curable compositions for forming inner primary, outer primary and ink coatings must have a very fast cure speed to ensure complete cure of the coatings and matrix material. In addition, the compositions should not contain ingredients that can migrate to the surface of the optical fiber and cause corrosion. Such additives are “fugitive” or free to migrate from the cured coating. Fugitive additives are generally undesirable because they might, for example, migrate and attack the optical fiber or be incompatible and cause loss of optical clarity. The compositions should also not contain ingredients which can cause instability in the protective coatings or matrix material. Ink coatings for optical fibers should be color fast for decades. The coatings and matrix material should not cause attenuation of the signal transmission and be impervious to cabling gels and chemicals.
Each of the coatings on the optical fiber and matrix material should be resistant to degradation caused by heat or light which can result in discoloration or even loss of integrity of the coatings or matrix material. If coating integrity is lost, the optical fiber may not be adequately protected from the environment resulting in signal attenuation. If one of the coating layers discolors, misidentification of the individual optical fibers may occur during splicing. Thus, there is a need for a radiation-curable coating composition suitable for application as a coating on an optical fiber, such as an inner primary coating, outer primary coating, colored secondary coating, ink coating, bundling material, ribbon matrix material and colored matrix material that exhibits substantial resistance to degradation caused by heat or light.
Current optical fiber coatings and matrix materials utilize acrylate functional monomers and acrylate functional oligomers. The oligomer backbone is usually derived from one or more polyether, polycarbonate, polyester or hydrocarbon polyols bound together via urethane linkages, to which acrylate functional groups are bound via urethane linkages. Thus, the oligomers used are generally acrylated polyurethanes. Optical fiber coatings and matrix materials can degrade when exposed to heat, causing undesirable yellowing and even loss of integrity of the coating or matrix material. Thus, there is also a need for radiation-curable compositions which exhibit enhanced resistance to thermal degradation.
Urethane acrylate oligomers are most widely used in the industry. Organofunctional silane coupling agents (or “adhesion promoters”) are also commonly used in the inner primary coating. For outer primary coatings, colored outer primary coatings and matrix materials, important additives include slip additives which function to lower the coefficient of friction of the cured material. A low coefficient of friction is important for processing and handling of co
DSM Desotech Inc.
McClendon Sanza
Pillsbury & Winthrop LLP
Seidleck James J.
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