Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-02-18
2001-02-20
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S257000, C156S275700, C427S493000, C427S508000, C427S513000, C427S163200
Reexamination Certificate
active
06190483
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of manufacturing an optical conductor. It relates more particularly to setting the coverings on optical fibers by exposing them to ultraviolet radiation.
An optical conductor for conveying data comprises a glass fiber having a diameter of about one hundred microns, typically of 125 &mgr;m, and at least one protective covering generally made up of two insulating layers. The protective covering is itself covered with a coloring layer for fiber coding or recognition purposes. The outside diameter of such a conductor lies in the range 245 &mgr;m to 250 &mgr;m.
A plurality of optical conductors can be associated in parallel to form a ribbon. In which case, coating is provided to hold the conductors together.
The coverings and the coating are made of polymers that can be cured (i.e. cross-linked) by exposing them to ultraviolet radiation.
In practice, to make the covering of a conductor, the fibers are surrounded in a layer of liquid polymer, and that material is solidified by being exposed to ultraviolet radiation. The two protective layers can be manufactured either serially, i.e. the first layer is manufactured prior to the second layer, or else in parallel, with both layers being deposited simultaneously and being cured together. Currently, the coloring layer and the coating covering (for forming a ribbon) are manufactured serially, one after the other.
To achieve the cross-linking, photo-initiator elements are inserted into the material to be polymerized. By means of the photo-initiators, curing by exposure to ultraviolet radiation causes a chemical polymerization reaction to take place, thereby setting the material. For example, the material to be polymerized can be an acrylate.
Curing by exposure to ultraviolet radiation is generally performed by means of two arc lamps. A first lamp produces radiation, the most intense wavelengths of which lie approximately in the range 350 nm to 400 nm. The first lamp principally performs in-depth cross-linking. A second arc lamp emits ultraviolet radiation that is rich in shorter wavelengths, of about 300 nm. The second lamp principally performs surface cross-linking.
The arc lamps give off large quantities of heat. It is thus necessary to cool them. It is also necessary to cool the optical conductor being manufactured because, at the end of the first exposure to ultraviolet radiation, the temperature of the covering is high and lies in the range 100° C. to 1000° C., and cross-linking does not take place correctly at high temperatures. Unfortunately, the reduction in temperature that can be obtained is relatively small, in particular because optical conductors must be manufactured at high speed, and often at speeds exceeding 100 meters per minute (m/min). Under such conditions, the quantity of photo-initiator material that needs to be used is greater than the quantity that would be necessary if the temperature were close to ambient.
SUMMARY OF THE INVENTION
The invention remedies the above drawbacks.
The method of the invention is characterized in that, to cross-link an optical conductor covering advancing at a speed of at least 10 meters per minute (m/min), and preferably higher than 100 m/min, a monochromatic or quasi-monochromatic UV radiation source such as a laser or an excimer lamp is provided that emits UV radiation making it possible to achieve cross-linking mainly on the surface, and an arc lamp is provided that makes it possible to achieve cross-linking mainly in depth.
Preferably, the monochromatic or quasi-monochromatic source precedes the arc lamp.
After exposure to the monochromatic or quasi-monochromatic UV radiation, the temperature of the cross-linked product is not significantly different from ambient temperature. It is therefore not necessary to provide cooling means. In addition, the cross-linking is significantly more effective because the product is at a temperature that is optimal for such cross-linking.
It should be noted that it has already been proposed to use a monochromatic or quasi-monochromatic source for cross-linking. But, it has been observed that use of such a monochromatic source does not, on its own, achieve complete cross-linking.
Thus, the invention, which relates to the combined use of a monochromatic or quasi-monochromatic source and of an arc lamp, makes it possible to achieve complete cross-linking with a minimum amount of photo-initiator material. In addition, the method does not give rise to any significant complication of the manufacturing installation.
Furthermore, it has been observed that better results are obtained by providing, upstream from the arc lamp, two monochromatic or quasi-monochromatic sources having different wavelengths to achieve the surface cross-linking. The second monochromatic source contributes to the cross-linking in depth, and the arc lamp finishes off this in-depth cross-linking.
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patent: 5015068 (1991-05-01), Petisce
patent: 5891530 (1999-04-01), Wright
patent: 5993896 (1999-11-01), Unterberger et al.
patent: 6018605 (2000-01-01), Mills et al.
patent: 0 440 1787 A1 (1991-08-01), None
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patent: 2 155 357 (1985-09-01), None
Patent Abstracts of Japan, vol. 013, No. 293 (C-615), Jul. 6, 1989 corresponding to JP 01 087536 A (Sumitomo Electric Ind, Ltd) Mar. 31, 1989.
Database WPI, Section CH, Week 8909, Derwent Publications Ltd., London, GB; Class 182, AN 89-065968 corresponding to JP 01 018 948 A (Sumitomo Electric Ind Co) Jan. 23, 1989.
Benzel David
McNutt Christopher
Yang Michael
Alcatel
Ball Michael W.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Tolin Michael A
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