A METHOD OF APPLYING A PROTECTIVE ORGANIC COATING TO AN OPTICAL GLASS FIBRE

Abstract: The invention relates to a method of applying a protective organic coating to an optical glass fibre, said glass fibre is drawn from a preform and passed through a liquid which contains the material for forming said organic coating, once the amount of liquid coating material to be applied to the fibre has been adjusted, said coating material is hardened, while a gas is passed along the liquid wherein nitrous oxide (an N>2<O-containing gas) is used as said gas. The invention also relates to the coated optical glass fibre, produced by that method.

Description: A method of applying a protective organic coating to an optical glass fibre. The invention relates to a method of applying a protective organic coating to an optical glass fibre or to a coated optical glass fibre, wherein said glass fibre is drawn from a preform and passed through a liquid which contains the material for forming said organic coating, once the amount of liquid coating material to be applied to the fibre has been adjusted, said coating material is hardened and a gas is passed along the coating material. A method of this kind is known from EP-A-0 261 772. In the claims of said patent application it is stated that C0 2 is used as said gas, thus minimizing the number of air inclusions that may form upon forming of the coating. The surface of the coating material of the glass fibre is conditioned by means of C0 2 . It is stated in the introduction of EP-A-0261 772 that various gases may be used, such as nitrogen, carbon dioxide, noble gases, especially xenon, neon and argon, and chemically inert gaseous hydrocarbons such as chloroform, Freon (brand name), halogen hydrocarbons or other chlorine- or fluorine-substituted hydrocarbons. In particular, however, C0 2 is used. A method of the above kind is also known from EP-B-0 200256, wherein it is indicated that xenon and dichlorodifluoro- methane are gases which are usable within this framework. Jochem et al "High-speed bubble-free coating of optical fibres on a short drawing tower" (I00C and EC0C), Venice, 1985, part 1, pages 515-518, Istituto Internazionale Delle Co unicazoni discloses the use of several gases in such a process to draw optical fibres. In table 2 one mentioned air, He, A, Xe and CC12 2 - However Jochem et al did not indicate the gascomposition used according to the invention. From EP-A-0635554 it is known that an optical fibre can be coated with hydrogen silsesquioxane by heating the fiber at a temperature of 50-1000 °C during up to 6 hours. The heating may be conducted at any pressure and under oxidizing or non-oxidizing gaseous environment usch as air, O2, an inert gas (N2, etc.), ammonia, amines, moisture, N2O, hydrogen and hydrocarbons. From this disclosure the specific gas used according to the invention can not be derived. Further research has shown that a higher-quality bond of the organic material to the glass fibre is obtained by using a specific gas. According to the invention, the method as stated in the introduction is therefore characterized in that nitrous oxide (an N 2 0-containing gas) is used as said gas. The term nitrous oxide as used herein should be understood to mean a gas which contains at least 50% N 2 0. Preferably, the gas is introduced at the upper side of the device for applicating the organic coating material to the fibre and carried downstream along with the glass fibre. We also found that with the method according to the invention it also is possible to applicate a second or third organic coating layer to an allready coated fibre. The amount of gas supplied to the liquid organic coating material depends on the construction of the device for applicating the coating material and the drawing speed. Nevertheless this amount must be sufficient for preventing entrained air, that comes along with the fibre, to become entrapped in the coating. This amount of gas can be minimized by using specific nozzles or a small diameter shaft. The invention furthermore relates to the optical glass fibre provided with a protective organic coating formed in accordance with a method wherein an N 2 0-containing gas is used as said gas.

Claims: CLAIMS 1. A method of applying a protective organic coating to an optical glass fibre or a coated optical glass fibre, wherein said glass fibre is drawn from a preform and passed through a liquid which contains the material for forming said organic coating, once the amount of liquid coating material to be applied to the fibre has been adjusted, said coating material is hardened, while a gas is passed along the liquid, characterized in that nitrous oxide (an N 2 0-containing gas) is used as said gas. 2. A method according to claim 1, characterized in that said nitrous oxide is introduced to said liquid at the upper side, at the place where the fibre is supplied. 3. A glass fibre provided with a protective organic coating, characterized in that said glass fibre has been obtained by using a method as defined in claims 1 - 2.

Inventors: BREULS ANTONIUS HENRICUS ELISA, DE FOUW MARINUS JACOB, BREULS, ANTONIUS, HENRICUS, ELISABETH, DE FOUW, MARINUS, JACOB
Applicants: BREULS ANTONIUS HENRICUS ELISA, FOUW MARINUS JACOB DE, PLASMA OPTICAL FIBRE BV, BREULS, ANTONIUS, HENRICUS, ELISABETH, DE FOUW, MARINUS, JACOB, PLASMA OPTICAL FIBRE B.V.
Application year: 1999
Main classification: C03C25
IPC codes: C03C25, G02B6