JPH0366271B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing an optical fiber in which a carbon coating layer is formed on the surface of the optical fiber, and is particularly suitable for use in combination with high-speed spinning of the optical fiber. .

<Prior Art> Optical fibers have the disadvantage that minute cracks occur on their surfaces during manufacturing and subsequent handling, and they quickly break even when a relatively small stress is applied to them. Furthermore, it is generally known that even if the optical fiber does not break, water may enter the crack after long-term use, causing deterioration over time, which gradually reduces the strength of the optical fiber. For this reason, in the past, the surface of the optical fiber was coated with a synthetic resin immediately after spinning to prevent cracks from forming on the surface of the optical fiber, but even this method does not completely prevent the occurrence of cracks. It has become impossible. Furthermore, the synthetic resins currently used as coating materials have water permeability and moisture permeability, although only slightly, which is an undesirable characteristic for products that require extremely long-term reliability, such as communication optical fibers. , some improvement is needed. Therefore, a method has been developed in which a thin film of an inorganic compound or an inorganic substance with essentially no water permeability or moisture permeability is formed on the surface of the optical fiber immediately after spinning, and then a synthetic resin coating is applied. It is hoped that this will help improve.

<Problems to be Solved by the Invention> However, CVD (chemical vapor deposition) has been adopted or considered as a method for forming thin films of inorganic compounds or inorganic substances, which requires large-scale equipment and is difficult to react to. A tube had to be installed between the spinning furnace and the die storing the synthetic resin for coating, which was technically difficult and inconvenient.

On the other hand, as high-speed spinning of optical fibers has been promoted in recent years, high-temperature optical fibers are fed into dies storing synthetic resin for coating before the temperature has sufficiently decreased. The problem of poor adhesion of the resin is beginning to appear. Therefore, since the temperature of the optical fiber becomes high after spinning, it is necessary to actively lower the temperature before the optical fiber reaches the die storing the synthetic resin, which is extremely unreasonable. .

From the above-mentioned viewpoints, the present invention makes it possible to coat the optical fiber with an inorganic material using very simple equipment, and to actively lower the temperature of the optical fiber before it reaches the die storing the synthetic resin. It is an object of the present invention to provide a method for manufacturing an optical fiber that allows high-speed spinning to be performed without any inconvenience.

<Means for Solving the Problems> In order to achieve the above object, the present inventors have conducted intensive research and have focused on the fact that compounds such as olefins easily decompose at several hundred degrees Celsius to form carbon. However, if a high-temperature optical fiber is passed through such a gaseous raw material that becomes carbon at low temperatures, carbon is deposited on the surface of the optical fiber due to an endothermic chemical reaction since it does not involve oxygen, and the optical fiber is cooled at the same time. We have discovered that this method has the effect of killing two birds with one stone by achieving our goals.

In other words, the structure of the present invention is to pass an optical fiber that has just been spun, whose temperature is controlled to a predetermined temperature, through a raw material gas atmosphere that will become a carbon coating layer, and to utilize the heat of the optical fiber. The method is characterized in that the raw material gas is subjected to an endothermic chemical reaction on the surface of the optical fiber, the carbon coating layer is deposited on the surface of the optical fiber, and then a synthetic resin is applied.

The present invention will be explained in detail below.

In the present invention, raw material gases that can be converted into carbon at temperatures of about several hundred degrees Celsius include those that undergo an endothermic chemical reaction on the surface of the optical fiber without the intervention of oxygen, such as paraffin, olefin, and aromatic hydrocarbon compounds. In addition, since the temperature of the optical fiber greatly depends on its spinning speed, if the reaction temperature is relatively high for the raw material gas or the spinning speed of the optical fiber is slow, the optical fiber immediately after spinning can be heated with a laser beam, a tungsten lamp, or an electron beam. It is desirable to provide supplementary heating using an external heat source such as Even if the optical fiber is heated auxiliary in this way, heat is inevitably absorbed due to the endothermic chemical reaction involved in the dehydrogenation reaction based on the decomposition of the raw material gas that forms the carbon coating layer while passing through the raw material gas atmosphere. Ru. Therefore, by the time the synthetic resin that will become the coating material in the next step reaches the stored die, the temperature has dropped sufficiently, and there is no risk that the adhesiveness of the synthetic resin will deteriorate. On the surface of the optical fiber in the raw material gas atmosphere, the raw material gas is decomposed by the heat immediately after spinning, and inorganic substances such as carbon adhere to the surface of the optical fiber due to an endothermic chemical reaction, eventually forming a coating layer. In this case, it is naturally possible to make the coating layer multilayer.

<Example> Hereinafter, an example of the optical fiber manufacturing method according to the present invention will be described with reference to drawings showing the working principle. Helium gas is supplied as a carrier gas from a helium gas cylinder 11 to a bubbler 12
The gas 14 of benzene 13 is blown from a nozzle 15 onto the surface of an optical fiber 18 immediately after spinning an optical fiber base material 17 to a predetermined diameter in a spinning furnace 16. The gas 14 decomposes on the surface of the optical fiber 18 due to residual heat during spinning, and as a result of a dehydrogenation reaction, it polymerizes and becomes carbon containing almost no hydrogen, which adheres and deposits on the surface of the optical fiber 18 to form a coating layer. . In this case, the non-liquid gas 14
This has the advantage that a carbon coating layer with a uniform thickness can be formed on the surface of the optical fiber 18. Due to this endothermic chemical reaction, the optical fiber 18 absorbs heat and its temperature decreases, and is fed to the die 20 in which the thermosetting resin 19 for coating is stored.
Thermosetting resin 19 adheres to the surface of optical fiber 18 while passing through zero, and is hardened and fixed in baking furnace 21. In this case, the optical fiber 18 is kept at a sufficiently low temperature by forming the carbon coating layer through an endothermic chemical reaction, so that the adhesiveness of the thermosetting resin 19 will not deteriorate even when high-speed spinning is performed. There is no risk.

In this embodiment, for some reason, the optical fiber 18
Optical fiber 18 is used as an auxiliary material when using a raw material gas whose temperature is low or whose reaction temperature is high.
An auxiliary heat source 22 for heating the optical fiber 18 and a temperature detector 23 for detecting the temperature of the optical fiber 18 and controlling the operation of the auxiliary heat source 22 as necessary are installed directly below the spinning furnace 16. does not need to be provided.

Further, in this embodiment, the gas 14 is sprayed onto the surface of the optical fiber 18 by the nozzle 15, but any means can be used as long as it can create an atmosphere of the gas 14 around the optical fiber 18. Of course, it can be anything.

In this example, since the gas 14 is blown onto the optical fiber in an open state,
When a room is provided, there is no fear that soot will float and adhere to the surface of the optical fiber. Moreover, in this case, the device can also be made compact.

<Effects of the Invention> As described above, according to the optical fiber manufacturing method of the present invention, the raw material gas is subjected to an endothermic chemical reaction on the surface of the optical fiber using the residual heat of the optical fiber due to high-speed spinning, and the carbon coating layer is formed on the optical fiber. Since the temperature of the optical fiber is lowered by this endothermic chemical reaction, there is no risk that the adhesion of the synthetic resin will decrease even during high-speed spinning, and highly reliable optical fibers can be spun compactly and at high speed. be able to.

[Brief explanation of drawings]

The drawing is a conceptual diagram of an embodiment of the optical fiber manufacturing method according to the present invention. In the drawing, 13 is benzene (liquid), 14 is gas,
15 is a nozzle, 16 is a spinning furnace, 18 is an optical fiber, 19 is a thermosetting resin, 20 is a die, and 22 is an auxiliary heat source.

Claims (1)

[Claims] 1. An optical fiber that has just been spun and whose temperature is controlled to a predetermined temperature is passed through a raw material gas atmosphere that will become a carbon coating layer, and the heat of the optical fiber is utilized. A method for producing an optical fiber, comprising: causing the raw material gas to undergo an endothermic chemical reaction on the surface of the optical fiber, depositing the carbon coating layer on the surface of the optical fiber, and then coating the optical fiber with a synthetic resin. 2. The method for manufacturing an optical fiber according to claim 1, wherein the carbon coating layer formed on the surface of the optical fiber is multilayered.