JPS6045138B2 - Optical fiber manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a glass fiber for optical transmission, and more particularly to a coating treatment for an optical fiber.

Glass fibers (hereinafter simply referred to as optical fibers) used as optical transmission media usually have a diameter of 200 μm or less and are extremely brittle, so their surface may be damaged during manufacturing, cable production, or storage. It has the disadvantage that scratches are easily generated, and these scratches become a stress concentration source, and the optical fiber easily breaks when stress is applied from the outside.

For this reason, it is extremely difficult to use optical fiber as it is as a medium for optical transmission. To solve this problem, a method has been proposed in which the surface of the optical fiber is coated with plastic following the drawing process, thereby maintaining its initial strength and producing an optical fiber that can withstand long-term use. ing. Examples of this type of method include coating an optical fiber with a thermoplastic resin such as polyethylene terephthalate by extrusion molding to improve the strength (see British Patent No. 1371318), and vinylidene fluoride-tetrafluoroethylene coating. It is known to coat and cure polymers, epoxy acrylate polymers, etc. on optical fibers. By the way, optical fiber coatings usually include, in addition to the primary coating described above to maintain the initial strength, a secondary coating made by extrusion molding of a thermoplastic resin such as polyamide or polyethylene to cope with cable formation. A buffer layer made of rubber-like elastic material is provided between the primary coating layer and the secondary coating layer in order to prevent an increase in transmission loss during transmission. The layer is formed subsequent to drawing the glass fiber. However, the current primary coating materials, urethane and epoxy resins, have a slow curing speed and require a long time to cure and dry, which limits the drawing speed of optical fibers, which is one of the problems in mass production of optical fibers. It has become.
In addition, the current buffer layer material used is silicone rubber that cures at room temperature due to its transmission characteristics, so its viscosity increases just by leaving it at room temperature, making it unable to withstand long-term wire drawing. Since rubber has relatively high adhesiveness, it has disadvantages such as easy attachment of dust, etc., which adversely affects the secondary coating. The present invention has been made in view of the above-mentioned current situation, and its purpose is to provide a manufacturing method that improves mass productivity and manufacturing workability of optical fibers.

The method for manufacturing an optical fiber of the present invention that achieves the above object includes applying a resin composition containing a polymer compound having an azide group to the surface of a glass fiber for optical transmission, and then curing the resin composition by irradiating the resin composition with light. It is characterized by

When the resin composition applied to the surface of the optical fiber is irradiated with light, the azide groups bonded to the polymer compound are decomposed into nitrogen and nitrene.

This nitrene is said to be a biradical having two unpaired electrons, each of which exists in a different orbit. Since this triplet state nitrene is active, it causes various chemical reactions such as hydrogen abstraction reaction, double bond insertion reaction, recombination, C-H bond insertion reaction, and oxidative addition reaction to phenols. . Therefore, when a polymer compound containing an azide group is irradiated with light, the above reaction occurs between the polymer compounds and the resin composition is rapidly cured. Polymeric compounds containing an azide group used in the present invention include polyazidovinyl benzoate, polyazidovinyl phthalate, polyazidostyrene, polyvinylazidobenzalacetal, polyvinylazidonaphthyl acetal, polyvinylcinnamate, poly( (vinyl acetate 3-azidophthalate), poly(vinyl acetate 4-azidophthalate), poly(vinyl acetate 3,4-azidophthalate), poly(vinyl acetate P-azidobenzoate) , styrene maleate of 3-(4-azidophenoxy)ethanol, and the like.

The main component of the resin composition in the present invention is the above-mentioned azide group-containing polymer compound, but also aromatic ketones, aromatic nitro compounds, and triphenylmethane dyes that promote photodecomposition of the azide group. Photosensitizers such as glass (optical fiber) and coatings. γ to increase the adhesion of the covering material
- Silane coupling agents such as methacryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane,
Contains benzene, toluene, etc. to adjust viscosity. A solvent can be added.

Since the resin composition used in the present invention has a fast curing speed, it is possible to draw optical fibers at high speed, and the mass productivity of optical fibers is improved.

Another feature of using this resin composition is that nitrogen gas is released upon irradiation of the azide group with light. When this resin composition is applied as a coating material for optical fibers, nitrogen gas generated by light irradiation passes through the coating until the thickness of the coating is about 20 to 25 μm, so a uniform coating without pinholes can be obtained. It will be done. Therefore, the resin composition of the present invention achieves the same effects as ordinary primary coating materials. If the thickness of the film exceeds 20 to 25 μm, nitrogen generated by light irradiation will be trapped inside the film, resulting in a foamable film. Since this foamable film plays the role of relieving external pressure, it can be used in the same way as silicone resin, which is currently widely used as a buffer layer material, and has the advantage of a longer pot life than silicone resin. There is.
When the resin composition of the present invention is directly applied to an optical fiber to form a thick film, the inside of the film is uniform within a thickness of 20 to 25 μm, and the part beyond that becomes a foam, so one coating operation and the same process are required. There is an advantage that the primary coating and the buffer layer coating can be formed at the same time using this material. This is much more advantageous in terms of mass production of optical fibers and manufacturing workability than the current method in which primary coating and buffer layer coating are performed separately. Furthermore, if the resin composition used in the present invention is coated on an optical fiber as described above and cured, then the surface thereof is coated with a thermoplastic resin, a thermosetting resin, or a photocurable resin. It has the advantage that it can be directly cabled without secondary sheathing. Next, the present invention will be described with reference to Examples, but the present invention is not limited thereto in any way.

Example 1 An optical fiber base material was heated to about 2000°C and drawn at a drawing speed of 80 rn/min, resulting in a fiber diameter of 13
A 0 pm monofilament optical fiber is manufactured, and then a resin composition made of poly(vinyl acetate P-azidobenzoate) is applied to the optical fiber immediately after drawing, and irradiated with light using an ultraviolet lamp with an output of 2 KW x 4. and cured.

The coating material was completely cured, and a uniform film with an average thickness of 12 μm was obtained. The average breaking strength of optical fiber is 475k
It was 9/Mi. Example 2 The base material of optical fiber was heated to about 2000°C, and the drawing speed was 3.
The drawing operation was performed at 0 rn/min to obtain a monofilament optical fiber with a diameter of 130 μm.

Next, poly(vinyl acetate 4-azidophthalate)
A resin composition consisting of the above was applied to an optical fiber immediately after being drawn, and then irradiated with ultraviolet rays (output 2 KW x 4) to cure it. The coating material was completely cured, and an optical fiber having a foamable coating with an average thickness of 80 μm was obtained. The average wave intensity of this fiber was 502k9/Td. As is clear from the above description, according to the present invention, the resin composition has a long pot life because it is a photocurable material.
Furthermore, since the curing speed is fast, it is possible to draw optical fibers at high speed, and furthermore, it has the advantage of improving the mass production and manufacturing workability of optical fibers, such as being able to perform primary coating and buffer layer coating in one coating and curing process.

Claims (1)

[Claims] 1. A method for manufacturing an optical fiber, which comprises applying a resin composition containing a polymer compound having an azide group to the surface of a glass fiber for optical transmission, and then irradiating the resin composition with light to cure the resin composition.