JPH06144888A - Production of metal-coated optical fiber - Google Patents

Abstract

PURPOSE:To enable the removal of a resin coating layer of optical fiber without carrying out the screening in a method for producing metal-coated optical fiber by performing the spinning and resin coating, then removing the resin and further coating the optical fiber with the metal. CONSTITUTION:Optical fiber 51 spun with a spinning furnace 11 is coated with a resin in a resin coating device 21 and the resin is then irradiated and cross- linked with ultraviolet rays in a resin cross-linking device 22. An ultraviolet ray shielding cylindrical unit 26 of a shutter device 25 is moved to periodically shield the ultraviolet rays and prepare optical fiber having a resin coating layer in which cross-linked parts and uncross-linked parts alternately appear. The resultant optical fiber is then dipped in an organic solvent to initially peel the resin in the uncross-linked parts and the organic solvent is subsequently penetrated into the cross-linked parts. Thereby, even the resin in the cross-linked parts is peeled to coat the optical fiber with the metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metal-coated optical fiber, and more particularly to an improvement in the step of removing a resin coating layer which has to be coated in the production process before the metal coating step. .

[0002]

2. Description of the Related Art A silica-based optical fiber is coated with a resin on-line during spinning to protect its surface in order to maintain its mechanical strength during manufacture and use. However,
At a high temperature of 100 ° C. or higher, the coating resin portion is damaged, so that the heat resistance of the optical fiber is limited by the heat resistance of the resin portion. It has been reported that a polyimide-based polymer is used as the coating resin to improve heat resistance, but the limit temperature is 200 ° C.
It is only up to the level, and it is not possible to expect epoch-making improvement in characteristics.

Therefore, conventionally, a technique of hermetically coating the surface of an optical fiber with a metal instead of a resin has been extensively studied as a method for a heat-resistant optical fiber.

As a method for producing this metal-coated optical fiber, there are a method of coating metal online while spinning as in the case of resin, and a method of spinning once and then performing metal coating treatment. is there. As the former example, an aluminum-coated optical fiber by the dip foam method is known. Further, as a method corresponding to the latter, a sputtering method and a plating method are known. Since the coefficient of thermal expansion greatly differs between the coated metal and the glass of the optical fiber, the former case is likely to cause loss deterioration due to thermal stress strain. In this respect, according to the latter method, since the treatment temperature can be set to near room temperature, the influence of thermal stress strain can be relaxed.

By the way, in the latter manufacturing method, even when the fiber is once spun and then metal-coated, the resin coating at the time of spinning is indispensable in order not to deteriorate the strength of the optical fiber. Therefore, it is necessary to remove the resin coating layer when performing the metal coating treatment later. Therefore, as shown in FIG. 3, after the spinning process 10 and the subsequent resin coating process 20 are performed online, a resin removing process 30 and a metal coating process 40 are performed.
Will be done.

Therefore, the key point is how to reliably remove the resin without deteriorating the mechanical strength of the optical fiber before the metal coating treatment. On the other hand, as the resin coating layer, it is necessary to avoid extreme deposition shrinkage after the coating process. Therefore, normally, use a thermally crosslinkable silicone resin or UV crosslinkable UV resin to perform the coating process by the crosslinking reaction. I have to. Since the resin coating layer is a crosslinkable polymer in this way, even if it is attempted to remove it using an organic solvent in the resin removal step, it does not give fluidity to the extent that it swells in the organic solvent, so that it is batch-like. The resin cannot be removed by any treatment, and some kind of surface screening is necessary.

Therefore, a mechanical method using a blade is widely used in the step of removing the resin coating layer on the surface of the optical fiber in the conventional method for producing a metal-coated optical fiber.

[0008]

However, in the conventional method of mechanically removing the resin coating layer on the surface of the optical fiber by using a blade, the positioning accuracy of the optical fiber and the processing accuracy for cutting are required. In addition, in order to completely remove the resin, it is unavoidable that the blade comes into contact with the glass surface of the optical fiber, which causes a scratch on the optical fiber surface.

In order to avoid such problems, an organic solvent having a high permeability, for example, acetone or dichloromethane is used for liquid immersion, and the organic solvent permeates the interface between the coating resin and the glass of the optical fiber. A method is conceivable in which the resin coating layer is removed by causing swelling centering around and giving a simple screening. However, this is possible if the resin is removed in a short region, but it cannot be used in a long optical fiber or when the resin is removed while the optical fiber is continuously running. That is, the organic solvent penetrates only from the terminal and cannot penetrate into the resin-glass interface throughout. Even if the resin layer swells, if the resin layer does not crack in the process, the resin remains cylindrical and only changes in volume, and the change ends. May occur, and as a result, a part that cannot be peeled off may occur. further,
The resin coating layer occupies 75% or more of the entire optical fiber in terms of cross-sectional area. However, if the resin after peeling is not continuously discharged from the resin removing system at the same time as the peeling operation, it will be reattached in the system. Will end up.

In view of the above, the present invention is a method for producing a metal-coated optical fiber by continuously removing the resin coating layer of a long optical fiber without fear of damaging the surface of the optical fiber. The purpose is to provide.

[0011]

In order to achieve the above-mentioned object, according to the present invention, a spinning process, a subsequent cross-linking resin coating process, and the removal of the resin separated from these processes are carried out. In the method for producing a metal-coated optical fiber including a step and a metal coating step, in the step of coating the crosslinkable resin, a resin coating layer having a high degree of crosslinking and a resin coating layer having a low degree of crosslinking alternate in the optical fiber length direction. In the resin removing step, the optical fiber having the resin coating layer is immersed in the organic solvent in the step of removing the resin.

[0012]

When the optical fiber is immersed in the organic solvent in the resin removing step, the resin coating layer of the optical fiber has high cross-linking portions and low cross-linking portions alternately appearing in the length direction. First, the portion with a low degree of crosslinking becomes a fluid state and peels off. Then, the peeled portion becomes a portion where the organic solvent penetrates into the resin coating layer of the portion having a high degree of crosslinking, and the portion having a high degree of crosslinking is also peeled from the optical fiber.
Therefore, it is possible to continuously remove the resin coating layer of the optical fiber and perform the subsequent metal coating step without performing screening.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings. As shown in FIG. 1, a spinning process is performed in a spinning furnace 11, and the spun optical fiber 51 is immediately sent to a resin coating device 21 to perform resin coating. The coated resin is crosslinked by the resin crosslinking device 22. Here, the resin to be coated is a UV-crosslinkable UV resin, which is crosslinked by irradiating it with UV rays.

That is, in this embodiment, the bridging device 22 uses the ultraviolet lamp 23 and the optical fiber 51 for transmitting the ultraviolet light.
It is composed of a semi-cylindrical reflecting mirror 24 for condensing light on the. A shutter device 25 that blocks this ultraviolet ray is provided.
The shutter device 25 includes a cylindrical body 26 for blocking ultraviolet rays and a guide shaft 27 for moving the cylindrical body 26. The cylindrical body 26 is made of, for example, a thin aluminum plate coated with gold, and has a guide shaft 27.
When it is moved upward along the direction, the cylindrical body 26 wraps the optical fiber 51 and shields the ultraviolet rays from the ultraviolet lamp 23 and the reflecting mirror 24.

This shutter is opened and closed by the optical fiber 51.
Is performed every 100 mm to 300 mm in the length direction. As a result, the cross-linked portions and the non-cross-linked portions alternately appear at the above intervals, and the optical fiber 5
1 has no adverse effect on the draw-spinning and has a sufficient function as a protective coating layer for the optical fiber 51. The opening and closing of the shutter, that is, the vertical movement of the cylindrical body 26 can be automatically performed by, for example, an air driving method, but not limited to this. Further, the shutter device 25 itself does not move such a cylindrical body 26, but may be variously opened and closed such as opening and closing a window of a shielding body surrounding the ultraviolet lamp 23.

An optical fiber 51 having such a resin coating layer in which cross-linked portions and non-cross-linked portions alternately appear.
Immediately before the subsequent metal coating, the resin coating layer is removed by the resin removing device 31 shown in FIG.

The resin removing device 31 comprises an overflow unit 32 and a pit 33 for receiving it.
The organic solvent 34 is poured. This overflow unit 32 has slits 35 and 36, and the poured organic solvent 3
4 overflows from the slits 35 and 36 and flows into the pit 33. The optical fiber 51 is run through the slits 35 and 36, and the resin coating layer is peeled off by the organic solvent 34. In order to discharge the peeled resin, a resin discharge hole 37 is provided near the bottom surface of the overflow unit 32.
Is provided. Then, the organic solvent 34 accumulated in the pit 33 is again poured into the overflow unit 32 by the pump 38, and is circulated in this way.

Here, the optical fiber 51 immersed in the organic solvent 34 in the overflow unit 32 has a resin coating layer in which cross-linked portions and non-cross-linked portions alternate as described above. When introduced into the unit 32, first, the resin in the portion having a low degree of cross-linking becomes fluid and the portion is peeled off. Then, the peeled portion is the organic solvent 34 for the crosslinked resin coating layer.
Becomes an infiltration site, and that part is also peeled off without screening. Since the peeled resin is discharged from the resin discharge hole 37, it does not reattach to the optical fiber 51.

Thus, the optical fiber 51 from which the resin has been removed
Is continuously sent to a metal coating treatment device (not shown), and its surface is coated with a metal coat.

The overflow unit 32 described above is used.
Since there is a possibility of redeposition of resin inside this unit 3,
You may make it provide two or more steps. Further, instead of performing no screening at all, a soft screening type resin removing unit may be combined with the above overflow unit 32, and thereby more complete resin removal can be performed.

Although an ultraviolet-crosslinkable resin is used in the above description, a silicone resin-based thermally crosslinkable resin may be used. However, since the shutter device blocks heat, it is inferior in terms of responsiveness to the case of using the ultraviolet-crosslinkable resin.

[0022]

As described above, according to the present invention, in the method for producing a metal-coated optical fiber in which spinning and resin coating are carried out, and then the resin is removed and metal coating is carried out, the spinning process is affected to a particular extent. It is possible to remove the resin coating layer without performing the screening without performing the application, and to perform the metal coating process without damaging the surface of the optical fiber. Moreover, this resin removing step can be continuously and efficiently performed. Therefore, according to the method for manufacturing a metal-coated optical fiber of the present invention, it is possible to manufacture a low-loss metal-coated optical fiber with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a spinning process and a resin coating process according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a resin removing step of the same embodiment.

FIG. 3 is a block diagram showing the overall steps of a method for manufacturing a metal-coated optical fiber.

[Explanation of symbols]

 10 Spinning Process 11 Spinning Furnace 20 Resin Coating Process 21 Resin Coating Device 22 Resin Crosslinking Device 23 Ultraviolet Lamp 24 Reflector 25 Shutter Device 26 Cylindrical Body 27 Guide Shaft 30 Resin Removal Process 31 Resin Removal Device 32 Overflow Unit 33 Pit 34 Organic Solvent 35 , 36 Slit 37 Resin discharge hole 38 Pump 40 Metal coating process 51 Optical fiber

Claims (1)

[Claims] 1. A method for producing a metal-coated optical fiber, comprising a spinning step, a subsequent coating step of a crosslinkable resin, a resin removing step separated from these steps, and a metal coating step, The cross-linking resin coating step includes a cross-linking step in which a resin coating layer having a high degree of cross-linking and a resin coating layer having a low degree of cross-linking alternately appear in the length direction of the optical fiber. A method for producing a metal-coated optical fiber, which is performed by immersing an optical fiber having the above resin coating layer in a liquid.