JPH07267686A - Method for coating optical fiber and device therefor - Google Patents

Abstract

PURPOSE:To provide a method for coating an optical fiber, capable of preventing adhesion of a deposit to be a hindering cause of process.quality in a secondary coating device, smoothing a coating process in a spinning process and forming a high-quality optical fiber in a high-speed.continuous spinning process of optical fiber. CONSTITUTION:A primary coated optical fiber 7 before being introduced into a secondary coating device 8 is sprayed with a purge gas 24 adversely to the traveling direction of the primary coated optical fiber 7. The spray with the purge gas is carried out by using a device comprising a purge part 20 in which the purge part 20 has a tapered tubular conduit part 22 with a diameter gradually increasing in the advance direction of the optical fiber, the purge gas 24 is blown from a large diameter part 23 of the conduit part 22 into the conduit part 22 and blown off from an inlet hole 21 of the optical fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber coating method and apparatus advantageously used in a high speed and long spinning process of an optical fiber. In the coating process of the optical fiber for coating, curing, and then secondary coating, it is possible to prevent a process and quality obstacle caused by the volatile components accompanying the primary coating optical fiber adhering to the secondary coating device. The present invention relates to a coating method of an optical fiber and an apparatus thereof, which enables a long and high-quality optical fiber to be manufactured at high speed.

[0002]

2. Description of the Related Art An optical fiber is usually a bare optical fiber,
First, it is first coated with a curable resin with a relatively low Young's modulus,
Then, it is secondarily coated with a curable resin having a relatively high Young's modulus to obtain an optical fiber strand. This coating process is performed as part of the optical fiber spinning process. FIG. 4 shows an example of a conventional optical fiber spinning process. In FIG. 4, the optical fiber preform 1 is melt-spun in a heating furnace 2 at about 2000 ° C., and the formed optical fiber bare wire 3 is introduced into a primary coating device 4 to be an ultraviolet curing type or a thermal curing type for primary coating. It is coated with a resin 5 such as a mold, and then is cured by a primary curing device 6 by irradiation with ultraviolet rays or heating to obtain a primary coated optical fiber 7. The primary coated optical fiber 7 is then introduced into a secondary coating device 8 and coated with a resin 9 for secondary coating, and then cured by a secondary curing device 10 to have an optical fiber having two layers of cured resin coating. It is the wire 11. This step is performed on a vertical line from the upper side to the lower side in order to avoid obstacles such as uneven thickness of the coating.

[0003]

Recently, as the production of optical fibers has become faster and longer, various problems have occurred in the above-mentioned coating process. As one of them, as shown in FIG. 5, when the primary coating optical fiber 7 is introduced into the secondary coating device 8, the nipple 12 of the secondary coating device 8 is introduced.
There is a problem that the deposit 14 adheres to the inner wall and the peripheral portion of the coating port 13 which is the introduction hole of the primary coated optical fiber 7 formed in the above. When the deposit 14 adheres to and accumulates on the inner wall of the coating port 13, the liquid coating resin 9 overflows from the coating port 13 or the coating die 1
Bubbles are mixed in the coating resin 9 extruded from the resin 5 to form voids in the secondary coating 16, which deteriorates the quality of the product, sometimes causes wire breakage, etc.

In the primary coating step, the deposit 14 generates heat due to the heat of polymerization during the curing of the primary coating resin, and an unpolymerized component having a relatively low molecular weight is generated as a volatile component, which is a component of the primary coated optical fiber 7. It is considered that the particles reach the nipple 12 in a state where they are accompanied by the surroundings and are condensed on the inner wall of the coating port 13 and the peripheral portion thereof. Even in the primary curing device, the volatile matter adheres to, for example, an ultraviolet lamp and causes an obstacle such as lowering its efficiency. Therefore, measures such as flowing a clean gas into the ultraviolet lamp irradiation chamber are provided. However, it cannot be sufficiently removed when high-speed and long-spinning is performed, and the nipple 12 of the secondary coating device cannot be removed.
Accompanied by. Accumulation of the deposit 14 in the nipple 12 of the secondary coating device 8 has become a serious problem as the spinning speed and length are increased.

The present invention solves this problem,
The purpose is to prevent adhesion of deposits to the nipple of the secondary coating device during high-speed and long-spinning to facilitate the coating process,
Another object of the present invention is to provide an optical fiber coating method and apparatus for obtaining a high-quality optical fiber strand.

[0006]

The above problems can be solved by blowing a purge gas onto the primary coated optical fiber before it is introduced into the secondary coating device, in a direction opposite to the traveling direction of the primary coated optical fiber. . In this method, a purging unit is provided between the primary curing device and the secondary coating device, and the purging unit has a conduit portion into which the primary coating optical fiber is introduced and discharged in a non-contact manner. The part of the optical fiber is formed in a tapered tubular shape whose diameter gradually increases in the traveling direction of the primary coated optical fiber, and the large diameter part of this conduit part is provided with a purge gas blowing part for blowing the purge gas into the conduit part. It can be performed using a coating device. The introduction hole of the primary coated optical fiber of the conduit portion preferably has a diameter within a range of 2 to 8 times the diameter dimension of the introduced primary coated optical fiber. Further, two or more purging units may be installed in series between the primary curing device and the secondary coating device, and in this case, each of the purging units is configured such that the primary coating optical fiber does not come out from the respective introduction holes. At least one of the purge sections has a conduit section which is introduced and discharged in a contact manner, and at least one of the purge sections has a tapered tubular section whose diameter gradually increases in the traveling direction of the primary coated optical fiber. A purge gas blowing section for blowing the purge gas into the conduit section is provided in the diameter section.

[0007]

When the purge gas is blown in the direction opposite to the traveling direction of the primary coated optical fiber, the jet flow of the purge gas exerts an air knife effect on the peripheral surface of the optical fiber, and blows off the volatile components accompanying the peripheral surface. To do. Therefore, no deposits accumulate on the nipple of the secondary coating device.

The present invention will be described in detail below with reference to the drawings. In the following description, the same components as those of the conventional example described with reference to FIG. FIG. 1 shows an embodiment of a coating method using an example of the coating apparatus of the present invention. In FIG. 1, the purge unit 20 is mounted between the primary curing device (not shown) and the secondary coating device 8 in contact with the secondary coating device 8 and coaxially with the traveling axis of the primary coating optical fiber 7. Has been. That is, the primary coated optical fiber 7 is
Before being introduced into the secondary coating device 8, it is introduced into the purge section 20.

The purging section 20 has a conduit section 22 into and out of which the primary coated optical fiber 7 is introduced in a non-contact manner. The conduit section 22 is gradually expanded in the traveling direction of the primary coated optical fiber 7. It is formed in a tapered tubular shape. The purge gas 24 is supplied to the large-diameter portion 23 of the conduit portion 22.
A purge gas blowing part 25 having a diffuser for evenly blowing the gas into the inside 2 is provided.

During the operation of the coating process, the purge gas 24 is blown into the conduit portion 22 from the purge gas blowing portion 25,
When this is blown out from the introduction hole 21 of the primary coating optical fiber 7 in the conduit portion, the purge gas 24 is supplied to the primary coating optical fiber 7 before being introduced into the secondary coating device 8 in the traveling direction of the primary coating optical fiber 7. Volatile components that are blown in the opposite direction and onto the peripheral surface of the primary coated optical fiber 7 and are accompanied by the primary coated optical fiber 7 are blown away from the periphery of the optical fiber by the purge gas 24 and removed. Therefore, the deposits do not adhere to the nipple 12 of the secondary coating device 8. Since the purge gas 24 is evenly sprayed on the peripheral surface of the primary coated optical fiber 7, the primary coated optical fiber 7 does not cause line runout or the like.

The introduction hole 21 of the purge section 20 preferably has a diameter within a range of 2 to 8 times the diameter dimension of the primary coated optical fiber 7 to be introduced. For example, if the diameter of the primary coated optical fiber 7 is 0.2 mm, the diameter of the introduction hole 21 is preferably selected within the range of 0.4 mm to 1.6 mm. If the diameter is less than twice, there is a possibility that the primary coated optical fiber 7 in the vicinity of the introduction hole 21 may come into contact with the hole wall and be damaged due to minute line deflection. Further, when it exceeds 8 times, the air knife effect due to the purge gas 24 weakens,
Removal of volatiles becomes difficult. From this point of view, the diameter is preferably 3 to 6 times, especially about 5 times, the diameter of the primary coated optical fiber 7 to be introduced.

The taper angle and the length of the conduit portion 22 are not particularly limited, and the traveling speed of the primary coating optical fiber 7, the supply pressure of the secondary coating resin 9 in the secondary coating device 8 and the flow rate of the purge gas ( Volume velocity), the diameter of the introduction hole 21, the diameter of the coating port 13 and the like, and determine by experiment so that the air knife effect by the purge gas 24 is maximized within a range where the optical fiber does not cause excessive line deflection. Is preferred. Further, the purge unit 20 may be prepared with several types having different taper angles and lengths, and may be replaced with an optimum one according to the operating conditions of the coating process. Generally, although not limited to this, for example, when the diameter of the introduction hole 21 is 1.0 mm, the taper angle is within the range of 5 ° to 30 ° with respect to the optical fiber traveling axis, and particularly 10 °. Within 15 °, length within 10mm-50mm, especially 10mm
Within the range of ˜20 mm.

The purge gas 24 may be any purified inert gas. Nitrogen gas is an example of one that can always be obtained at low cost, but carbon dioxide gas, argon gas, xenon gas, silane gas, chlorofluorocarbon gas, etc. can also be conveniently used. The purge gas 24 is introduced at a constant flow rate from the purge gas blowing section 25 after being cleaned by a filter or the like. As a result, the purge gas 24 rises along the tapered tubular wall surface of the conduit portion 22 while being gradually accelerated and pressurized against the traveling of the primary coated optical fiber 7, and acts as an air knife from the gap between the introduction hole 21 and the primary coated optical fiber 7. It is evenly jetted toward the peripheral surface of the primary coated optical fiber 7 at an effective angle.

Although the purging section 20 shown in FIG. 1 is directly attached to the secondary coating apparatus 8, if the purging section 20 is installed at an intermediate position between the primary curing apparatus and the secondary coating apparatus 8. It is not limited to this example. However, when the purge unit 20 is installed at an independent position, the purge gas 24 is efficiently blown out from the introduction hole 21,
For example, as shown in FIG. 2, it is preferable to provide a gas seal portion 27 on the optical fiber lead-out portion side of the purge portion 20. The gas seal portion 27 is formed with a lead-out hole 26 through which the primary coated optical fiber 7 passes without contact. The purge gas 24 blown from the purge gas blowing section 25 is
A part of the gas leaks downward through the outlet hole 26, but by adjusting the flow velocity of the blown gas, an effective amount of the purge gas 24 flows backward from the running direction of the primary coated optical fiber 7 and blows out from the inlet hole 21. You can

The purging section may be installed in series with a plurality of two or more as long as it is between the primary curing apparatus and the secondary coating apparatus 8. In this case, each purge unit may have the same shape or different. However, at least one of these purge sections has a tapered tubular conduit section whose diameter gradually increases in the traveling direction of the primary coated optical fiber, and a purge gas blowing section is provided in the large diameter section of this conduit section. There is.

An example in which two purge units are installed in series is shown in FIG.
Shown in. In this example, the purge parts 20a and 20b shown in FIG. 1 having the same shape are installed so as to share the respective purge gas blowing parts 25 and joined in opposite directions. Therefore, when the purge gas 24 is blown from the common purge gas blowing portion 25, the purge gas 24 passes through the respective conduit portions 22a and 22b and the respective introduction holes 21.
Blow out from a and 21b. Even in this case, at least one of the purging parts 20a is provided with the primary coated optical fiber 7
Has a tapered tubular conduit portion 22a whose diameter gradually increases in the advancing direction and a large diameter portion of the conduit portion 22a is provided with a purge gas blowing portion 25, so that part of the purge gas is supplied to the primary coated optical fiber 7. The volatile component can be effectively removed by going backward in the traveling direction and uniformly sprayed on the peripheral surface of the primary coated optical fiber. At this time, the other introduction hole 21b plays the role of the above-mentioned gas seal portion, and the wide gas flow space 28 formed by combining the two conduit portions 22a and 22b of the purge portion forms the primary coated optical fiber 7 The volatile substances contained in the coating layer are also diffused, and the effect of enhancing the adhesion between the primary coating and the secondary coating is brought about.

Of course, it is also possible to arrange the two or more purging parts in a stacked umbrella shape so that all the conduit parts are tapered so that the diameter gradually increases in the traveling direction of the primary coated optical fiber 7. In this case, the purge gas blown out from each of the introduction holes exhibits an air knife effect, so that the removal efficiency of volatile components is extremely high and the drawing speed is increased.
It can be used even when the length is further increased.

[0018]

EXAMPLE In the optical fiber spinning process shown in FIG.
A combination of the purge unit 20 and the secondary coating device 8 shown in FIG. 1 was used to perform high-speed, long-length drawing, and a comparison was made with the case where the purge unit 20 was not used (comparative example). The diameter of the introduction hole 21 of the purge section 20 was 1.0 mm, the taper angle of the conduit section 22 was 10 °, and the length thereof was 15 mm. Purge gas 24
Was used, and the supply gas amount was 5 l / min. The diameter of the primary coated optical fiber 7 was 0.2 mm.

The drawing speed was 10 m / s and the drawing length was 150 km. In the case of the example, the drawing could be completed without problems under the above conditions. Further, in the inspection after completion of the drawing, accumulation of deposits on the nipple 12 of the secondary coating device 8 was not observed. On the other hand, in the case of the comparative example in which drawing was performed under the same conditions, the drawing length was 80
The inclusion of voids was observed in the secondary coating 16 at 100 km.
The coating was impossible because the secondary coating resin 9 overflowed from the nipple 12 at km. From this result, the purging unit 20 used in the example effectively removes the volatile matter, and the nipple 12
It is clear that the high-speed and long wire drawing was enabled by preventing the adhered substances from sticking.

[0020]

According to the optical fiber coating method of the present invention, the purge gas is blown to the primary coated optical fiber before being introduced into the secondary coating device in the direction opposite to the traveling direction of the primary coated optical fiber. The purge gas exerts an air knife effect to blow off the volatile components that accompany the primary coated optical fiber, prevent the deposits from adhering to the nipple of the secondary coating device, and speed up and lengthen the optical fiber spinning. The optical fiber coating apparatus of the present invention is provided with a purge section between the primary curing apparatus and the secondary coating apparatus, and the purge section has a tapered tubular conduit section whose diameter gradually increases in the traveling direction of the optical fiber. Since the purge gas is blown from the large-diameter portion of the purge section and blown out from the optical fiber introduction hole of the conduit section, the purge gas exhibits the air knife effect, and the volatile components accompanying the primary coated optical fiber can be efficiently blown off. it can.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is a sectional view showing still another embodiment of the present invention.

FIG. 4 is a process drawing showing an example of an optical fiber spinning process.

FIG. 5 is a cross-sectional view showing one aspect of a conventional optical fiber spinning process.

[Explanation of symbols]

7 ... Primary coated optical fiber, 8 ... Secondary coating device, 20 ... Purge part, 21 ... Optical fiber introduction hole, 22 ... Conduit part, 23
... large-diameter portion of conduit, 24 ... purge gas, 25 ... purge gas blowing section.

Claims (3)

[Claims] 1. A primary coating is applied to a bare optical fiber, which is cured to form a primary coated optical fiber, which is then introduced into a secondary coating device and secondary coated to produce an optical fiber strand. A purge gas is blown to the primary coated optical fiber before it is introduced into the secondary coating device in a direction opposite to the traveling direction of the primary coated optical fiber to remove volatile components from the primary coated optical fiber which accompany the primary coated optical fiber. A method for coating an optical fiber, which comprises removing the optical fiber. 2. An optical fiber coating device having a primary curing device for curing a primary coating applied to a bare optical fiber and a secondary coating device for applying a secondary coating to the primary coated optical fiber thus cured. Therefore, a purge unit is provided between the primary curing device and the secondary coating device to remove volatile components accompanying the primary coating optical fiber. Has a conduit portion that is introduced into and discharged from the conduit, the conduit portion being formed in a tapered tubular shape that gradually expands in diameter in the traveling direction of the primary coated optical fiber, and the purge gas is introduced into the large diameter portion of the conduit portion. An apparatus for coating an optical fiber, characterized in that it is provided with a purge gas blowing part for blowing into the inside. 3. The introduction hole of the primary coated optical fiber of the conduit section of the purge section has a diameter within a range of 2 to 8 times the diameter dimension of the introduced primary coated optical fiber. An optical fiber coating device as described.