JP2001278641A - Manufacturing method of coated optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a coated optical fiber which is provided with a primary coating and a secondary coating on an optical fiber where for the material of the secondary coating which is frame retardant and in case of burning hardly generate halogen gas, and the cut surfaces of the coatings are sharp and beautiful when the primary and secondary coatings are stripped en bloc and coatings of coated fibers are prevented from adhering to each other. SOLUTION: On the outside of elementary optical fiber 3 which is provided with the primary coating 2 of ultra violet curing type resin on optical fiber 1, the secondary coating 4 of flame retardant polyethylene resin which is obtained by adding fire retardant to EEA, etc., is extruded to form coating and successively is irradiated with electron beam of 50-300 kV acceleration voltage by an electron beam irradiator 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical fiber having a primary coating and a secondary coating on an optical fiber.

[0002]

2. Description of the Related Art An outer diameter of 0.12 mainly composed of quartz glass.
An optical fiber core wire provided with a primary coating of 0.25 mm in outer diameter made of UV-curable resin and a secondary coating of 0.9 mm in outer diameter made of vinyl chloride resin on a 5 mm optical fiber is used for optical cords, etc. This is known as an optical fiber core. In addition, the optical cord is provided with an outer coating made of a vinyl chloride resin or the like on the outside of the optical fiber with a tensile strength fiber along the tensile fiber, and is used for wiring of optical communication equipment and the like. Further, the above-mentioned optical fiber core wire may be used as it is for wiring of an optical communication device without being processed into an optical cord.

In addition, an outer diameter of which is 0.1 mm mainly composed of quartz glass.
An optical fiber having a primary coating of 0.25 mm in outer diameter made of an ultraviolet curable resin on an optical fiber of 125 mm is also referred to as an optical fiber, and is used in a large amount for a tape-shaped optical fiber core which is a main member of an optical cable. , The production cost is relatively low. Therefore, an optical fiber core wire in which a secondary coating made of a vinyl chloride resin is provided on the optical fiber wire is inexpensive and useful.

[0004]

However, an optical fiber core wire provided with a primary coating made of an ultraviolet-curable resin and a secondary coating made of a vinyl chloride resin on an optical fiber may generate chlorine gas during combustion, or Conversion of secondary coating materials is required as an environmental measure because it causes dioxins and the like. Therefore, a material that substitutes for vinyl chloride resin is required, but in addition to the requirement that the resin price be inexpensive and that it has flame retardancy, when the coating on the terminal is removed using a coating removal tool described later The cut section of the coating should be sharp and clean.
It is required that the so-called blocking phenomenon in which the coatings adhere to each other even when allowed to stand closely for 2 hours does not occur.

FIG. 2 is a view showing a sheath removing tool used for removing the sheath of an optical fiber core wire. FIG. 2 (A) is a side view of the sheath removing tool, and FIG. 2 (B) is a sectional view in the X direction. , FIG. 2
(C) is a perspective view which shows a part of inner surface of a plate-shaped lever member. In FIG. 2, reference numeral 20 denotes a coating removing tool, 21a, 21
b is a plate-like lever member, 22 is a blade, 22a is a depression, 23 is a guide plate, 23a is a V groove, and 24 is an optical fiber core.

[0006] The coating removing tool 20 has two pairs of guide plates 23 and a pair of blades inside the plate-like lever members 21a and 21b, one ends of which are pivotally connected to each other, near the open / close side ends thereof. 22 are fixed vertically toward the inside, and the plate-like lever members 21a and 21b are closed with a position about 40 mm away from the end of the optical fiber core wire 24, thereby closing each of the two pairs of guide plates 23. The optical fiber core 24 is held in the V-groove 23a, and the coating of the optical fiber core 24 is cut with a pair of blades 22. Blade 22
Has a semicircular recess 22a at the cutting edge, so that the cutting edge does not reach the surface of the optical fiber in the optical fiber core wire 24, and the optical fiber is not damaged.

While the plate-like lever members 21a and 21b are closed, the coating removing tool 20 is connected to the optical fiber core 24.
To the terminal side of the optical fiber 2
The terminal side portion of the coating of No. 4 is pulled out in the terminal direction to expose the optical fiber at the terminal portion of the optical fiber. At this time, since there is a small gap between the surface of the optical fiber and the cutting edge and between the cutting edges, the coating of the gap portion is not cut by the cutting of the cutting edge but is cut by the movement of the cutting edge.
However, when the tensile elongation of the coating is large, the coating does not cut cleanly but a part of the coating grows like a whisker, and is thereafter torn. On the other hand, in the coating removing operation, it is required that the coating be sharply and sharply cut on a plane perpendicular to the axial direction. If the length extending without cutting the coating exceeds 0.5 mm, the appearance of the cut section of the coating is considered to be poor and is regarded as poor. Therefore, the length extending without cutting the coating is required to be 0.5 mm or less.

[0008] Nylon resin, polyolefin resin, etc. used as a covering material for insulated wires and the like do not emit toxic gas when burned, but the cut surface of the covering when the covering is removed by a covering removing tool is elongated to form a beard. There is a problem that can be made, can not be used as it is.

The present invention solves the above-mentioned problems of the prior art and provides a method of manufacturing an optical fiber cable which is flame-retardant, has a clean cut surface when the coating is removed, and does not cause a blocking phenomenon. To provide.

[0010]

According to the present invention, there is provided a method for manufacturing an optical fiber core wire, comprising providing a primary coating made of an ultraviolet curable resin on an optical fiber, and a secondary coating made of a flame-retardant polyethylene resin on the outside of the primary coating. And irradiating the secondary coating with an electron beam. Since this optical fiber core uses a flame-retardant polyethylene resin for the secondary coating, it is relatively inexpensive, has flame retardancy, and generates chlorine gas or dioxin during combustion. It will not be. In addition, since electron beam irradiation is performed after the secondary coating is applied, slippage between molecules is reduced due to crosslinking and tensile elongation is reduced compared to the case where the secondary coating is not irradiated with electron beam. It is possible to obtain an optical fiber with good coating removal properties and good blocking properties.

[0011]

FIG. 1A is a cross-sectional view of an optical fiber core manufactured by the method of manufacturing an optical fiber core according to the present invention, and FIG. It is a front view explaining the main process of the manufacturing method of an optical fiber core. In FIG. 1, 1 is an optical fiber, 2 is a primary coating, 3 is an optical fiber, 4 is a secondary coating, 5 is an optical fiber core, 6 is a supply reel, 7 is a tension control device, 8 is an extruder, 9 is a crosshead, 10 is a cooling water tank, 11 is an electron beam irradiation device,
12 is a take-up machine, and 13 is a take-up reel.

A primary coating 2 is provided around an optical fiber 1 to form an optical fiber 3, and a secondary coating 4 is provided around the optical fiber 3 to form an optical fiber 5. The optical fiber 1 has an outer diameter of 125 μ
It is manufactured by drawing a transparent glass rod-shaped optical fiber preform with a drawing device (not shown). The optical fiber 1 has, for example, a core obtained by adding a dopant such as germanium dioxide to silicon dioxide, and a clad provided around the core and containing silicon dioxide as a main component. Further, an optical fiber may be obtained by adding a dopant for lowering the refractive index to the clad without adding a dopant for increasing the refractive index to the core, so that the core and the clad have a different refractive index.

The primary coating 2 is made of an ultraviolet curable resin such as a urethane acrylate resin. On the optical fiber 1 obtained by drawing, an ultraviolet-curable resin is applied by a coating resin coating device (not shown), and then the applied resin is cured by irradiating ultraviolet rays with an ultraviolet irradiation device to form a primary coating 2. Thus, the optical fiber 3 is obtained. In addition, the outer diameter of the primary coating 2 is relatively large about 0.25 mm, but may be another outer diameter.

The secondary coating 4 is made of ethylene ethyl acrylate resin (EEA), ethylene vinyl acetate resin (EVA), and low density polyethylene resin (LDP).
E), a flame-retardant polyethylene resin containing a polyethylene resin such as a high-density polyethylene resin (HDPE) as a main component and a flame retardant such as magnesium hydroxide or aluminum hydroxide added thereto. It is provided around the optical fiber 3 by the manufacturing process shown in FIG.

As shown in FIG. 1B, the optical fiber 3 is fed from a supply reel 6 and supplied to a crosshead 9 of an extruder 8 through a tension control device 7. Crosshead 9
Then, the flame-retardant polyethylene resin which becomes the secondary coating 4 is extruded and coated on the optical fiber 3. It is guided to a cooling water tank 10 to cool and harden the resin, and the resin is irradiated with an electron beam by an electron beam irradiator 11 to form an optical fiber core 5. The acceleration voltage of the electron beam by the electron beam irradiation device 11 is desirably 50 kV or more and 300 kV or less.

If the accelerating voltage is less than 50 kV, the cut section of the coating when the primary coating 2 and the secondary coating 4 are removed from the optical fiber core 5 at a time is not clean, and a part of the coating is stretched to form a beard. Sometimes things can be done. When the accelerating voltage is 3
If it exceeds 00 kV, the electron beam penetrates and irradiates the part of the optical fiber 1 inside the optical fiber core 5, causing a problem that the transmission loss of the optical fiber increases.
In addition, if the electron beam is not irradiated, not only the coating removability is deteriorated, but also the coatings adhere to each other when the optical fiber core wires are stuck and left at a high temperature, which may cause a problem of so-called blocking. .

The outer diameter of the secondary coating 4 may be various depending on the requirements of the configuration of an external protective layer further provided on the optical fiber 4 when processing the optical cord or the like. The diameter is often about 0.4 mm to 1.0 mm.

The electron beam irradiation apparatus 11 can be installed in a step separate from the step of extruding the secondary coating to perform the electron beam irradiation, but as shown in FIG.
After that, if the electron beam irradiation device 11 is installed and the electron beam is irradiated continuously with the extrusion of the secondary coating, the equipment cost and the processing cost can be reduced as compared with the case where the process is performed in a separate process. If an electron beam irradiator Min-EB manufactured by Ushio Inc. is used as the electron beam irradiator 11, the electron beam irradiator can be installed in the same step as the extrusion step because of its small size.

It is desirable that the material of the secondary coating 4 does not contain at least a polyacrylate-based crosslinking agent. When the polyacrylate-based cross-linking agent is added to the material for the secondary coating 4, the tensile elongation of the coating increases, and the cut surface of the coating when the primary coating 2 and the secondary coating 4 are removed from the optical fiber 5 at once is beautiful. In some cases, a whisker-like portion may be formed on the cut section of the coating.

[0020]

EXAMPLE A urethane acrylate ultraviolet curable resin was applied as a primary coating on a single mode optical fiber mainly composed of quartz glass having an outer diameter of 0.125 μm, and cured by irradiating ultraviolet rays thereto. , Outer diameter 0.25
An optical fiber of μm was used. A resin obtained by adding 28% by weight of magnesium hydroxide as a flame retardant to EEA and 3% by weight of an antioxidant to EEA is coated on the optical fiber as a secondary coating by extrusion, and an electron beam is applied to the resin as follows. Irradiation was performed under the conditions to obtain an optical fiber core. The production linear velocity during electron beam irradiation was 100 m / min.

Experiment Nos. 1 to 7 shown in Table 1 are examples of optical fiber cores manufactured by changing the accelerating voltage and electron flow of the electron beam without adding a crosslinking agent to the secondary coating resin. It is. In Experiment Nos. 8 and 9 shown in Table 2, as a secondary coating, a resin obtained by adding 28% by weight of magnesium hydroxide and 3% by weight of an antioxidant to EEA was further added with 2% by weight of a polyacrylate crosslinking agent. 1 is an example of an optical fiber core manufactured using a resin as described above. Experiment No. 10 shown in Table 3
11 is an example of an optical fiber core manufactured without adding a crosslinking agent to the resin for secondary coating and without irradiating the secondary coating with an electron beam.

With respect to the optical fiber cores completed in Experiment Nos. 1 to 11, the removability of the coating, the blocking property, and the transmission loss of the optical fiber were measured. The results are also shown in Tables 1, 2 and 3. The respective measuring methods are as follows.

Regarding the removability of the coating, when the primary coating and the secondary coating of the 40 mm long terminal portion of the optical fiber core were removed at once using the coating removing tool shown in FIG. 0.5 mm in the longitudinal direction of the optical fiber
mm or less and a sharp cut at a clean cut surface is regarded as “good”, and the elongation at the coated cut surface is 0.
If the cut surface had a beard-like shape exceeding 5 mm, it was regarded as "poor".

The blocking property is 1000 m in length.
Optical fiber core wire, trunk diameter 280cm, trunk length 100mm
After being wound on a reel, the optical fiber core wire is removed from the reel to form a circular bundle, which is placed in a thermostat at 85 ° C. for 12 hours.
It was left for a while, and the quality was judged based on whether or not the coatings adhered to each other. When the bundle taken out of the thermostatic bath was placed on a table and the terminal portion was lifted up, the one that could be lifted without the coatings sticking together was regarded as “good”. In addition, a case in which the coatings were stuck together and a portion other than the terminal portion was lifted up together was defined as “defective”.

Further, the transmission loss was measured at a wavelength of 1.55 μm with respect to an optical fiber core having a length of 2000 m according to JIS.
It was measured by the backscattering method of C 6826. Good if the transmission loss is 0.24 dB / km or less, but bad if more.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

According to the results shown in Table 1, when the secondary coating is irradiated with an electron beam at an accelerating voltage of 50 kV to 300 kV, the removability of the coating, the blocking property, and the transmission loss of the optical fiber are all good. When the acceleration voltage is 30 kV, the removability of the coating is poor. When the accelerating voltage is 500 kV, the transmission loss of the optical fiber is as large as 15.0 dB / km, which is not good. Therefore, the electron beam irradiation on the secondary coating is desirably 50 kV to 300 kV. Also, according to the results in Table 2, those with the addition of the polyacrylate-based crosslinking agent were:
Poor removability of coating. Therefore, it is desirable that the flame-retardant polyethylene resin used for the secondary coating does not contain a crosslinking agent. According to the results shown in Table 3, when no electron beam was irradiated, the coating removal property and the blocking property were poor.

[0030]

The method for manufacturing an optical fiber core according to the present invention comprises:
A primary coating made of an ultraviolet curable resin is provided on the optical fiber, a secondary coating made of a flame-retardant polyethylene resin is applied to the outside thereof, and electron beam irradiation is performed from above the secondary coating. Optical fiber cores produced by the method are relatively inexpensive and flame retardant. Also, even during combustion, there is no generation of chlorine gas or generation of dioxin or the like. Further, since electron beam irradiation is performed after the secondary coating is applied, both the coating removability and the blocking characteristics are better than those in which the secondary coating does not irradiate the electron beam.

Further, the accelerating voltage of the irradiated electron beam is set to 50
By setting the kV to 300 kV, the removability of the coating is good,
It is possible to obtain an optical fiber core having good transmission loss of the optical fiber. In addition, by not adding a crosslinking agent to the resin of the secondary coating, coating removability can be improved. Furthermore, the extrusion device and the electron beam irradiation device are installed in a continuous process,
If the extrusion coating of the secondary coating and the electron beam irradiation are performed continuously, the equipment cost and the processing cost of the optical fiber core can be reduced.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of an optical fiber core manufactured by a method of manufacturing an optical fiber core of the present invention, and FIG. 1B is a cross-sectional view of the optical fiber core manufacturing method of the present invention. It is a front view explaining the main process of.

2 (A) is a side view of the coating removing tool, FIG. 2 (B) is a cross-sectional view in the X direction, and FIG. 2 (C) is an inner surface of a plate-like lever member. It is a perspective view which shows a part of.

[Explanation of symbols]

 1: Optical fiber 2: Primary coating 3: Optical fiber 4: Secondary coating 5: Optical fiber core 6: Supply reel 7: Tension controller 8: Extruder 9: Crosshead 10: Cooling water tank 11: Electron beam Irradiation device 12: Take-up machine 13: Take-up reel

Claims (4)

[Claims] 1. A method according to claim 1, wherein a primary coating made of an ultraviolet curable resin is provided on the optical fiber, a secondary coating made of a flame-retardant polyethylene resin is applied outside the primary coating, and an electron beam is irradiated from above the secondary coating. A method for producing an optical fiber core, comprising: 2. The flame-retardant polyethylene resin is EE
A, EVA, LDPE, HDPE based on any one or more, and containing one or more of magnesium hydroxide and aluminum hydroxide as a flame retardant, and not containing a polyacrylate-based crosslinking agent The method for manufacturing an optical fiber core according to claim 1, wherein: 3. The optical fiber according to claim 1, wherein a secondary coating made of the flame-retardant polyethylene resin is formed by extrusion, and the electron beam irradiation is performed continuously to the extrusion step. Manufacturing method of core wire. 4. An accelerating voltage in the electron beam irradiation is 5
The method according to claim 1, wherein the voltage is 0 kV to 300 kV.