JP2928723B2 - Optical fiber manufacturing method - Google Patents

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 an optical fiber in which a plurality of coating layers are formed on a bare optical fiber to form an optical fiber, and various coating layers are overcoated thereon. By controlling the degree of hardening of the outermost layer of the strand, the adhesion to the overcoat layer to be applied thereon is improved to improve the workability of the terminal treatment.

[0002]

2. Description of the Related Art Conventionally, when an optical fiber is manufactured, a method as shown in FIG. 2 is employed. That is, first, the optical fiber preform 1 is drawn while being melted in the heating furnace 2 at about 2000 ° C., and the obtained bare optical fiber is cooled to a temperature of about 100 ° C. or lower by passing through the cooling device 3.
Then, the coating device 4 has a relatively low Young's modulus.
In addition, a resin (primary coating layer) of an ultraviolet curing type or a thermosetting type having a higher refractive index than quartz glass is coated, and the resin is cured through a resin curing device 5. Then, the resin is passed through a coating device 4 'to coat a UV-curable or thermosetting resin (secondary coating layer) having a relatively high Young's modulus, and the resin is cured by a resin curing device 5'. Let it cure. The obtained optical fiber is taken out by the take-up device 6 and taken up by the take-up device 7.

[0003]

By the way, a plurality of optical fiber strands thus obtained are usually arranged in parallel, and the outer periphery thereof is coated with resin at a time to be used as an optical fiber tape core. In order to connect the individual optical fibers of the optical fiber ribbon, it is necessary to carry out a terminal treatment of removing each coating layer of the optical fiber ribbon. When exposing the bare optical fiber after removing these coating layers, if the adhesive strength between the bare optical fiber and the primary coating layer is stronger than the adhesive strength between the other layers, the primary coating on the bare optical fiber is performed. Layers may remain. For this reason, there is a problem that the workability of the terminal processing of each optical fiber strand of the optical fiber ribbon is impaired.

In such an optical fiber ribbon, a colored layer may be formed on each of the optical fibers in order to identify each of the optical fibers. Even in this case, in order to connect each optical fiber, it is necessary to remove each coating layer of the optical fiber ribbon. When removing these coating layers from the bare optical fiber, if the adhesion between the colored layer and the secondary coating layer is low, the secondary coating layer is not separated from the bare optical fiber and the primary coating layer. In some cases, the primary coating layer and the secondary coating layer are left on the bare optical fiber, and the coating layer cannot be removed.
For this reason, there is a problem that the workability of the terminal processing of each optical fiber strand of the optical fiber ribbon is impaired.

The present invention has been made in view of these circumstances, and an object of the present invention is to provide a method of manufacturing an optical fiber in which the workability of terminal processing of an optical fiber is improved.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to form at least two resin coating layers on a bare optical fiber to form an optical fiber, and further, when forming an overcoat layer thereon, the optical fiber. The problem is solved by setting the degree of curing of the resin coating layer as the outermost layer of the fiber strand to 90 to 99%, and substantially completely curing just before the formation of the overcoat layer.
Here, the meaning of the layer overcoated on the optical fiber is either a layer formed immediately above the optical fiber or a collective coating layer when a plurality of optical fibers are arranged in parallel and collectively coated. Shall be included.

[0007]

According to the present invention, when forming an overcoat layer on an optical fiber, the degree of curing of the outermost layer of the optical fiber is set to 90 to 99% in advance, and the curing is performed immediately before the formation of the overcoat layer. Since this is a method of completely curing the degree, the adhesion between the two is improved. If the degree of cure of the outermost resin coating layer of the optical fiber is less than 90%, it is not preferable for the following reasons. That is, stickiness on the surface of the optical fiber becomes a problem. More specifically, when the wound optical fiber is fed out to form the overcoat layer, the feeder dancer pulley hunts and the overcoat material cannot be coated. Further, since the pass line itself is also sticky, dust and the like are attached. On the other hand, if the degree of cure of the coating layer exceeds 99%, it is not preferable because the adhesion to the overcoating material cannot be improved. Thus, the degree of cure of the coating layer is 90
Up to 99%, the bonding strength between the outermost resin coating layer and the coating layer is improved over the bonding strength between the bare optical fiber and the primary coating layer immediately above the bare optical fiber when exposing the bare optical fiber. This prevents the primary coating layer from remaining on the bare optical fiber.

[0008]

Next, the method for producing the optical fiber of the present invention will be described in detail. FIG. 1 shows a colored layer forming step of the manufacturing apparatus used in the present invention. First, as shown in FIG. 2, an optical fiber preform 1 was drawn while being melted in a heating furnace 2 at about 2000 ° C.
And cooled to about 100 ° C. or less.

As the refrigerant gas used at this time, it is preferable to use any one of argon, helium, nitrogen, carbon dioxide, air, etc., or a mixed gas.
The gas flow rate can be appropriately selected in the range of 1 to 40 liter / min. In addition, when the machine is not operated or the spinning speed is low, the supply of the cooling gas can be stopped or the flow rate can be reduced. Adjustment of the flow rate of these cooling gases can be changed as appropriate by adjusting a flow meter or a mass flow controller (not shown).

Next, the bare optical fiber is passed through a coating apparatus 4 where it is coated with an ultraviolet-curable or thermosetting resin (primary coating layer). Thereafter, the resin is almost completely cured through a resin curing device 5 such as a UV irradiation furnace or a heating furnace. Then, the resin is passed through a coating device 4 ', and is coated with an ultraviolet-curing or thermosetting resin (secondary coating layer). The resin is cured to a curing degree of 90 to 99% by a resin curing device 5'. . The obtained optical fiber is taken up by a take-up machine 6 and taken up on a take-up drum 7 by a take-up device.

Thereafter, as shown in FIG.
Immediately before forming a colored layer for identifying the optical fiber strand, the optical fiber strand is passed through a resin curing device 9 so that the optical fiber strand is wound up. Almost 100% curing degree of outer layer (secondary coating layer)
To Next, the optical fiber is passed through a coating device 10 containing a coloring material to form a colored layer on the outer periphery of the optical fiber. Here, the coloring material is composed of various pigments and an ultraviolet curable or thermosetting resin mixed with the pigments. Next, this is passed through a resin curing device 11 to cure the coloring material to form a coloring layer. The obtained optical fiber is wound by a winding drum 12.

For example, four optical fibers thus obtained are sent out in parallel and passed through a coating device (not shown), whereby the outer periphery of the optical fibers is collectively coated and formed to form an optical fiber ribbon. The optical fiber ribbon is wound up by a winding drum (not shown).

In order to connect each bare optical fiber of the obtained optical fiber ribbon, all layers of the collective coating layer, the colored layer, the secondary coating layer, and the primary coating layer are peeled off from the bare optical fiber. By tapping, each bare optical fiber is terminated. These are connected by fusion, a connector or the like, and an optical fiber bare wire is connected.

In such an optical fiber manufacturing method, a primary coating layer and a secondary coating layer are sequentially formed on an bare optical fiber to form an optical fiber, and when a colored layer is formed thereon, first, Curing degree of the secondary coating layer of the optical fiber is 90
Since the optical fiber is passed through the resin curing device 9 immediately before the colored layer is formed thereon, a curing reaction of the secondary coating layer occurs immediately before the coating device 10 containing the colored layer. The surface of the secondary coating layer is activated, and a part of the secondary coating layer undergoes a chemical reaction with the coloring layer, so that the adhesion between the coloring layer and the secondary coating layer is further improved.

As described above, since the adhesion between the secondary coating layer and the colored layer is improved, it is possible to prevent the secondary coating layer and the colored layer from peeling off from each other. The primary coating layer and the secondary coating layer can be prevented from remaining. Therefore, the workability of the terminal processing of the optical fiber can be improved. In addition, since it is not necessary to completely cure the secondary coating layer, the spinning speed can be increased. Further, in the above embodiment, the optical fiber is manufactured and wound once, but may be continuously performed until the colored layer forming step.

(Example 1) Hereinafter, the effects of the present invention will be clarified by showing specific examples. First, about 20 optical fiber preforms
After heating to 00 ° C., the fiber is spun at 500 m / min to obtain a bare optical fiber having a clad diameter of 125 μm. Then
This is passed through a cooling device and cooled so that the surface temperature of the bare optical fiber is 100 ° C. or less. For cooling, a mixed gas of nitrogen and helium (1: 1 ratio) is flowed at 5 liter / min.

Then, a urethane acrylate UV resin is applied by a coating apparatus (primary coating layer), and immediately, the resin is almost completely cured in a UV irradiation furnace (resin curing apparatus). At this time, the diameter of the bare optical fiber and the primary coating layer is 200 μm. Next, the resin is passed through a coating apparatus, and a resin having a relatively high Young's modulus is applied as described above (secondary coating layer), and immediately, the resin is cured in a UV irradiation furnace. At this time, the degree of cure of the resin is set to 90%, and the degree of cure of the resin is controlled by the number of UV lamps in the UV irradiation furnace, the electric energy of the UV lamps, and the spinning speed. In this way, an optical fiber having a diameter of 250 μm is manufactured, which is once taken up by a take-up machine and wound up by a take-up device.

Thereafter, the wound optical fiber is sent out, and the optical fiber is passed through a UV irradiation furnace immediately before the coating device containing the colored layer. At this time, the degree of cure of the resin (secondary coating layer) is increased to almost 100%.
Subsequently, this is passed through a coating device containing a UV-curable coloring material, passed through a UV irradiation furnace, once taken up by a take-up machine, and taken up by a take-up device.

Thereafter, the four optical fibers with the colored layers are sent out in parallel, passed through a coating device, coated with UV resin at a time, and irradiated with UV for curing to obtain an optical fiber ribbon.

The quality of the optical fiber ribbon obtained in this manner is evaluated by the degree of curing of the secondary coating layer (%) of the optical fiber, the number of times of removing the coating layer, and the variation in the feeding of the optical fiber. Table 1
Summarized in Here, the degree of cure of the secondary coating layer refers to the degree of cure during formation. The degree of curing of the secondary coating layer was defined by measuring its Young's modulus. The coating removal property is such that, when batch removal for removing the overcoat layer at once is performed 200 times with a hot stopper, even the first coating layer or the subsequent coating layer remains on the bare optical fiber even in one out of four cores. Shows the number of times

Example 2 An optical fiber ribbon was prepared in the same manner as in Example 1 except that the degree of curing of the secondary coating layer constituting the optical fiber was 93%. In addition, the degree of secondary coating layer hardening and the coating layer removability were performed in the same manner as in Example 1.
These results are summarized in Table 1.

Example 3 An optical fiber ribbon was produced in the same manner as in Example 1 except that the degree of curing of the secondary coating layer constituting the optical fiber was 96%. In addition, the degree of secondary coating layer hardening and the coating layer removability were performed in the same manner as in Example 1.
These results are summarized in Table 1.

Example 4 An optical fiber ribbon was produced in the same manner as in Example 1 except that the degree of curing of the secondary coating layer constituting the optical fiber was set to 99%. In addition, the degree of secondary coating layer hardening and the coating layer removability were performed in the same manner as in Example 1.
These results are summarized in Table 1.

(Example 5) The spinning linear speed was 1000 m / min.
The degree of cure of the secondary coating layer constituting the optical fiber is 95%
An optical fiber ribbon was prepared in the same manner as in Example 1 except that the above procedure was adopted. Further, the degree of secondary coating layer hardening and the coating layer removability were measured in the same manner as in Example 1, and the results are summarized in Table 1.

Example 6 The spinning speed was 1500 m / min.
The degree of cure of the secondary coating layer constituting the optical fiber is 94%.
An optical fiber ribbon was prepared in the same manner as in Example 1 except that the above procedure was adopted. Further, the degree of secondary coating layer hardening and the coating layer removability were measured in the same manner as in Example 1, and the results are summarized in Table 1.

Comparative Example 1 An optical fiber ribbon was produced in the same manner as in Example 1 except that the degree of curing of the secondary coating layer constituting the optical fiber was 85%. In addition, the degree of secondary coating layer hardening and the coating layer removability were performed in the same manner as in Example 1.
These results are summarized in Table 1.

Comparative Example 2 An optical fiber ribbon was produced in the same manner as in Example 1 except that the degree of curing of the secondary coating layer constituting the optical fiber was changed to 88%. In addition, the degree of secondary coating layer hardening and the coating layer removability were performed in the same manner as in Example 1.
These results are summarized in Table 1.

(Comparative Example 3) The degree of curing of the secondary coating layer constituting the optical fiber was set to 90%, and a colored layer was formed on the secondary coating layer as it was without being completely cured. Created a line. Also, the degree of secondary coating layer curing,
The coating layer was removed in the same manner as in Example 1, and the results are summarized in Table 1.

(Comparative Example 4) The degree of curing of the secondary coating layer constituting the optical fiber was set to 99%, and a colored layer was formed on the secondary coating layer as it was not completely cured to form an optical fiber tape core. Created a line. Also, the degree of secondary coating layer curing,
The coating layer was removed in the same manner as in Example 1, and the results are summarized in Table 1.

Comparative Example 5 A secondary coating layer constituting an optical fiber was completely cured (curing degree: 100%), and a colored layer was formed thereon to produce an optical fiber tape.
Further, the degree of secondary coating layer hardening and the coating layer removability were measured in the same manner as in Example 1, and the results are summarized in Table 1.

[0031]

[Table 1]

As is clear from Table 1, Examples 1 to 6 of the method of the present invention in which the degree of curing of the secondary coating layer of the optical fiber was initially set to 90 to 99%, and completely cured immediately before the formation of the colored layer,
Irrespective of the spinning speed, both the coating removal property and the tension fluctuation at the time of feeding the optical fiber are preferable.

On the other hand, in Comparative Examples 1 and 2 in which the degree of curing of the secondary coating layer of the optical fiber was initially 90% or less, the stickiness was large. The variation in tension during feeding was large, and the result was that the colored layer could not be coated and formed uniformly. The degree of cure of the secondary coating layer of the optical fiber is in the range of 90% to 99%, but Comparative Example 3 in which the colored layer is formed with the same hardness.
In Nos. To 4, the adhesion to the colored layer was low, and the coating removability was extremely poor. Further, in Comparative Example 5, in which the degree of curing of the secondary coating layer of the optical fiber was set to 100% and the coloring layer was formed thereon, the coating removal property was not satisfactory.

[0034]

As described above, according to the optical fiber manufacturing method of the present invention, at least two resin coating layers are formed on the bare optical fiber to form an optical fiber.
When a coating layer is formed thereon, the degree of curing of the resin coating layer as the outermost layer of the optical fiber is set to 90 to 99%, and almost completely cured immediately before the formation of the coating layer thereon. Therefore, the adhesion between the two is improved. For this reason, when the optical fiber is terminated, the coating layer is removed at a time, and when the bare optical fiber is exposed, it is possible to prevent the resin fiber from peeling off between the resin coating layers. The coating layer can be prevented from remaining. Therefore, when connecting each bare optical fiber, the coating layer can be removed from the bare optical fiber to expose the bare optical fiber, so that the workability of the terminal treatment of the bare optical fiber can be improved. .

[Brief description of the drawings]

FIG. 1 is a schematic structural view showing one embodiment of a method for producing an optical fiber of the present invention and showing a colored layer forming step.

FIG. 2 is a schematic configuration diagram showing one embodiment of a conventional optical fiber manufacturing method.

[Explanation of symbols]

2 ... Heating furnace, 3 ... Cooling device, 4,4 '... Coating device, 5 5' ... Resin curing device, 9 ... Resin curing device, 10
... Coating equipment containing coloring material.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-13105 (JP, A) JP-A-60-171246 (JP, A) JP-A-3-96907 (JP, A) JP-A-3-9695 109512 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C03C 25/02

Claims (2)

(57) [Claims] At least two resin coating layers are formed on a bare optical fiber to form an optical fiber, and when an overcoat layer is formed thereon, a resin of an outermost layer of the optical fiber is formed. The curing degree of the coating layer is set to 90 to 99%,
A method for producing an optical fiber, wherein the optical fiber is almost completely cured immediately before the formation of the overcoat layer. 2. The method for producing an optical fiber according to claim 1, wherein the overcoat layer formed on the optical fiber is a colored resin coating layer.