JP3408591B2 - 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 a high quality optical fiber strand at high speed.

[0002]

2. Description of the Related Art Conventionally, a method as shown in FIG. 2 is adopted when manufacturing an optical fiber. That is, first, the optical fiber preform 1 is drawn in a heating furnace 2 at about 2000 ° C. while being drawn, and the obtained bare optical fiber is passed through a cooling device 3 to be cooled to a temperature of about 100 ° C. or lower.
Then, a coating device 4 coats an ultraviolet-curable or thermosetting resin, the resin curing device 5 cures the resin, and the obtained optical fiber wire is passed through a pulley 6 to wind it up. Take up with 7.

However, when the spinning speed is increased,
Since the cooling is not sufficient, the surface temperature of the outermost coating layer of the optical fiber element wire becomes high. Therefore, when the optical fiber element wire and the pulley 6 which is a solid matter come into contact with each other, the outermost coating of the optical fiber element wire is obtained. Since the layer is largely deformed on the pulley 6, there is a problem that the amount of line blur increases, resulting in defective coating and reduced strength. In particular, when the surface temperature of the outermost coating layer was equal to or higher than the glass transition temperature of the coating material constituting the outermost coating layer, the outermost coating layer of the optical fiber element was significantly deformed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of these circumstances, and suppresses the deformation of the outermost coating layer of an optical fiber element wire, and provides an optical fiber of stable quality at high speed. It is intended to provide a method of manufacturing.

[0005]

The object is to form an optical fiber element wire by forming a coating layer made of an ultraviolet curable resin on an optical fiber bare wire, and the optical fiber element wire first comes into contact with a solid material. By lowering the surface temperature of the outermost coating layer of the optical fiber wire by 12 ° C. or more than the glass transition temperature of the coating material forming the outermost coating layer, the light at the position 20 cm above the solid material is This can be solved by setting the amount of line blur of the fiber strand to 0.06 mm or less. For this reason,
It is preferable to install a cooling device in the preceding stage of the solid matter.

[0006]

The surface temperature of the outermost coating layer of the optical fiber is 12 ° C. or more higher than the glass transition temperature of the coating material constituting the outermost coating layer.
20 cm above the solid by lowering
Set the amount of line blurring of the optical fiber strand to 0.06 mm or less.
The outermost coating layer does not deform even if it contacts a solid substance and external force is applied.

[0007]

Next, the method for producing the optical fiber of the present invention will be described in detail. FIG. 1 shows an example of a manufacturing apparatus used in the present invention. First, the optical fiber preform 11 is drawn in a heating furnace 12 at about 2000 ° C. while being drawn to form a bare optical fiber, and then the bare optical fiber is passed through a cooling device 13 to be 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 and the like, or a mixed gas.
The gas flow rate can be appropriately selected within the range of 1 to 40 l / min. Also, when not operating or when the spinning speed is low,
It is also possible to stop the supply of the cooling gas or reduce the flow rate. Adjustment of the flow rate of these cooling gases can be appropriately changed by adjusting a flow meter or a mass flow controller (not shown).

Then, the bare optical fiber is passed through a coating device 14, where it is coated with an ultraviolet-curing or thermosetting resin. Then, the resin is cured through a resin curing device 15 such as a UV irradiation furnace or a heating furnace to prepare an optical fiber element wire.

Then, the optical fiber element wire is again passed through a cooling device 13 similar to the cooling device 13, and the surface temperature of the outermost coating layer of the optical fiber element wire is equal to or lower than the glass transition temperature of the coating material constituting the outermost coating layer. Cool to. At this time, cooling is preferably performed so that the difference between the surface temperature of the outermost coating layer of the optical fiber element wire and the glass transition temperature of the coating material forming the optical fiber strand is 12 ° C. or more. Due to the nature of the glass, the outermost coating layer may be slightly softened near the glass transition temperature even if it does not reach the glass transition temperature. Therefore, contact with the pulley 16 causes the outermost coating layer to be softened. Is expected to deform.

The flow rate of the cooling gas is 2 to 30 l /
min is preferred. This is because even if it exceeds 30 l / min, the excess does not contribute to the cooling of the optical fiber wire, and the flow of gas causes the optical fiber wire to vibrate, causing deformation and damage. Is. Also,
If it is 2 l / min or less, the flow rate control by the flow meter or the mass flow controller becomes unstable, and the optical fiber strand cannot be efficiently cooled while the optical fiber strand passes through the cooling device 13. is there.

The optical fiber thus obtained is measured for its surface temperature using a non-contact type thermometer 18 immediately before passing through the pulley 16 equipped with a tensiometer, and is wound by a winding device 17. It should be noted that the present invention is not limited to the above embodiment, and the specific configuration can be changed as appropriate. For example, after curing the coating material, increase the distance to the pulley 16 where the optical fiber strand first contacts.
That is, the optical fiber strand can be cooled by increasing the line length by air cooling.

In such an optical fiber manufacturing method, a coating layer is formed on an optical fiber bare wire to form an optical fiber element wire,
By the time the optical fiber wire first contacts the pulley 16, the surface temperature of the outermost coating layer of the optical fiber wire is made equal to or lower than the glass transition temperature of the coating material constituting the optical fiber wire.
Since the outermost coating layer does not deform even when the optical fiber wire comes into contact with the pulley 16 and an external force is applied, the outermost coating layer of the optical fiber wire caused by the optical fiber wire coming into contact with the pulley 16 Is suppressed, so that it is possible to reduce the amount of line blurring and prevent strength failure.

(Embodiment 1) The effects of the present invention will be clarified by showing concrete examples below. First, after heating the optical fiber preform 11 to about 2000 ° C., spinning at 200 m / min,
A bare single mode optical fiber having a cladding diameter of 125 μm was obtained. Then, this was passed through a cooling device 13 and cooled so that the surface temperature of the bare optical fiber was 100 ° C. or lower. For cooling, mixed gas of nitrogen and helium (1: 1
Flow rate of 5 l / min.

Then, urethane = acrylate UV resin is applied in the coating device 14, and immediately U
The resin was cured in the V irradiation furnace 15 to prepare an optical fiber elemental wire. The coating diameter of this optical fiber is 250 μm
Therefore, the coating layer is two layers. The surface temperature of the optical fiber thus obtained is measured by using a non-contact type thermometer 18 immediately before passing through the pulley 16, and the winding device 17
It was wound up by. The distance between the UV irradiation furnace 15 and the pulley 16 at this time was 1.5 m. In this example, since the spinning speed was as slow as 200 m / min, the cooling device 13 was not provided directly below the UV irradiation furnace 15, and the cooling was performed naturally. As the coating material for the outermost coating layer, one having a glass transition temperature of 81 ° C. by the TMA method was used.

The quality of the optical fiber strand thus obtained was evaluated by the results of the amount of line blurring, the number of coating defects and the number of proof test breaks, and summarized in Table 1.
The amount of line blur represents the amount of line blur at 20 cm above the pulley 16 that the optical fiber bare first contacts after forming the coating layer. The number of coating defects is 100
At 0 km, the number of times the coating of the UV resin became defective is shown. The number of breaks in the proof test indicates the number of breaks of the optical fiber strand when the screening was performed at 1.0% / min in the optical fiber strand of 1000 km.

(Test Example 1) An optical fiber strand was prepared in the same manner as in Example 1 except that the spinning speed was 500 m / min. A quality inspection for checking the amount of line blurring, the number of coating defects, and the number of proof test breaks was performed in the same manner as in Example 1, and these results are summarized in Table 1.

(Example 2) A diameter of 15 m was provided between the UV irradiation furnace 15 and the pulley 16.
An optical fiber element wire was prepared in the same manner as in Test Example 1 except that the cooling device 13 having a m, a length of 800 mm, and a stainless steel cooling cylinder was installed, and helium gas was supplied as a cooling gas at 8 l / min. did. The results of the quality inspection are summarized in Table 1.

Example 3 An optical fiber strand was prepared in the same manner as in Example 2 except that the spinning speed was 1000 m / min and the flow rate of helium gas was 20 l / min. Table 1 shows the results of quality inspection.
Summarized in.

(Comparative Example 1) The spinning speed was 1000 m / mi.
An optical fiber elemental wire was prepared in the same manner as in Example 1 except that n was used. The results of the quality inspection are summarized in Table 1.

[0021]

[Table 1]

Example 4 As a coating material, urethane having a glass transition temperature of 93 ° C. =
An optical fiber element wire was prepared in the same manner as in Example 1 except that the acrylate UV resin was used. The results of the quality inspection of this are summarized in Table 2.

(Test Example 2) An optical fiber element wire was prepared in the same manner as in Example 4 except that the spinning speed was 500 m / min. The results of the quality inspection are summarized in Table 2.

(Example 5) A diameter of 15 m was provided between the UV irradiation furnace 15 and the pulley 16.
An optical fiber element wire was prepared in the same manner as in Test Example 2 except that the cooling device 13 having a m, a length of 800 mm and a stainless steel cooling cylinder was installed, and helium gas was supplied as a cooling gas at 8 l / min. did. The results of the quality inspection are summarized in Table 2.

Example 6 An optical fiber strand was prepared in the same manner as in Example 5 , except that the spinning speed was 1000 m / min and the flow rate of helium gas was 20 l / min. Table 2 shows the results of quality inspection.
Summarized in.

Comparative Example 2 Example 4 was repeated except that the spinning speed was set to 1000 m / min.
An optical fiber strand was prepared in the same manner as in. The results of the quality inspection are summarized in Table 2.

[0027]

[Table 2]

Examples 1 to 3, Test Example 1 and Comparative Example 1,
The results of Examples 4 to 6, Test Example 2 and Comparative Example 2 will be described. First, the coating material has a glass transition temperature of 8
The case of using a urethane = acrylate UV resin at 1 ° C. will be described. As in Example 1, the spinning speed was 2
At a low speed of 00 m / min, even if the cooling device 13 is not installed between the UV irradiation furnace 15 and the pulley 16, the surface temperature of the optical fiber just before passing through the pulley 16 is 61%.
The glass transition temperature of the coating material constituting the outermost coating layer was 81 ° C. or lower at 81 ° C. However, as in Comparative Example 1, when the spinning speed was increased to 1000 m / min, the surface temperature of the optical fiber just before passing through the pulley 16 was 92 ° C., which was above the glass transition temperature.

Here, by comparing Example 1 with Comparative Example 1, the surface temperature of the optical fiber wire after the coating layer was formed is the outermost temperature before the contact with the pulley 16. It is possible to know the degree of quality deterioration due to the glass transition temperature of the coating material constituting the coating layer or higher. Comparing Example 1 and Comparative Example 1, the line blur amount of Comparative Example 1 was about 3 times that of Example 1, and the proof test result was about 4 times. Further, in Example 1, no defective portion of the coating was observed, whereas in Comparative Example 1, the quality was remarkably deteriorated, such as 15 times.

However, the UV irradiation furnace 15 and the pulley 16
In Example 3 in which the surface temperature of the optical fiber strand was set to the glass transition temperature or less by installing the cooling device 13 also between and, the spinning speed was low even though the spinning speed was as high as 1000 m / min. A quality similar to that of the spun example 1 was obtained. Also, spinning was performed at a medium speed of 500 m / min.
In Test Example 1 , the surface temperature of the optical fiber element wire rose to near the glass transition temperature. In Example 2 in which the glass transition temperature was lowered to the glass transition temperature in the cooling device 13, an optical fiber strand having better quality than that in Test Example 1 was obtained.

Further, Examples 4 to 5 using urethane = acrylate UV resin having a glass transition temperature of 93 ° C.
It was found that similar results were obtained for Example 6 and Test Example 2 .

[0032]

As described above, the method for producing an optical fiber according to the present invention uses the ultraviolet curable resin on the bare optical fiber.
Comprising a coating layer is formed by an optical fiber and, by this optical fiber is in contact with the first solid surface temperature of the outermost coating layer of the optical fiber, constituting the outermost coating layer By lowering the glass transition temperature of the coating material by 12 ° C. or more, the amount of line blur of the optical fiber element wire at a position 20 cm above the solid material is 0.06 mm or less. Since the strength of the outermost coating layer of the fiber strand can be kept constant, deformation of the outermost coating layer of the optical fiber strand that occurs when contacting with solid matter is suppressed, the amount of line blurring is reduced, and it is even. It is possible to obtain stable optical fiber strands, such as excellent coating strength and good strength. Further, even if the spinning process is carried out at a high speed, it is possible to obtain the effect that the above advantages are not impaired.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an optical fiber manufacturing method of the present invention.

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

[Explanation of symbols]

12 ... Heating furnace, 13 ... Cooling device, 14 ... Coating device, 15 ... Resin curing device, 16 ... Pulley, 17 ... Winding device, 18 ... Non-contact type thermometer

Continued front page    (72) Inventor Koichi Takahashi               1440 Rokuzaki, Sakura City, Chiba Prefecture               Zikura Sakura Factory (72) Inventor Munehisa Fujimaki               1440 Rokuzaki, Sakura City, Chiba Prefecture               Zikura Sakura Factory                (56) References JP-A-53-141048 (JP, A)

Claims (2)

(57) [Claims] 1. Is an ultraviolet curable resin on the bare optical fiber ?
And the optical fiber to form a Ranaru coating layer, until the optical fiber is in contact with the first solid surface temperature of the outermost coating layer of the optical fiber, constituting the outermost coating layer By lowering the glass transition temperature of the coating material by 12 ° C. or more, the amount of line blur of the optical fiber strand at a position 20 cm above the solid is reduced to 0.06 mm or less. . 2. A cooling device comprising an outer cylindrical cooling cylinder, a supply pipe for supplying a cooling gas to the cooling cylinder, and a gas tank connected to the supply pipe is installed in a preceding stage of the solid matter, The optical fiber manufacturing method according to claim 1, wherein the optical fiber strand is cooled.