JPH04240136A - Production of optical fiber - Google Patents

Abstract

PURPOSE:To improve the linear speed of production (to improve the max. linear speed at which a coating resin can cure completely) and to improve productivity by improving the efficiency of curing of a UV curing type resin coating in the process for producing the optical fiber having the coating resin. CONSTITUTION:The UV curing type resin is applied on the outer periphery of the drawn optical fiber and is then irradiated with UV rays by which the coating resin is cured. The optical fiber emerging from a UV irradiation device is passed in a heat insulating cylinder or heating cylinder, by which the cooling of the fiber is prevented. The reaction curing is continued and the curing efficiency is improved in this way and, therefore, the increase of the max. linear speed is possible. The fiber is passed in cooling preventive means during the time of irradiation if the execution of the irradiation with the UV rays plural times.

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 optical fibers, and more particularly to a method for manufacturing optical fibers coated with ultraviolet curable resin at high speed.

0002

2. Description of the Related Art The outer periphery of an optical fiber is usually coated with a resin in order to protect it from external mechanical forces, and from the viewpoint of curability, ultraviolet curable resin is commonly used as the resin. In recent years, as the demand for optical fibers has increased, there has been a need to increase the manufacturing speed, and research is underway to improve the resin composition and increase the intensity of ultraviolet rays irradiated as a way to increase the curing speed of the resin. However, curing of the resin remains one of the most important factors limiting improvement in linear speed.

Conventionally, optical fibers have been coated with two layers of resin using a device as shown in FIG. The optical fiber 3 drawn from the optical fiber base material 1 in the drawing furnace 2 is coated with resin in the resin coating device 4 and then transferred to the ultraviolet irradiation device 9.
While passing through the cylindrical body 6, the ultraviolet rays emitted from the ultraviolet irradiation lamp 5 are focused by the reflecting mirror 10 and irradiated onto the resin, thereby curing the resin and forming the resin-coated fiber 7.
becomes. 8 is a winder.

0004

[Problem to be solved by the invention] While the above-mentioned demand for improving the manufacturing line speed is becoming stronger and stronger, in response to this demand, the number of ultraviolet irradiation devices shown in Figure 2 has been increased for resin curing. This has been dealt with by arranging them in series. However, an increase in the number of ultraviolet irradiation devices causes an increase in equipment costs. Therefore, an important issue at present is how to efficiently cure resin without increasing costs.

[0005]

[Means for Solving the Problems] The present invention solves the above-mentioned problems in a method of manufacturing an optical fiber, in which an ultraviolet curable resin is applied to the surface of the optical fiber, and then ultraviolet rays are irradiated to cure the resin and form a coating. The method is characterized in that, after being irradiated with ultraviolet rays, the optical fiber is passed through a certain section having cooling prevention means. In the present invention, the section having the cooling prevention means may be passed through at least once during the plurality of UV irradiations. Particularly preferred examples of the cooling prevention means of the present invention include means for reducing heating or heat radiation from an external heat source.

FIG. 1 is a schematic sectional view showing a specific example of the present invention, in which a heat insulating cylinder 11 is provided directly below an ultraviolet irradiation device 9. As shown in FIG. The heat insulating cylinder 11 may be a simple cylindrical body attached to the optical fiber exit side of the ultraviolet irradiation device, into which purge gas heated within the ultraviolet irradiation device flows. More preferably, the cylinder is positively surrounded by a porous material or a felt material.

FIG. 2 is a schematic sectional view showing another embodiment of the present invention, in which a heating device is provided between a plurality of ultraviolet irradiation devices as cooling prevention means. As the heating device, a normal heating method such as arranging an electric heater around the outer periphery of the cylinder may be used. The heating temperature may be within a range that does not cause deterioration of the resin, and for example, 50 to 300°C is suitable.

In the present invention, there are no particular restrictions on the ultraviolet curable resin used to form the coating on the optical fiber, but examples include urethane (meth)acrylate, epoxy (meth)acrylate, and ester (meth)acrylate. be able to. The resin coated on the outer periphery of the optical fiber may be a single layer or a multilayer.

[0009]

[Operation] Fig. 3 shows the production of a fiber with a primary coating formed by changing the length of the heat insulating cylinder using the apparatus shown in Fig. 1.
FIG. 2 is a graph diagram showing the relationship between the measurement results of the Young's modulus of the primary coating and the length of the heat insulating cylinder. The resin used for coating has a Young's modulus of approximately 0.1 kg/mm 2 when fully cured. From FIG. 3, it can be seen that if the heat insulating cylinder is made sufficiently long to about 1 to 2 m, complete curing can be achieved even at a high speed of 500 m/min. In addition, if there is no insulation cylinder, 500
At a high speed of m/min, curing becomes insufficient.

FIG. 4 shows that the length 1 is obtained using the apparatus shown in FIG.
FIG. 3 is a graph showing the relationship between the Young's modulus of the secondary coating of the fiber manufactured by changing the heating temperature of the heating cylinder of 20 m and the heating temperature. The resin used for the coating in this example has a Young's modulus of approximately 45 kg/mm 2 when fully cured. From FIG. 4, it can be seen that by increasing the heating temperature, complete curing can be achieved even at a high speed of 700 m/min. In addition, if heating is not performed, curing will be insufficient at a high speed of 700 m/min.

As described above, by providing means for preventing cooling of the fiber and keeping the resin at a high temperature for a certain period of time after irradiation with ultraviolet rays, curing is promoted. Although the detailed mechanism of this is not yet clear, it is presumed that the curing reaction of UV-curable resins continues for a certain period of time depending on the temperature.

According to the conventional method of manufacturing an optical fiber, the optical fiber is run in a room temperature atmosphere immediately after being irradiated with ultraviolet rays, so that it is rapidly cooled down. In contrast, according to the method of the present invention,
Since rapid cooling of the fiber can be prevented, the curing reaction of the resin can be continued to some extent, and the manufacturing speed can be increased.

[0013]

EXAMPLES Example 1 Using a wire drawing apparatus configured as shown in FIG. 1, the maximum wire speed at which the coating resin could be completely cured was determined. As the coating resin, an ultraviolet curable urethane acrylate resin was used for both the first layer and the second layer. For a fiber diameter of 125 μm, the coating diameter of the first layer is 20 μm.
The thickness of the second layer is 0 μm, and the thickness of the second layer is 250 μm. The heat insulating tube uses glass fiber as a heat insulating material and has a length of 1.0 m and an inner diameter of 20 mm. The coating resin was completely cured at a maximum linear speed of 420 m/min (Example 1).

Note that under the same conditions as Example 1 except for the absence of the heat insulating tube, the maximum linear speed at which the coating resin is completely cured is 30
It was 0 m/min (Comparative Example 1).

Example 2 A coated fiber having the same structure as in Example 1 was manufactured using the apparatus shown in FIG. 2, with a heating cylinder having a length of 75 cm and using a nichrome wire heating method. The maximum linear speed at which the coating resin can be completely cured is 650 m/min when the heating cylinder is heated to 250°C.
(Example 2). On the other hand, under the same conditions as Example 2 except for the absence of the heating cylinder, the maximum linear speed was 550 m.
/min (Comparative Example 2).

[0016]

As explained above, according to the present invention, after the embodiment coated on the outer periphery of the fiber is irradiated with ultraviolet rays,
Because the fiber passes through at least a certain section of the cooling prevention means, the curing reaction can be continued without the temperature of the coating resin suddenly decreasing, so the resin can be cured with improved efficiency. . Therefore, even if the wire speed is increased, the coating resin is completely cured, and the production speed of optical fibers can be easily increased.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing a specific example of the present invention in which a heat insulating tube is used as a cooling prevention means.

FIG. 2 is a schematic explanatory diagram showing another specific example of the present invention in which a heating tube is used as a cooling prevention means.

FIG. 3 is a graph showing the change in the Young's modulus of the primary coating resin and the length of the insulation tube provided after the primary coating coating resin layer is irradiated with ultraviolet rays in the method of the present invention; the horizontal axis is the insulation tube length (m);
, the vertical axis is Young's modulus (kg/mm2).

FIG. 4 is a graph showing the change in the Young's modulus of the secondary coating resin and the temperature of the heating cylinder provided after the coating resin layer for secondary coating is irradiated with ultraviolet rays in the method of the present invention, the horizontal axis is the heating cylinder temperature (°C)
, the vertical axis is Young's modulus (kg/mm2).

FIG. 5 is a schematic explanatory diagram showing a conventional optical fiber manufacturing method.

[Explanation of symbols]

1 Optical fiber base material 2　Drawing furnace 3 Optical fiber 4 Resin coating equipment 5 Ultraviolet irradiation lamp 6 Cylindrical body 7 Resin coated optical fiber 8 Winder 9 Ultraviolet irradiation device 10 Reflector 11 Insulation cylinder 12 Heating device

Claims (4)

[Claims] 1. A method for manufacturing an optical fiber in which an ultraviolet curable resin is applied to the surface of the optical fiber and then irradiated with ultraviolet rays to cure the resin and form a coating, the method comprising means for preventing cooling of the optical fiber after irradiation with ultraviolet rays. A method of manufacturing an optical fiber, characterized by passing it through a certain section. 2. The method for manufacturing an optical fiber according to claim 1, wherein the optical fiber is passed through a section having cooling prevention means at least once during the plurality of UV irradiations. [Claim 3]
3. The method for manufacturing an optical fiber according to claim 1, wherein the cooling prevention means is heating by an external heat source. 4. The method of manufacturing an optical fiber according to claim 1, wherein the cooling prevention means is a means for reducing heat radiation of the optical fiber.