JPH08262285A - Optical fiber and its production - Google Patents

Abstract

PURPOSE: To prevent defefective coating of a secondary coating layer from occurring by forming a primary coating layer of a specified UV-curing resin (UV resin). CONSTITUTION: A UV resin for primary coating which is controlled to have 0.3wt.%/min volatilization rate at 100 deg.C is supplied to a first coater 5, while a UV resin for secondary coating is supplied to a second coater 7. An optical fiber preform 1 is fused by heating in a heating furnace 2 and drawn to obtain an optical fiber wire 3. Then the optical fiber core 3 is passed through the first coater 5 filled with the UV resin for primary coating so as to apply the resin on the fiber. Successively, after the UV resin for primary coating is cured in a curing device 6, the fiber is passed through the second coater 7 filled with the UV resin for secondary coating so as to apply the UV resin for the secondary coating on the primary coating layer. The UV resin for secondary coating is cured in a curing device 8 to obtain an optical fiber 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber element wire in which a primary coating layer and a secondary coating layer made of an ultraviolet curable resin are sequentially formed on the circumference of a bare optical fiber and a method for producing the same.

[0002]

2. Description of the Related Art An optical fiber element has a primary coating layer formed of, for example, an ultraviolet curable resin for protecting and strengthening a bare optical fiber. The primary coating layer is a primary coating layer and a secondary coating layer. Those formed of two layers are well known in the art. The primary coating layer is usually
The primary coating layer is made of a relatively soft resin and the secondary coating layer is made of a relatively hard resin in order to relieve the stress on the bare optical fiber and obtain an appropriate strength. It is also common practice to color the secondary coating layer.

Such a primary coating layer of bare optical fiber is usually formed in the process of drawing the optical fiber. In the drawing process of the optical fiber, in order to prevent the micro defects on the drawn glass surface from reacting with moisture in the air and becoming large,
This is because it is necessary to coat and protect the glass surface as quickly as possible. FIG. 1 shows an example of an apparatus for producing an optical fiber bare wire by forming a two-layer primary coating layer made of an ultraviolet curable resin (hereinafter referred to as UV resin) on a bare optical fiber in an optical fiber drawing process. It is the schematic block diagram which showed.
Reference numeral 1 in the figure indicates an optical fiber preform.

The optical fiber preform 1 is heated and melted in the heating furnace 2 and then drawn to form the bare optical fiber 3. The outer diameter of the bare optical fiber 3 is measured by the outer diameter measuring device 4, and the drawing conditions such as the drawing speed are controlled so that a constant outer diameter can be obtained.
The bare optical fiber 3 passes through the first coater 5 filled with the UV resin for the primary coating, so that the resin is coated on the circumference and the nipple 5a is formed to have a predetermined diameter.
Come out of. After this, a curing device 6 equipped with a UV lamp
The UV resin applied is cured while passing through the glass.

After the primary coating layer is formed in this manner, a second resin filled with a UV resin for secondary coating is formed.
By passing through the coater 7, the secondary coating UV resin is applied on the circumference of the primary coating layer and comes out from the nipple 7a having a predetermined diameter. And U
While passing through the curing device 8 equipped with the V lamp, the UV resin is cured to form the secondary coating layer, and the optical fiber strand 9 is obtained. The drawing of such an optical fiber is usually performed at a high speed of about 2 to 20 m / sec.

[0006]

However, the UV resin used for coating contains a monomer component, and this monomer component is generally highly volatile. The following inconveniences have occurred. That is, immediately after the primary coating UV resin on the bare optical fiber 3 is cured, it is considered that the surface of the primary coating layer has a relatively high temperature due to the irradiation heat of the UV lamp and the heat of polymerization of the UV resin. Therefore, when the primary coating layer is in a high temperature state, the secondary coating layer is formed on the circumference thereof. Therefore, when the secondary coating UV resin is applied on the periphery of the primary coating layer, a large amount of volatile gas is generated from the primary coating layer, and the coating of the secondary coating UV resin becomes unstable. As a result, there have been coating defects such as bubbles in the secondary coating layer or the inability to obtain a constant optical fiber diameter. Further, in the worst case, the resin may leak from the nipple 7a of the second coater 7 and a so-called "resin sag" may occur in which the coating layer cannot be formed. Since such a phenomenon becomes more severe as the production is performed at a higher speed, there is a problem that the production at a higher speed becomes difficult.

Further, in such an optical fiber element wire containing bubbles, when the jelly is filled around the optical fiber element wire and used as a jelly-filled type optical fiber cable, the jelly component is coated. Since the layer easily penetrates, there is a problem that the possibility of swelling of the coating layer and delamination between the bare optical fiber and the primary coating layer increases.

The present invention has been made in view of the above circumstances, and it is possible to prevent a defective coating when a primary coating layer is formed on the circumference of a bare optical fiber and a secondary coating layer is subsequently formed. An object of the present invention is to provide an optical fiber element wire and a method for manufacturing the optical fiber element wire.

[0009]

In order to solve the above problems, an optical fiber element wire of the present invention is an optical fiber element wire in which a primary coating layer and a secondary coating layer are formed on the circumference of a bare optical fiber. And the primary coating layer is
It is characterized in that an ultraviolet curable resin having a volatilization rate at 100 ° C. of 0.3 wt% / min or less is applied and cured. Further, in the method for producing an optical fiber bare wire of the present invention, an ultraviolet curable resin having a volatilization rate at 100 ° C. of 0.3 wt% / min or less is applied on the circumference of the bare optical fiber, and then this is cured. To form a primary coating layer, and subsequently to form a secondary coating layer on the periphery of the primary coating layer.

The present invention will be described in detail below. The optical fiber bare wire of the present invention is 100 ° C. on the circumference of the bare optical fiber.
The primary coating layer is formed by applying and curing a UV resin having a volatilization rate of 0.3 wt% / minute or less, and a secondary coating layer is formed on the periphery of the primary coating layer. The UV resin used for the primary coating layer may be any one of urethane acrylate, epoxy acrylate, silicon acrylate, ester acrylate, etc., which are generally used as coating materials for optical fibers. The type and composition of these UV resins are appropriately set depending on the application of the optical fiber strand. The volatilization rate of the UV resin used in the primary coating layer can be determined by appropriately selecting the type and content of the monomer component contained in the resin. However, if the content of the monomer component is too small, the viscosity of the resin becomes high and it becomes difficult to apply the resin on the circumference of the bare optical fiber, so the lower limit of the volatilization rate of the UV resin for primary coating is 0. It is preferably set to 01 wt% / min or more.

The UV resin used in the secondary coating layer is urethane acrylate, as in the primary coating layer,
Any of epoxy acrylate, silicon acrylate, ester acrylate, etc. can be used, and the type and composition thereof can be appropriately set depending on the use of the optical fiber element wire and the like. Further, the thickness and Young's modulus of the primary coating layer and the secondary coating layer can be appropriately set according to the application of the optical fiber element wire.

The optical fiber strand of the present invention can be manufactured by suitably using the manufacturing apparatus for the optical fiber strand shown in FIG. That is, the primary coating UV resin prepared to have a volatilization rate at 100 ° C. of 0.3 wt% / min or less is supplied to the first coater 5, and the secondary coating UV resin is supplied to the second coater 7. Then, the optical fiber preform 1 is heated and melted in the heating furnace 2 to draw the bare optical fiber 3. While measuring the outer diameter of the bare optical fiber 3 with the outer diameter measuring device 4, the drawing speed, the heating temperature, etc. are controlled so that the outer diameter of the bare optical fiber 3 becomes constant. The drawing speed is appropriately set depending on the composition of the glass forming the optical fiber, the temperature of the heating furnace 2, the curing speed of the UV resin used, and the like, but can be preferably set to, for example, about 5 to 20 m / sec. .

Then, the bare optical fiber 3 is passed through a first coater 5 filled with a UV resin for a primary coating, so that the resin is applied on the circumference thereof. here,
If the viscosity of the resin changes as a result of changing the composition of the UV resin for primary coating, the diameter of the nipple 5a of the first coater 5 and the structure of the resin container of the coater 5 should be changed as necessary. The outer diameter after primary coating can be adjusted to a predetermined value. Subsequently, the primary coating UV resin is cured by the curing device 6, and then passed through the second coater 7 filled with the secondary coating UV resin, so that the secondary coating UV resin is provided on the circumference of the primary coating layer. Apply. Then, the secondary coating UV resin is cured by the curing device 8 to obtain the optical fiber strand 9.

When the primary coating UV resin applied on the circumference of the bare optical fiber 3 is cured by the curing device 6, the surface of the primary coating layer is irradiated by the UV lamp and the heat of polymerization of the UV resin. Is over 100 ° C. In the method for producing an optical fiber bare wire of the present invention, a resin prepared so that the volatilization rate at 100 ° C. is 0.3 wt% / min or less is applied to the circumference of the bare optical fiber 3 and cured to form a primary coating layer. Therefore, after the primary coating layer is cured, when the secondary coating layer is formed on the circumference of the primary coating layer, generation of volatile gas from the primary coating layer is suppressed to a small amount. Therefore, the coating failure of the secondary coating layer due to the volatile gas generated from the primary coating layer can be prevented, and the secondary coating layer can be stably formed.

[0015]

EXAMPLE Optical fiber strands were manufactured using the manufacturing apparatus shown in FIG. The volatilization rate of the UV resin for primary coating was changed and the occurrence frequency of secondary coating defects was examined.
The outer diameter of the bare optical fiber is 125 μm, the outer diameter after the primary coating is 200 μm, and the outer diameter after the secondary coating is 250.
It was made to be μm. As the primary coating UV resin, a JSR-made urethane acrylate resin having a Young's modulus of about 0.1 kg / cm ² was used, and as the secondary coating UV resin, a JSR-made Young's modulus of about 70 kg / cm ² was used. . Further, the volatilization rate of the UV resin for primary coating was adjusted by replacing the monomer component having a low vapor pressure with that having a high vapor pressure.
The volatilization rate was measured by thermobalance analysis (TGA).
The amount of weight loss due to evaporation of volatile components when heated at 100 ° C. was measured for 30 minutes, and the evaporation rate per minute was calculated. In addition, the measurement of the occurrence of defective coating is performed under the same drawing conditions with a length of 1
Five optical fiber strands of 00 km were manufactured, and the coating diameter was abnormal.
The frequency of occurrence was defined as the number of defective coatings such as rough skin and resin sag.

(Experimental Example 1) The volatilization rate of the UV resin for primary coating was 0.2, 0.3, 0.4, 0.5, 0.6.
The occurrence frequency of the secondary coating failure when changing to (wt% / min) was examined. The drawing speed was 10 m / sec. The result is shown by a solid line in FIG. From this result, it was confirmed that the secondary coating failure did not occur when the volatilization rate was 0.3 wt% / min or less.

(Experimental Example 2) The relationship between the evaporation rate of the UV resin for the primary coating and the occurrence frequency of the secondary coating failure was examined in the same manner by setting the drawing speed in Experimental Example 1 to 15 m / sec which is 1.5 times. It was The result is shown by a broken line in FIG. From this result, it was confirmed that even when the drawing speed was increased, the secondary coating failure did not occur when the volatilization speed was 0.3 wt% / min or less.

[0018]

As described above, according to the present invention, the primary coating layer of the optical fiber element wire is formed by using the UV resin having the volatilization rate at 100 ° C. of 0.3 wt% / min or less. When forming the secondary coating layer on the circumference of the primary coating layer, the volatile gas generated from the primary coating layer can be suppressed. Therefore, it is possible to prevent the coating failure from occurring in the secondary coating layer due to the gas generation from the primary coating layer, so that it is possible to manufacture an optical fiber element wire having a stable property with high yield and at high speed. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an optical fiber bare wire manufacturing apparatus.

FIG. 2 is a graph showing the relationship between the volatilization rate of the primary coating resin and the frequency of occurrence of coating defects in the secondary coating layer.

[Explanation of symbols]

3 ... Bare optical fiber, 5 ... First coater, 6 ... Curing device, 7 ... Second coater, 8 ... Curing device, 9 ... Optical fiber bare wire.

Claims (2)

[Claims] 1. An optical fiber element wire having a primary coating layer and a secondary coating layer formed on the circumference of a bare optical fiber, wherein the primary coating layer has a volatilization rate of 0.3 wt% / 100 ° C. An optical fiber element wire, which is obtained by applying and curing an ultraviolet curable resin of not more than a minute. 2. An ultraviolet curable resin having a volatilization rate at 100 ° C. of 0.3 wt% / min or less is applied on the circumference of a bare optical fiber, and then cured to form a primary coating layer, A method for manufacturing an optical fiber elemental wire, characterized in that a secondary coating layer is subsequently formed on the periphery of the primary coating layer.