JPH0781969A - Method for coloring coated optical fiber - Google Patents

Abstract

PURPOSE:To color a coated optical fiber with a high productivity and with the stripping reduced. CONSTITUTION:A coated optical fiber 2 with at least the outermost layer coated with a UV-curing resin is irradiated with UV in a UV irradiation device 14 before being coated with a coloring resin and then supplied to a coloring resin coating device 4. The UV-curing resin contg. a colorant is supplied to the coating device 4 through a coloring resin feed line 5. The coated optical fiber 8 coated with the UV-curing resin contg. a colorant by the coating device 4 is then irradiated with UV in a UV irradiation device 9 to form a colored coated optical fiber 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of coloring an optical fiber core wire.

[0002]

2. Description of the Related Art An optical fiber obtained by drawing an optical fiber by melting and heating a glass base material for the optical fiber is provided with a protective coating layer such as an ultraviolet curable resin or a thermosetting resin for the purpose of protecting the optical fiber. It becomes an optical fiber core wire. Usually, a plurality of these optical fiber core wires are assembled to form an optical fiber cable. When this optical fiber cable is connected to another optical fiber cable, an optical fiber connector, or the like, it is necessary that each optical fiber core be individually recognizable on its connecting surface.
Therefore, the outer periphery of the protective coating layer of the optical fiber core is coated with a coloring layer made of an ultraviolet curable resin or a thermosetting resin containing a colorant for identifying each optical fiber. .

The resin forming each of the above-mentioned coating layers has advantages and disadvantages, and is used properly according to the intended use. However, from the viewpoint of ease of processing and the like, at present, it is general to use an ultraviolet curable resin as the resin for forming the protective coating layer and the coloring layer of the optical fiber core wire.

Coloring of such an optical fiber is shown in FIG.
It was performed using the coloring device as shown in FIG. That is, the optical fiber core wire 2 wound around the bobbin 1 and having at least the outermost layer coated with the ultraviolet curable resin is supplied to the colored resin coating device 4 via the pulley 3. An ultraviolet curable resin containing a colorant is supplied to the colored resin coating device 4 from a colored resin tank 6 via a colored resin supply path 5. In addition, an inert gas supply path 7 is provided in the colored resin tank 6.
An inert gas such as N ₂ gas is supplied via the above, and the ultraviolet curing resin containing a coloring agent is supplied to the coloring resin coating device 4 by the gas pressure. In this way, the optical fiber core wire 8 coated with the ultraviolet curable resin containing the colorant by the colored resin coating device 4 is subsequently irradiated with ultraviolet light by the ultraviolet light irradiation device 9, and the colored optical fiber core wire 1
It becomes 0. And the manufactured colored optical fiber core wire 10
Is taken down by a capstan 11 and taken up by a dancer 12 on a take-up bobbin 13 while adjusting the take-up speed of the colored optical fiber core wire 10.

[0005]

However, in the above-described conventional coloring method, the degree of fixation between the protective coating layer of the optical fiber core made of the ultraviolet curable resin and the colored layer of the ultraviolet curable resin containing the colorant is fixed. Since the colored layer was low, the colored layer was sometimes separated from the optical fiber core wire. This is a problem caused by insufficient transmission of the ultraviolet rays irradiated to cure the colored layer. It is presumed that when the irradiation amount of ultraviolet rays is insufficient, the ultraviolet rays do not sufficiently penetrate into the inside of the colored layer, and insufficient curing of the colored layer occurs near the interface between the colored layer and the protective coating layer.

A detailed description will be given below. The ultraviolet curable resin contains a photoinitiator that decomposes to generate radicals when absorbing ultraviolet light. The main component of the ultraviolet curable resin is an oligomer or monomer having a vinyl group. These contain one or more functional groups in one molecule and rapidly react with the radicals to cure. Therefore, since the curing of the UV curable resin is a radical chain reaction, the rate-determining step of the curing reaction is the decomposition of the photoinitiator. This ultraviolet ray
Irradiation is performed from the outside of the ultraviolet curable resin containing the colorant applied to the outer circumference of the optical fiber core. Since the ultraviolet curable resin is colored, it is difficult for the irradiated ultraviolet light to enter the inside of the ultraviolet curable resin. Specifically, as a colorant, a pigment for coloring, titanium white, or the like is added, which has lower ultraviolet light transmittance than an ordinary ultraviolet curable resin and is likely to cause insufficient curing.

Conventionally, it has not been easy to find an appropriate amount of UV irradiation. Therefore, in order to prevent the shortage of the ultraviolet ray irradiation amount, it is only possible to increase the number of lamps for ultraviolet ray irradiation to enlarge the ultraviolet ray irradiation device or increase the ultraviolet ray irradiation time so that the ultraviolet ray is excessively irradiated. However, in the conventional method, the economical cost is too high and the productivity is lowered. Therefore, there has been an urgent need to develop a method for coloring an optical fiber core wire, which has good productivity.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for coloring an optical fiber core wire which has good productivity and does not cause the problem of peeling. The present invention is a method for coloring an optical fiber core wire, wherein the optical fiber core wire having an ultraviolet curable resin layer at least the outermost layer is further coated with an ultraviolet curable resin containing a colorant, wherein the colorant is applied to the optical fiber core wire. It is characterized in that it is irradiated with ultraviolet rays immediately before coating with an ultraviolet curable resin containing

[0009]

The ultraviolet-curing resin for the protective coating layer of the optical fiber core is required to have a high curing speed in order to improve the productivity of the optical fiber core. Initiator is added. Therefore, even when ultraviolet rays are irradiated to cure the protective coating layer when manufacturing the optical fiber core, a part of the excess photoinitiator remains unreacted inside the ultraviolet curable resin. . When the UV curable resin containing the unreacted photoinitiator is irradiated with UV light again, the remaining photoinitiator decomposes to generate radicals, but long-term activity is obtained if there are no unreacted functional groups in the vicinity. I found out to keep.

Therefore, when the optical fiber core wire having the ultraviolet curable resin layer as the outermost layer of the protective coating layer is irradiated with ultraviolet rays before being coated with the ultraviolet curable resin containing the colorant, the unexposed portion of the protective coating layer is not covered. It has been found that a radical is generated by the photoinitiator of the reaction, and this radical promotes the curing reaction. That is, it was found that the ultraviolet curing reaction also proceeds from the interface between the colored layer and the protective coating layer. As a result, the colored layer and the protective coating layer are strongly bonded by a chemical bond, and the problem of peeling is solved.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. In Example 1, an optical fiber core wire was colored using a coloring device as shown in FIG. That is, at least the outermost layer wound on the bobbin 1 is coated with the ultraviolet curable resin, and the optical fiber core wire 2 is guided by the ultraviolet irradiation device 14 via the pulley 3, where it is first irradiated with ultraviolet rays and then, And is supplied to the colored resin coating device 4. An ultraviolet curable resin containing a colorant is supplied to the colored resin coating device 4 from a colored resin tank 6 via a colored resin supply path 5. Further, an inert gas such as N ₂ gas is supplied to the colored resin tank 6 through an inert gas supply passage 7. The ultraviolet curable resin containing the colorant is supplied to the colored resin coating device 4 by the gas pressure of the inert gas. In this way, the optical fiber core wire 8 coated with the ultraviolet curable resin containing the colorant by the colored resin coating device 4 is subsequently irradiated with ultraviolet light by the ultraviolet light irradiation device 9, and the colored optical fiber core wire 1
It becomes 0. And the manufactured colored optical fiber core wire 10
Is taken down by the capstan 11 and taken up by the dancer 12 on the take-up bobbin 13 while adjusting the take-up speed of the colored optical fiber core wire 10.

Specifically, as the optical fiber core wire 2, an optical fiber coated with an ultraviolet curable resin and having an outer diameter of 240 μm was used, and the thickness of the colored layer was set to 5 μm. Further, the degree of peeling of the colored layer was determined by whether or not the colored optical fiber core wire 10 was lightly rubbed with a cloth to be peeled off.

As a second embodiment, as shown in FIG. 2, an optical fiber core wire is used by using a coloring device in which a connecting pipe 15 for connecting the ultraviolet irradiation device 14 and the colored resin coating device 4 is further provided in the device of the first embodiment. Ten colors were applied. The conditions relating to this coloring method and the judgment method and criteria relating to the degree of peeling of the colored layer were all the same as in Example 1.

A comparative example of the present invention will be described below. As a comparative example, the optical fiber core wire was colored using a coloring device as shown in FIG. As is clear from FIG.
In the comparative example, the colored optical fiber core wire 10 was manufactured without irradiating the optical fiber core wire 2 with ultraviolet light immediately before coating the ultraviolet curable resin containing the colorant. In addition, all other conditions relating to the method for coloring the optical fiber core wire and the determination method and criteria regarding the degree of peeling of the colored layer in the comparative examples were the same as in Example 1.

Table 1 below summarizes the relationship between the degree of peeling of the colored layer of the colored optical fiber core wires obtained in Examples 1 and 2 and the comparative example and the linear speed (take-off speed of the colored optical fiber core wire). It was In Table 1, x indicates that the colored layer was peeled off, and ○ indicates that the colored layer was not peeled off.

[0016]

[Table 1]

As shown in Table 1, the adhesion between the protective coating layer and the colored layer in Examples 1 and 2 in which the colored layer was irradiated with ultraviolet rays was compared with the comparative example in which the conventional method was used. The strength was good and peeling of the colored layer was difficult to occur. The reason for this is
As described above, it is considered that the photoinitiator remaining in the protective coating layer generated radicals by the ultraviolet rays irradiated before applying the coloring layer, which also cured the coloring layer from the inside. It is presumed that, as a result, the adhesion between the protective coating layer and the colored layer was increased.

[0018]

According to the present invention, there is provided a method for coloring an optical fiber core wire which has good productivity and less peeling problems.

[Brief description of drawings]

FIG. 1 is a coloring device for an optical fiber core wire used in a first embodiment.

FIG. 2 is a coloring device for an optical fiber core wire used in a second embodiment.

FIG. 3 is a coloring device for an optical fiber core wire used in a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bobbin 2 ... Optical fiber core wire 3 ... Pulley 4 ... Colored resin coating device 5 ... Colored resin supply path 6 ... Colored resin tank 7 ... Inert gas supply path 8 ... Colored resin-coated optical fiber core wire 9 ... UV irradiation device 10 ... Colored optical fiber core wire 11 ... Capstan 12 ... Dancer 13 ... Winding bobbin 14 ... UV irradiation device 15 ... Connection pipe

Claims (1)

[Claims] 1. A method for coloring an optical fiber core wire, wherein at least the outermost layer of the optical fiber core wire is further coated with an ultraviolet curable resin containing a colorant, wherein the optical fiber core wire is colored. A method for coloring an optical fiber core wire, which comprises irradiating an ultraviolet ray immediately before coating with an ultraviolet curable resin containing an agent.