JP2003267758A - Die for coating optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new die for coating an optical fiber with the reduced fluctuation of coating thickness even if used for a long period of time. <P>SOLUTION: In the die for coating the glass fiber which is provided with a drawing hole 4 through which a glass strand 1 passes and to which a coating resin is fed to form the coating around the glass strand 1, round-shape processing is carried out on the outlet edge part 7 of the drawing hole 4 in the radius of 10-30 μm in the perimeter direction. The abrasion phenomenon of the outlet edge part 7 of the drawing hole 4 can be prevented thereby, which makes the die practically free from the fluctuation of coating thickness even if used for a long period of time. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber coating die for forming a coating resin around a glass element wire while allowing the glass element wire to pass therethrough.

[0002]

2. Description of the Related Art In a conventional optical fiber, as shown in FIG. 4, one or two or more resin protective layers 2 are formed around a glass element wire 1 composed of a core and a clad. This effectively protects the glass strand 1 from external damage.

For example, as shown in FIG. 5, the resin protective layer 2 has a glass element wire 1 drawn by melt-spinning a preform, and a wire drawing hole 4 of a die 3 to which a coating resin is supplied. When it is passed through, the coating is formed around it with a uniform thickness.

That is, the drawing hole 4 formed in the die 3 has a tapered portion 5 narrowed in the traveling direction of the glass strand 1 so as to guide the coating resin supplied to the glass strand 1 side as shown in the figure. And a parallel portion 6 extending from the tip of the taper portion 5 in parallel with the glass element wire 1. After the coating resin flowing into the taper portion 5 reaches the surface of the glass element wire 1, the parallel portion 6 is formed. 6, the adhesion amount, that is, the coating thickness is squeezed so that the coating thickness becomes constant, and the glass element wire 1 and the discharge end portion 7 of the parallel portion 6 are pulled out so that the thickness is uniform around the glass element wire 1. The resin protective layer 2 is formed.

[0005]

By the way, the coating resin drawn out from the discharge end portion 7 of the parallel portion 6 together with the glass element wire 1 does not form the resin protective layer 2 in its entirety, and A part of it flows out to the ejection surface 8 side of the die 3 as it is and collects on the ejection surface 8 to form a meniscus portion 9 having a half-moon shape in cross section.

However, if the shape of the meniscus portion 9 is unstable, a part of the resin forming the meniscus portion 9 adheres to the surface of the glass element wire 1 again, whereby the coating thickness of the resin protective layer 2 is increased. Has a disadvantage that it fluctuates greatly.

Further, since a part of the resin drawn out together with the glass element wire 1 flows out from the discharge edge portion 7 toward the discharge surface 8 side, the discharge edge portion 7 is gradually worn,
As a result, the resin coating diameter of the glass strand 1 may fluctuate (become large).

Therefore, the present invention has been devised in order to effectively solve such a problem, and an object thereof is to provide a novel optical fiber coating die in which the coating diameter hardly changes even after long-term use. Is provided.

[0009]

In order to solve the above-mentioned problems, a first aspect of the present invention, as set forth in claim 1, has a drawing hole through which a glass element wire is passed, and the drawing wire is supplied to the drawing hole. A die for optical fiber coating, which is formed by coating the above-mentioned coating resin around the glass element wire, wherein the discharge edge portion of the drawing hole is rounded in the circumferential direction within a radius of 10 to 30 μm. Is.

That is, as described above, the discharge edge of the wire drawing hole gradually wears due to long-term use, which increases the flow rate of the resin and changes the resin coating thickness of the glass element wire. Therefore, in the present invention, the discharge edge portion of the wire drawing hole where this wear occurs is subjected to R processing in advance, so that the wear of that portion is suppressed, and the fluctuation of the coating diameter due to the change of the flow rate of the resin is effective. Can be reduced to Then, as will be described later, this R processing can exert the most excellent effect in the range of a radius of 10 to 30 μm.

A second aspect of the present invention is, as set forth in claim 2, in which a coating layer for repelling the coating resin is formed on the discharge surface of the drawing hole, whereby a clean meniscus shape is formed. It is possible to prevent the fluctuation of the coating diameter due to the resin in the meniscus portion flowing back to the glass wire side again.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment for carrying out the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of an optical fiber coating die (hereinafter abbreviated as die) according to the present invention.

As shown in the drawing, a drawing hole 4 is formed at a central portion of the die 10 so as to vertically penetrate therethrough, and a glass element wire 1 drawn from a preform (not shown) is passed vertically. However, a coating resin, for example, an ultraviolet curable resin or the like is formed on the periphery thereof with a constant coating thickness.

Further, the drawing hole 4 has a tapered portion 5 which is spread upstream (upward) of the drawing hole 4 and the tapered portion 5.
Of the parallel part 6 extending from the tip of the, and after guiding the coating resin to the glass element wire 1 side by the taper part 5,
The parallel portion 6 narrows the coating diameter so that it is constant.

Further, in forming the coating resin around the glass element wire 1 in this manner, as shown in the drawing, the meniscus portion 9 is formed on the discharge surface 8 of the die 10.
However, as described above, in the meniscus portion 9, a part of the resin drawn out along with the passage of the glass element wire 1 directly flows to the ejection surface 8 side of the die and collects in the form of water drops. And is formed in a semicircular cross section having a ring shape centered on the drawing hole 4.

And, in the die 10 of the present invention,
As shown in FIG. 2, since the discharge edge portion 7 of the drawing hole 4 is R-processed in the circumferential direction in a range of a radius of 10 to 30 μm, the variation of the coating thickness is extremely long-term use. It can be reduced and good drawing can be achieved.

That is, as described above, this drawing hole 4
If the discharge edge portion 7 is in an acute angle state with a radius of less than 10 μm, the discharge edge portion 7 gradually wears due to long-term use, the discharge amount of resin increases, and the coating diameter of the glass strand 1 becomes thick. However, by subjecting this portion to R processing in advance as in the present invention, the wear phenomenon is almost eliminated, so that the discharge amount is almost unchanged from the initial stage, and the variation of the coating diameter is effective. It is possible to solve it.

Here, the reason why the R processing is limited within the range of 10 to 30 μm in radius is that when the radius is less than 10 μm, the phenomenon of R spreading due to wear becomes remarkable, and conversely, the radius of 30
If it exceeds μm, the flow rate of the resin to the ejection surface 8 increases, the shape of the meniscus of the resin formed on the ejection surface becomes unstable, and the coating thickness easily changes.

Further, as shown in the figure, the present invention is further provided with a coating layer 11 for repelling the coating resin on the discharge surface 8, whereby the meniscus portion 9 is formed.
It is possible to further stabilize the shape of and to reduce the variation of the coating diameter. That is, if the ejection surface 8 and the coating resin are well-adapted to each other, the shape of the meniscus portion 9 becomes unstable, and the resin forming the meniscus portion 9 flows backward in the direction of the glass element wire 1 again to cause a variation in the coating diameter. This is because there is a risk.

The coating layer 11 is not particularly limited as long as it is a material that repels the coating resin, and for example, SiC, Si, TiC, Au or the like can be used.

[0022]

EXAMPLE As described above, several types of dies having the discharge edge 7 of the drawing hole 4 R-processed were used to draw the melt-spun glass element wire 1 at a drawing speed of 1500 m / min while UV-curing the periphery thereof. After coating the urethane type acrylate resin of the mold, the variation of the coating diameter and the surface condition after coating were examined, and the results are shown in Table 1 below.

Further, in the die used here, as shown in FIG. 3, the taper angle of the drawing hole 4 was 6 °, the length of the parallel portion was 1 mm, and the hole diameter of the parallel portion was 0.24 mm. On the other hand, R of the discharge edge portion was different from 5 μm, 20 μm and 35 μm. Further, as the material of the die, a super hard material was used, and the discharge surface 8 used was mirror-finished and then coated with silicone.

The basic structural design of the die is an experiment (AG) in which the influence of the critical shear rate of Ferrari and the inlet angle is measured.
Ferrari, Wire & Wire Prod., 39,7,1030 (1964)), the smaller the taper angle (half angle) is between 90 and 3 °, the higher the limiting shear rate, and Hammond taper angle and coating surface roughness. Experiment observing (LKR Hamm
Ond, Wire & Wire Prod., 35,725 (1964)) referred to the report result that the coating surface condition became smoother when the taper angle was made smaller. In addition, the length of the parallel portion is the result of an experiment (P.L.Clegg, Plast.Ins) for obtaining the effect of the land length of Clegg.
t.Trans & J., 28,12,245 (1960)).

[0025]

[Table 1]

As a result, as can be seen from Table 1, the surface roughness was smooth and good regardless of which die was used, but in the case of the die having R of 5 μm, the coating diameter was Is 198.6 μm at the maximum and 194.8 at the minimum
μm, the fluctuation range is 3.8 μm, and R is 35
Maximum coating diameter is 204.5μ for μm dies
m, the minimum is 201.0 μm, and the fluctuation range is 3.5
μm, which was a wide fluctuation range.

On the other hand, R, which is within the specified value of the present invention,
If the die is 20 μm, the maximum coating diameter is 19
The variation range was 8.8 μm, the minimum was 197.2 μm, and the variation range was 1.6 μm, and the variation range of the coating diameter was extremely small.

[0028]

In summary, according to the present invention, since the discharge edge portion of the drawing hole is R-processed in advance in the radius range of 10 to 30 μm, the discharge amount of the resin hardly changes even after long-term use, and the coating is performed. The fluctuation range of the diameter can be surely reduced. Further, since the coating layer that repels the coating resin is formed on the ejection surface, a stable meniscus shape can be obtained, and the fluctuation range of the coating diameter due to instability beyond the meniscus can be surely reduced. Therefore, it is possible to exhibit excellent effects such as reduction of coating defects and the like in the coloring step which is a post-step and extension of the life of the die itself.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a die according to the present invention.

FIG. 2 is a partially enlarged view showing a portion A in FIG.

FIG. 3 is an explanatory diagram showing a die used in this example.

FIG. 4 is an enlarged cross-sectional view showing the structure of a glass strand.

FIG. 5 is an explanatory view showing a conventional die and drawing state.

[Explanation of symbols]

1 glass strand 2 Resin coating layer 3 dice (conventional) 4 wire drawing hole 5 Tapered part 6 parallel part 7 Discharge edge 8 Discharge surface 9 Meniscus part 10 dice (invention) 11 coating layer

Claims (2)

[Claims] 1. A wire drawing hole for passing a glass element wire,
In an optical fiber coating die in which the coating resin supplied to the drawing hole is coated around the glass wire, the discharge edge of the drawing hole has a radius of 10 in the circumferential direction.
A die for coating an optical fiber, which is R-processed in a range of ˜30 μm. 2. The optical fiber coating die according to claim 1, wherein a coating layer that repels the coating resin is formed on a discharge surface of the drawing hole.