JPH0995818A - Optical fiber and method and apparatus for manufacturing the same - Google Patents

Abstract

(57) [Summary] [Objective] When a sea-island type optical fiber having a plurality of wing materials is manufactured by a conventional spinning method, the wing materials are fused without adhering the sea part polymer sufficiently between adjacent wing materials. As a result, it may not be possible to manufacture a predetermined optical fiber. The present invention provides an optical fiber manufacturing apparatus that does not have this drawback. [Structure] A bottom plate of a spinning head 24 is provided with a plurality of tubular bodies 26 for reliably supplying a sea part fluid to the sea part between adjacent blade materials.
Connected to 25. According to the conventional method, the polymer is not sufficiently supplied and the wing materials located on both sides are likely to be fused to each other.The wing materials of the optical fibers are different from each other in the space between the wing materials according to the device of the present invention. It is reliably supplied and is not fused, and optical fibers having predetermined optical characteristics are spun.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a highly functional optical fiber by a melt spinning method, and more particularly to a sea-island type highly functional optical fiber composed of two or more kinds of fibers in a predetermined shape. The present invention relates to a method and a device for sure spinning.

[0002]

2. Description of the Related Art Conventionally, due to the tendency of users to become more likable and upscale, there has been a demand for a graceful and high-quality coloring structure which changes color depending on the viewing direction and has a color tone with higher saturation. This purpose is not achieved by dyes such as dyes and pigments alone, but is achieved by a structure that develops color by reflection, interference, diffraction or scattering of light, or by a combination of these with the dye or pigment, resulting in a deeper and more vivid image. A structure that develops color is under intense research and development. For example, a pearlescent composite fiber composed of two or more kinds of resins having different optical refractive indices (Japanese Patent Publication No. 43-14185, JP-A-1-139803).
(Patent Publication No.), a coloring material by forming a sandwich structure of a molecular orientation anisotropic film with a polarizing film (Journal of the Textile Machinery Society, Vol. 42, No. 2, page 55, No. 10, page 160, 1989).
), A coloring structure utilizing the coloring of a South American morpho butterfly, which is famous for changing the color tone depending on the viewing direction and having a vivid color effect (Japanese Patent Laid-Open No. 59-228042, Japanese Patent Publication No. 60-2484).
No. 7, Japanese Patent Publication No. 63-64535), and a structure which emits an interference color by providing a slit having a constant width on the fiber surface (Japanese Patent Laid-Open Nos. 62-170510 and 63-120642). Etc. have been proposed.

However, these coloring structures are difficult to control for obtaining a predetermined function, and a spinneret suitable for spinning a composite fiber having a complicated shape cannot be obtained. Had various problems. Therefore, the applicant of the present invention has proposed an optical fiber that is vivid and changes its color tone depending on the viewing direction, and has a reflective interference action that does not change over time (Japanese Patent Laid-Open No. 6-17349). This optical fiber has a sea-island type cross-sectional shape shown in Fig. 1 (a),
The island portion 3 in which a total of 10 pairs of blade materials 2 are provided in series on both sides of the core material 1 extending in the vertical direction in the figure, and the gap between the adjacent blade materials 2 of the island portion 3 and the island portion 3 It consists of the sea part 4 that fills the surrounding area. By making the optical refractive index of the material forming the island portion and the sea portion of this sea-island optical fiber different and satisfying the conditions of light reflection and interference, it is possible to provide an optical fiber in which the color is vivid and the tint changes depending on the viewing direction. . Also, as shown in FIG. 1 (b), this optical fiber is usually used as a fiber only for the island portion by dissolving the whole sea portion with a solvent.

In order to exhibit the optical function of this optical fiber, it is necessary to secure the above-mentioned shape and dimension, but the optical fiber is usually made of a wing material having a size of about 0.01 to 0.1 μm. And adjacent wing material 2
It is the most important point in the process from the melting of the polymer to the fiberization that the gap between them is surely separated and maintained in a predetermined shape. However, there has been a drawback that when the melted polymer is spun, the gap between the adjacent blade materials 2 is narrow and they are fused. In order to solve this drawback, the present applicants have proposed a spinneret for producing an optical fiber shown in FIGS.
-28519 and Japanese Patent Application No. 7-28521). 2 is a perspective view from below of an optical fiber manufacturing die in which the lower funnel-shaped spinning port is omitted, FIG. 3 (a) is a longitudinal sectional view including the lower spinning port, and FIG. 3 (b) is It is CC sectional view taken on the line of FIG.

In the spinning die 5 shown in the figure, a bottom plate 9 of a doughnut-shaped spinning head 8 having a bottom, which has a polymer introducing port 6 for islands and a polymer introducing port 7 for seas, is provided on the optical fiber of FIG. 1 (a). An uneven island flow path control partition 10 is formed so as to surround a space corresponding to the island 3, and a spinning pedestal 12 having a funnel-shaped spinning port 11 in the center is installed below the head 8. Has been done. As shown by the arrow in FIG. 3, the sea part polymer is introduced from the sea part polymer introduction port 7 into the space around the island part flow path control partition wall 10, and the island part flow passage control is performed from the island part polymer introduction port 6. When the island polymer is introduced into the partition wall 10, the island polymer is molded into a shape corresponding to the shape of the inner wall of the partition wall 10 corresponding to the island portion 3 of the optical fiber in FIG. On the other hand, the polymer for sea area around the island flow path controlling partition wall 10 is formed into a shape corresponding to the sea area 4 of the optical fiber of FIG. 1 (a) which is aligned with the outer wall of the partition wall 10. The two polymers are integrated in the descending inside of the spinning port 11 by bringing the matching surfaces into contact with each other and integrating them into a sea-island type optical fiber as shown in FIG. 1 (a).

[0006]

Problems to be Solved by the Invention In this spinning method, the marine portion polymer introduced through the marine portion polymer inlet 7 is shown in FIG.
When it is introduced into the gap between the adjacent outwardly projecting island-portion flow path control partition walls, the sea-part polymer has sufficiently entered between the adjacent blade materials 2 shown in Fig. 1 (a), and spinning is performed in that state. Then, the adjacent wing materials 2 are spun into a predetermined shape without being fused to each other, and the optical fiber having the above-described characteristics is manufactured. However, this optical fiber has a very fine size, and thus the gap between the adjacent blades 2 is smaller. For example, in order to obtain a wavelength of 0.47 μm (which means the peak wavelength in the reflection spectrum) that produces blue color, the thickness of the blade plate is 0.08 μm (the optical refractive index n of the constituent materials is 1.56, as will be described later in detail).
The distance is about 0.12 μm (with the optical refractive index n of the constituent material being 1.0 for air), and the number of blades must be at least 8 to generate sufficient reflection interference of light. . In order to accurately obtain such a minute dimension, the sea polymer supplied from the sea member introduction port 7 of FIG. 3 sufficiently enters into the space between the island polymer wings to form the wing material. It is necessary to be able to separate each piece so that the dimensions can be accurately maintained. For that purpose, the height of the partition wall that separates the blade material from the blade material should be long enough to allow the sea polymer to enter sufficiently. It is necessary to make the dimension of the direction. However, if the dimensions of the island flow paths that make up the blade material are reduced, the width and spacing of this blade material will become narrower, and even with high-precision machining technologies such as laser machining and electrical discharge machining, existing machining techniques will produce high height products. It was difficult to do so, and I had no choice but to lower the height.

The optical fibers spun in this manner often do not have desired optical characteristics because the adjacent blades 2 are likely to come into contact with each other and are easily fused to each other, which is a major impediment to the practical use of the optical fibers. Has become. The present invention has the problems of these prior arts, that is, it is difficult to increase the height of the partition walls with high accuracy even by precision machining to obtain such fine dimensions. It is an object of the present invention to provide a manufacturing apparatus for optical fibers having predetermined optical characteristics, by preventing the blade materials from being fused with each other.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a plurality of sea-portion forming tubular bodies having upper and lower openings on the bottom surface are arranged at regular intervals, and the inner thickness or inner diameter of the tubular body and the tubular bodies are separated from each other. Interval ratio is 3
A sea part fluid and an island part are provided in the cylindrical body and the polymer flow path of the spinning head in which the polymer flow path for the island part is formed around the cylindrical body so as to be in the range of 0: 1 to 1:30. A method for producing an optical fiber, which comprises supplying each of the polymers for use and spinning through a funnel-shaped spinneret of a spinning pedestal located below the tubular body, and an apparatus usable for the method. As described above, in the apparatus of the present invention, the height of the partition wall can be made thin and the height of the partition wall can be satisfied as desired by installing the tubular body in the spinneret.

Hereinafter, the present invention will be described in detail. In the method for producing an optical fiber of the present invention, when a tubular body having a rectangular or oval cross section is used as the tubular body for forming a sea part, an optical fiber as shown in FIG. 4 is obtained. The optical fiber of FIG. 1 (b) is manufactured by dissolving this optical fiber in the sea portion with a solvent. In the optical fiber shown in FIG. 4, a total of 20 rectangular portions are formed. In this specification, this portion is called a sea portion 14 in accordance with FIGS. 1 (a) and 1 (b), and an island located between adjacent sea portions 14 is formed. Part 15
This part is particularly called a wing material 16. This optical fiber strongly exerts an optical function when the ratio of the thickness of the sea portion 14 to the thickness of the blade member 16 is in the range of 30: 1 to 1:30. More specifically, using the reflection interference condition, when the ratio of the optical thickness of the sea part to the optical thickness of the blade material is in the range of 1: 5 to 5: 1, the optical function is strongly exerted, and the ratio is 1: When it is 1 (so-called quarter wavelength), the optical function is maximized. Here, "optical thickness" means Kaifu,
It is defined by “geometrical thickness (usually simply referred to as“ thickness ”) × optical refractive index” of each blade.

In the optical fiber of FIG. 4, the sea portion 14 may be left as it is. Normally, as shown in FIG. 4, by dissolving the sea part 14 with a solvent, only the island part is left and the sea part is used as an air layer,
The target optical fiber can be obtained. Generally, as a condition for color development, it is necessary that the refractive index of the island material and the refractive index of the sea material are different, and if desired, it is preferable that at least the refractive index ratio of both is 1: 1.1 or more.
However, it may be difficult to obtain a large optical refractive index between the polymers forming the fiber. However, if one is a polymer material (for example PET) and the other is an air layer, the ratio of the optical refractive indices of both is 1.56: 1, which is a very large value, so high reflectance can be obtained even with a small number of blades. It is important to use a gas for one side, such that the obtained color is very bright. In the present invention, the sea portion gas can be supplied to the sea portion forming tubular body instead of the conventional sea portion polymer, and spinning can be performed while supplying the island portion polymer to the periphery thereof, whereby the sea portion 14 is formed. The hollow optical fiber shown by the solid line in FIG. 4 is obtained. Therefore, in the present invention, the sea portion fluid, that is, the sea portion polymer or sea portion gas is supplied to the sea portion forming tubular body.

When the island portion is made of polymer and the sea portion is made to be an air layer or other gas layer by using the apparatus shown in FIGS. 2 and 3, the wing material and the wing material are joined and integrated at the stage of entering the inlet. However, the island portion having a plurality of desired wing materials 16 cannot be formed. On the contrary, when the island part is an air layer and the sea part is a polymer, the introduction flow path that constitutes this air layer has a structure in which the wing material is connected throughout, so it leads from the introduction port to the discharge hole and is spun from the discharge hole. By the time the gas is removed, the shape of the gas changes from the initial shape due to the ambient pressure (polymer discharge pressure), and the target shape cannot be exhibited. On the other hand, in the device of the present invention, the fluid for the sea portion, which corresponds to the sea portion polymer that fills the space between the blades 2 in the optical fiber of FIG. 1, is guided by the tubular body connected to the spinning head. The entire amount of the fluid for the sea portion that has been reached surely reaches the spinneret inlet. In other words, since the marine fluid reaches the spinneret through a single path, unlike the apparatus shown in FIGS. 2 and 3, the optics having predetermined optical characteristics are always filled or separated between the adjacent blades with the marine fluid. Fibers can be produced.

The cross-sectional shape of the tubular body is not limited to a rectangular shape or an oval shape, and in order to obtain an optical fiber having a cross-sectional shape other than that shown in FIG. Further, for example, it may have an overlapping portion having a layered shape such as an elliptical cross section. In order to obtain a specific optical fiber, it is desirable that adjacent sea parts be formed in parallel rectangular shapes or oval shapes, and if the cylindrical body has a circular cross-sectional shape, predetermined optical characteristics cannot be obtained. However, when the optical fiber whose sea portion is circular is compressed from the direction perpendicular to the cross section, the circle is deformed and becomes an ellipse, and an optical fiber having good optical characteristics is obtained. In this case, it is necessary that there be islands around the sea,
It cannot be applied to the conventional optical fiber shown by the dotted line in FIG.
The cross section of the sea part forming tubular body does not have to have the same diameter along the flow of the sea part fluid, and may be tapered, for example. The material of this tubular body is not particularly limited,
It can be composed of any material that is resistant to the sea fluid and island polymer used and does not adversely affect both polymers or fluids.

The sea part polymer and the island part polymer which compose the optical fiber spun by the device of the present invention are required to have different optical characteristics, especially optical refractive index, and polyolefins such as polyethylene and polypropylene, polyethylene terephthalate, In addition to polyesters such as polytetramethylene terephthalate, polystyrene, polycarbonate, polyfluorinated ethylene, polyacetal, polyphenylene sulfide, and the like can be used, and copolymers thereof may be used. As the sea gas, any gas that does not react with the island polymer and does not corrode the tubular body, such as nitrogen gas, can be used.

Next, an example of the optical fiber manufacturing apparatus according to the present invention will be described in detail with reference to the accompanying drawings. 5 to 9 show an example of an optical fiber manufacturing apparatus according to the present invention.
Is a vertical sectional view thereof, FIG. 6 is a vertical sectional view taken along the line AA of FIG.
5 is a vertical sectional view taken along line BB of FIG. 5, FIG. 8 is a sectional view taken along line CC of FIG. 5, and FIG. 9 is a partially cutaway perspective view.

In the illustrated optical fiber manufacturing apparatus 21, a doughnut-shaped spinning head 24 having a bottom and having a relatively large diameter fluid inlet 22 for the sea portion and a plurality of polymer inlets 23 for the islands in the peripheral portion is provided in the center. On the bottom plate 25, a total of 30 sea-part forming tubular bodies 26 corresponding to the sea part 14 in FIG. Below the head 24 and the tubular body 26, a funnel-shaped spinneret 27 is formed in the central portion corresponding to the lower side of the tubular body 26.
The spinning pedestal 28 having the above is installed. When the sea part polymer and the island part polymer are respectively supplied from the sea part fluid introduction port 22 and the island part polymer introduction port 23 of the optical fiber manufacturing apparatus configured as described above, the sea part polymer is the bottom surface of the head 24. 25 to the above-mentioned sea part forming tubular body 26
On the other hand, the polymer for islands is introduced from the outlet of the polymer inlet 23 for islands to the bottom plate 25 of the head 24 and the pedestal 28.
The space between the adjacent cylindrical bodies 26 and the space around the cylindrical bodies 26 are filled by entering into the space formed by the top plate.

Both polymers supplied to the inside and outside of the tubular body 26 are integrated below the tubular body, and are spun down while descending through the funnel-shaped spinning port 27 to be taken out as optical fibers. In the optical fiber spun in this way, the polymer for the sea portion surely reaches the inlet of the spinneret 27 by the tubular body 26 and is then spun, so that the sea portion 14 adjoins the island portion 15 as shown in FIG. The blade members 16 to be separated are reliably separated from each other, and the adjacent blade members 16 are not fused to each other, have predetermined optical characteristics, and the optical characteristics of the obtained optical fiber are not impaired.

When the sea portion gas and the island portion polymer are supplied to the sea portion fluid inlet port 22 and the island portion polymer inlet port 23, respectively, the sea portion gas is supplied from the bottom surface 25 of the head 24 to the sea portion forming cylinder. The polymer for islands enters the body 26, while the polymer for islands is supplied from the outlet of the polymer inlet 23 for islands to the head.
It enters into the space formed by the bottom plate 25 of 24 and the top plate of the pedestal 28. Next, during the spinning of the island polymer while descending through the spinneret 27, gas is always present between the adjacent blade materials 16 to prevent contact between both blade materials 16, so that the sea portion 14 becomes hollow. The optical fiber shown in is obtained.

Next, examples relating to the production of optical fibers using the apparatus of the present invention will be described, but the examples do not limit the present invention.

Example 1 Optical fibers were produced using the spinning device shown in FIGS. The dimensions of the stainless steel tubular body shown in FIG. 8 are a = 0.3 mm, b = 0.6 mm, the thicknesses are each 0.05 mm, and the straight length of the entire introduction channel is 8 mm, and 6 mm from the spinneret to the outflow side. It was made to project from the pedestal at the height of. There were 30 tubular bodies in total, and 15 tubular bodies were arranged in parallel in two rows, each of which had a pitch interval of 0.6 mm. As a result, the width ratio of the opening of the tubular body forming the sea portion and the dimension ratio of the interval between the parallel tubular bodies forming the island portion became 1: 1.5.
On the other hand, the size of the inlet of the funnel-shaped spinneret 27 shown in FIG.
= 1.6 mm, j = 9.9 mm, q = 0.2 mm, r = 0.9 mm, the length of the straight part is 5 mm, and the funnel-shaped spinning port 27 has a discharge hole size of 0.2 mm x 0.2 mm and is straight. Length 0.
It was set to 5 mm. As the extrusion device for spinning, the device having the specifications shown in Table 1 was used.

[0019]

[Table 1]

The polymer used was polyethylene terephthalate (PET) as the island polymer and polystyrene (PS) as the sea polymer, and the spinning temperature was 270-290.
℃, the number of rotations of the gear pump is 14 rpm for sea-part polymers, 1.5-3 rpm for island-part polymers, winding speed 5000 m /
Spinning was done in minutes. As a result, the outer dimensions of the spun fiber are 3.3 μm in the direction in which the sea layer is arranged in 15 rows, the thickness of the wing material is 0.08 μm, and the distance between the wing material and the wing material is 0.12 μm. A fiber with optical function could be obtained.

[0021]

Example 2 The spinning device shown in FIGS. 10 and 11 was used as the spinning device. FIG. 10 is a vertical sectional view thereof, and FIG. 11 is BB of FIG.
FIG. This spinning device is similar to the spinning device shown in FIG. 5, and differs from the spinning device shown in FIG. 5 only in that the periphery of the tubular body 26 does not contact the peripheral portion of the upper end of the spinneret 27 and a gap is formed. The other members are given the same reference numerals as those in FIG. 5 and their explanations are omitted. The shape of the opening of the tubular body was the same as in Example 1, and the inlet dimensions of the funnel-shaped spinneret 27 were k = 2.6 mm, l = 9.9 mm, m = 0.2 mm, and n = 3 mm, as shown in FIG. The other parts had the same dimensions as in Example 1. The spinning conditions were the same as in Example 1 except that air was sent in place of the sea part polymer. The outer dimensions of the fibers were 4.0 mm in the direction in which the air layers were arranged in 15 rows, and the thickness of the wing material was 0.08
A fiber having two rows in which the air layer was 0.12 μm in the gap between the blades and the blade material was obtained, and this fiber exhibited a good optical function.

[0022]

According to the present invention, the above-mentioned tubular shape of the spinning head in which a plurality of sea-portion forming tubular bodies having upper and lower openings are installed on the bottom surface and the polymer channels for islands are formed around the tubular body. A method for producing an optical fiber, characterized in that a fluid for sea and a polymer for island are respectively supplied to a body and a polymer channel, and spinning is performed by a funnel-shaped spinning port of a spinning pedestal located below the tubular body. (Claim 1)

In the method of the present invention, the fluid for the sea portion, which is filled between the adjacent blade materials of the island portion or separates the blade materials, is guided by the tubular body to reach the inlet of the spinneret and can pass through another path. Absent. Therefore, the sea fluid is reliably supplied to a predetermined position, that is, the space between the adjacent blades, and is present in the space during the spinning process to block the space. When the fluid for the sea part is a polymer, both supplied polymers pass through two kinds of paths, and the ratio of the polymers passing through both paths causes a large amount of the polymer to be filled between the blade materials, thereby obtaining an optical fiber. Unlike conventional devices that adversely affect the optical characteristics of
Since all of the supplied sea area polymer is reliably guided to the tubular body and used for forming the sea area, optical characteristics without fusion of adjacent wing materials without devoting attention to the determination of the supply route. An excellent optical fiber can be obtained.

On the other hand, when the sea portion fluid is gas (claim 2), the tubular portion is formed in the space between the adjacent wing materials when the island portion polymer is spun into optical fibers having a predetermined shape in the spinning step. Since the gas guided through the body is supplied, there is no contact between the adjacent blades in the spinning process,
Therefore, an optical fiber having a hollow sea part of a predetermined shape without fusion of both is provided. In this method, the number of steps is greatly reduced compared to the method of manufacturing an optical fiber in which the sea part is filled with the polymer by using the above-mentioned two kinds of polymers, and the sea part is melted. The desired optical fibers can be produced advantageously.

In order to obtain an optical fiber having a predetermined optical characteristic, it is necessary that the sea portion is layered, in other words, the square sea portion is generally located in parallel. An optical fiber having a rectangular or oval sea portion is obtained by making it rectangular or oval (claim 3),
Even if the shape of the sea part is elliptical, almost the same optical characteristics are exhibited. The final shape of the sea part of the optical fiber must be such as a square, but the sea part forming tubular body has a circular cross section, and the sea part with the obtained circular cross section is compressed and transformed into an oval sea part. You may make it (Claim 4). The optical fiber according to the present invention is produced by the method described in any one of claims 1 to 4 (claim 5), and the optical fiber has excellent optical characteristics as described above.

In the device of the present invention, a plurality of sea part forming tubular bodies having upper and lower openings are installed on the bottom surface, a sea part fluid inlet for supplying a sea part fluid to the tubular body, and the tubular body. A spinning head having an island polymer inlet for supplying the island polymer to the space between and around the tubular body, and at least the island polymer located below the tubular body is spun. An optical fiber manufacturing apparatus (Claim 6) comprising a spinning pedestal having a funnel-shaped spinning port. The optical fiber produced by this apparatus also has desired optical characteristics as described above.

[Brief description of drawings]

FIG. 1 (a) is a cross-sectional view of an optical fiber having a sea-island type cross-sectional shape that can be manufactured by a conventional technique and an apparatus of the present invention, and FIG. 1 (b) is a chamfered optical fiber of FIG. 1 (a). FIG.

FIG. 2 is a perspective view from below of an optical fiber manufacturing die proposed to solve the problems of the prior art.

3 (a) is a longitudinal sectional view of a spinning device using the spinneret of FIG. 2, and FIG. 3 (b) is a sectional view taken along line CC of FIG. 3 (a).

FIG. 4 is a diagram illustrating a cross section of an optical fiber obtained by the device of the present invention.

FIG. 5 is a cross-sectional view showing an example of an optical fiber manufacturing apparatus according to the present invention.

FIG. 6 is a vertical sectional view taken along line AA of FIG. 5;

7 is a vertical cross-sectional view taken along the line BB of FIG.

8 is a vertical cross-sectional view taken along the line CC of FIG.

9 is a partially cutaway perspective view of the device of FIG.

FIG. 10 is a cross-sectional view showing another example of the optical fiber manufacturing apparatus according to the present invention.

11 is a vertical cross-sectional view taken along the line BB of FIG.

[Explanation of symbols]

14 ・ ・ ・ Sea part 15 ・ ・ ・ Island part 16 ・ ・ ・ Wing material 21 ・ ・ ・
Optical fiber manufacturing equipment 22 ・ ・ ・ Fluid inlet for sea area 23 ・ ・
・ Polymer inlet for islands 24 ・ ・ ・ Spinning head 25 ・
..Bottom plate 26 ... Cylinder for forming sea part 27 ... Spinning port
28 ... Spindle for spinning

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kanaya Kumazawa, 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Hiroshi Tabata, 2 Takara-cho, Kanagawa, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (6)

[Claims] 1. A plurality of sea-portion forming tubular bodies having upper and lower openings on the bottom surface are arranged at regular intervals, and the ratio of the inner thickness or diameter of the tubular bodies to the spacing between the tubular bodies is 30: 1 to 1. The fluid for sea and the polymer for island are respectively supplied to the tubular body and the polymer channel of the spinning head in which the polymer channel for the island portion is formed around the tubular body in the range of 30 Then, the method for producing an optical fiber is characterized in that spinning is performed by a funnel-shaped spinning port of a spinning pedestal located below the tubular body. 2. The manufacturing method according to claim 1, wherein the sea-part flow path is gas. 3. The production method according to claim 1, wherein the sea part forming tubular body has a rectangular or oval cross section, and an optical fiber having a rectangular or oval sea part is obtained. 4. The production method according to claim 1, wherein the sea part forming tubular body has a circular cross section, and the sea part having a circular cross section obtained is compressed to obtain an optical fiber having an oval sea part. . 5. An optical fiber produced by the method according to any one of claims 1, 2, 3 and 4. 6. A plurality of sea-portion forming tubular bodies having upper and lower openings on the bottom surface are arranged at regular intervals, and the ratio of the inner thickness or diameter of the tubular bodies to the spacing between the tubular bodies is 30: 1 to 1. : A sea part fluid inlet for supplying a sea part fluid to the tubular body, and a space for the island part polymer in the space between the tubular bodies and around the tubular body. A spinning head having an island polymer introduction port for supplying, and a spinning pedestal located below the tubular body and having a funnel-shaped spinning port for spinning at least the island polymer. An optical fiber manufacturing apparatus characterized by: