JP5497539B2 - Plastic optical fiber manufacturing apparatus and plastic optical fiber manufacturing method - Google Patents

Description

  The present invention relates to a plastic optical fiber manufacturing apparatus and a plastic optical fiber manufacturing method.

  A plastic optical fiber (hereinafter referred to as “POF”) has a shorter transmission distance than a glass optical fiber, but is easy to handle and handle, is inexpensive and lightweight, and can be set to a large diameter. Has the advantage of Therefore, POF is used in various applications such as lighting, sensors, and communication. Furthermore, in addition to the above uses, it is also used for in-vehicle uses, and the production amount of POF tends to increase. As such a POF, a core-sheath POF in which a sheath having a lower refractive index than the core is formed concentrically around a core formed of polymethyl methacrylate (PMMA) or the like is widely used. It has been.

  By the way, when a daylighting system or the like is constructed using POF, a plurality of POFs are bundled and used for the purpose of increasing the amount of light to be captured. However, when a plurality of POFs having a circular cross section that are normally used are bundled, a gap is formed between the POFs, so that the light capturing efficiency is low. As a method for solving this problem, there is a method in which the cross-sectional shape of the POF is a regular hexagonal shape that can be closely packed.

  In Patent Document 1, in a spinneret that compositely spins a core component and a sheath component into a core-sheath structure, the core component supply port has a desired cross-sectional shape, and the sheath portion is removed from the spun composite fiber. A method for producing a fiber having the following cross-sectional shape is shown. According to this method, a fiber having a desired cross-sectional shape can be stably produced. However, this method is a method in which a circular sheath portion is temporarily formed around the core component in order to stably obtain a desired cross-sectional shape. Therefore, even if this method is applied, a POF having a core-sheath structure having a desired cross-sectional shape cannot be obtained.

  In Patent Document 2, as a method for producing a core-sheath structure POF having a desired cross-sectional shape, a core part having a desired cross-sectional shape is formed, and then a sheath material is supplied around the core, A method of forming a cross-sectional sheath is described. However, in this method, since the core portion and the sheath portion are sequentially formed, it is difficult to make the central axis of the core portion coincide with the central axis of the sheath portion and to make the thickness of the sheath portion uniform. In POF, when the axial displacement of the core portion and the sheath portion and the thickness unevenness of the sheath portion occur, light leaks from the side surface and transmission loss increases.

Japanese Patent Laid-Open No. 2-74667 JP 2007-94148 A

  The present invention relates to a POF manufacturing apparatus and manufacturing method capable of easily manufacturing a POF having a core-sheath structure having a desired cross-sectional shape while suppressing axial misalignment between the core and the sheath and uneven thickness of the sheath. The purpose is to provide.

The present invention employs the following configuration in order to solve the above problems.
[1] A plastic optical fiber manufacturing apparatus provided with a spinning means for compositely spinning a core material and a sheath material into a core-sheath structure, wherein the flow path cross section is circular in the resin flow path inside the spinning means, A core having a circular cross-sectional shape is supplied at the center thereof, a sheath material is supplied around the core material, and a composite portion in which the core material and the sheath material are combined into a concentric core-sheath structure, and a flow path cross section Is a non-circular shape combining straight lines and / or curves, and a cross-sectional shape imparting portion that imparts a non-circular cross-sectional shape to a composite molten resin having a circular cross-section compounded at the composite portion; and the composite portion; Provided between the cross-sectional shape imparting portions, the shape of the cross section of the flow path smoothly changes from the circular shape to the cross-sectional shape of the cross-sectional shape imparting portion so that the cross-sectional area gradually decreases from the composite portion side. And a tapered portion provided with a plastic. Apparatus for manufacturing a click optical fiber.
[2] The plastic optical fiber manufacturing apparatus according to [1], wherein the cross-sectional shape of the cross-sectional shape imparting portion is a regular hexagon.
[3] A plastic having a spinning process in which the core material and the sheath material are combined and spun into a core-sheath structure by the spinning means of the manufacturing apparatus using the plastic optical fiber manufacturing apparatus according to [1] or [2]. An optical fiber manufacturing method, comprising: forming a composite molten resin in which a core material and a sheath material having a circular cross-sectional shape are combined in a concentric core-sheath structure; A method for producing a plastic optical fiber, comprising: smoothly deforming from a circular shape so that the area gradually decreases, forming a non-circular cross-sectional shape, and spinning.

If the POF manufacturing apparatus of the present invention is used, a POF having a core-sheath structure having a desired cross-sectional shape can be easily manufactured while suppressing axial misalignment between the core and the sheath and uneven thickness of the sheath. .
Further, according to the POF manufacturing method of the present invention, a POF having a core-sheath structure having a desired cross-sectional shape can be easily controlled by suppressing axial misalignment between the core and the sheath and non-uniform thickness of the sheath. Can be manufactured.

It is the schematic diagram which showed an example of embodiment of the manufacturing apparatus of POF of this invention. It is the longitudinal cross-sectional view (A) which showed an example of embodiment of the spinning means in this invention, and the enlarged view (B) of the taper part 17. FIG. It is the top view which showed a mode that the nozzle 12 of the spinning means of FIG. 2 was seen from the upper surface. It is sectional drawing which showed an example of POF manufactured with the manufacturing apparatus of POF of this invention. It is the longitudinal cross-sectional view which showed other example embodiments of the spinning means in this invention.

[POF manufacturing equipment]
Hereinafter, an example of an embodiment of a POF manufacturing apparatus according to the present invention will be described in detail.
As shown in FIG. 1, a POF manufacturing apparatus 100 of the present embodiment (hereinafter simply referred to as “manufacturing apparatus 100”) includes a spinning means 1 for compositely spinning a core material and a sheath material into a core-sheath structure, and a molten state. A core material extruder 2 for extruding the core material, a metering pump 3 for controlling the flow rate of the core material supplied from the core material extruder 2 to the spinning means 1, a sheath material extruder 4 for extruding the molten sheath material, A metering pump 5 for controlling the flow rate of the sheath material supplied from the sheath material extruder 4 to the spinning means 1, a stretching means 6 for stretching the POF 20 spun by the spinning means 1, and a winding for winding the stretched POF 20 The take-off means 7 and the guide member 8 that regulates the travel of the POF 20 are provided.
The core material extruder 2 and the metering pump 3, the metering pump 3 and the spinning means 1, the sheath material extruder 4 and the metering pump 5, and the metering pump 5 and the spinning means 1 are each supplied with molten resin (core material and sheath material). Connected through a pipe.

The spinning means 1 comprises a first nozzle 11 and a second nozzle 12 as shown in FIG. The first nozzle 11 has a core flow path portion 13 through which the core material supplied from the core material extruder 2 circulates as a resin flow path through which the molten resin flows, and a sheath. A sheath material flow path portion 14 through which the sheath material supplied from the material extruder 4 flows is provided. The second nozzle 12 has a circular cross-sectional shape as a resin flow channel through which the molten resin flows, and a core material is supplied from the core material flow channel portion 13 to the center of the second nozzle 12, and a sheath around the core material. The sheath part is supplied from the material flow path part 14 and the composite part 15 in which they are combined into a concentric core-sheath structure, and the cross-sectional shape of the flow path is non-circular and the composite part 15 is combined. A cross-sectional shape imparting portion 16 for imparting a non-circular cross-sectional shape to the composite molten resin, and the composite section 15 and the cross-sectional shape imparting portion 16. A tapered portion 17 that changes to the cross-sectional shape of the cross-sectional shape imparting portion 16 so as to gradually decrease from the side is provided.
In the resin flow path of the spinning means 1, the central axes of the core material flow path portion 13, the composite portion 15, the taper portion 17, and the cross-sectional shape imparting portion 16 coincide.

  In the spinning means 1, the core material is supplied from the core material supply port 1 a to the core material flow channel portion 13, the sheath material is supplied from the sheath material supply port 1 b to the sheath material flow channel portion 14, and the composite material 15 supplies the core material. And the sheath material are combined in a concentric core-sheath structure, and the composite molten resin combined in the core-sheath structure is distributed through the tapered portion 17 and the cross-sectional shape imparting portion 16 to be shaped into a desired cross-sectional shape. , And discharged from the discharge port 1c.

As the material of the first nozzle 11 and the second nozzle 12, those normally used as a POF spinning nozzle can be used, and stainless steel (SUS) is preferable from the viewpoint of heat resistance, corrosion resistance, strength, and the like.
The cross-sectional shape of the core material flow path part 13 is circular.
What is necessary is just to select suitably the internal diameter of the core material flow-path part 13 according to the diameter of the core part of POF to manufacture, and 4-10 mm is preferable.
The cross-sectional shape and inner diameter of the sheath material flow path portion 14 are not particularly limited. The cross-sectional shape of the sheath material flow path portion 14 is preferably circular, and the inner diameter is preferably 1 to 3 mm.

The composite portion 15 is a portion that forms a composite molten resin having a circular cross section in which a core material and a sheath material are combined into a concentric core-sheath structure.
The cross-sectional shape of the composite part 15 is circular as shown in FIG. 3, and the center thereof coincides with the center of the core material flow path part 13. That is, a core material having a circular cross section is supplied from the core material flow path portion 13 to the central portion of the composite portion 15. Further, the sheath material flow path portion 14 and the composite portion 15 communicate with each other in the vicinity of the inner wall of the composite portion 15, and the sheath material is supplied around the core material in the composite portion 15.

  Since the cross-sectional shape of the composite part 15 is circular, the shape of the sheath material supplied around the core material passing through the center of the composite part 15 is also circular. Thus, in the composite section 15 having a circular cross-sectional shape, the form in which the sheath material is concentrically combined with the circular cross-section core material is a form in which the sheath material is combined with the non-circular cross-section core material. In comparison, pressure is uniformly applied to the core material and the sheath material. Therefore, in the composite molten resin in which the core material and the sheath material are composited in the core-sheath structure, it is suppressed that the center axis of the core material and the center axis of the sheath material are displaced and the thickness of the sheath material is uneven. The

In addition, as shown in FIGS. 2A and 3, the composite portion 15 preferably has a groove 15 a formed in an annular shape on the bottom surface. The center of the composite portion 15 coincides with the center of the circle of the groove 15a.
If the annular groove 15a is formed on the bottom surface of the composite part 15, the sheath material supplied from the sheath material flow path part 14 in the vicinity of one inner wall of the composite part 15 moves along the groove 15a. Easily reach the other side evenly. Thereby, it is easy to suppress a force applied to the core material passing through the composite portion 15 in the flow direction of the sheath material due to the flow of the sheath material from the sheath material flow path portion 14 side to the opposite side. Become. For this reason, in the composite molten resin, it is easy to suppress a shift between the central axis of the core material and the central axis of the sheath material, and unevenness in the thickness of the sheath material.
The position where the groove 15 a is formed may be a position where the sheath material is supplied in the composite portion 15, that is, a position closer to the center than the connection position of the sheath material flow path portion 14 and the composite portion 15.

  The cross-sectional shape imparting portion 16 is a portion that imparts a desired cross-sectional shape to the composite molten resin having a core-sheath structure having a circular cross-sectional shape combined by the composite portion 15. That is, by making the cross-sectional shape of the cross-sectional shape imparting section 16 the desired cross-sectional shape, the composite molten resin can be shaped and spun into the cross-sectional shape, and a POF having the desired cross-sectional shape can be obtained. It is done.

The cross-sectional shape of the cross-sectional shape imparting unit 16 is a non-circular shape combining straight lines and / or curved lines. Examples of the non-circular cross-sectional shape include a triangle, a quadrangle, a pentagon, a hexagon, an octagon, and the like. Preferably, the non-circular cross-sectional shape is a shape that can be closely packed, and position stability when a plurality of POFs are bundled From the viewpoint of properties, a regular hexagon is particularly preferable.
In this example, the cross-sectional shape of the cross-sectional shape imparting portion 16 is a regular hexagon. The core-sheath structure of the core part 21 and the sheath part 22 has a cross-sectional shape of a regular hexagon, as shown in FIG. Of POF20 is obtained. Further, if the cross-sectional shape of the cross-sectional shape imparting portion 16 is a pentagon, octagon, or triangle, the core has a pentagon, octagon, or triangle cross-section as shown in FIGS. 4 (B) to 4 (D). The POF 20 having a core-sheath structure of the portion 21 and the sheath portion 22 can be obtained.

The cross-sectional area S ₁ of the cross-section of the flow path of the cross-sectional shape imparting portion 16 is the cross-sectional area of the composite molten resin immediately after being combined with the core-sheath structure having a circular cross section at the composite portion 15, that is, on the composite portion 15 side in the tapered portion 17. smaller than the cross-sectional area _{S 2} of the open end 17a. The ratio (S ₁ / S ₂ ) between the cross-sectional area S ₁ and the cross-sectional area S ₂ is preferably 0.5 to 0.9. If the ratio (S ₁ / S ₂ ) is within the above range, in the obtained POF, it is easy to suppress the deviation of the central axis between the core part and the sheath part and the uneven thickness of the sheath part.

The taper portion 17 is a portion that deforms the cross-sectional shape of the composite molten resin having a circular cross-section in which the core material and the sheath material are combined into a concentric core-sheath structure in the composite portion 15 into the cross-sectional shape of the cross-sectional shape imparting portion 16. It is.
The tapered portion 17 is provided between the composite portion 15 and the cross-sectional shape imparting portion 16. The flow path cross section of the tapered portion 17 smoothly changes to the cross sectional shape of the cross sectional shape imparting portion 16 so that the cross sectional area gradually decreases from the composite portion 15 side. In this example, the tapered portion 17 has a conical shape such that the cross-sectional shape of the opening end portion 17a on the composite portion 15 side is the same circular shape as that of the core material flow path portion 13, and the cross-sectional area gradually decreases. However, the cross-sectional shape is a shape that smoothly changes to a regular hexagon.

Thus, by providing the taper part 17 between the composite part 15 and the cross-sectional shape provision part 16, it can suppress that a resin pool is formed between the composite part 15 and the cross-sectional shape provision part 16, and a core. It is possible to change the cross-sectional shape of the composite molten resin while suppressing the deviation of the central axis between the material and the sheath material and the occurrence of uneven thickness of the sheath material.
The inclination angle (taper angle) θ (FIG. 2B) of the inner wall of the tapered portion 17 is preferably 15 to 45 °. If the inclination angle θ is 15 ° or more, it is possible to suppress the overall length (axial length) of the tapered portion 17 from becoming too long, so that the core material and the sheath material are thermally deteriorated, increasing the POF transmission loss. It is easy to suppress. If the inclination angle θ is 45 ° or less, the change in the cross-sectional shape of the flow path becomes more gradual, so that the composite molten resin can be suppressed while suppressing the axial deviation of the core material and the sheath material and the uneven thickness of the sheath material. It becomes easy to shape the cross-sectional shape into a desired shape (the cross-sectional shape of the cross-sectional shape imparting portion 16). Therefore, in the obtained POF, it becomes easy to prevent the center axis of the core portion and the sheath portion from shifting to cause interface irregularity of the core-sheath structure or uneven sheath thickness. From the above concept, the inclination angle θ of the tapered portion 17 is more preferably 20 to 40 °, and further preferably 25 to 35 °.

The stretching means 6 performs a stretching process on the POF 20 spun by the spinning means 1. By subjecting the POF 20 to stretching, the mechanical strength of the POF 20 can be improved, or the diameter of the POF 20 can be adjusted to be constant.
The stretching means 6 only needs to be able to perform a stretching process on the POF 20, and it is preferable to use a heating type stretching furnace 61 as shown in FIG. In the stretching furnace 61, the POF 20 is stretched while being heated by heated gas or steam (steam) supplied into the furnace.
Before and after the drawing furnace 61, a drive-type feeding side drawing roll 62 and a take-up side drawing roll 63 are provided. The POF 20 is guided to the drawing furnace 61 by the feed-side drawing roll 62 and taken out from the drawing furnace 61 by the take-up drawing roll 63. At this time, by making the take-up speed of the take-side stretching roll 63 faster than the feed speed of the feed-side stretching roll 62, the stretching process can be performed smoothly.

  The winding means 7 only needs to be able to wind the POF 20 on a bobbin or the like. For example, in order to prevent deterioration of characteristics due to damage of the POF, the interval (pitch) between the POFs is narrowed so that no winding collapse occurs. And those which can be wound with a tension as low as possible (see JP-A-1-321259). As an apparatus for winding the POF 20 around the bobbin while controlling the tension, an apparatus having a configuration in which the tension of the POF is controlled by a tension roll, a torque motor or the like and the POF is wound while traversing the guide or the bobbin is preferable.

The guide member 8 regulates the travel of the POF 20 from the spinning means 1 to the drawing means 6 and the winding means 7 in the manufacturing apparatus 100. By providing the guide member 8, it is possible to suppress the drooping of the yarn, thereby preventing the POF 20 from being melted and contacted between the inside and outside of each means and in the vicinity of the entrance / exit.
As the guide member 8, those usually used for manufacturing POF can be used, and examples thereof include a metal or ceramic guide member.

  As described above, in the manufacturing apparatus 100, the sheath material is supplied around the core material supplied in a circular cross section in the composite section 15 having a circular cross section, and these are combined into a concentric core sheath structure. . Therefore, the core material and the sheath material can be stably combined into the core-sheath structure while suppressing the occurrence of axial misalignment between the core material and the sheath material and the occurrence of uneven thickness of the sheath material. Further, the cross-sectional shape of the composite molten resin having a circular cross-section is changed by the tapered portion 17, and a desired cross-sectional shape is provided by the cross-sectional shape providing portion 16. Therefore, the composite molten resin can be shaped into a desired cross-sectional shape while suppressing the occurrence of axial misalignment between the core material and the sheath material and the occurrence of unevenness in the thickness of the sheath material. Therefore, a high-quality POF having the desired cross-sectional shape can be easily obtained. Can be manufactured. Thus, if the manufacturing apparatus 100 is used, even if the POF has a cross-sectional shape capable of being densely packed, the axial displacement of the core portion and the sheath portion and the uneven thickness of the sheath portion are suppressed, and the side surface is suppressed. High-quality POF with low transmission loss and no leakage of light can be easily produced.

The POF manufacturing apparatus of the present invention is not limited to the manufacturing apparatus 100 described above. For example, the tapered portion only needs to be provided between the composite portion and the cross-sectional shape imparting portion, and the cross-sectional shape of the flow path is circular between the composite portion 15 and the tapered portion 17 as shown in FIG. Alternatively, the manufacturing apparatus may include a spinning unit 9 provided with a composite molten resin flow path portion 18 in which a composite molten resin having a circular cross-section flows.
Moreover, the manufacturing apparatus provided with the cooling means which cools POF20 immediately after spinning may be sufficient. Moreover, the manufacturing apparatus in which the extending | stretching means is not provided may be sufficient.

[Production method of POF]
Next, the manufacturing method of POF of this invention is demonstrated. The method for producing POF of the present invention is a method having a spinning step of compositely spinning a core material and a sheath material into a core-sheath structure, wherein the core material and the sheath material are combined into a concentric core-sheath structure Then, the cross-sectional shape of the composite molten resin is deformed so that its cross-sectional area gradually decreases, and is shaped into a non-circular cross-sectional shape and spun. Hereinafter, as an example of the POF manufacturing method of the present invention, a POF manufacturing method using the above-described manufacturing apparatus 100 will be described.

The POF manufacturing method using the manufacturing apparatus 100 includes a spinning process in which the core material and the sheath material are combined and spun into a core-sheath structure having a desired cross-sectional shape by the spinning means 1, and the drawn POF 20 is drawn by the drawing means 6. A stretching step for performing the treatment, and a winding step for winding the stretched POF 20 by the winding means 7.
As the core material and the sheath material, those usually used for POF can be used. Examples of the core material include acrylic resins such as polymethyl methacrylate (PMMA). Examples of the sheath material include a fluororesin composition such as a vinylidene fluoride polymer.

  In the spinning step, the core raw material resin is melted by the core material extruder 2 and extruded as a core material, and the metering pump 3 is used to feed the core material flow path of the spinning means 1 from the core material supply port 1a at a constant flow rate. To the unit 13. Similarly, a resin as a sheath material is melted by a sheath material extruder 4 and extruded as a sheath material, and a sheath material flow passage section of the spinning means 1 is fed from the sheath material supply port 1b at a constant flow rate using a metering pump 5. 14.

  In the composite part 15 of the spinning means 1, a core material having a circular cross section is supplied from the core material flow path part 13 so as to pass through the center of the composite part 15, and a sheath material is supplied around the core material. A composite molten resin is formed in which the sheath material is composited into a concentric core-sheath structure. Thereafter, the composite molten resin having a circular cross-section is deformed into a non-circular desired cross-sectional shape (in this example, a regular hexagon) by the cross-sectional shape imparting portion 16 at the tapered portion 17, and the discharge port Spinned from 1c.

  As described above, in the POF manufacturing method using the manufacturing apparatus 100, in the spinning process, after the core material and the sheath material once form a composite molten resin having a concentric core-sheath structure and a composite cross-sectional circular shape, A circular cross-sectional shape is deformed so that its cross-sectional area gradually decreases, and is shaped into a non-circular cross-sectional shape and spun. Thereby, the axial deviation of a core part and a sheath part and the nonuniformity of the thickness of a sheath part are suppressed.

In the stretching process, the stretching means 6 performs a stretching process on the spun POF 20.
The heating temperature of the POF 20 in the stretching furnace 61 is preferably Tgc-30 ° C. or higher and Tgc or lower. Here, Tgc is the glass transition temperature of the core material. The stretching treatment can be performed by a method of stretching while blowing a heated gas or steam heated to a temperature in the above range.
In the winding process, the winding means 7 winds the POF 20 that has been subjected to the stretching process. The winding can be performed using a bobbin or the like.

  According to the manufacturing method of the present invention described above, a POF having a desired cross-sectional shape is spun while suppressing the shift of the central axis between the core and the sheath and the uneven thickness of the sheath by the spinning process. it can. Therefore, even a POF having various cross-sectional shapes such as a cross-sectional shape that can be densely packed can easily manufacture a high-quality POF with no light leakage from the side surface and low transmission loss.

  The manufacturing method of the present invention is not limited to the method using the manufacturing apparatus 100, and may be a method using a POF manufacturing apparatus including the spinning means 9. Further, a method in which a cooling step for cooling the POF immediately after spinning may be provided between the spinning step and the drawing step, or a method in which no drawing means is provided may be used.

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following description.
The POF obtained in this example was evaluated by the following method.
[Measurement of maximum vertex distance]
The hexagonal maximum vertex distance in the cross-sectional shape of the obtained POF was measured using a digital microscope (VH-7000, lens magnification: 70 to 100 times) manufactured by Keyence Corporation.

[Measurement of transmission loss]
The transmission loss (dB / km) of POF was measured by the cut-back method of 25m-5m. The measurement wavelength was 650 nm and the excitation NA was 0.1.

[Evaluation of light leakage]
Light leakage from the side surface of the obtained POF was visually evaluated.

[Example 1]
Polymethyl methacrylate was used as the core material, and vinylidene fluoride / tetrafluoroethylene copolymer (mixing ratio = 80/20 (mol%)) was used as the sheath material. By using the manufacturing apparatus 100 provided with the spinning means 1 illustrated in FIG. 2 (the cross-sectional shape of the cross-sectional shape imparting portion 16 is a regular hexagon), a POF having a regular hexagonal cross-sectional shape and a maximum vertex distance of about 3 mm is obtained. The book was manufactured. The spinning means 1 has an inner diameter of the core material flow path portion 13 of 8 mm, an inner diameter of the sheath material flow path portion 14 of 1.6 mm, an inner diameter of the composite portion 15 of 8 mm, an inclination angle θ of the taper portion 17 of 30 °, and a cross-sectional shape. The maximum inter-vertex distance in the regular hexagon of the flow path cross section of the applying portion 16 was 7 mm.

[Example 2]
In the same manner as in Example 1, three POFs having a regular hexagonal cross-sectional shape and a maximum vertex distance of about 1.5 mm were manufactured.

[Example 3]
In the same manner as in Example 1, three POFs having a regular hexagonal cross-sectional shape and a maximum vertex distance of about 0.75 mm were manufactured.
Table 1 shows the results of measuring the maximum vertex distance and transmission loss of each POF in Examples 1 to 3 and evaluating the light leakage from the side surfaces.

As shown in Table 1, in Example 1 using the manufacturing apparatus 100 provided with the spinning means 1 of the present invention, the maximum distance between the apexes of the hexagonal cross sections of the three obtained POFs was 2949 μm, 2987 μm, A POF having a regular hexagonal cross-sectional shape equivalent to 2968 μm could be stably produced. Similarly, in Examples 2 and 3, three POFs having the same maximum hexagonal distance between hexagonal cross sections were obtained, and a POF having a desired regular hexagonal cross sectional shape could be stably produced.
In addition, the POFs obtained in Examples 1 to 3 had no light leakage from the side surfaces, the transmission loss was suppressed to a low level, and the axial deviation of the core part and the sheath part and the thickness unevenness of the sheath part were suppressed. .

DESCRIPTION OF SYMBOLS 1 Spinning means 11 1st nozzle 12 2nd nozzle 13 Core material flow path part 14 Sheath material flow path part 15 Composite part 16 Section shape provision part 17 Taper part 100 POF manufacturing apparatus

Claims (3)

A plastic optical fiber manufacturing apparatus provided with a spinning means for compositely spinning a core material and a sheath material into a core-sheath structure,
In the resin flow path inside the spinning means,
The flow channel has a circular cross section, and a core material having a circular cross section is supplied at the center thereof, a sheath material is supplied around the core material, and the core material and the sheath material are combined into a concentric core sheath structure. And the composite part
A cross-sectional shape imparting section for imparting a non-circular cross-sectional shape to a composite molten resin having a cross-sectional circular shape combined with the composite section, the flow path cross-section is a non-circular shape combining straight lines and / or curves, and
Provided between the composite portion and the cross-sectional shape imparting portion, the cross-sectional shape of the flow path is changed from a circular shape to a cross-sectional shape of the cross-sectional shape imparting portion so that the cross-sectional area gradually decreases from the composite portion side. And the taper part smoothly changing,
An apparatus for producing a plastic optical fiber, comprising:   The plastic optical fiber manufacturing apparatus according to claim 1, wherein a cross-sectional shape of the cross-sectional shape imparting portion is a regular hexagon. A method for producing a plastic optical fiber comprising a spinning step in which a core material and a sheath material are combined and spun into a core-sheath structure using the plastic optical fiber production apparatus according to claim 1 or 2 by a spinning means of the production apparatus. There,
After forming a composite molten resin in which a core material and a sheath material having a circular cross-sectional shape are combined into a concentric core-sheath structure, the cross-sectional shape of the composite molten resin is reduced so that the cross-sectional area gradually decreases. A method for producing a plastic optical fiber, wherein the plastic optical fiber is smoothly deformed from a shape, shaped into a noncircular cross-sectional shape, and spun.

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