JP4217363B2 - Plastic optical fiber, plastic optical fiber cable, and manufacturing method of plastic optical fiber cable with plug - Google Patents

Description

【００５７】
【発明の効果】
以上の説明から明らかなように本発明によれば、耐熱性および力学的強度に優れたＰＯＦ、ＰＯＦケーブル、プラグ付きＰＯＦケーブルを生産性よく製造することができる。
【図面の簡単な説明】
【図１】本発明で用いられる製造装置の概略図である。
【図２】芯材のＴｇ付近のＤＳＣ曲線の模式図である。
【図３】実施例および比較例における熱処理時間に対する熱収縮率を示したグラフである。
【図４】熱処理時の荷重が熱収縮率に及ぼす影響を説明するためのグラフである。
【図５】本発明の製造方法において、張力がかからない状態で熱処理するために、ＰＯＦを円筒形状の容器のなかに振り込む様子を示した図である。
【符号の説明】
１、２ ニップローラー
３ 加熱炉
４ プラスチック光ファイバ
５ ＳＵＳ製容器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plastic optical fiber excellent in heat resistance, a plastic optical fiber cable, and a method for manufacturing a plastic optical fiber cable with a plug.
[0002]
[Prior art]
Conventionally, as an optical fiber, an inorganic glass-based optical fiber capable of performing excellent light transmission over a wide wavelength region is known and put to practical use mainly in a trunk line system, but this optical fiber is expensive and processed. There is a disadvantage that the nature is bad. For this reason, plastic optical fibers having advantages such as lower cost, larger diameter, end face processing, and easy handling have been developed. For example, in the fields of lighting, sensors, wiring between OA and FA devices for communication, etc. It has been put into practical use.
[0003]
In general, a plastic optical fiber (hereinafter referred to as “POF”) is made of a polymer having a high refractive index and excellent light transmittance, such as polymethyl methacrylate, polycarbonate, polystyrene, or amorphous polyolefin. It is made of a fiber having a core-sheath structure in which a transparent polymer having a smaller refractive index and a transparent polymer is used as a sheath material.
[0004]
As an industrial manufacturing process of such a POF, a core polymer and a sheath polymer are generally arranged concentrically using a composite spinning nozzle, melt-spun and shaped into a fiber, and then mechanically A stretching process under heating is performed for the purpose of improving the strength.
[0005]
Among the POF core materials, polymethyl methacrylate is excellent in transparency, weather resistance, and mechanical strength, and is used on an industrial scale as a core material for high-performance POF.
[0006]
However, the glass transition temperature (hereinafter referred to as “Tg”) of polymethyl methacrylate is not sufficiently high at about 112 ° C. (DSC method, heating rate: 10 ° C./min), and heat resistance is required. It is difficult to apply to applications.
[0007]
For this reason, for example, Japanese Patent Application Laid-Open No. 58-18608 proposes to form a structure of three or more layers in which a protective layer is further provided around the sheath material to enhance heat resistance. Even if the heat resistance of the resulting material is improved, there is a disadvantage that the core material itself causes thermal shrinkage when the use temperature reaches the vicinity of Tg of the core material. This thermal shrinkage phenomenon causes a significant increase in coupling loss with these elements even when the POF is used for coupling with a light source or a photoelectric conversion element at the end thereof even if the shrinkage is slight.
[0008]
Japanese Patent Laid-Open No. 4-16905 discloses a method for improving transmission loss by heat-treating at 60 to 100 ° C. for a long time in a POF using polycarbonate as a core material. The heat resistance of the POF is not improved because the heat treatment time is shorter than the Tg by 50 ° C. or more.
[0009]
[Problems to be solved by the invention]
For the purpose of improving various properties such as heat resistance of POF, for example, JP-A-62-131206, JP-A-63-303304, JP-A-2-68503, JP-A-5-11128, JP-A-5-11128 In JP-A-6-201270, JP-A-62-299912, etc., by performing in-line non-contact heat treatment after the stretching process, the orientation of the polymer chain in the POF axial direction imparted in the stretching process is maintained as much as possible. A method for suppressing shrinkage at high temperatures has been proposed.
[0010]
However, with this method, the removal of strain is insufficient, and the heat resistance cannot be sufficiently improved. Also, if the temperature of the non-contact heating furnace is increased to remove strain, the orientation of the polymer chain cannot be maintained, leading to a decrease in the mechanical strength of the POF or an increase in the POF diameter spot. There was a problem.
[0011]
Thus, the POF manufactured by the conventional method can sufficiently suppress the occurrence of heat shrinkage when used for optical communication and sensors in a high temperature environment such as an engine room of a car or a car in midsummer. However, the optical transmission characteristics deteriorated due to heat shrinkage, wiring troubles occurred in the connector portion, etc., making it difficult to apply to fields requiring heat resistance.
[0012]
On the other hand, in Japanese Patent Laid-Open No. 6-347650, for the purpose of providing a POF having a small transmission loss and high heat resistance, the core part is a POF made of polycarbonate, and the polycarbonate of the core part is 10 ° C. / A POF characterized by a polycarbonate having an endothermic peak in a range of 100 ° C. or higher and 200 ° C. or lower when differential thermal analysis is performed at a rate of temperature increase of min, and an endothermic amount of 1.5 mJ / mg or higher. As a method for producing such a POF, a method for producing a POF characterized by heat-treating the core part for at least 8 hours at a temperature 10 ° C. or more lower than the Tg of the polycarbonate forming the core part is described. Yes. However, since this manufacturing method requires a heat treatment for 8 hours or more, there is a problem in productivity.
[0013]
Accordingly, an object of the present invention is to provide a method capable of manufacturing a POF, a POF cable having excellent heat resistance, and a POF cable with a plug with high productivity.
[0014]
[Means for Solving the Problems]
The present invention can et is by melt spinning, the heat drawn POF,
The present invention relates to a method for producing POF, characterized in that heat treatment is performed at a temperature of [Tg of core material (hereinafter referred to as “Tgc”) − 30] ° C. to Tgc ° C. in a state where tension due to heat shrinkage generated in the POF is not generated.
[0015]
Further, the present invention provides a POF obtained by melt spinning and heated and stretched,
After continuously passing through a heating device (core glass transition temperature -5) ° C. and above (core glass transition temperature +80) continuous heat treatment at a temperature of not more than 80 ° C. ,
The present invention relates to a method for producing POF, characterized in that heat treatment is performed again at a temperature of (Tgc-30) ° C. or higher and Tgc ° C. or lower in a state where tension due to thermal shrinkage generated in the POF is not generated.
[0016]
Furthermore, this invention relates to the manufacturing method of the POF cable which has the process of forming a coating layer in the outer peripheral part of POF obtained by the said manufacturing method.
[0017]
The present invention also relates to a method for manufacturing a plug-attached POF cable having a step of arranging a plug at the tip of at least one of the POF cables obtained by the above manufacturing method.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described.
[0019]
In the POF production method, a stretching operation is generally performed in order to improve mechanical strength. However, although the molecules are oriented by the POF stretching and the mechanical strength is improved, the residual stress different from this orientation, that is, the residual strain, is frozen. Therefore, as the POF is heated to near the temperature near Tgc, the frozen residual strain is released and the POF contracts greatly.
[0020]
Therefore, heat treatment is performed to remove the residual strain and prevent thermal shrinkage. In order to remove the residual strain without impairing the mechanical strength imparted while maintaining the molecular orientation by stretching, it is effective to perform a heat treatment of POF in the vicinity of Tgc. At this time, if the heat treatment temperature exceeds Tgc, not only the residual strain is removed, but also the orientation is relaxed, so that the mechanical strength is also impaired. On the other hand, in the case of Tgc or less, the relaxation of molecular orientation is suppressed, but the lower the heat treatment temperature, the longer the time for the residual strain to be relaxed. In order to reduce the shrinkage rate, a heat treatment time of several hours to several tens of hours is required.
[0021]
As described above, since the heat treatment at Tgc or less takes a long time, in order to shorten the heat treatment time, it is conceivable to perform the heat treatment in a batch heat treatment, for example, in a substantially constant length state wound around a bobbin. . However, in this method, a new strain is generated due to the shrinkage stress caused by the heat treatment, and as a result, it takes a long time to remove the residual strain.
[0022]
FIG. 4 shows the measurement results of the thermal shrinkage rate of POF that was heat-treated with different loads. POF uses a polymethyl methacrylate homopolymer obtained by continuous bulk polymerization as a core material, and a copolymer of vinylidene fluoride and tetrafluoroethylene (copolymerization ratio: 80/20 mol%) as a sheath material. -What has a sheath structure was used. The heat treatment was performed at a heat treatment temperature of 110 ° C., different loads (0, 981 mN (100 gf), 1961 mN (200 gf)), and different heat treatment times (0, 30 seconds, 60 seconds). The heat shrinkage was measured by heating at 90 ° C. for 65 hours by the method described later. From this figure, it can be seen that the thermal contraction rate can be reduced as the POF is heat-treated with a small load.
[0023]
In the POF manufacturing method of the present invention, the batch heat treatment at Tgc or less is performed in a state where no tension is generated in the POF, so that the residual heat is compared with the heat treatment in a substantially constant length state such as bobbin winding. The time required for strain removal can be shortened, and the heat shrinkage rate can be sufficiently reduced in a short time, so that productivity can be improved.
[0024]
In the present invention, in order to perform heat treatment in a state where no tension is generated in POF, for example, POF that has been heat-drawn after melt spinning, or POF that has been heat-drawn and continuously heat-treated after melt spinning, is placed in a box or the like. Move the POF into a rounded-out state by swinging it in as it is, or put the POF once wound up on the bobbin into the box, etc. There is a method of bringing it into the atmosphere and performing heat treatment at a predetermined temperature for a predetermined time.
[0025]
A known method such as a dry hot air method, a vacuum heating method, or a wet heat heating method can be used for the heat treatment performed in a state where no POF tension is generated.
[0026]
The heat treatment temperature in this heat treatment is appropriately selected according to the Tgc of the POF to be treated, and is in the range of (Tgc-30) ° C. to Tgc ° C., preferably (Tgc-15) ° C. to Tgc ° C. For example, when the core material is polymethyl methacrylate (methyl methacrylate homopolymer), it is preferably 85 ° C. or higher and Tgc ° C. or lower, and more preferably 100 ° C. or higher and Tgc ° C. or lower. When the heat treatment temperature exceeds Tgc ° C., the mechanical strength imparted by stretching decreases. On the other hand, if the heat treatment temperature is lower than (Tgc-30) ° C., it takes a long time until the desired heat resistance is obtained, or sufficient heat resistance cannot be obtained.
[0027]
The heat treatment time cannot be generally specified depending on the physical properties of the core material, the heat treatment temperature, etc., but is preferably 15 seconds or longer and 5 hours or shorter, more preferably 20 seconds or longer and 2 hours or shorter. If the heat treatment time is too short, the effect of improving the heat resistance may be insufficient, and if the heat treatment time is too long, the mechanical strength imparted by stretching may be reduced.
[0028]
In the production method of the present invention, the heat-stretched POF can be subjected to a heat treatment in a state in which no tension is generated in the POF after a continuous heat treatment. In this case, the continuous heat treatment of POF can be performed by winding the heated and stretched POF around a bobbin once and performing the continuous heat treatment again, and winding the heat-stretched POF around a bobbin or the like. It is also possible to perform a continuous heat treatment as it is.
[0029]
The stretching ratio in the heat stretching, that is, when the POF is stretched by placing a roller for running the POF before and after the heating device, the ratio of the circumferential speeds of the front and rear rollers (rear roller circumferential speed / front roller circumferential speed) is 1. It is preferable to set it as 1-3.5, and it is more preferable to set it as 1.5-3.0. If the draw ratio is too small, the mechanical strength may not be sufficiently imparted by stretching, and if it is too large, uniform stretching may be difficult.
[0030]
In the continuous heat treatment of POF, the heat treatment temperature is preferably (Tgc-5) ° C. or more and (Tgc + 80) ° C. or less, more preferably (Tgc-5) ° C. or more and (Tgc + 60) ° C. or less, (Tgc -5) More preferably, the temperature is set to be equal to or higher than C and equal to or lower than (Tgc + 30) ° C., and particularly preferably equal to or higher than Tgc ° C. and equal to or lower than (Tgc + 15) ° C. If the heat treatment temperature is too low, the effect of improving the heat resistance by the heat treatment is insufficient, and if the heat treatment temperature is too high, the orientation imparted by stretching is relaxed and the mechanical properties of the POF may be reduced.
[0031]
For continuous heat treatment of POF, a known method such as a hot air method, a wet heat heating method, or a hot water method can be used. This heat treatment is performed by a constant-length heat treatment (when a roller for running the POF is disposed before and after the heating device to heat the POF, the roller peripheral speed ratio is 1) or the relaxation heat treatment (the roller peripheral speed ratio is less than 1). be able to. When performing the relaxation heat treatment, the ratio of the peripheral speeds of the front and rear rollers (rear roller peripheral speed / front roller peripheral speed) is preferably 0.5 or more and 0.98 or less, and 0.7 or more and 0.95 or less. More preferably. If the peripheral speed ratio is too small, the orientation imparted by stretching is relaxed, and the mechanical properties of POF may be reduced.
[0032]
In general, Tg of a polymer compound is measured by DSC, and when a material is heated from a low temperature side at a constant rate, the specific heat (that is, heat capacity) of the material changes before and after Tg. Therefore, Tg can be determined by measuring the temperature at which the so-called baseline changes and changes as in the DSC curve schematically shown in FIG. Since the Tg measurement by DSC changes slightly depending on the heating rate, in the present invention, the temperature rising rate is set to 10 ° C./min.
[0033]
The heat resistance test was performed by measuring the heat shrinkage rate as follows. The POF was previously marked with a predetermined length interval as a measuring section, and this POF was suspended in a dry heat dryer set at 90 ° C. At this time, the POF measurement unit should not come into contact with the wall or shelf of the dry heat dryer body. After heating for a predetermined time, this POF was taken out, the length of the measurement part was measured, and the thermal contraction rate was obtained.
[0034]
The thermal shrinkage rate, which is an index of heat resistance in the present invention, is the shrinkage rate in the longitudinal direction of POF, and is obtained by the following equation. The smaller the shrinkage rate, the more excellent the heat resistance.
[0035]
Thermal contraction rate (%) = [(L ₀ −L ₁ ) / L ₀ ] × 100
Here, L ₀ is the initial length of POF, and L ₁ is the length after heating POF at 90 ° C. for a predetermined time.
[0036]
In the POF manufacturing method of the present invention, the heat treatment conditions (conditions of each heat treatment when performing multiple heat treatments) are set so that the heat shrinkage rate after heating POF at 90 ° C. for 65 hours is 0.6% or less. It is desirable to set. According to the present invention, the heat shrinkage ratio of POF after heating at 90 ° C. for 65 hours can be reduced to 0.6% or less by a relatively short heat treatment.
[0037]
In the present invention, as the POF core material, an amorphous transparent polymer is suitable. For example, a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate and other monomers (methacrylic acid). Methyl copolymer) is preferred. Further, methacrylic acid esters such as cyclohexyl methacrylate, t-butyl methacrylate, isobornyl methacrylate, adamantyl methacrylate, benzyl methacrylate, phenyl methacrylate, naphthyl methacrylate, and other monomers copolymerizable with these monomers Copolymer, polycarbonate, polystyrene, styrene-methacrylic acid ester copolymer, or deuterated polymers in which all or part of the hydrogen atoms of these polymers are substituted with deuterium atoms can be used. Of course, other transparent polymers and transparent blends can also be used.
[0038]
As the methyl methacrylate copolymer, the total monomer amount of the raw material is 100% by mass, methyl methacrylate 70% by mass or more, and other monomers copolymerizable with methyl methacrylate 30% by mass or less. A copolymer obtained by polymerization is preferred. Examples of other monomers copolymerizable with methyl methacrylate include methacrylic acid esters such as cyclohexyl methacrylate, isobornyl methacrylate, benzyl methacrylate, phenyl methacrylate, and 2,2,2-trifluoroethyl methacrylate. , Monomers such as acrylic acid esters such as methyl acrylate and ethyl acrylate, and maleimide compounds such as N-cyclohexylmaleimide and N-isopropylmaleimide for the purpose of improving heat resistance.
[0039]
The method for producing the core material is not particularly limited and can be produced by a known polymerization method. However, it is preferable to employ a continuous bulk polymerization method or a continuous solution polymerization method from the viewpoint of mixing of foreign matters.
[0040]
A known material can be used as the sheath material. From the viewpoint of improving the handleability of POF during heat treatment and reducing POF diameter spots, those that do not enter a molten state at (Tgc + 10) ° C. or lower are preferable. In addition, a fluorine methacrylate homopolymer, a copolymer of a fluorine methacrylate and a methacrylic acid ester monomer, a vinylidene fluoride-tetrafluoroethylene copolymer in that a POF having good transmission characteristics can be obtained. It is preferable to use a copolymer having a vinylidene fluoride unit as a main component, an α-fluoromethacrylate resin, and a mixture thereof.
[0041]
In the present invention, a known POF structure is used, for example, a POF having a core-sheath two-layer structure, a graded index POF having a refractive index distribution in the core, a core, or Examples thereof include a POF having a structure in which a plurality of types of polymers are arranged in a core and a sheath in a multilayer shape, and a multi-core POF having a plurality of core / sheath structures in one fiber. It is also possible to coat the outer periphery of these POFs with a protective layer having functions such as solvent resistance and heat resistance. As the protective layer, a known material can be used, but a vinylidene fluoride-tetrafluoroethylene copolymer excellent in mechanical strength is preferably used.
[0042]
An optical fiber cable can be manufactured by using the POF described above and forming a coating layer on its outer periphery by a known method. As a material for the coating layer, conventionally used nylon 12, polyvinyl chloride, polychlorotrifluoroethylene copolymer, polyethylene, polyurethane, perprene and the like can be used.
[0043]
Moreover, it can use as an optical fiber cable with a plug by arrange | positioning a plug by the well-known method at the front-end | tip of the optical fiber cable manufactured as mentioned above. A well-known plug can be used as the plug.
[0044]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the evaluation method and manufacturing apparatus used in the Example are as follows. In the horizontal axis and the vertical axis in the figure, the direction of the tip of the arrow indicates a larger value.
[0045]
(Manufacturing equipment)
An example of the manufacturing apparatus used in the present invention is shown in FIG. In the figure, reference numerals 1 and 2 denote nip rollers, respectively, which have a function of feeding and taking out POF indicated by 4 at a constant speed. 3 is a heating furnace in which POF is heated by hot air or pressurized steam. The melt-spun unstretched POF is stretched between the roller 1 and the roller 2. The draw ratio is set by adjusting the peripheral speeds of the roller 1 and the roller 2.
[0046]
(Measurement of glass transition temperature)
DSC-220 manufactured by Seiko Instruments Inc. was used. The sample was heated to 200 ° C. at a heating rate of 10 ° C./min, held for 10 minutes and melted, then rapidly cooled to 20 ° C., and then heated again at a heating rate of 10 ° C./min. From the DSC curve showing the endothermic behavior and the straight line A obtained by extending the base line on the low temperature side to the high temperature side rather than the step-like change part of the glass transition as shown in FIG. 2, and the step-like change part of the glass transition The intersection point P of the tangent line B of the DSC curve at the point where the gradient of the DSC curve of the sample becomes the maximum was taken as the glass transition temperature (edited by the Japan Society for Thermal Measurement, “Basics and Applications of New Thermal Analysis” (1989), Realize Co., Ltd. Issue, see page 54).
[0047]
(Measurement of heat shrinkage)
Marks were placed on the POF at intervals of 50 cm as measurement parts, and this POF was placed in a dry heat dryer set at 90 ° C. At this time, the POF was suspended in the dryer so that the POF measurement part did not touch the surface of the inner member such as the wall or shelf of the dryer body. This is because when the POF comes into contact with the surface of an inner member such as a shelf or a wall surface, the environment such as temperature changes, and an accurate heat shrinkage rate cannot be obtained. After heating for 65 hours in a dryer set at 90 ° C., the product was allowed to cool to room temperature (10 ° C.), and the length of the measurement part was measured. The thermal shrinkage was calculated by the following formula.
[0048]
Thermal contraction rate (%) = {[50− (length of measurement part after heating)] / 50} × 100
[0049]
(Comparative Examples 1-9)
The core material is polymethyl methacrylate obtained by continuous bulk polymerization, and the sheath material is 51 parts by mass of 2,2,2-trifluoromethyl methacrylate and 1,1,2,2-tetrahydroperfluorodecyl methacrylate. 30 parts by mass, a copolymer obtained by copolymerizing 18 parts by mass of methyl methacrylate and 1 part by mass of methacrylic acid, and a copolymer of vinylidene fluoride and tetrafluoroethylene as a protective layer (copolymerization ratio: 80 / 20 mol%) was used.
[0050]
Using these polymers, unstretched POF was prepared by melt spinning. The obtained unstretched POF was stretched using a stretching apparatus including the roller 1, the roller 2, and the non-contact heating furnace 3 shown in FIG. At that time, the non-contact heating furnace was set to 140 ° C., and the peripheral speed ratio of the roller (roller 2 peripheral speed / roller 1 peripheral speed) = 2.0 was set to stretch the unstretched POF. POF4 consisting of a core-sheath-protective layer having a diameter of 1000 μm was obtained.
[0051]
The obtained POF4 core material had a Tg of 112 ° C. (DSC method, heating rate: 10 ° C./min).
[0052]
In order to heat-treat this POF4 at a constant length, the bobbin was wound, and heat treatment was performed at a temperature and time shown in Table 1 using a commercially available dry heat dryer. The thermal shrinkage rate of the obtained POF is shown in Table 1 and FIG.
[0053]
(Examples 1-6)
In the same manner as in the comparative example, POF4 composed of a core-sheath-protective layer having a diameter of 1000 μm was obtained.
[0054]
Using this cylindrical SUS container 5 having an inner diameter of 565 mm and a height of 600 mm without winding the POF 4 around the bobbin, the POF 4 is directly introduced into the container 5 from the nip roller 2 as shown in FIG. Then, the POF was placed in a rounded state. Thereafter, heat treatment was performed at a temperature and time shown in Table 1 using a commercially available dry heat dryer.
[0055]
The thermal shrinkage rate of the obtained POF4 is shown in Table 1 and FIG. As is apparent from FIG. 3, it has been clarified that the POF 4 heat-treated by such a method can reduce the thermal shrinkage rate in a short time as compared with the POF 4 which is wound around the bobbin and heat-treated at a constant length.
[0056]
[Table 1]

[0057]
【The invention's effect】
As is apparent from the above description, according to the present invention, a POF, POF cable and POF cable with a plug excellent in heat resistance and mechanical strength can be produced with high productivity.
[Brief description of the drawings]
FIG. 1 is a schematic view of a production apparatus used in the present invention.
FIG. 2 is a schematic diagram of a DSC curve near Tg of a core material.
FIG. 3 is a graph showing the heat shrinkage ratio with respect to the heat treatment time in Examples and Comparative Examples.
FIG. 4 is a graph for explaining the influence of the load during heat treatment on the thermal shrinkage rate.
FIG. 5 is a view showing a state in which POF is transferred into a cylindrical container in order to perform heat treatment without applying tension in the manufacturing method of the present invention.
[Explanation of symbols]
1, 2 Nip roller 3 Heating furnace 4 Plastic optical fiber 5 SUS container

Claims (8)

A plastic optical fiber obtained by melt spinning and heated and stretched,
A plastic light characterized by being heat-treated at a temperature of (core glass transition temperature -30) ° C. or more (core glass transition temperature) ° C. or less in a state where tension due to thermal shrinkage generated in the plastic optical fiber is not generated. Fiber manufacturing method. A plastic optical fiber obtained by melt spinning and heated and stretched,
After continuously passing through a heating device (core glass transition temperature -5) ° C. and above (core glass transition temperature +80) continuous heat treatment at a temperature of not more than 80 ° C. ,
A plastic characterized by being heat-treated again at a temperature of (core glass transition temperature-30) ° C. or higher (core glass transition temperature) ° C. or lower in a state where no tension is generated due to heat shrinkage generated in the plastic optical fiber. An optical fiber manufacturing method. The said continuous heat processing is a manufacturing method of the plastic optical fiber of Claim 2 which makes the said plastic optical fiber run with the roller arrange | positioned before and behind the said heating apparatus, and lets it pass through this heating apparatus.   (The glass transition temperature of the core material -30) The heat treatment performed at a temperature of not lower than (° C) and not higher than (the glass transition temperature of the core material) is performed in a state where the plastic optical fiber is wound and wound around. 4. The method for producing a plastic optical fiber according to any one of 3 above.   The method for producing a plastic optical fiber according to any one of claims 1 to 4, wherein the core material is a methyl methacrylate homopolymer or a copolymer of methyl methacrylate and another copolymerizable monomer.   (The glass transition temperature of the core material-30) The heat treatment performed at a temperature of not less than 30 ° C. and the glass transition temperature of the core material is 0 ° C. or less. The shrinkage rate of the plastic optical fiber when heated at 90 ° C. for 65 hours is 0. The method for producing a plastic optical fiber according to any one of claims 1 to 5, wherein the plastic optical fiber is produced so as to be 6% or less.   The manufacturing method of the plastic optical fiber cable which has the process of forming a coating layer in the outer peripheral part of the optical fiber obtained by the method as described in any one of Claim 1 to 6.   The manufacturing method of the plastic optical fiber cable with a plug which has the process of arrange | positioning a plug at the front-end | tip of at least one of the optical fiber cable obtained by the method of Claim 7.

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