JP2002107552A - Plastic multi-filament type optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic multi-filament type optical fiber which is bright in a transmission picture, has no pixel fault and has low transmission loss. SOLUTION: In the plastic multi-filament type optical fiber having a sea and island structure in which light guiding island parts are arranged in a sea part, the number of dust of >=0.5 μm contained in 1 g of resin composing a core through which light passes mainly out of the islands is <=4,000. Also, in the same optical fiber, the number of dust of >=0.5 μm contained in 1 g of the resin composing the sheath or the sea is <=4,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic multifilament optical fiber having few pixel defects.

[0002]

2. Description of the Related Art A multifilament optical fiber in which quartz optical fibers having a fiber diameter of 200 μm or less are arranged in a good array and the fibers are bonded with an adhesive can transmit an image by light. The use of endoscopes is being promoted mainly in the field of medical equipment.

[0003] Glass-based optical fibers are relatively easy to reduce the fineness as compared with plastic-based optical fibers, so that multifilament optical fibers having a large number of pixels exceeding 10,000 are being developed. However, since the optical fiber used here is extremely fine and has a low resistance to bending, the individual optical fibers constituting the pixels are relatively formed by the bending operation when using the multifilament optical fiber. It is easily cut off, and this portion is regarded as a major drawback that causes a pixel defect of the multifilament optical fiber.

A multifilament optical fiber made of a glass-based optical fiber cannot be prevented from being rigid due to its characteristics, and when used as an image scope, it is difficult to obtain a large bending angle. There is also a disadvantage that the surveillance field of view cannot be made very wide.

Therefore, conventionally, a plastic multifilament optical fiber in which a plurality of plastic optical fibers having characteristics of being less likely to be broken and being easily bent as compared with glass-based optical fibers has been attempted. And US Pat. No. 3,556,635 and JP-A-56-39505.

However, it is difficult to produce a fiber having a large number of pixels in a plastic-based multifilament optical fiber, and its practical use has been delayed.

In particular, in order to obtain a multifilament optical fiber used for an endoscope, it is necessary to increase the number of pixels in order to increase the resolution of an image and improve the transmission performance of an image. It is desirable to use a multi-filament optical fiber having 1,000 pixels or more, more preferably 3,000 pixels or more, especially when it is necessary to observe a wide range on one screen such as a gastroscope, etc. An optical fiber is desired.

However, in the case of a plastic multifilament optical fiber in which the number of pixels is increased while the pixel diameter is kept constant, the outer diameter of the optical fiber becomes large, the flexibility is lost, and the use becomes difficult. In particular, an endoscope that is used in a thin and bent portion like a blood vessel endoscope cannot reduce the flexibility, and the pixel diameter is reduced to reduce the outer diameter of the plastic multifilament optical fiber. Need to ensure flexibility.

However, a plastic multifilament optical fiber having a core diameter of, for example, 20 μm or less, particularly 10 μm or less, makes it difficult for light to be transmitted, so-called pixel defects that darken a transmitted image increase sharply, and the transmitted image has a large size. There is a problem that the resolution performance deteriorates.

Further, light is transmitted on a specific island, but if the amount (the amount of transmitted light) is smaller than the amount of light transmitted through the surrounding islands, the portion becomes "stained",
A problem arises in that the quality of the image is reduced.

The invention disclosed in US Pat. No. 3,556,635 is to manufacture a multifilament optical fiber made of plastic using a sea-island composite spinning nozzle having a specific structure shown in the publication. The sea-island composite spinning nozzle used in the present invention is a pipe for forming a core component of an optical fiber,
The structure is extremely complex because the shell component forming pipes are planted in the sea component forming base plate, and the sheath component forming pipes are planted in the sea component forming base plate. A dead space is created in the planting area, and a hot-melt polymer band is formed in the area during composite spinning, and the polymer is thermally deteriorated and foreign matters are easily generated. It is difficult to produce a plastic multifilament optical fiber having few pixel defects. There is a disadvantage.

[0012]

The inventors of the present invention have studied for the purpose of developing a multifilament type optical fiber having a high resolution. As a result, the present inventors have found that a few hundred light guide islands do not transmit light. The number of islands that become pixel defects is 1 or less,
More preferably, when the number is 0.1 or less, the quality of the transmitted image is improved. Pixels that cause "stain" in an image (hereinafter abbreviated as "stain pixels")
Indicates that the amount of transmitted light is 0.
It is found that the number of islands is 7 times or less, and the number is 10 islands.
It has been found that if the number is less than or equal to three, and preferably less than or equal to one, the quality of the transmitted image is further improved. In addition, the inventors have noted that the above-described pixel defect and reduction in the amount of transmitted light
Not only the foreign matter or dust contained in the resin constituting the core, which is the main optical path of the island, but also the resin constituting the multifilament optical fiber due to the foreign matter or dust contained in the resin constituting the sheath and the sea It has been found that by reducing the size and number of dust particles therein, a multifilament optical fiber can be obtained in which the number of pixel defects can be reduced to a number that does not substantially matter.

That is, the gist of the present invention is a plastic multifilament optical fiber having a sea-island structure in which a light-guiding island portion is arranged in a sea portion, and constitutes a core through which light mainly passes among the islands. 0.5 contained in 1 g of resin
The plastic multifilament optical fiber is characterized in that the number of dust having a size of μm or more is 4000 or less.

In the present invention, the number of dusts contained in the resin constituting the optical fiber was measured by the following method.
A certain amount of the resin is dissolved in a solvent, and the resin concentration of the resin is 0.1.
% Of the dilute solution, and the number of foreign substances contained in a certain amount of the dilute solution is determined by a liquid fine particle counting device (HIAC / RO).
YAC Co., Ltd., Hiac Leuco Liquid Fine Particle Counter)
And converted into the number of foreign substances contained in 1 g of the resin.

The present invention is particularly useful for a plastic multifilament optical fiber having a small core diameter, preferably having a core diameter of 20 μm or less, more preferably 10 μm or less. If the diameter of the core exceeds 20 μm, the flexibility of the multifilament type optical fiber becomes insufficient, and there is a possibility that the multifilament type optical fiber may become inadequate as an image transmitting body for endoscopy, which requires flexibility. is there. In a multifilament optical fiber having a core diameter of 2 μm or less, the optical transmission loss of the plastic multi-optical fiber is as large as 3 dB / m or more. It is not preferable because it is recognized.

The size and number of dusts contained in the resin constituting the optical fiber of the present invention are important because they greatly affect the number of pixel defects and transmission loss of the plastic multifilament optical fiber. At present, the lower limit of foreign substance detection is 0.5 μm, and foreign substances having a size smaller than 0.5 μm cannot be measured. However, if the number of foreign substances having a size of 0.5 μm or more exceeds 10,000 per 1 g of resin constituting an optical fiber, pixel defects may occur. This is undesirably increased significantly, and the transmission loss also increases.

In particular, foreign matter in the resin constituting the core and the sheath, through which light actually passes, causes pixel defects and causes the image quality to be darkened. In particular, the increase in the optical transmission loss of the multifilament optical fiber due to foreign matter tends to increase in the short wavelength region, the transmittance of the short wavelength component decreases, and the image is colored yellow. It becomes impossible to do. In order to prevent the coloring of the image, it is preferable to reduce the number of foreign substances in the resin constituting the core and the sheath constituting the light guide path as much as possible. It is desirable that the number be 4000 or less, preferably 2000 or less. It is also desirable that the number of foreign substances having a size of 0.5 μm or more contained in 1 g of the resin constituting the sheath or the sea be 4000 or less.

Further, among the foreign substances, dust or foreign substances having a size of 70% or more of the diameter of the core (hereinafter referred to as "large foreign substances").
Has a very high probability of generating pixel defects and "stain" pixels (hereinafter, both are abbreviated as "pixel defects") of the multifilament optical fiber of the present invention, so that it is contained in 1 g of the resin constituting the core. The number of coarse foreign matters is preferably 50 or less, more preferably 20 or less, particularly preferably 10 or less. The number of coarse foreign substances contained in 1 g of the resin constituting the sheath is preferably 50 or less, more preferably 20 or less. In order to reduce the content of foreign substances contained in the resin, the raw material to be subjected to the polymerization of the resin is finely filtered through a hollow fiber filtration membrane or the like, and the polymerization atmosphere,
The object of the present invention can be achieved by making the spinning atmosphere or the like a clean room and providing a microfiltration filter immediately before the spinning nozzle.

Specific examples of the plastic for forming the core component and the sheath component of the multifilament optical fiber of the present invention include the following.

Polymethyl methacrylate (n = 1.4)
9; n represents a refractive index; the same shall apply hereinafter) and methyl methacrylate
Copolymer containing nylate as a main component (n = 1.47-
1.50), polystyrene (n = 1.58) and styrene
A copolymer containing len as a main component (n = 1.50 to 1.5
8), styrene / acrylonitrile copolymer (n =
1.56), poly 4-methylpentene 1 (n = 1.4
6), ethylene / vinyl acetate copolymer (n = 1.46-1.
50), polycarbonate (n = 1.50 to 1.5)
7), polychlorostyrene (n = 1.61), polychlorinated
Vinylidene (n = 1.63), polyvinyl acetate (n =
1.47), methyl methacrylate / styrene, vinyl
Toluene or α-methylstyrene / maleic anhydride
Terpolymer or quaternary copolymer (n = 1.50-1.
58), polydimethylsiloxane (n = 1.40),
Riacetal (n = 1.48), polytetrafluoroe
Tylene (n = 1.35), polyvinylidene fluoride (n =
1.42), polytrifluoroethylene (n = 1.4)
0), perfluoroethylene (n = 1.34), and
Binary or ternary copolymers of these fluorinated ethylenes
-(N = 1.35 to 1.40), polyvinylidene fluoride
And polymethyl methacrylate blend polymer (n =
1.42 to 1.46), a general formula CH_Two= X-CCOOR
Co containing fluorinated methacrylate represented by f as a main component
In the polymer, the group Rf is (CH_Two)_n(CF_Two)_nH
Copolymer (n = 1.33 to 1.42), and Rf is (C
H_Two)_m(CF_Two)_mF (n = 1.37-1.4)
0), and Rf is CH · (CF_Three)_Two(N = 1.3
8), Rf is C (CF_Three)_Three(N = 1.36),
Rf is CH_TwoCF_TwoCHFCF_Three(N = 1.4
0), Rf is CH_TwoCF (CF_Three)_Two(N = 1.
37), and copolymers of these fluorinated methacrylates
(N = 1.36 to 1.40) and their
Methacrylate copolymer of methylated methacrylate
(N = 1.37 to 1.43), general formula CH_Two＝ CH ・ C
Fluorinated acrylate represented by OORf 'as a main component
Where Rf 'is (CH _Two)_m(CF_Two)_n
F (n = 1.37 to 1.40), Rf ′ is (CH
_Two) _m(CF_Two)_mH (n = 1.37 to 1.4)
1), Rf 'is CH_TwoCF_TwoCHF / CF_Three(N
= 1.41) and Rf 'is CH (CH_Three)_Two(N =
1.38), and these fluorinated acrylate copolymers
(N = 1.36 to 1.41), and these fluorides
Acrylate and the fluorinated methacrylate copolymer (n
= 1.36 to 1.41), and these acrylyl fluorides
Methacrylate and methyl methacrylate
Polymer (n = 1.37 to 1.43), general formula CH_Two=
Α-Fluoroacryle represented by CF ・ COOR''f
-Based polymers and their copolymers
(N = 1.33 to 1.42) (where R ″ f is C
H_Three, (CH_Two)_m(CF_Two)_nF, (CH_Two)_m(C
F_Two) _nH, CH_TwoCF_TwoCHFCF_Three, C (CF_Three)
_TwoH) perfluoro (2,2-dimethyl-1,3)
-Dioxole) -based fluoropolymer (n = 1.298-
1.45) can be usefully used,
The difference in refractive index (n) between the polymer and the sheath-forming polymer is 0.0
It is good to be 05 or more, preferably 0.01 or more.

Examples of the plastic which can be used as a sea component include, in addition to the above-mentioned plastics, polyamide, polyester elastomer, polyamide elastomer, polystyrene elastomer, polyolefin elastomer,
Specific examples thereof include poly-4-methylpentene 1, polyvinylidene fluoride, ionomer, ethylene / ethyl acrylate copolymer, ethylene / vinyl acetate copolymer, vinylidene fluoride copolymer, polymethyl methacrylate, polystyrene, ABS, polybutylene terephthalate, and polyethylene. However, it is necessary to select a polymer for forming the sea component such that the fluidity of these polymers is larger than the fluidity during spinning of the polymer for forming the sheath, which is an island component. Preferred for making multi-optical fibers.

The melt flow index [MF] which indicates the thermal fluidity of the polymer constituting the core, sheath and sea during spinning.
R ₁ ], [MFR ₂ ] and [MFR ₃ ] are [MFR ₃ ] ≧
It is convenient to select such that [MFR ₂ ] ≧ [MFR ₁ ] to obtain a multifilament type plastic optical fiber having excellent image transmission characteristics.

The plastic multifilament optical fiber of the present invention preferably has a bales stacking structure as shown in FIGS. 2 and 3 in which the islands arranged in the sea section are arranged. FIG. 1 is an enlarged sectional view of the multifilament plastic optical fiber of the present invention. In FIG. 1, 21 is a core section, 22 is a sheath component, and 23 is a sea component. A high resolution multifilament optical fiber having a high pixel density can be obtained by making the arrangement of island components in a sea component cross section into a bale-stacked structure.

FIG. 4 is a sectional view of an example of a spinneret preferably used in producing the plastic multifilament optical fiber of the present invention. This spinneret is composed of an optical fiber core forming base plate 31 serving as an island component, a sheath component forming base plate 32, a sea component forming base plate 33, and a multifilament optical fiber collecting base plate 38, and four base plates. This is a composite spinneret for the production of sea-island multifilament optical fibers.

In the figure, reference numerals 31a and 33a denote a spinning hole for a core component serving as an island component and a sea component spinning hole, respectively.

One of the features of this spinneret is the lowermost die plate, that is, the die plate installed immediately above the fiber assembly die plate 38. It is in the shape of the spinning hole 33 a of the sea component forming base plate 33. This shape is shown in FIG. 5 in an enlarged view in the vicinity thereof. In the figure, reference numeral 43 denotes a sea component forming base plate,
3a is a sea-island component spinning hole. This sea-island component spinning hole 43
a is characterized in that it opens in a trumpet shape toward the lower surface of the sea component base plate as shown in FIG.
It is preferable to form a tapered hole that spreads downward from the middle of a. Further, it is preferable that the lower end of the spinning hole be the lower end of the sea-island component spinning hole adjacent to each other.

The spinning hole 43a satisfies the relationship of R ≧ P, especially 2P ≧ R, where P is the distance between adjacent hole centers and R is the diameter of the lower end of the spinning hole 3a. good to have, more preferably set as R = √P ^2/3. The horn-like opening angle θ of the spinning hole 3a is preferably in the range of 10 ° <θ <45 °.

With the above-described base structure, the flow of the molten polymer at the junction between the island component and the sea component becomes extremely smooth, and the flow of the island component and the sea component in each spinning hole also becomes laminar. Since the state can be secured, the island component can be maintained in a substantially circular shape close to a perfect circle, and the cross-sectional shape of the obtained optical fiber component of the multi-optical fiber is compared with the conventional technology. As shown in FIG. 2, it can be made very uniform.

Further, if the spout hole of the sea component forming die has a trumpet-shaped opening toward the lower end surface of the die as described above, the sea component of the plasticized yarn formed in the sea-island structure can be formed. Since the nozzle is well separated from the forming nozzle and does not meander or eccentric, it can efficiently prevent the occurrence of fineness unevenness and lack of roundness. It can be secured.

Next, a large number of yarns leaving the nozzle holes 43a are collected by a fiber collecting die plate having a sectional shape as shown in FIG. 3 (38) and an appearance as shown in FIG. The intended plastic-based multifilament optical fiber can be obtained.

When a fiber collecting base as shown in FIG. 6A is used as a collecting base, a multifilament optical fiber having a substantially rectangular cross section is obtained. When a fiber collecting base as shown in FIG. 6B is used. A multifilament optical fiber having a substantially hexagonal cross section is obtained, and a multifilament optical fiber having a substantially circular cross section is obtained by using a fiber assembly die as shown in FIG. In order to obtain a multi-pixel multi-filament optical fiber obtained by further laminating the obtained multi-filament optical fiber, it is preferable to use one having a substantially rectangular or substantially hexagonal cross section.

[0032]

The plastic multi-optical fiber of the present invention can provide a bright transmission image and no pixel defects, and can be used not only in medical fields such as endoscopes but also in various fields. It can be usefully used.

Hereinafter, the present invention will be described in more detail with reference to examples.

Embodiments 1 to 4 A spinneret having a sectional structure as shown in FIG. 4, wherein the angle θ shown in FIG. 5 is 15 ° and the shape of the collective spinneret is shown in FIG.
The number of holes is set to the number of holes shown in Table 1 using a fiber assembly die having a structure as shown in Table 1. Polymethyl methacrylate having a refractive index of 1.492 is used as a core component constituting an island component, and a refractive index is used as a sheath component. The composite spinning was performed using a polyfluorinated methacrylate polymer having a ratio of 1.415 and methyl methacrylate as a sea component to obtain a multifilament optical fiber having the characteristics shown in Table 1. The number of foreign substances in the polymethyl methacrylate used as the core component was as shown in Table 1. In this embodiment, the core diameter is 7 μm and the diameter of the coarse foreign matter is about 5 μm.

In this embodiment, a multifilament type optical fiber having good transmission loss and few pixel defects is obtained because polymethyl methacrylate polymer and polyfluorinated methacrylate polymer having a small number of coarse foreign substances are used as the core and the sheath. Was. It was also confirmed that as the number of foreign substances in the sheath material decreased, the number of pixel defects and the value of optical transmission loss decreased.

Comparative Example 1 A multifilament optical fiber was obtained in the same manner as in Example 1 except that a polyfluorinated methacrylate polymer having a large number of foreign substances was used as the sheath material. The evaluation results are shown in Table 1. As shown in Table 1, the number of foreign substances in the sheath material was larger than the predetermined number, and the number of foreign substances in the multifilament optical fiber 1g was also larger than the predetermined value. Therefore, only the multifilament optical fiber having many pixel defects and large transmission loss was used. Could not be obtained.

Examples 5 to 8 Multifilament optical fibers were obtained in the same manner as in Example 1, except that polymethyl methacrylate having the number of foreign substances shown in Table 1 was used as the core material.

Since the number of foreign substances in the core material, the sheath material, and the multifilament optical fiber was smaller than a predetermined value, pixel defects were small and the transmission loss was low. Further, as the number of foreign substances in the core material decreases, the pixel defect and the transmission loss value decrease.

Comparative Example 2 A multifilament optical fiber was obtained in the same manner as in Example 1 except that polymethyl methacrylate having a large number of foreign substances was used as the core material.
It was shown to.

Since the number of foreign substances in the core material was larger than a predetermined value, and as a result, the number of foreign substances in the multifilament optical fiber 1g was larger than a predetermined value, only a multifilament optical fiber having many pixel defects and a large transmission loss could be obtained. Was.

Example 9 A fiber assembly die of the type shown in FIG. 6B was used as the spinneret with 3043 holes, and the discharge amount of the core, sheath and sea material was twice that of Example 5. A multifilament optical fiber having a round cross section was obtained in the same manner as in No. 5, and the characteristics are shown in Table 1.

There were few pixel defects and good characteristics for image transmission. In addition, since the outer diameter of the fiber is small, it is a multifilament type optical fiber which is rich in flexibility.

Example 10 A multifilament optical fiber was obtained in the same manner as in Example 9 except that polyfluorinated methacrylate having the number of foreign substances shown in Table 1 was used as the sheath material, and the evaluation results are shown in Table 1. Was.

Since the number of foreign substances in the core material, the sheath material and the multifilament type optical fiber was smaller than a predetermined number, the pixel defect was small and the transmission loss was low.

[0045]

[Table 1] Example 11 A multifilament optical fiber was obtained in the same manner as in Example 10 except that the core diameter was changed to 5 μm, and the evaluation results are shown in Table 2. In this example, the coarse foreign matter was a foreign matter having a diameter of 3.5 μm or more.

Since the number of foreign substances in the core material, the sheath material, and the multifilament optical fiber was smaller than a predetermined number, pixel defects were small and transmission loss was low.

[0047]

[Table 2] Examples 12 to 15 A multifilament optical fiber was obtained in the same manner as in Example 9 except that the core material, the sheath material, and the sea material used in Example 1 were used, and the characteristics were measured. It was shown to.

There were few pixel defects and good characteristics for image transmission. In addition, as the number of foreign substances in the sheath material decreases, the number of pixel defects and the transmission loss decrease.

Comparative Example 3 A multifilament optical fiber was obtained in the same manner as in Example 12, except that a polyfluorinated methacrylate polymer having a large number of foreign substances was used as the sheath material. Table 3 shows the evaluation results. As shown in Table 3, the number of foreign substances in the sheath material was larger than the predetermined number, and the number of foreign substances in the multifilament optical fiber 1 g was also larger than the predetermined value. Therefore, only the multifilament optical fiber having many pixel defects and large transmission loss was used. Could not be obtained.

Examples 16 to 18 A multifilament optical fiber was obtained in the same manner as in Example 9 except that the same core material and sheath material as those used in Example 5 were used. It was shown to.

Since the number of foreign substances in the core material, the sheath material, and the multifilament optical fiber was smaller than a predetermined number, the pixel defect was small and the transmission loss value was low. Further, as the number of foreign substances in the core material decreases, the pixel defect and the transmission loss value decrease.

Comparative Example 4 A multifilament optical fiber was obtained in the same manner as in Example 12 except that polymethyl methacrylate having a large number of foreign substances was used as the core material.
It was shown to.

Since the number of foreign substances in the core material was larger than a predetermined value, and as a result, the number of foreign substances in the multifilament type optical fiber 1 g was larger than a predetermined value, only a multifilament type optical fiber having many pixel defects and a large transmission loss could be obtained. Was.

[0054]

[Table 3]

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a multifilament optical fiber according to the present invention.

FIG. 2 is a diagram showing an optical fiber arrangement state of the present invention.

FIG. 3 is a diagram showing an optical fiber arrangement state of the present invention.

FIG. 4 is a cross-sectional view showing an example of a spinneret used when manufacturing the optical fiber of the present invention.

FIG. 5 is a partially enlarged view of a lowermost spinneret plate.

FIG. 6 is a perspective view showing an example of a fiber assembly die.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Katsuhiko Shimada 20-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Central Research Laboratory F-term (reference) 2H046 AA02 AC05 AD01 AZ03 AZ08 4L045 AA05 BA02 BA20 BA52 CB15 CB16

Claims (9)

[Claims] 1. A plastic multifilament optical fiber having a sea-island structure in which a light-guiding island portion is arranged in a sea portion, and a resin 1g constituting a core through which light mainly passes among the islands
3. The plastic multifilament optical fiber according to claim 1, wherein the number of dusts having a size of 0.5 μm or more contained therein is 4000 or less. 2. The plastic multifilament optical fiber according to claim 1, wherein the number of dusts of 0.5 μm or more contained in 1 g of the resin constituting the sheath or the sea is 4000 or less. 3. A plastic multifilament optical fiber having a sea-island structure in which a light-guiding island portion is arranged in a sea portion, wherein the number of dust particles of 0.5 μm or more contained in 1 g of a resin constituting the optical fiber is reduced. 3. The plastic multifilament optical fiber according to claim 1, wherein the number is 10,000 or less. 4. The method according to claim 1, wherein the number of refuse having a size of 70% or more of the diameter of the core is 50 or less per 1 g of resin constituting a core through which light mainly passes among the islands. Claim 2
Or a plastic multifilament optical fiber according to claim 3. 5. The method according to claim 4, wherein the number of refuse having a size of 70% or more of the diameter of the core is 10 or less per 1 g of resin constituting a core through which light mainly passes among the islands. Plastic multifilament optical fiber. 6. 0.5 contained in 1 g of the resin constituting the core.
6. The plastic multifilament optical fiber according to claim 1, wherein the number of dust having a size of not less than μm is 50 or less. 7. A plastic multifilament optical fiber having a sea-island structure in which a light-guiding island portion is arranged in a sea portion, wherein the number of island portions through which light does not pass is one or less. 7. The plastic multifilament optical fiber according to claim 1, 2, 3, 4, 5, or 6. 8. The plastic multifilament optical fiber according to claim 7, wherein the number of islands through which light does not pass is 0.1 or less per 100 islands. 9. When the average value of the transmitted light amounts of all the island portions is M, the number of the island portions having the transmitted light amount of M × 0.7 or less is 3 or less per 100 island portions. Claim 6
Or a plastic multifilament optical fiber according to claim 8.