JPH0651141A - Production of multifilament type optical fiber made of plastic and optical fiber for endoscope formed by using the same - Google Patents

Abstract

PURPOSE:To obtain uniform and bright images by discharging a polymer for forming a sea part to coat the outer peripheries of island parts having light transmittability and integrally coating the outer peripheral part thereof with a polymer for forming a protective layer added with specific coloring agents. CONSTITUTION:The polymer for forming the sea part is discharged to coat the outer peripheries of many pieces of the light transmittable island parts each having an approximately circular section and 2 to 70mum diameter. These island parts are arranged, joined and spun to a piling structure or square stacking structure. The outer peripheral part thereof is integrally coated with the polymer for forming the protective layer added with >=1 pt.wt. and <=10 pts.wt. per 100 pts.wt. polymer for constituting the protective layer within the nozzle at the time of spinning. The sectional shape of the peripheral part fibers 13 is provided with the approximately circular section like the section of the fibers 14 in the central part by the protective layer 12 applied on the outer peripheries of the multifilament type optical fibers at the time of spinning. Sufficiently high optical performance is thus maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic multi-filament type optical fiber having a high pixel number of 50 to 20,000, an extremely bright transmission image, and the effect of external light. The present invention relates to a method for manufacturing a plastic multi-filament type optical fiber which is difficult to receive, and a light guide integrated optical transmitter for endoscopes using the same.

[0002]

2. Description of the Related Art A multi-filament type optical fiber in which silica-based optical fibers having a fiber diameter of 200 μm or less are arranged in the closest packing state and the fibers are joined by an adhesive can transmit images by light, and As an endoscope including a camera, its use is being promoted mainly in the medical device field. Compared to plastic optical fibers, glass-based optical fibers are relatively easy to make finer, and are being used as multi-filament optical fibers with more than 10,000 pixels. Since each optical fiber constituting the filament type optical fiber has a very fineness and a small resistance to bending, it is relatively easily broken by a bending operation when the multifilament type optical fiber is used. It is considered to be a great difficulty that a portion thereof becomes a pixel defect of the multifilament type optical fiber. In addition, the multi-filament type optical fiber made of glass-based optical fiber is inevitably rigid due to its characteristics, and when used as an image scope, it is difficult to set a large bending angle, and the monitoring field of view is There is also the drawback that it cannot be taken too wide.

Therefore, it has been attempted to develop a plastic-based multifilament type optical fiber in which a large number of plastic-based optical fibers having the characteristics of being less likely to be broken and easier to bend than glass-based optical fibers are assembled.
The present inventors previously proposed in EP0.207705 a method for producing an excellent plastic multifilament type optical fiber. The present invention relates to a composite for producing a sea-island type multi-filament fiber in which a base plate having a large number of island component forming nozzle holes, a base plate having a sea component forming nozzle hole, and a base plate having a fiber collecting nozzle hole are stacked. It is a method using a spinneret, the nozzle hole of the spinneret plate installed directly above the lowermost spinneret plate has a trumpet-shaped opening toward the lower end surface of the spinneret plate, and is provided directly above the lowermost spinneret plate. A large number of filaments that were composite-spun using a spinneret with a sea component flow path between two other spinnerets were assembled by a collecting nozzle to form a bales-stacked array structure of island components within the cross section of the sea component. It is to obtain a plastic multi-filament type optical fiber.
It became clear that a plastic multi-filament type optical fiber having an excellent image transmission property can be produced by this method.

[0004]

An endoscope using a multifilament type optical fiber as an image transmission body generally includes an image transmission body and a light guide for transmitting light for illuminating an observed portion. A so-called optical fiber has a structure in which it is inserted in a protective tube in a parallel state and in contact with each other. However, when the multi-filament optical fiber is bent with a small bending radius or when light having a numerical aperture larger than that of the fiber is incident, transmitted light may leak out and accurate image transmission may not be possible. As a light guide, an optical fiber with a high numerical aperture is generally arranged around the outer circumference of the multifilament type optical fiber to widen the light irradiation range. If the transmitted light leaks out and enters into the optical fiber for image transmission, the leaked light lowers the contrast of the transmitted image and only an unclear transmitted image can be obtained.

In order to prevent light leaking from the optical fiber for illumination from entering the optical fiber for image transmission, a colored polymer having a light shielding effect is provided on the outer peripheral portion of the image transmission body made of a multifilament type optical fiber. It may be covered, that is, formed into a cable. This optical fiber is usually made into a cable by once adjusting the multifilament type optical fiber, and then using the extrusion die of the cable forming polymer, the multifilament type optical fiber is passed through the extrusion die to coat the cable forming polymer. It is done by. However, when the multifilament type optical fiber passes through the extrusion die, there is a problem that the island component in the peripheral portion of the fiber is damaged and the optical performance thereof is deteriorated. That is, due to the blurring of the multi-filament type optical fiber passing through the die, mechanical damage to the fiber itself caused by contact with the die, and thermal damage received at the time of making the cable, the transmission loss of the island component at the outer periphery is remarkable. It becomes big. As a result, the image transmitted by the cabled multi-filament type optical fiber has a bright central part and a dark peripheral part, and an image with uniform brightness cannot be obtained. Was needed.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have completed the present invention as a result of investigations for the purpose of obtaining a plastic multi-filament type optical fiber in the form of a cable which is further excellent in image transmission. , The gist is that it has a large number of substantially circular cross sections and a diameter of 2 to 70
The outer periphery of the light-transmitting islands of μm is coated with a polymer for sea formation and discharged, and the fibers are spun by being arrayed and joined in a bale stacking structure or a four-sided stacking structure, and at the outer periphery of the inside of the nozzle during spinning. The effect of preventing external light from entering the fiber by integrally coating the protective layer-forming polymer with 1 to 10 parts by weight of coloring agent added per 100 parts by weight of the protective layer-forming polymer And a method of manufacturing a plastic multi-filament optical fiber characterized by having a light guide integrated endoscope in which an optical fiber for illumination is integrated in or around a protective layer of an image transmission body. For optical transmission.

In the present invention, the structure of the island portion having an optical transmission property is as follows:
It may have a core-sheath structure or a core alone. When the island portion has a core-sheath structure, light is transmitted by repeating total reflection at the interface between the core and the sheath of each island. If it is composed only of the core of the island, the sea will act as a sheath. Therefore, in the case of a multi-filament type optical fiber in which the island portion has only a core, it is necessary to select a polymer having the characteristics that the sheath forming polymer should have as the sea forming polymer. In the following description, unless otherwise specified, the case where the structure of the island portion is the core-sheath structure will be described as an example for the sake of simplicity.

In carrying out the present invention, carbon black, lead oxide, titanium oxide, and the like are added as colorants added to the polymer for forming the protective layer component for the purpose of blocking external light.
Or an organic pigment etc. can be mentioned. A migrating colorant such as an organic dye is preferable because it migrates from the protective layer forming polymer to the light transmitting island forming polymer while leaving the fiber for a long time, and significantly reduces the light transmission performance of the fiber. Absent. It is desirable that the colorant is added to the polymer constituting the protective layer as much as possible in order to enhance the effect of blocking light. However, excessive addition significantly changes the physical properties of the polymer constituting the protective layer, and as a result, stable spinning becomes impossible, so the colorant is added in an amount of 1 to 10 parts by weight based on 100 parts by weight of the polymer for forming the protective layer. It is good to set the range. Further, the thicker the protective layer, the greater the light-shielding effect can be obtained by adding a smaller amount of the coloring agent. However, if the thickness of the protective layer is increased, the outer diameter of the multi-filament optical fiber is increased, and the flexibility of the fiber is reduced. Therefore, the thickness of the protective layer is preferably as thin as possible in the range where the necessary light-shielding effect can be obtained, and usually, the thickness is preferably 2 to 50 μm.

Further, the melt flow rate of the protective layer-forming colored polymer decreases as the amount of the coloring agent added increases. By the way, when the melt flow rate of the polymer forming the protective layer is lower than the melt flow rate of the polymer forming the sea part and the island part, the island part in the outer peripheral part is deformed and the arrangement is disturbed at the time of spinning, and that part has a clear transmission image. Will not be obtained. Therefore, it is desirable that the melt flow rate of the colored polymer that forms the protective layer be equal to or higher than the melt flow rate of the polymer that forms the sea part and the island part.

It is preferable that the cross-sectional shape of the island of the multifilament type optical fiber of the present invention is substantially circular, and the number of islands, that is, the number of pixels is in the range of 50 to 20,000.
If the number of islands is too large, it is difficult to maintain the uniformity of the multifilament optical fiber. Further, in a multi-filament optical fiber having less than 50 islands, the number of pixels in one multi-filament optical fiber is too small, so that it is difficult to achieve image transmission with good resolution. In the present invention, a multifilament type optical fiber having 150 to 12,000 islands is particularly preferable.

FIG. 1 is a cross-sectional view of an example of a plastic multi-filament optical fiber (11) provided with a light-shielding protective layer of the present invention. The protective coating on the outer periphery of the multi-filament optical fiber during spinning. Due to the layer (12), the cross-sectional shape of the peripheral fiber (13) is substantially the same as that of the central fiber (14), and a sufficiently high optical performance can be maintained.

Further, in the plastic multi-filament type optical fiber of the present invention, the islands arranged in the sea surface may be arranged in a bale stacking structure or a four-sided stacking structure. By making the arrangement state of island components in the sea component cross-section a bale stacking structure, it is possible to prevent the cross-sectional shape from being deformed into a polygonal shape, and to make a multifilament type optical fiber with high pixel density and high resolution. be able to.

FIG. 2 is a cross-sectional view of an example of a spinneret preferably used for manufacturing the multifilament type optical fiber of the present invention. This spinneret consists of an optical fiber core forming die plate (21) which is an island component and a sheath component forming die plate (2).
2), base plate for forming sea component (23), forming a protective layer, and
It comprises a multi-filament type optical fiber collecting spinneret (29), a protective layer forming spinneret (41) and a sea-island composite spinning spinneret in which five spinnerets are stacked. In the figure, (21a), (22a), and (23a) are the core component spinhole, the sheath component spinhole, and the sea component spinhole, respectively, which are island components.

One of the features of this spinneret is the shape of the spinning hole (23a) of the sea component forming spinneret (23), which is a spinneret installed directly above the protective layer-forming spinneret (31). It is in. This sea-island component spinning hole (23a) is characterized in that it opens in a trumpet shape toward the lower surface of the sea component mouth plate as shown in the figure.
In particular, it is preferable to form a tapered hole that spreads downward from the middle of the spinning hole (23a). Further, it is preferable that the lower ends of the spinning holes are the lower ends of the sea-island component spinning holes that are adjacent to each other.

With the above-described spinneret structure, the flow of the molten polymer at the junction of 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 is almost laminar. Therefore, the island component can be held in a substantially circular shape close to a perfect circle, and the cross-sectional shape of the island component constituting the obtained multifilament optical fiber can be made extremely uniform. You can do it.

When the spinning hole of the sea component forming spinneret has a trumpet-shaped opening toward the lower end surface of the spinneret as described above, the sea component forming of the plastic yarn formed in the sea-island structure is formed. The nozzle is well separated from the work nozzle, and there is no meandering or eccentricity of the fiber when this nozzle is separated.
Since it is possible to efficiently prevent the occurrence of fineness unevenness and the lack of circularity, it is possible to ensure the evenness of the sea-island fiber.

Further, in FIG. 2, the protective layer forming die plate (31) and the fiber collecting die plate (29) are independent die plates. When the nozzle having such a structure is used, the protective component polymer mainly has a very complicated structure by simply touching the protective layer forming die plate (31) and the fiber collecting die plate (29). Since it does not touch the sea component spinning hole (23a) of the plate (23), when cleaning the nozzle when nozzle maintenance is necessary, even if a polymer with high adhesiveness to the nozzle is used as a protective component, it is complicated. Because of the structure, the sea component forming die plate (33), which is difficult to wash, does not come in contact with this polymer, and the operability and simplicity of nozzle washing are extremely excellent.

Next, a large number of the yarns leaving the nozzle hole (23a) are coated with the protective component supplied from the protective layer forming portion (28b) shown in FIG. It Unlike the conventional post-process cable forming method, the multi-filament optical fiber and the protective layer provided on the outer periphery are formed all at once in the molten polymer state during spinning, so island components around the multi-filament optical fiber are damaged. It is hardly received or deformed, and uniform optical performance can be maintained for both the central island component and the peripheral island component of the multifilament optical fiber. Further, at the lower part of the fiber collecting port plate (29), the yarns are assembled and integrated to obtain the plastic multi-optical fiber which is the object of the present invention.

Specific examples of the plastic for forming the core component and the sheath component of the multifilament type optical fiber of the present invention include the following. Polymethylmethacrylate (n = 1.49) and methylmethacrylate-based copolymers (n = 1.47 to 1.50), polystyrene (n = 1.5
8) and styrene-based copolymers (n = 1.50 to 1.
58), styrene acrylonitrile copolymer (n = 1.56), poly 4-methylpentene 1 (n = 1.46), ethylene / vinyl acetate copolymer (n = 1.46 to 1.50), polycarbonate (n = 1.50 to 1.5)
7), polychlorostyrene (n = 1.61), polyvinylidene chloride (n = 1.63), polyvinyl acetate (n = 1.47), methylmethacrylate / styrene, vinyltoluene or α-methylstyrene / maleic anhydride ternary copolymer or Quaternary copolymer (n = 1.50 to 1.58), polydimethylsiloxane (n = 1.4
0), polyacetal (n = 1.48), polytetrafluoroethylene (n = 1.35), polyvinylidene fluoride (n = 1.42), polytrifluoroethylene (n = 1.40), perfluoropropylene
(n = 1.34), and binary or ternary copolymers of these fluorinated ethylenes (n = 1.35 to 1.40), polyvinylidene fluoride and polymethylmethacrylate blend polymers (n =
1.42 to 1.46), a copolymer represented by the general formula CH ₂ = C (CH ₃ ) COOR _f and containing fluorinated methacrylate as a main component, in which the group R _f is
-(CH ₂ ) _m (CF ₂ ) _n H is a copolymer (n = 1.37 to 1.42), R _f is
-(CH ₂ ) _m (CF ₂ ) _n F (n = 1.37 to 1.40), R _f is -CH ・ (C
F ₃ ) ₂ (n = 1.38), R _f is -C (CF ₃ ) ₃ (n = 1.36), R _f
Of --CH ₂ CF ₂ CHFCF ₃ (n = 1.40), R _f of --CH ₂ CF (CF ₃ ) ₂ (n = 1.37), and copolymers of these fluorinated methacrylates (n = 1.36 to 1.40). ), And their fluorinated methacrylate and methyl methacrylate copolymers (n = 1.37 ~
1.43), the general formula CH ₂ = CH · COOR 'polymer composed mainly of fluorinated acrylate represented by _f, however, R' _f is - (CH _2)
m (CF ₂₎ those _{n F (n = 1.37 ~1.40)} , R 'f is _{- (CH 2) m (CF} 2)
those _{n H (n = 1.37 ~1.41)} , ' what _f is _{-CH 2 CF 2 CHF · CF 3} (n = 1.41), R' R f is -CH (CH _{3) 2} ones (n = 1.38 ), And these fluorinated acrylate copolymers (n = 1.36 to 1.41),
And these fluorinated acrylates and the fluorinated methacrylate copolymers (n = 1.36 to 1.41), and these fluorinated acrylates and fluorinated methacrylates and methyl methacrylate copolymers (n = 1.37 to 1.43), the general formula CH ₂ = CF ・ COOR "
A polymer mainly composed of 2-fluoroacrylate represented by _f , and a copolymer thereof (n = 1.37 to 1.42), where R " _f is -CH ₃ ,-(CH ₂ ) _m (CF ₂ ). _n F,-(CH ₂ ) _m (CF ₂ )
_n H, -CH ₂ CF ₂ CHFCF ₃ , and -C (CF ₃ ) ₂ are shown. ) Is mentioned.

Examples of plastics that can be used as the sea component and the protective layer component include, in addition to the above plastics, for example, polyamide, polyester elastomer, polyamide elastomer, polystyrene elastomer, polyolefin elastomer, poly 4-methylpentene 1, polyvinylidene fluoride elastomer, Ionomer, ethylene / ethyl acrylate copolymer, ethylene / vinyl acetate copolymer, vinylidene fluoride copolymer, polymethylmethacrylate,
Polystyrene, ABS, polybutylene terephthalate,
Specific examples thereof include polyethylene and polyvinyl chloride, but the formation of the sea component and the protective layer component in which the fluidity of these polymers is greater than the fluidity during spinning of the sheath-forming polymer that is the island component Choosing a polymer for use is preferred for making multifilament optical fibers that transmit clear and bright images. According to the present invention, a plastic multi-filament type optical fiber having an extremely excellent image transmission property without the uneven brightness as seen in the plastic multi-filament type optical fiber cable produced by the conventional post-process cabling method is used. Fibers can be obtained easily.

The present invention will be further described below with reference to examples.

[0022]

Example 1 Using a spinneret having the structure as shown in FIG. 2, the number of holes was set to the number of holes shown in Table 1, and polymethylmethacrylate having a refractive index of 1.492 was used as the core component of the island component and the sheath component. As a composite component, a polyvinylidene fluoride polymer having a refractive index of 1.415 is used as the sea component, polyvinylidene fluoride copolymer is used as the sea component, and 3% by weight of carbon black is mixed as the protective layer component, and the colored polyvinylidene copolymer is used. A multifilament type optical fiber made of plastic having the characteristics as shown in (3) was obtained. The plastic multi-filament type optical fibers obtained as shown in Experiment Nos. 1, 2, 3 and 4 of Table 1 have an island component in a bales stack as shown in FIG. 1, which is clear and delicate. The image could be transmitted, and the brightness of the transmitted image was extremely bright. Also, good contrast could be maintained even when the image was transmitted through the fiber under illumination of 100Lx.

[Table 1]

[0023]

Example 2 Using a spinneret having the structure as shown in FIG. 2, the number of holes was set as shown in Table 2, polymethylmethacrylate having a refractive index of 1.492 as a core component, and a refractive index of 1.416 as a sheath component. Composite spinning was carried out in the same manner as in Example 1 using trifluoromethacrylate homopolymer, using polyvinylidene fluoride copolymer as the sea component and ethylene / vinyl acetate copolymer containing 5% by weight of carbon black as the protective layer component. A multi-filament type optical fiber having a light-shielding protective layer having the characteristics shown in Table 2 was manufactured. This optical fiber had a bales of island components and was able to transmit a clear and delicate image, and the brightness of the transmitted image was extremely bright. Moreover, even when the fiber was placed under illumination with an illuminance of 100 Lx, images could be transmitted while maintaining good contrast.

[Table 2]

[0024]

[Comparative Example 1] A plastic multi having a three-layer structure of core-sheath-sea using the same spinneret, core polymer, sheath polymer and sea polymer except that the polymer for forming a protective layer was not used in Example 1. A filament type optical fiber was manufactured under the same conditions as in Experiment Nos. 1 to 4 in Table 1 as in Example 1. Then, the outermost layer of these fibers was coated with polyethylene added with Ketjen black at a temperature of 150 ° C. using a commonly used cable coating device.
When an image was transmitted using these four types of optical fibers, the image transmitted by any of the multi-filament optical fibers had a dark image in the peripheral portion, and the brightness unevenness in the central portion and the peripheral portion became remarkable, Obtaining a clear image was extremely difficult.

[0025]

Comparative Example 2 The same table as in Example 2 was used except that the same spinneret, core polymer, sheath polymer, sea polymer and protective layer polymer as in Example 2 were used, except that the protective layer polymer to which no colorant was added was used. The multi-filament type optical fibers manufactured under the conditions of Experiment Nos. 5 to 7 in
When the image was transmitted by placing it under the illumination of 100Lx, the contrast of the transmitted image was poor in any case, and it was difficult to obtain a clear image.

[0026]

Example 3 Three types of plastic multi-filament optical fibers obtained in Experiment Nos. 2 to 4 of Table 1 in Example 1 were used as image transmitting bodies, and 10 plastic optical fibers having a diameter of 100 μm were provided on the outside thereof. As a result of assembling an endoscope using the light guide, a clear and delicate image was obtained. Also, even if some of the light guides were cut at the center of the endoscope and the transmitted light leaked out, there was no reduction in the contrast of the transmitted image due to the leaked light, and it was clear and delicate. .

[0027]

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a plastic multifilament optical fiber of the present invention.

FIG. 2 is a partial cross-sectional view of a spinneret used for carrying out the present invention.

[Explanation of symbols]

 11 ………… Optical fiber 12 ………… Protective layer 13 ………… Peripheral fiber 21 ………… Core forming die plate 22 ………… Sheath component forming die plate 23 ………… Sea component Forming base plate 29 ………… Fiber gathering base plate 31 ………… Protective layer forming base plate

Claims (3)

[Claims] 1. A multiplicity of substantially circular cross sections having a diameter of 2 to
The sea-forming polymer of 70 μm was coated on the outer periphery of the island and discharged, and spun by arranging and joining them in a bales-stacking array structure or a four-sided stacking array structure, and inside the nozzle during spinning. 1 per 100 parts by weight of protective layer polymer
A method for producing a plastic multi-filament type optical fiber, characterized in that a light-shielding protective layer containing a coloring agent in an amount of 10 parts by weight or more and 10 parts by weight or less is coated and discharged. 2. A melt flow rate of the protective layer structure polymer with added colorant [MFR _1] is, from the melt flow rate of the sea-forming polymer [MFR _2] and a melt flow rate of the island portion configure polymer [MFR _3] The method for producing a plastic multi-filament optical fiber according to claim 1, characterized in that it is also composed of a large polymer. 3. A multiplicity of substantially circular cross sections having a diameter of 2 to
The outer periphery of the light-transmitting island of 70 μm is coated with a polymer for forming a sea portion and discharged, and the fibers are spun by being array-bonded in a bales-stacking array structure or a four-sided stacking array structure, and a spinning nozzle on the outer periphery. Illumination on the outer circumference of the multi-filament type optical fiber provided with a light blocking protective layer containing 1 to 10 parts by weight of the light blocking coloring agent per 100 parts by weight of the polymer for forming the protective layer, or in the light blocking protective layer. A multi-filament type optical fiber for an endoscope, which is provided with an optical fiber for use.