JP2005258217A - Method and apparatus for manufacturing clad pipe for plastic optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a clad pipe which has improved smoothness of an outer peripheral surface. <P>SOLUTION: Poly(vinylidene fluoride) (PVDF) is melted by heating at 180°C to 240°C. PVDF is made to pass through a sizing die 45 from an extruding die 43 as a molten pipe 44. The sizing die 45 has a lot of suction holes 73 and is installed in a cooling vacuum device 46. Inside of the cooling vacuum device 46 is decompressed in 60kPa to 95kPa and cooling water 75 of 3°C ejects out of a shower 74. An outer peripheral surface of the molten pipe 44 is molded at a molding surface of the sizing die 45. The molten pipe 44 becomes a pipe 51 after cooling solidification. The pipe 51 is made to pass through a vacuum chamber 71 and a water bath 72. Vacuum seals 76, 77, 50 formed of a sponge are attached to respective baths. Since vibration is absorbed by respective vacuum seals 76, 77, 50, vibration can be prevented from being propagated to the molten pipe 44. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  In recent years, with the development of the communication industry, the demand for optical fibers has increased, transmission loss is low, and low cost is required. The plastic optical member has advantages such as easy manufacture and processing and low cost compared to the quartz optical member having the same structure. In particular, the plastic optical fiber has a disadvantage that the transmission loss is slightly larger than that of the silica-based optical fiber because the material is made entirely of plastic. However, it has the advantages of having good flexibility, light weight, good workability, and easy manufacturing of an optical fiber having a large diameter compared to a quartz optical fiber. Further, it has an advantage that it can be manufactured at low cost. Therefore, various studies have been made on optical transmission bodies for short distances where the magnitude of transmission loss is not a problem (see, for example, Patent Document 1).

  A plastic optical fiber (hereinafter referred to as an optical fiber) includes a plastic core (hereinafter referred to as a core or core portion) and an outer shell (hereinafter referred to as a cladding or cladding portion) made of plastic having a lower refractive index than the core portion. It consists of and. As one of optical fiber manufacturing methods, there is known a method in which a pipe-shaped clad portion (hereinafter referred to as a clad pipe) is formed by a melt extrusion method, and a core portion is formed in the clad pipe. In particular, a refractive index distribution type (graded index type, hereinafter referred to as GI type) optical fiber having a core part having a distribution of refractive index from the center toward the outside has a bandwidth of an optical signal to be transmitted. Since it can be made large, it has recently attracted attention as an optical fiber having a high transmission capacity. As one of the manufacturing methods of such a GI type optical fiber, a method of producing a preform (base material) using an interfacial gel polymerization method and then stretching the preform is proposed ( For example, see Patent Document 2.)

  In addition, there is a demand for improvement in the surface smoothness of the outer peripheral surface of the clad pipe as well as improvement in the quality of the core portion serving as an optical transmission line in the optical fiber. When there are obvious streaks or irregularities on the outer peripheral surface of the clad pipe, in the preform drawing process (stretching process), the diameter variation (also referred to as diameter blurring) in which the optical fiber diameter becomes thicker or thinner becomes larger, Deterioration of transmission loss due to optical fiber structural irregularities cannot be ignored. In order to smoothly mold the outer peripheral surface of the clad pipe, it is important to adjust the conditions at the time of molding finishing. However, if the adjustment takes time, there is a problem that a large amount of raw material is lost.

  Therefore, as a method of smoothing the outer peripheral surface of a plastic pipe used for a clad pipe or the like, there is a method of improving the uniform cooling property of the pipe by winding a water-containing felt or the like around the inlet of the cooling tank and taking it smoothly. Are known. This method is effective as a molding method that is once molded into a pipe shape and then introduced into the cooling water tank (see, for example, Patent Document 3).

JP-A-61-130904 Japanese Patent No. 3332922 Japanese Patent Laid-Open No. 7-40423

  However, in recent years, it has become necessary to increase the productivity of clad pipes. Therefore, after the raw material polymer is extruded from the extrusion die of the melt extrusion apparatus, the form of the clad pipe is adjusted using a sizing die (molding die) provided in the cooling vacuum water tank. Subsequently, a method of forming a clad pipe by cooling while reducing the pressure in a cooling water tank is performed. When a packing such as a felt is installed as a vacuum seal at the outlet of the cooling vacuum water tank in order to take up the clad pipe by this method, the felt has a high hardness and cannot sufficiently absorb the vibration generated in the manufacturing apparatus. Therefore, when the vibration of the clad pipe is transmitted to the extrusion die and the raw material polymer is pushed out, it is pushed out while being vibrated, so that there is a problem that stepped streaks are generated on the outer peripheral surface of the clad pipe.

  When this stepped streak occurs, the position of the clad pipe may be finely adjusted by shifting the position of the packing that is vacuum-sealed. In the worst case, it is necessary to pass the clad pipe again, and there is a problem that time and raw material loss are large.

  An object of the present invention is to provide a method and an apparatus for producing a clad pipe for plastic optical fiber, which can improve the smoothness of the outer peripheral surface of the clad pipe and cause as little loss as possible at the start of production.

  The method for producing a clad pipe for plastic optical fiber according to the present invention includes melting a polymer, forming the polymer into a pipe shape through a sizing die, forming the pipe into a pipe in a vacuum cooling water tank, and taking out from the vacuum cooling water tank. In the pipe manufacturing method, a packing-like vacuum seal formed from a sponge-like material is used at the outlet of the pipe of the cooling vacuum water tank.

  The hardness of the sponge-like material is preferably in the range of 15 degrees to 35 degrees, more preferably in the range of 20 degrees to 30 degrees, as measured with SRIS0101 (C type). The diameter of the pipe passage hole of the packing-like vacuum seal is preferably (D1-0.5 (mm) or more and less than D1 (mm) with respect to the pipe diameter D1 (mm). It is preferable that the packing is composed of 2 or more and 4 or less packings, preferably a vacuum seal presser made of stainless steel is attached to the packing-like vacuum seal, and the diameter of the pipe passage hole of the vacuum seal presser. (Mm) is preferably (D1 + 20) mm or more and (D1 + 60) mm or less when the diameter of the pipe is D1 (mm), and the thickness of the packing is preferably 1 mm or more and 20 mm or less. It is preferable to use a water seal at the outlet of the pipe of the cooling vacuum water tank.

  The polymer is preferably a fluororesin. The present invention also includes a plastic optical fiber manufactured using a clad pipe manufactured by the method for manufacturing a plastic optical fiber clad pipe.

  An apparatus for producing a clad pipe for plastic optical fiber according to the present invention includes a sizing die that forms a molten polymer into a pipe shape, a vacuum cooling water tank that cools the pipe polymer to form a pipe, and the vacuum cooling water tank. In a plastic optical fiber clad pipe manufacturing apparatus including a pipe take-up means, a packing-like vacuum seal formed of a sponge-like material is provided at the pipe outlet of the vacuum cooling water tank.

  It is preferable that the hardness of the sponge-like material is in a range of 15 degrees or more and 35 degrees or less as measured by SRIS0101 (C type). It is preferable that the vacuum seal is composed of two or more and four or less packings. A vacuum seal presser formed from stainless steel is preferably attached to the packing-like vacuum seal. The diameter (mm) of the pipe passage hole of the vacuum seal presser is preferably (D1 + 20) mm or more and (D1 + 60) mm or less when the diameter of the pipe is D1 (mm). It is preferable to use a water seal at the outlet of the pipe of the cooling vacuum water tank.

  According to the method and apparatus for producing a clad pipe for plastic optical fiber of the present invention, a polymer is melted, the polymer is formed into a pipe shape through a sizing die, molded into a pipe in a vacuum cooling water tank, and taken up from the vacuum cooling water tank In the manufacturing method of the clad pipe for optical fibers, since a packing-like vacuum seal formed of a sponge-like material is used at the outlet of the pipe of the cooling vacuum water tank, it is possible to suppress vibration generated in a production line or the like from being transmitted to the pipe. Therefore, it is possible to obtain a clad pipe excellent in surface smoothness with no stepped streaks on the outer peripheral surface of the pipe. Further, in the conventional method, when stepped streaks are generated on the outer peripheral surface, the streaks are eliminated by finely adjusting the contact between the pipe and the packing-like vacuum seal. Since generation | occurrence | production of this can be suppressed, manufacture of a clad pipe can be started rapidly and time and raw material loss can be reduced.

  Moreover, the clad pipe manufactured by the method for manufacturing a clad for plastic optical fiber of the present invention is excellent in the smoothness of the outer peripheral surface. Therefore, when a preform produced using this is drawn, it is possible to prevent the occurrence of radial blurring of the optical fiber, so that a plastic optical fiber with a small transmission loss can be produced.

  FIG. 1 shows a method of manufacturing a plastic optical fiber manufactured using the plastic optical fiber clad pipe according to the present invention. In the clad pipe production step 11, the clad pipe 12 is produced by melt extrusion of the raw material polymer. A method for manufacturing the clad pipe 12 will be described later in detail. Next, a liquid for forming an outer core containing a polymerizable composition (hereinafter referred to as an outer core liquid) is prepared, and the outer core polymerization step 13 is performed using the liquid, and the outer core is attached to the hollow portion of the clad pipe 12. Form. Further, a liquid for forming an inner core (hereinafter referred to as an inner core liquid) is prepared, an inner core polymerization step 14 is performed to form an inner core, and a preform 15 is obtained. The preform 15 is heated, melted and stretched in a stretching step 16 to obtain a plastic optical fiber (hereinafter referred to as POF) 17. The POF 17 can be used as an optical transmission body as it is. However, it is preferable to form a protective layer in order to facilitate handling and to prevent damage to the outer surface of the POF 17. The protective layer is formed by the coating step 18, and a plastic optical fiber core wire (hereinafter referred to as an optical fiber core wire) 19 in which a coating material is formed as a protective layer on the outer peripheral surface of the POF 17 can be obtained. Furthermore, it can also be used as an optical fiber cable in which a plurality of optical fiber cores are bundled.

  FIG. 2A shows one form of the cross section of the preform 15. The inner core 30 is preferably of a graded index type (hereinafter referred to as GI type) in which the refractive index continuously decreases from the central part to the outer peripheral part so as to obtain high transmission characteristics (hereinafter referred to as GI type). b)). When the inner core 30 is formed, the outer core 31 is formed of a material capable of interfacial gel polymerization. Hereinafter, the raw material of the clad pipe for plastic optical fibers according to the present invention will be described. Next, the manufacturing method of the clad pipe for plastic optical fibers according to the present invention using the raw material will be described. Thereafter, a method for producing a preform from the clad pipe and producing POF and an optical fiber core wire from the preform will be described.

  A fluororesin is preferably used as a clad of an optical member because it has a low refractive index, excellent transparency, flexibility, and excellent mechanical strength. Further, since the fluororesin is generally hardly soluble in an organic solvent, the molding is mainly performed by melt molding at a high temperature. Examples of the fluororesin include polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorotrifluoroethylene (PCTFE), and the like.

  Among the fluororesins, polyvinylidene fluoride (PVDF) is preferably used, and a copolymer thereof is also preferably used. For example, a vinylidene fluoride-tetrafluoroethylene copolymer (preferably containing 50% by weight or more of vinylidene fluoride, more preferably containing 70% by weight or more and 90% by weight or less), vinylidene fluoride-hexafluoro Propylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride-trifluoroethylene copolymer, and a ternary or more copolymer of vinylidene fluoride. The clad pipe raw material according to the present invention is not limited to the fluororesin.

  FIG. 3 shows an embodiment of a production line 40 used in the method for producing the clad pipe 12 according to the present invention. In addition, the manufacturing method which uses PVDF as a cladding pipe raw material is illustrated. A hopper 42 for charging PVDF, which is a raw material polymer, is attached to the extruder 41. The extrusion part 41a of the extruder 41 is heated to a range of 180 ° C. to 240 ° C. to melt the charged PVDF. PVDF melted from the extrusion die 43 is extruded into a pipe shape using a screw (not shown) provided in the extrusion portion 41a. Hereinafter, this pipe is referred to as a melting pipe 44. The melting pipe 44 is passed through a sizing die 45 that molds its outer shape. The sizing die 45 is provided in the cooling vacuum device 46. The cooling vacuum device 46 is provided with a water supply device 47 and a drainage device 48 for supplying cooling water. Further, a vacuum device 49 is connected to reduce the inside of the cooling vacuum device 46 to a desired pressure. A vacuum seal 50 is provided at the pipe outlet of the cooling vacuum device 46, and the pressure in the cooling vacuum device 46 is adjusted to be within a desired pressure range. The pipe thickness (outer thickness) and outer diameter of the cooled pipe 51 (hereinafter referred to as a cooling pipe) 51 sent out from the cooling vacuum device 46 are measured by a thickness / outer diameter measuring device 52. Based on these measured values, the PVDF extrusion speed and the like are adjusted by a control unit (not shown).

  The cooling pipe 51 is changed to a pipe 54 by the take-up machine 53. The take-up machine 53 is provided with a pair or a plurality of pairs of driving rollers 57 and 58 and nip rollers 59 and 60 to which motors 55 and 56 are connected. By conveying the cooling pipe 51 with the driving rollers 57 and 58 and the nip rollers 59 and 60, tension can be applied to the cooling pipe 51. Then, the obtained pipe 54 is cut into a desired length and used as the clad pipe 12.

  FIG. 4 shows a schematic cross-sectional view of the cooling vacuum device 46. The cooling vacuum device 46 includes a cooling vacuum water tank 70, a vacuum chamber 71, and a water tank 72. A water supply device 47, a drain device 48 and a vacuum device 49 are attached to the cooling vacuum water tank 70. A large number of showers 74 are connected to the water supply device 47. The melt pipe 44 extruded from the extrusion die 43 is fed into a sizing die 45. A large number of suction holes 73 are formed in the sizing die 45, and the inner surface is a molding surface. Since the inside of the cooling vacuum water tank 70 is depressurized, the outer peripheral surface of the molten pipe 44 is sucked into the molding surface of the sizing die 45 by the suction hole 73. The outer peripheral surface of the melting pipe 44 is smoothed by the molding surface of the sizing die 45 and sent out. Cooling water 75 is supplied from the water supply device 47 to each shower 74. The cooling water 75 is sprayed from each shower 74 to the melting pipe 44 and the sizing die 45, so that the melting pipe 44 is solidified while its outer peripheral surface is molded (smoothed). The cooling water 75 is recovered by the drainage device 48 and reused. The temperature of the cooling water 75 is not particularly limited, but it is preferable to adjust the temperature of the cooling water 75 to a range of 1 ° C. to 20 ° C. and supply water to each shower 74.

  The inside of the cooling vacuum water tank 70 is depressurized by the vacuum device 49 so that the outer peripheral surface of the molten pipe 44 is brought into close contact with the molding surface of the sizing die 45. Further, by reducing the pressure, it is possible to prevent dust and the like from adhering to the molten pipe 44, and to prevent irregularities in the outer peripheral surface of the molten pipe 44 due to fluctuations in the flow of wind. Since the cooling water 75 is constantly discharged into the cooling vacuum water tank 70, the degree of vacuum does not have to be particularly high. However, in order to obtain a desired pressure in the cooling vacuum water tank 70, the pressure (absolute pressure) is preferably in the range of 60 kPa to 95 kPa.

  The cooling pipe 51 is sent from the cooling vacuum water tank 70 to the vacuum chamber 71. Although the vacuum device 49 is also connected to the vacuum chamber 71, a separate vacuum device may be attached to the vacuum chamber 71. A vacuum seal 76 is attached to the outlet of the cooling vacuum water tank 70, and the degree of vacuum of each of the cooling vacuum water tank 70 and the vacuum chamber 71 is adjusted to a desired range, and minute vibrations in the production line 40 are caused by cooling pipes. 51 is suppressed. When minute vibration is transmitted to the cooling pipe 51, the molten pipe 44 also vibrates, and as a result, fine vibration is generated in the resin extruded from the extrusion die 43, causing streaks.

  A schematic view of the outlet of the cooling vacuum water tank 70 is shown in FIG. The vacuum seal 76 is configured by overlapping packings 80 and 81. A sponge is preferably used as the material of the packings 80 and 81. Various types of sponges include polyethylene foam, polystyrene foam, polyurethane foam, chloroprene rubber, and the like. However, in the present invention, when the hardness (C type) measured by SRIS0101 (Japanese rubber industry standard) is 15 degrees or more and 35 degrees or less, the surface smoothness of the cooling pipe 51 is improved. . In addition, it is more preferable to use a thing of 20 degrees or more and 30 degrees or less. The hardness of SRIS0101 (C type) is a value read using a C type of a durometer (spring type hardness meter) which is a measuring instrument defined in the Japan Rubber Association standard.

  The thicknesses of the packings 80 and 81 are not particularly limited. However, the thickness L1 (mm) of the packing 80 and the thickness L2 (mm) of the packing 81 are preferably 1 mm or more and 20 mm or less, respectively. As shown in FIG. 5, when using a plurality of packings, the same material or thickness may be used for each packing, or different materials may be used. In addition, if two packings are used as shown in FIG. 5, the packings 80 and 81 absorb minute vibrations, so that the effect of not transmitting vibrations is more manifested. However, one packing is used for the vacuum seal. May be. Further, when using a plurality of packings, there is no particular limitation on the number of sheets to be used, but it is more preferable that the number is 4 or less from the viewpoint of alignment of mounting positions and cost.

  In addition, by setting the passage hole of the cooling pipe 51 formed in the packings 80 and 81 to be equal to or less than the diameter D1 (mm) of the cooling pipe 51, the degree of vacuum of the cooling vacuum water tank 70 can be maintained. More preferably, a through hole smaller than the diameter D1 (mm) is formed. Even if the passage hole is smaller than the diameter D <b> 1 of the cooling pipe 51, the packing is formed from a sponge, so that it is spread by its elastic force and allows the cooling pipe 51 to pass. When the vacuum seal of the vacuum cooling water tank 70 is a water seal that uses flowing water, the packing made of sponge contains water, and the gap between the pipe and the pipe is filled with a water layer formed by the surface tension of the water. As a result, the sealing performance is improved, and the vacuum degree can be efficiently controlled. On the other hand, if the passage holes of the packings 80 and 81 are too small, the tension applied to the cooling pipe 51 becomes too large, and problems such as poor conveyance and structural irregularities may occur. Therefore, in the present invention, the diameter of the passage hole is preferably (diameter D1 (mm) −0.5 mm) or more and less than the diameter D1 (mm), more preferably (diameter D1 (mm) −0.2 mm). ) The diameter is less than D1 (mm).

  The packings 80 and 81 may be directly fixed with screws, but are fixed with the screws 83 via the packing presser 82, thereby suppressing the vacuum sealability from being impaired due to excessive deformation of the packing. Therefore, the long-term usability of the packings 80 and 81 can be improved. The material of the packing retainer 82 is not particularly limited, but it is preferable to use stainless steel having excellent corrosion resistance. The diameter D2 (mm) of the passage hole 82a of the cooling pipe 51 of the packing retainer 82 is preferably in the range of (diameter D1 (mm) +20 mm) or more and (diameter D1 (mm) +60 mm) or less of the cooling pipe 51. If the diameter D2 of the passage hole 82a is less than (diameter D1 (mm) +20 mm), the packing may not sufficiently exhibit the ability to absorb vibration. On the other hand, if it is larger than (diameter D1 (mm) +60 mm), the exposed area of the packing is increased, and the function of protecting the packing may not be sufficiently exhibited. Or it is preferable that it is the range of 1.4 * D1 <= D2 (mm) <= 3.0 * D1.

  As shown in FIG. 4, the cooling vacuum device 46 preferably includes a water tank 72. A vacuum seal 77 having the same form as the vacuum seal 76 is preferably attached to the outlet of the vacuum chamber 71. Water 78 is placed in the water tank 72. The water 78 is absorbed by the packing of the vacuum seal 77 because the water 78 is sucked toward the vacuum chamber 71 held in a reduced pressure state. The gap of the packing is reduced and the vacuum degree of the vacuum chamber 71 is increased. Further, since water 78 is included in the packing of the vacuum seal 77, it is possible to prevent the occurrence of scratches that occur when the cooling pipe 51 contacts the vacuum seal 77. Further, when water 78 is put into the water tank 72 and the cooling pipe 51 passes through the water 78, the influence of vibration generated by the production line 40 or the external environment on the outer peripheral surface of the cooling pipe 51 is further reduced. It becomes possible. In addition, it is more preferable to attach the vacuum seal 50 of the same form as the vacuum seal 76 at the outlet of the water tank 72 in order to suppress appearance defects such as streaks on the outer peripheral surface of the cooling pipe 51. The water 78 may be stored as shown in FIG. 4 or may be circulated. The cooling pipe 51 is taken from the water tank 72 by the take-up machine 53.

  The raw material of the core part for making the plastic optical fiber is particularly limited as long as the polymer is light-transmitting to the transmitted light and has a refractive index higher than that of the cladding part. Although it is not a thing, it is preferable to use the material with little transmission loss of the optical signal transmitted.

  Particularly preferably used are organic materials which are generally known as raw materials having high light transmittance, such as (meth) acrylic acid esters (fluorine-free (meth) acrylic acid esters (a), Fluorine (meth) acrylic acid ester (b)), styrene compound (c), vinyl esters (d), polycarbonates and the like can be exemplified, and these homopolymers or two or more of these monomers And a mixture of homopolymers and / or copolymers. Among these, those containing (meth) acrylic acid esters as a composition can be more preferably used.

Specific examples of the polymerizable monomer listed above include (a) fluorine-free methacrylic acid ester and fluorine-free acrylic acid ester: methyl methacrylate (MMA), ethyl methacrylate, isopropyl methacrylate, methacrylic acid-tert -Butyl, benzyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, diphenylmethyl methacrylate, tricyclo [ ^5.2.1.0.2,6 ] decanyl methacrylate, adamantyl methacrylate, isobornyl methacrylate, etc. And methyl acrylate, ethyl acrylate, tert-butyl acrylate, and phenyl acrylate. In addition, (b) fluorine-containing acrylic acid ester and fluorine-containing methacrylate ester include 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3 , 3-Pentafluoropropyl methacrylate, 1-trifluoromethyl-2,2,2-trifluoroethyl methacrylate, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 2,2, 3,3,4,4-hexafluorobutyl methacrylate and the like. Furthermore, (c) styrene compounds include styrene, α-methylstyrene, chlorostyrene, bromostyrene, and the like. Furthermore, (d) vinyl esters include vinyl acetate, vinyl benzoate, vinyl phenyl acetate, vinyl chloroacetate and the like. Of course, it is not limited to these. The type and composition ratio of the constituent monomers are selected so that the refractive index of the polymer of the core portion made of a monomer alone or a copolymer is equal to or higher than that of the cladding portion. A particularly preferred polymer is polymethyl methacrylate (PMMA), which is a transparent resin.

  Furthermore, when the optical member is used for near-infrared applications, an absorption loss due to the C—H bond constituting the polymer of the core portion occurs, so that a deuterated polymer as described in Japanese Patent No. 3332922 and the like is used. Deuterium hydrogen atoms (H) of C—H bonds, including methyl methacrylate (PMMA-d8), polytrifluoroethyl methacrylate (P3FMA), polyhexafluoroisopropyl 2-fluoroacrylate (HFIP 2-FA), etc. By using a polymer substituted with atoms (D), fluorine (F), or the like, the wavelength region causing this transmission loss can be lengthened, and the loss of transmission signal light can be reduced. In addition, in order not to impair the transparency after polymerization of the raw material monomer, it is desirable to sufficiently reduce impurities and foreign substances that become scattering sources before polymerization.

  In the case of producing a polymer by polymerizing monomers, polymerization may be carried out with a polymerization initiator. In this case, as an initiator for initiating the polymerization reaction of the monomer, for example, benzoyl peroxide (BPO), tert-butylperoxy-2-ethylhexanate (PBO), di-tert- Examples thereof include peroxide compounds such as butyl peroxide (PBD), tert-butyl peroxyisopropyl carbonate (PBI), and n-butyl-4,4-bis (tert-butylperoxy) valerate (PHV). 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2-methylpropane), 2,2′-azobis (2-methylbutane), 2,2′-azobis (2-methylpentane), 2,2′-azobis (2,3-dimethylbutane), 2,2 '-Azobis (2-methylhexane), 2,2'-azobis (2,4-dimethylpentane), 2,2'-azobis (2,3,3-trimethylbutane), 2,2'-azobis (2 , 4,4-trimethylpentane), 3,3′-azobis (3-methylpentane), 3,3′-azobis (3-methylhexane), 3,3′-azobis (3,4-dimethylpentane), 3,3'-azobis 3-ethylpentane), dimethyl-2,2′-azobis (2-methylpropionate), diethyl-2,2′-azobis (2-methylpropionate), di-tert-butyl-2,2 ′ -Azo compounds such as azobis (2-methylpropionate). Of course, the polymerization initiator is not limited to these, and two or more kinds may be used in combination.

  It is preferable to adjust the degree of polymerization in order to keep various physical properties such as mechanical properties and thermophysical properties uniform throughout. A chain transfer agent can be used to adjust the degree of polymerization. About a chain transfer agent, according to the kind of polymerizable monomer used together, a kind and addition amount can be selected suitably. The chain transfer constant of the chain transfer agent for each monomer can be referred to, for example, Polymer Handbook 3rd edition (edited by J. BRANDRUP and EH IMMERGUT, published by JOHN WILEY & SON). The chain transfer constant can also be obtained by experiment with reference to Takayuki Otsu and Masaaki Kinoshita "Experimental Method for Polymer Synthesis", Kagaku Dojin, published in 1972.

  Examples of the chain transfer agent include alkyl mercaptans (eg, n-butyl mercaptan, n-pentyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, tert-dodecyl mercaptan), thiophenols (eg, thiophenol, m- Bromothiophenol, p-bromothiophenol, m-toluenethiol, p-toluenethiol, etc.) are preferably used. In particular, it is preferable to use an alkyl mercaptan such as n-octyl mercaptan, n-lauryl mercaptan, and tert-dodecyl mercaptan. A chain transfer agent in which a hydrogen atom of a C—H bond is substituted with a deuterium atom (D) or a fluorine atom (F) can also be used. Of course, the chain transfer agent is not limited to these, and two or more of these chain transfer agents may be used in combination.

  In the case where the core part, which is the center part of the plastic optical fiber, is a GI cloth type plastic optical fiber having a refractive index distribution from the center of the core part toward the outer peripheral direction, transmission performance is improved. And can be preferably used for high-performance communication applications. As a method for imparting a refractive index distribution, a combination of polymers having a plurality of refractive indexes or a copolymer obtained by combining them is used for the polymer forming the core, or the refractive index distribution is applied to the polymer matrix. It is necessary to add a dopant which is an additive for imparting.

The dopant is a compound different from the refractive index of the polymerizable monomer used in combination. The refractive index difference is preferably 0.005 or more. The dopant has the property that the polymer containing it has a higher refractive index than the additive-free polymer. These have a difference in solubility parameter of 7 (cal / cm ³ ) in comparison with a polymer produced by monomer synthesis as described in Japanese Patent No. 3332922 and JP-A-5-173026. ^{In addition to being} within ^1/2 , the difference in refractive index is 0.001 or more, and the polymer containing this has the property of changing the refractive index as compared with the additive-free polymer. Any of those which can coexist and are stable under the polymerization conditions (polymerization conditions such as heating and pressurization) of the polymerizable monomer which is the above-mentioned raw material can be used.

  Using the above-mentioned properties as a dopant that can stably coexist with the polymer and is stable under the polymerization conditions (polymerization conditions such as heating and pressurization) of the above-described raw material polymerizable monomer. Can do. In the present embodiment, the core portion-forming polymerizable composition contains a dopant, and in the step of forming the core portion, the progress of polymerization is controlled by the interfacial gel polymerization method, and the concentration of the dopant is given a gradient. A method of forming a refractive index distribution structure based on the dopant concentration distribution in the part is illustrated. In this way, the core portion having the refractive index distribution is referred to as a “refractive index distribution type core portion”. By forming the gradient index core portion, the obtained optical member becomes a gradient index plastic optical transmission body having a wide transmission band. In addition, a method of diffusing a dopant after forming a preform is also known. In addition, the dopant may be a polymerizable compound, and when a dopant of the polymerizable compound is used, a copolymer containing this as a copolymerization component has an increased refractive index as compared with a polymer not containing this. Those having the property to Specific examples include MMA-BzMA copolymers.

  Examples of the dopant include benzyl benzoate (BEN), diphenyl sulfide (DPS), triphenyl phosphate (TPP), benzyl-n-butyl phthalate (BBP), diphenyl phthalate (DPP), and biphenyl (DP). , Diphenylmethane (DPM), tricresyl phosphate (TCP), diphenyl sulfoxide (DPSO) and the like, among which BEN, DPS, TPP and DPSO are preferable. The dopant may be a polymerizable compound such as tribromophenyl methacrylate. In that case, when forming the matrix, the polymerizable monomer and the polymerizable dopant are copolymerized, so that various properties (especially optical properties). ) Is more difficult to control, but may be advantageous in terms of heat resistance. By adjusting the concentration and distribution of the dopant in the core, the refractive index of the plastic optical fiber can be changed to a desired value. The amount added is appropriately selected according to the use and the core material to be combined.

(Other additives)
In addition, other additives can be added to the core part, the clad part, or a part thereof within a range that does not deteriorate the optical transmission performance. For example, a stabilizer can be added to the core portion or a part thereof for the purpose of improving weather resistance, durability and the like. In addition, for the purpose of improving optical transmission performance, a stimulated emission functional compound for optical signal amplification can also be added. By adding the compound, the attenuated signal light can be amplified by the excitation light, and the transmission distance can be improved. For example, it can be used as a fiber amplifier in a part of the optical transmission link. These additives can also be contained in the core part, the clad part, or a part of them by adding to the raw material monomer and then polymerizing.

  The pipe 54 obtained by the above method is used as the clad pipe 12. The outer core polymerization step 13 for forming the outer core 31 in the hollow will be described. The outer core liquid is prepared by adding a desired additive (for example, a polymerization initiator, a chain transfer agent, a dopant, etc.) with methyl methacrylate (hereinafter referred to as MMA) as a main component as a main component. The outer core 31 is formed on the inner surface of the clad pipe 12 by a rotational polymerization method so as to form a hollow cylinder for forming an inner core. In the rotation polymerization method, the outer core liquid is put into the hollow portion of the clad pipe 12. The clad pipe 12 is preferably preliminarily polymerized with shaking in warm water to increase the viscosity of the outer core liquid. Thereafter, the clad pipe 12 is held in a horizontal direction (a state in which the height direction of the clad pipe is horizontal), and rotational polymerization is performed while heating.

  Next, the inner core polymerization step 14 for forming the inner core 30 will be described. The inner core liquid is prepared by adding a polymerization initiator, a chain transfer agent, a dopant and the like to MMA which is a polymerizable monomer. And using this inner core liquid, the method described in the international publication 93/08488 pamphlet and patent 3332922 is applied, the GI type (graded index type) inner core 30 is formed, A reform 15 is obtained (see FIG. 2). The form of the preform 15 is not particularly limited, but after forming the outer core 31 having a thickness t2 of 3 mm to 10 mm using a thickness t1 of the clad pipe 12 of 0.1 mm to 30 mm, the diameter D is It is preferable to form an inner core 30 of 5 mm to 20 mm. By using the preform 15 of this form, a POF 17 having excellent optical characteristics and mechanical strength can be obtained when a stretching process 16 described later is performed.

  The method for producing the GI preform used in the present invention is not limited to the interfacial gel polymerization method as described above. As described above, as the resin composition, those in which a dopant is added to a resin composition having a single refractive index, those in which resins having different refractive indexes are mixed, copolymers, and the like are used. In addition to the GI type, plastic optical fibers having various refractive index profiles such as a single mode type and a step index type are known, and the present invention is applicable to any of these plastic optical fiber manufacturing methods. You can also

  In the present invention, the method for producing the core portion is not limited to the above method. For example, it can also be formed by a rotational polymerization method in which interfacial gel polymerization is performed while rotating the inner core. In this case, after injecting the inner core liquid into the hollow of the clad pipe in which the outer core is formed, one end thereof is sealed and the horizontal state in the rotation polymerization apparatus (the height direction of the clad pipe is horizontal) ) And rotating while rotating. At this time, the inner core liquid may be supplied all at once or sequentially or continuously. At this time, by adjusting the supply amount, composition and degree of polymerization of the polymerizable composition for the inner core, in addition to the GI type having a continuous refractive index distribution, a multi-step type light having a stepped refractive index distribution It can also be applied to fiber production. In the present invention, this polymerization method is referred to as a core part rotation polymerization method (core part rotation gel polymerization method).

  In the core part rotational polymerization method, the surface area of the core liquid can be increased as compared with the interfacial gel polymerization method during the polymerization, so that bubbles generated from the core liquid can be easily degassed. Therefore, it can suppress that a foam contains in the preform obtained. Further, when the core part is formed by the core part rotational polymerization method, a preform having a hollow center part may be obtained. When the preform is used for a plastic optical member, particularly a plastic optical fiber, there is no particular problem because the hollow is closed while being melt-drawn. Further, when the preform is used for another optical member, for example, a plastic lens, it is possible to obtain a preform in which the hollow of the central portion is closed by performing melt drawing so as to close the hollow portion of the preform. It is possible to produce a plastic lens or the like from this preform.

  By stretching the preform 15, a POF 17 having a desired diameter, for example, 300 μm or more and 1000 μm or less can be obtained. There is no restriction | limiting in particular regarding the manufacturing method performed at the extending | stretching process 16, A known method can be applied equally. In addition, the residual monomer and water | moisture content in a preform can be reduced by drying the preform 15 under reduced pressure before performing the extending | stretching process 16. FIG. Thereby, the generation | occurrence | production of the extending | stretching bubble which arises by the residual monomer and water | moisture content at the time of melt-heating extending | stretching volatilizing and foaming can be suppressed.

  In the stretching step 16, the preform 15 is heated and melted and stretched. The heating temperature can be appropriately determined according to the material of the preform 15 and the like. In general, it is preferably performed in an atmosphere at 200 ° C to 250 ° C. The stretching conditions (stretching temperature and the like) can be appropriately determined in consideration of the diameter of the preform 15, the diameter of the POF 17, the material used, and the like. For example, as described in JP-A-7-234322, the drawing tension is set to 0.1 N or more in order to orient the molten polymer, or described in JP-A-7-234324. Thus, in order not to leave distortion after melt drawing, it is preferable to be 1N or less. Further, as described in JP-A-8-106015, a method of providing preheating at the time of stretching can be used. Regarding the POF 17 obtained by the above method, the bending elongation and lateral pressure characteristics of the optical fiber cable described later can be improved by defining the breaking elongation and hardness as described in JP-A-7-244220.

  The POF 17 can be used as it is, for example, as an optical transmission body such as an optical fiber. Usually, a protective layer is provided on the outer periphery of the POF 17 to protect the POF 17 and provide various functions. For example, products with improved bending and weather resistance of optical fibers, suppression of performance degradation due to moisture absorption, improved tensile strength, imparting stepping resistance, imparting flame resistance, protection from chemical damage, prevention of noise from external light, coloring, etc. For the purpose of improving the value and the like, the surface of the POF 17 is coated with one or more protective layers 18 and used as a plastic optical fiber core 19. The material for the protective layer and the method for forming the protective layer on the optical fiber are not particularly limited. Further, an optical fiber cable in which a plurality of optical fiber core wires 19 are bundled may be used.

  As a material for forming the protective layer, a material that does not cause thermal damage (for example, deformation, modification, thermal decomposition, etc.) to the POF 17 is selected. Specific examples include the following materials. Since these have high elasticity, they are also effective in terms of imparting mechanical properties such as bending. First, rubber which is one form of polymer can be used. Specifically, isoprene rubber (for example, natural rubber, isoprene rubber, etc.), butadiene rubber (for example, styrene-butadiene copolymer rubber, butadiene rubber, etc.), diene special rubber (for example, nitrile rubber, chloroprene rubber, etc.) ), Olefin rubber (for example, ethylene-propylene rubber, acrylic rubber, butyl rubber, halogenated butyl rubber, etc.), ether rubber, polysulfide rubber, urethane rubber and the like.

  It is possible to use a liquid rubber that exhibits fluidity at room temperature and cures when heated to lose its fluidity. Specifically, polydiene-based (for example, basic structure is polyisoprene, polybutadiene, butadiene-acrylonitrile copolymer, polychloroprene, etc.), polyolefin-based (for example, basic structure is polyolefin, polyisobutylene, etc.), polyether-based (for example, , Basic structure is poly (oxypropylene), etc., polysulfide type (eg, basic structure is poly (oxyalkylene disulfide), etc.), polysiloxane type (eg, basic structure is poly (dimethylsiloxane), etc.) Can do.

  Thermoplastic elastomers (TPE) can also be used. Thermoplastic elastomers are a group of substances that exhibit rubber elasticity at room temperature and are plasticized at high temperatures and are easy to mold. Specific examples include styrene TPE, olefin TPE, vinyl chloride TPE, urethane TPE, ester TPE, amide TPE, and the like. The polymers listed above are not limited to the above materials as long as they can be molded at a glass transition temperature Tg (° C.) or less of the POF17 polymer. Can also be used.

  Moreover, what hardens the liquid which mixed the polymer precursor, the reactive agent, etc. can be used. Examples thereof include a one-component thermosetting urethane composition produced from an NCO block prepolymer and a fine powder coating amine described in JP-A-10-158353. In addition, a one-component thermosetting urethane composition composed of an NCO group-containing urethane prepolymer described in WO95 / 26374 and a solid amine of 20 μm or less can also be used. In addition, additives such as flame retardants, antioxidants, radical scavengers, lubricants, and various fillers composed of inorganic compounds and / or organic compounds can be added for the purpose of improving performance.

  Furthermore, a multilayer coating layer may be used as necessary. When the primary coating has a sufficient thickness, thermal damage to the optical fiber core 19 is reduced. Therefore, the limit of the curing temperature of the optical fiber core 19 is looser than that in the case of directly coating the POF 17. can do. You may introduce | transduce into a secondary coating layer a flame retardant, a ultraviolet absorber, antioxidant, a radical scavenger, a light raising agent, a lubricant, etc. Some flame retardants include halogen-containing resins such as bromine, additives and phosphorus, but metal hydroxides can be preferably used as flame retardants from the viewpoint of safety such as reduction of toxic gases. .

  Moreover, in order to provide a plurality of functions, coatings having various functions may be laminated. For example, in addition to the above-mentioned flame retardancy, a barrier layer for suppressing moisture absorption of POF 17 and a moisture absorbing material for removing moisture, for example, a moisture absorbing tape and a moisture absorbing gel can be included in the coating layer or between the coating layers. A flexible material layer for relaxing stress at the time of flexibility, a cushioning material such as a foam layer, a reinforcing layer for increasing rigidity, and the like can be selected and provided depending on the application. In addition to the resin, when the thermoplastic resin contains a fiber having a high elastic modulus (so-called tensile fiber) and / or a highly rigid metal wire or the like, the mechanical strength of the optical fiber core wire 19 obtained can be increased. It is preferable because it can be reinforced. Examples of the tensile strength fiber include aramid fiber, polyester fiber, and polyamide fiber. Examples of the metal wire include stainless steel wire, zinc alloy wire, copper wire and the like. None of these are limited to those described above. In addition, a metal tube exterior for protection, an aerial support line, and a mechanism for improving workability during wiring can be incorporated.

  Also, depending on the type of use, the cable shape is a collective cable in which optical fibers are concentrically arranged, an aspect called a tape core wire arranged in a row, and a collective cable in which they are gathered together with a presser roll or wrap sheath The form can be selected according to the situation.

  Moreover, it is preferable that the optical transmission body using the POF 17 and the optical fiber core wire 19 manufactured by using the clad pipe 12 according to the present invention is securely fixed at the end using a connection optical connector. . As the connector, it is possible to use various commercially available connectors such as PN type, SMA type, SMI type, F05 type, MU type, FC type, and SC type that are generally known.

  An optical fiber as an optical member manufactured using the clad pipe 12 of the present invention, and a system for transmitting an optical signal using an optical fiber cable include various light emitting elements, light receiving elements, optical switches, optical isolators, optical An optical signal processing device including optical components such as an integrated circuit and an optical transceiver module is used. Moreover, you may combine with another optical fiber etc. as needed. Any known technique can be applied as a technique related to them. For example, the basic and actual of plastic optical fiber (published by NTS Corporation), Nikkei Electronics 2001.1.2.3, pages 110 to 127, “Printed Wiring You can refer to "This time, optical components are mounted on the board." Combined with various technologies described in the above documents, internal wiring in computers and various digital devices, internal wiring in vehicles and ships, optical terminals and digital devices, optical links between digital devices, general households and housing complexes・ Suitable for optical transmission systems suitable for short distances such as high-speed, large-capacity data communications and control applications that are not affected by electromagnetic waves, including optical LANs in factories, offices, hospitals, schools, etc. Can be used.

  Furthermore, IEICE TRANS. ELECTRON., VOL. E84-C, No.3, MARCH 2001, p.339-344 “High-Uniformity Star Coupler Using Diffused Light Transmission”, Journal of Japan Institute of Electronics Packaging Vol.3, No.6, 2000 pages 476 to 480 described in “interconnection by optical sheet bus technology”, and JP-A-10-123350, JP-A-2002-90571, JP-A-2001-290055, etc. Optical bus; described in JP-A-2001-74971, JP-A-2000-329962, JP-A-2001-74966, JP-A-2001-74968, JP-A-2001-318263, JP-A-2001-31840, etc. Optical star couplers described in JP 2000-241655 A, etc .; JP 2002-62457, JP 2002-101044, JP 20 Optical signal transmission device and optical data bus system described in each publication such as JP-A-305395; Optical signal processing apparatus described in JP-A-2002-23011; Optical signal cross-connect described in JP-A-2001-86537 System; optical transmission system described in JP-A-2002-26815; multi-function system described in JP-A-2001-339554, JP-A-2001-339555, etc .; and various optical waveguides, optical splitters, By combining with an optical coupler, optical multiplexer, optical demultiplexer, etc., a more advanced optical transmission system using multiplexed transmission / reception can be constructed. In addition to the above light transmission applications, it can also be used in the fields of illumination (light guide), energy transmission, illumination, and sensors.

  Hereinafter, the present invention will be described more specifically with reference to Example 1. The types of materials, their proportions, operations and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. The description will be made in detail in Experiment 1 according to the present invention, and in Experiments 2 to 4, description of the same conditions will be omitted. Further, also in Experiments 5 and 6 which are comparative examples, descriptions of the same conditions as in Experiment 1 are omitted.

  In Experiment 1, PVDF (polyvinylidene fluoride; KF polymer # 850 manufactured by Kureha Chemical Industry Co., Ltd.) was extruded into a pipe shape at an extrusion temperature of 180 ° C. with a single screw extruder 41 (plastic engineering research company, screw diameter φ50 mm). Using a sizing die 45 of about φ20 mm, a pipe having an outer diameter of φ20 mm and an inner diameter of φ18 mm (thickness t1 = 1 mm) was formed at a take-up speed of 1.0 m / min. The pipe was cooled by spraying cooling water (temperature 3 ° C.) 75 in the cooling vacuum water tank 70 in the form of a mist, and cooling from the outer surface of the sizing die 45 and the outer surface of the molten pipe 44. Two pieces of chloroprene rubber sponge packing (manufactured by INOAC Corporation) having a hardness of 5 degrees and a thickness of 5 mm were used at the outlet of the cooling vacuum water tank 70. In addition, the passing hole of packing used what was formed in 24.8 mm. The same was also attached to the vacuum seal 77 at the outlet of the vacuum chamber 71 and the vacuum seal 50 of the water tank 72. In addition, water was poured into the internal outlet of the vacuum cooling water tank 70 to form a water seal. The cooling pipe 51 is taken up while the thickness and outer diameter are measured by the thickness / outer diameter measuring device 52, and the take-up speed is finely adjusted as appropriate, so that the outer diameter is in the range of ± 100 μm and the thickness is ± 20 μm. I did it. The time required for stable molding was 20 minutes.

  The formed pipe 54 was cleaved, and the outer peripheral surface was observed at 500 times with a digital microscope, VH-8000 manufactured by Keyence Corporation. The smoothness of the outer peripheral surface is evaluated by visual inspection based on the size of the stepped streaks in the digital microscope image, and ◎ (no streaks), ○ (with weak streaks), △ (medium streaks) There was no streak (◎) when evaluated in four stages: Yes) and x (with large streaks).

  Next, using the obtained pipe 54 for the clad pipe 12 for the preform 15, the preform 15 was manufactured, and POF 17 was manufactured from the preform 15 to measure the radial blur and the transmission loss.

  The clad pipe 12 was inserted into a sufficiently rigid polymerization vessel having an inner diameter of 20 mm and a length of 600 mm. The clad pipe 12 was washed with pure water and dried at 90 ° C. Thereafter, using the same PVDF as that of the clad pipe, bottoming was performed on one end at 230 ° C. for 20 minutes.

  Next, the outer core polymerization step 13 was performed. In an Erlenmeyer flask, 120 g of methyl methacrylate (MMA, manufactured by Wako Pure Chemical Industries, Ltd.), 0.06 g of 2,2′-azobis (methyl isoacetate), and dodecyl mercaptan (manufactured by Wako Pure Chemical Industries, Ltd.) ) Was added to 0.48 g to prepare an outer core solution. The outer core liquid was put into the clad pipe 12. The air at the tip of the clad pipe 12 was replaced with argon. Thereafter, the tip of the clad pipe 12 was sealed using a silicon stopper and a sealing tape. The clad pipe 12 in which the outer core solution was put was placed in a 70 ° C. hot water bath and subjected to prepolymerization for 3 hours while shaking. Thereafter, the pre-polymerized clad pipe 12 is heated for 3 hours (rotational polymerization) while rotating at 3000 rpm while maintaining a temperature of 65 ° C. in a horizontal state (a state in which the height direction of the clad pipe is horizontal). Went. Thereafter, rotational polymerization was carried out at a rotational speed of 3000 rpm for 70 hours at 70 ° C. and further at 3000 rpm for 90 hours at 3 hours. A cylindrical tube having an outer core 31 made of PMMA inside the clad pipe 12 was obtained. The outer core 31 had a thickness t2 of 3.8 mm.

  Next, the inner core polymerization process 14 was performed. In an Erlenmeyer flask, 60 g of MMA (manufactured by Wako Pure Chemical Industries, Ltd.), 10 μL of di-t-butyl peroxide, 0.17 g of dodecyl mercaptan (manufactured by Wako Pure Chemical Industries, Ltd.), diphenyl sulfide An inner core solution was prepared from 4.2 g of Wako Pure Chemical Industries, Ltd. The clad pipe 12 on which the outer core 31 was formed was kept at 80 ° C. for 20 minutes, and then the inner core liquid was injected into the hollow portion. One end of the clad pipe 12 was covered with a seal tape, and then the clad pipe 12 was placed vertically in the autoclave (the bottom part was down and the part covered with the seal tape was up), and then the autoclave lid was set. The air in the autoclave was replaced with argon gas, and an atmosphere in which a pressure of 0.05 MPa was applied. Polymerization was performed by an interfacial gel polymerization method at 100 ° C. for 48 hours. Thereafter, heat polymerization and heat treatment were further performed at 120 ° C. to obtain a preform 15. Thereafter, the preform 15 was taken out of the autoclave.

  A stretching step 16 was performed by stretching the preform 15 to form POF 17. The preform 15 was placed in a heater having four temperature zones in the vertical direction. The temperature adjustment section was adjusted to 250 ° C., 220 ° C., 160 ° C., and 130 ° C. in order from the top. The POF 17 which was heated, melted and stretched and drawn from the heater was cooled with cooling water. The cooling water was put in the water tank and adjusted to 25 ° C. The stretching speed was 5 m / min, and the film was taken up by a take-up roller. In the take-up roller, a tension of 0.2 N was applied to the POF 17.

  1000 m of POF 17 was obtained. The diameter fluctuation of the POF 17 was measured. The measurement method is to measure an arbitrary part of POF17 using a laser size measuring instrument (manufactured by Keyence Co., Ltd.) and set the maximum outer diameter (μm) −minimum outer diameter (μm) = diameter blur (μm). About ± 20 μm. The average outer diameter of POF 17 was 330 μm. Furthermore, when the transmission loss value of POF17 was measured by a known method, it was 160 dB / km at a wavelength of 650 nm.

  In Experiment 2, a sponge packing made of chloroprene rubber having the same hardness and thickness as in Experiment 1 was used at the outlet of the cooling vacuum water tank. Further, a SUS packing presser 82 having a hole diameter of 55 mm and a thickness of 1 mm was used. The other conditions were the same as in Experiment 1. The evaluation result of the outer peripheral surface of the obtained pipe 54 was ○. The time required for stable molding was 15 minutes. Further, a preform 15 was produced from the clad pipe 12 obtained by cutting the pipe 54 under the same conditions as in Experiment 1, and then stretched to obtain POF 17. The average outer diameter was 330 μm, and the diameter blur was about ± 5 μm. The transmission loss value at a wavelength of 650 nm was 160 dB / km.

  In Experiment 3, using the chloroprene rubber sponge packing of the same hardness and thickness as in Experiment 1 at the outlet of the cooling vacuum tank, the outer peripheral surface of the pipe 54 obtained after being worn and deformed by continuous operation for 4 days was evaluated. As a result, there were large streaks (×). Further, a preform 15 was produced from the clad pipe 12 obtained by cutting the pipe 54 under the same conditions as in Experiment 1, and then stretched to obtain POF 17. The average outer diameter was 330 μm, and the diameter blur was about ± 40 μm. The transmission loss value at a wavelength of 650 nm was 220 dB / km.

  In Experiment 4, chloroprene rubber sponge packing having the same hardness and thickness as in Experiment 2 was used at the outlet of the cooling vacuum water tank, and the same packing presser 82 was used. As a result of evaluating the outer peripheral surface of the pipe 54 obtained after being worn and deformed by continuous operation for 4 days, there was a medium streak (Δ). Further, a preform 15 was produced from the clad pipe 12 obtained by cutting the pipe 54 under the same conditions as in Experiment 1, and then stretched to obtain POF 17. The average outer diameter was 330 μm, and the diameter blur was about ± 30 μm. The transmission loss value at a wavelength of 650 nm was 200 dB / km.

  In Experiment 5 which is a comparative experiment, a rubber packing having a thickness of 2 mm which is not sponge-like and has a hardness of 60 degrees was used at the outlet of the cooling vacuum water tank. As a result of evaluating the outer peripheral surface of the obtained pipe 54, there was a large streak (×). Further, a preform 15 was produced from the clad pipe 12 obtained by cutting the pipe 54 under the same conditions as in Experiment 1, and then stretched to obtain POF 17. The average outer diameter was 330 μm, and the diameter blur was about ± 40 μm. The transmission loss value at a wavelength of 650 nm was 250 dB / km.

  In Experiment 6 which is a comparative experiment, the pipe 54 was visually observed under the conditions of Experiment 5 to measure the time until the outer peripheral surface did not have stepped streaks and could be molded stably. When the same experiment was repeated three times, the average time required for stabilization was about 30 minutes. A preform 15 was produced from the clad pipe 12 obtained by cutting the pipe 54 under the same conditions as in Experiment 1, and then stretched to obtain POF 17. The average outer diameter was 330 μm, and the diameter blur was about ± 35 μm. The transmission loss value at a wavelength of 650 nm was 220 dB / km.

  In Experiment 1 according to the present invention, a pipe without streaks on the outer peripheral surface could be stably formed in 20 minutes. Further, in Experiment 2, although a slight streak was generated on the outer peripheral surface, it could be stably produced in 15 minutes. Then, it was found that the fine streak was in a range that hardly caused the deterioration of POF transmission loss. From Experiment 3 and Experiment 4, it was confirmed that using a packing presser during the long-term continuous operation has an effect of maintaining the smoothness of the outer peripheral surface of the manufactured pipe.

  Experiment 5, which is a comparative experiment, was in a state where adjustment of the vacuum seal was necessary because large stepped streaks were generated on the outer peripheral surface and the level required for the product was not reached. In Experiment 6, stepped streaks were generated on the outer peripheral surface once out of three times, and it could be avoided by fine adjustment of the vacuum seal portion, but it took about 30 minutes until stable molding was possible.

  From the above results, it has been clarified that a pipe made of a sponge material can be rapidly formed by using a packing made of a sponge material as a vacuum seal at the outlet of the cooling vacuum water tank. When using a packing presser, the smoothness of the outer surface is slightly inferior, but the time required for stable molding can be shortened. It was revealed that raw materials and time loss can be reduced. Furthermore, it has been found that the use time of the packing can be improved by using the packing presser.

It is a flowchart for demonstrating the manufacturing method of a plastic optical fiber. It is a figure for demonstrating sectional drawing and refractive index distribution of the preform manufactured using the plastic pipe which concerns on this invention. It is the schematic of the manufacturing line for manufacturing the plastic pipe which concerns on this invention. It is principal part sectional drawing of the manufacturing line of FIG. It is a principal part enlarged view of the manufacturing line of FIG.

Explanation of symbols

12 Cladding pipe 40 Production line 45 Sizing die 46 Cooling vacuum device 50, 76, 77 Vacuum seal 70 Cooling vacuum water tank 80, 81 Packing 82 Packing presser

Claims (9)

In the method for producing a clad pipe for plastic optical fiber, melting a polymer, forming the polymer into a pipe shape through a sizing die, forming the pipe in a vacuum cooling water tank, and taking out from the vacuum cooling water tank,
A method for producing a clad pipe for plastic optical fiber, comprising using a packing-like vacuum seal formed of a sponge-like material at an outlet of the pipe of the cooling vacuum water tank. The sponge-like material has a hardness of
2. The method for producing a clad pipe for plastic optical fiber according to claim 1, wherein the clad pipe is in a range of 15 degrees to 35 degrees as measured by SRIS0101 (C type). The diameter of the pipe passage hole of the packing-like vacuum seal is relative to the pipe diameter D1 (mm).
(D1-0.5 (mm) or more and less than D1 (mm), The manufacturing method of the clad pipe for plastic optical fibers of Claim 1 or 2 characterized by the above-mentioned.   The method for producing a clad pipe for plastic optical fiber according to any one of claims 1 to 3, wherein the packing-like vacuum seal is composed of two or more and four or less packings.   The method for producing a clad pipe for plastic optical fiber according to any one of claims 1 to 4, wherein a vacuum seal presser formed of stainless steel is attached to the packing-like vacuum seal. The diameter (mm) of the pipe passage hole of the vacuum seal presser is
6. The method for producing a clad pipe for plastic optical fiber according to claim 5, wherein the diameter of the pipe is (D1 + 20) mm or more and (D1 + 60) mm or less when D1 (mm) is used.   The method for producing a clad pipe for plastic optical fiber according to any one of claims 1 to 6, wherein a water seal is used at an outlet of the pipe of the cooling vacuum water tank.   The method for producing a clad pipe for plastic optical fiber according to any one of claims 1 to 7, wherein the polymer is a fluororesin. A plastic optical fiber clad comprising: a sizing die that forms a molten polymer into a pipe shape; a vacuum cooling water tank that cools the pipe-shaped polymer to form a pipe; and a take-up means that draws the pipe from the vacuum cooling water tank In pipe manufacturing equipment,
An apparatus for manufacturing a clad pipe for plastic optical fiber, comprising a packing-like vacuum seal formed of a sponge-like material at the pipe outlet of the vacuum cooling water tank.

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