JP2005181445A - Preform for plastic optical member, its manufacturing method, plastic optical member, and plastic optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress bubble from being contained in a base material for a plastic optical fiber. <P>SOLUTION: A hollow tube is manufactured from polyvinylidene fluoride to use as a clad pipe. The method for manufacturing a base material for a plastic optical member includes a process in which the hollow tube is heated and evacuated to remove impurities and water before an area composed of polymers is formed by infusing polymeric composition (MMA) that becomes a core part. Since the bubble is suppressed from being contained in the base material for the plastic optical member, generation of bubbles can be inhibited at the time of heating, fusing and drawing of the material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a preform for a plastic optical member, a manufacturing method thereof, a plastic optical member, and a plastic optical fiber.

  Plastic optical members have advantages such as easy manufacture and processing and low cost compared to quartz optical members having the same structure. In recent years, optical fibers and optical lenses, Various applications such as waveguides have been attempted. Among these optical members, plastic optical fibers, in particular, have the disadvantage that the transmission loss is slightly larger than that of quartz-based materials because all the strands are made of plastic, but they have good flexibility and are lightweight. Therefore, the processability is good, and it is easy to manufacture as an optical fiber having a large diameter as compared with a silica-based optical fiber, and it can be manufactured at a lower cost. Accordingly, various studies have been made on optical communication transmission media for short distances where the magnitude of transmission loss does not become a problem (see, for example, Patent Document 1).

  A plastic optical fiber generally has a core made of an organic compound having a polymer matrix (hereinafter referred to as a core part or a core) and an organic material having a refractive index different from that of the core part (generally having a low refractive index). It is composed of an outer shell made of a compound (hereinafter referred to as a clad portion or a clad). In particular, a refractive index distribution type (hereinafter referred to as GI type) plastic optical fiber having a core having a distribution of refractive index from the center toward the outside can increase the bandwidth of an optical signal to be transmitted. Since it is possible, it has recently attracted attention as an optical fiber having a high transmission capacity. As one of the methods for producing such a GI type optical member, there has been proposed a method of producing a preform (base material) using an interfacial gel polymerization method and then stretching the preform (for example, , See Patent Document 2).

JP-A-61-130904 Japanese Patent No. 3332922

  By the way, when this plastic optical fiber is manufactured from a polymerizable composition containing a monomer or the like, voids due to volume reduction due to polymerization shrinkage of the monomer, by-products of the polymerization reaction, or foaming due to dissolved low-boiling substances are generated. May happen. In addition, as a method for manufacturing an optical member, there is a method in which a preform is manufactured once and the preform is processed to obtain, for example, an optical fiber. In this case, after forming a preform having a diameter larger than that of the optical fiber, it is melt-drawn to obtain an optical fiber. For this reason, even if the preform does not contain bubbles, the low-boiling substance dissolved by heating may foam and bubbles may be generated in the optical fiber. Since the bubbles cause light scattering, there arises a problem that performance as an optical member is lowered and productivity is lowered.

  The objective of this invention is providing the plastic optical fiber manufactured from the preform for plastic optical members in which foaming was suppressed, its manufacturing method, and the preform for plastic optical members.

  According to the first method for producing a preform for a plastic optical member of the present invention, the cladding portion is a hollow tube made of a polymer, and a polymerizable composition is injected into the hollow tube and polymerized to produce a core portion. In the method for producing a preform for a member, the hollow tube is heat-treated at a temperature not lower than 40 ° C. and not higher than the heat distortion temperature (° C.) of the polymer before the core portion is manufactured.

  According to the second method for producing a preform for a plastic optical member of the present invention, the cladding portion is a hollow tube made of a polymer, and a polymerizable composition is injected into the hollow tube and polymerized to produce a core portion. In the method for producing a preform for a member, before the core part is manufactured, the hollow tube is subjected to a decompression process at a temperature of 15 ° C. or more and a temperature equal to or lower than the heat distortion temperature (° C.) of the polymer.

  It is preferable to wash the hollow tube before the heat treatment or the pressure reduction treatment. When the polymerization of the core portion is performed, the hollow tube can be rotated while the axis of the hollow tube is horizontal. A step of producing a hollow tube in which at least one layer made of a polymer is formed in the hollow tube may be included. It is preferable that a plastic optical fiber is obtained when the preform for the plastic optical member is heated, melted and stretched. The present invention also includes a plastic optical member preform produced by the method for producing a plastic optical member preform described above. The preform for a plastic optical member of the present invention is a plastic optical having a clad formed from a hollow tube made of a polymer, and a core formed by injecting and polymerizing a polymerizable composition into the hollow tube. In the member preform, the core portion has a refractive index distribution from the center to the radial direction. It is preferable that the core portion has a refractive index distribution that continuously decreases from the center to the radial direction. It is preferable that the refractive index of the cladding part is smaller than the refractive index of the core part. The clad portion is also made of a fluoropolymer. Furthermore, the present invention includes a plastic optical fiber obtained by heating and stretching the preform for a plastic optical member described above.

  The plastic optical member of the present invention has a clad portion as a hollow tube made of a polymer, a polymerizable composition is injected into the hollow tube and polymerized, and a preform for the plastic optical member having a core portion produced by heating is stretched. In the obtained plastic optical member, the stretched plastic optical member has less than 200 bubbles having a minor axis diameter of 10 μm or more per 100 m of the stretched plastic optical member. A plastic optical fiber obtained by cutting out a certain length from the plastic optical member can be obtained in which the plastic optical fiber has less than 20 bubbles with a minor axis diameter of 10 μm or more per 10 m of the plastic optical fiber. When producing the core part of the preform for the plastic optical member, it is preferable to perform polymerization while rotating the hollow tube.

  According to the first method for producing a preform for a plastic optical member of the present invention, since the hollow tube is heat-treated before the core portion is manufactured, residual monomers, solvents, impurities, etc. of the hollow tube can be removed. It is possible to suppress the generation of bubbles in the preform. In addition, since the heat treatment temperature is in the range of 40 ° C. or more and the heat deformation temperature (° C.) or less of the polymer constituting the hollow tube, it is possible to efficiently remove residual monomers, solvents, impurities, etc. Thermal damage to the tube can be suppressed.

  According to the second method for producing a preform for a plastic optical member of the present invention, the hollow tube is subjected to a decompression process before the core portion is manufactured, so that residual monomers, solvents, impurities, etc. of the hollow tube can be removed. Thus, it is possible to suppress the generation of bubbles in the preform. Further, when the treatment is performed, the hollow tube is placed under reduced pressure, and the heating temperature is set to 15 ° C. or more and the heat deformation temperature (° C.) or less of the polymer constituting the hollow tube. , Impurities and the like can be removed even at a lower temperature than in the first method. Since heat treatment is possible at a lower temperature, thermal damage to the hollow tube can be further suppressed.

  Further, in the first and second production methods, by washing the hollow tube before performing the respective treatments, a part of the residual monomer, solvent, impurities, etc. contained in the hollow tube, particularly the surface or the surface Since nearby objects can be removed, the time for performing each subsequent process can be shortened.

  According to the method for producing a preform for a plastic optical member of the present invention, the hollow tube is subjected to the heat treatment or the decompression treatment, and the hollow tube is rotated when the core portion is polymerized. In addition, the foam is suppressed from being contained in the core part. Thereby, the deterioration of the transmission loss of the plastic optical fiber obtained by heating, melting and stretching the preform for plastic optical member can be extremely prevented.

  In addition, the method of the present invention can be preferably applied when processing a hollow tube in which at least one layer made of a polymer is formed in the hollow tube. That is, when the polymer layer is an outer core layer, by performing at least one of the heat treatment or the reduced pressure treatment according to the present invention, residual monomers, solvents, Impurities can be easily removed. When high excitation light is incident on the plastic optical fiber obtained by using this preform, there is no defect due to residual monomer in the outer core layer that is the main transmission path of the light. Can be suppressed.

  In addition, since the plastic optical fiber obtained from the preform has very few defects, one having excellent transmission characteristics can be obtained. The core portion of the optical fiber according to the present invention can be applied to any of graded index type, step index type, and multi-step index type. Furthermore, the present invention can also be applied to those in which the clad portion is formed from a fluoropolymer.

  The plastic optical member of the present invention has a clad portion as a hollow tube made of a polymer, a polymerizable composition is injected into the hollow tube and polymerized, and a preform for the plastic optical member having a core portion produced by heating is stretched. In the plastic optical member obtained in the above, the foam having a minor axis diameter of 10 μm or more in the stretched plastic optical member can be suppressed to less than 200 per 100 m of the stretched plastic optical member. Deterioration of transmission loss due to light scattering and reflection is suppressed. For this reason, the plastic optical fiber obtained by cutting out a certain length from the plastic optical member suppresses the deterioration of transmission loss. The plastic optical fiber is obtained by polymerizing the hollow tube while rotating the core portion.

  A method for producing a preform for a plastic optical member (hereinafter referred to as a preform) according to the present invention is shown in FIG. In the clad production step 11, a hollow cylindrical clad pipe 12 is produced. Next, an outer core part preparation pretreatment step 13 is performed to remove residual monomers and residual moisture from the clad pipe 12. 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 process 14 is performed using the liquid, and the outer core is attached to the hollow portion of the clad pipe 12. Form. Next, an inner core part preparation pretreatment step 15 is performed to remove residual monomers and residual moisture in the outer core and impurities generated during the formation of the outer core part. Furthermore, a liquid for forming an inner core (hereinafter referred to as an inner core liquid) is prepared, an inner core is formed by an inner core polymerization step 16, and a preform for plastic optical member (hereinafter referred to as a preform) 17 is manufactured. . The preform 17 is heated, melted and stretched in a stretching step 18 to obtain a plastic optical fiber (hereinafter referred to as an optical fiber) 19. The optical fiber 19 can be used as an optical fiber in the form of a bare wire. However, it is preferable to form a protective layer in order to facilitate handling or to prevent damage to the outer surface of the optical fiber 19. The protective layer can be formed by the coating step 20 to obtain a plastic optical fiber cable (hereinafter referred to as an optical fiber cable) 21 in which the outer peripheral surface of the optical fiber 19 is coated.

  FIG. 2A shows one form of the cross section of the preform 17. The inner core 30 is preferably a GI type whose refractive index continuously decreases from the center to the outer periphery so that high transmission characteristics can be obtained (see FIG. 2B). The outer core 31 is formed of a material capable of interfacial gel polymerization in forming the inner core 30. The clad pipe 12 is preferably formed of a material that has excellent mechanical strength and does not emit transmitted light outside the clad pipe 12. The present invention will be described in detail by taking as an example a method for manufacturing the preform 17 shown in FIG. First, the cladding material, the core material, and the desired additive will be described, and then the preform manufacturing method will be described. Note that this exemplification is only for explaining the present invention in detail, and does not limit the present invention.

  The clad material is generally required to be a thermoplastic polymer having transparency. In addition, light having a refractive index lower than that of the core part is used so that light transmitted through the core part is totally reflected at the interface between the core part and the clad part. The difference is not particularly limited, but is preferably 0.03 or less. Further, an amorphous polymer is used so that optical anisotropy does not occur. Furthermore, those having good adhesion to the core part, excellent toughness, and excellent heat and humidity resistance are preferably used.

  For example, such a polymer includes polymethyl methacrylate (hereinafter referred to as PMMA). A copolymer of methyl methacrylate (hereinafter referred to as MMA) and fluorinated (meth) acrylate such as trifluoroethyl methacrylate (hereinafter referred to as 3FMA) or hexafluoroisopropyl methacrylate can also be used. Moreover, the copolymer with alicyclic (meth) acrylates, such as branched (meth) acrylates, such as tert-butyl methacrylate, and isobornyl methacrylate, is mentioned. Furthermore, polycarbonate, norbornene resin (for example, ZEONEX (registered trademark: manufactured by Nippon Zeon)), functional norbornene resin (for example, ARTON (registered trademark: manufactured by JSR)), fluorine resin (for example, polytetrafluoroethylene) Fluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.) can also be used. In addition, a fluororesin copolymer (for example, PVDF copolymer), tetrafluoroethylene-perfluoro (alkyl vinyl ether) (PFA) random copolymer, chlorotrifluoroethylene (CTFE) copolymer, or the like is used. You can also Moreover, the hydrogen loss (H) of these polymers can be substituted with deuterium atoms (D) to reduce transmission loss.

  The material of the core part is not particularly limited as long as the optical transmission function is not impaired. Particularly preferably used are raw materials having high light transmittance as an organic material. For example, the following (meth) acrylic acid esters (fluorine-free (meth) acrylic acid ester (a), fluorine-containing (meth) acrylic acid ester (b)), styrenic compound (c), vinyl esters (D), bisphenol A, which is a raw material of polycarbonates, can be exemplified, and these homopolymers, copolymers composed of two or more of these monomers, and homopolymers and / or copolymers A mixture is mentioned. 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, the present invention is not limited to these, and the types and composition ratios of the constituent monomers are set so that the refractive index of the polymer consisting of the monomer alone or the copolymer is equal to or higher than that of the clad portion. Is preferred. A particularly preferred polymer is polymethyl methacrylate (PMMA), which is a transparent resin.

  Furthermore, when transmitting near-infrared rays to an optical fiber or an optical fiber cable, absorption loss due to the C—H bond to be formed occurs, and therefore deuterated polymethyl as described in Japanese Patent No. 3332922 and the like. Deuterium atoms include hydrogen atoms (H) of C—H bonds, including methacrylate (PMMA-d8), polytrifluoroethyl methacrylate (P3FMA), polyhexafluoroisopropyl 2-fluoroacrylate (HFIP 2-FA), and the like. By using a polymer substituted with (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.

  When a polymer is produced by polymerizing a polymerizable monomer, 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 chain transfer agents include alkyl mercaptans (for example, n-butyl mercaptan, n-pentyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, tert-dodecyl mercaptan, etc.), thiophenols (for example, 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 or a fluorine atom 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.

  When the core part is a GI type having a refractive index distribution from the center toward the outer peripheral direction, transmission performance is improved, so that broadband optical communication can be performed, and this is preferably used for high-performance communication applications. Can do. 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 an additive for imparting (hereinafter referred to as a dopant).

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.

  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. It is preferable to use those having the property of 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 refractive index adjusting agent has a gradient. The method of forming the refractive index distribution structure based on the concentration distribution of the refractive index adjusting agent in the core portion is exemplified, but other methods are also known in which the refractive index adjusting agent is diffused after the preform is formed. . Hereinafter, the core portion having a refractive index distribution is referred to as a GI-type core portion. By forming the GI-type core portion, the obtained optical member becomes a GI-type plastic optical member having a wide transmission band.

  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 the movement of the dopant can be suppressed, which may be advantageous in terms of stability of the refractive index distribution against heat. By adjusting the concentration and distribution of the refractive index adjusting agent 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 intended use, usage pattern, core material to be combined, and the like.

  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. Further, for the purpose of improving optical transmission performance, a stimulated emission functional compound for optical signal amplification can be added. By adding the compound, the attenuated signal light can be amplified by the pumping light, and the transmission distance is 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.

  In the manufacture of the preform, a clad pipe 12 is first produced by a clad production step 11. The production method of the clad pipe 12 is not particularly limited, and any known method can be used. For example, a thermoplastic polymer can be used as a raw material for the clad pipe 12, and a polymer produced by a melt extrusion method in which a polymer is heated and melted and extruded into a hollow tube can be used. In this method, any of the aforementioned polymers can be used arbitrarily, but a fluororesin can be preferably used from the viewpoint of physical properties such as refractive index and performance, and PVDF can be particularly preferably used. PVDF is preferably used as a material for a clad pipe because it has excellent mechanical strength and has a low refractive index and thus has a high ability to confine light transmitted through an optical fiber. The clad pipe 12 itself becomes a reaction vessel (polymerization vessel) when a preform is produced by the interfacial gel polymerization method. Therefore, one end of the hollow cylindrical clad pipe 12 manufactured by the melt extrusion method is bottomed using the same polymer as the clad pipe material, or a highly chemical-resistant material (fluororesin from the viewpoint of preventing contamination) Etc.) is preferably sealed. In addition, as a material of the clad pipe 12, acrylic resin (also referred to as methacrylic resin) such as PMMA can be used.

  Moreover, the clad pipe 12 can also be manufactured by the clad preparation process 11 using a rotation polymerization method. For example, when the clad pipe 12 is formed from PMMA, MMA is used as the polymerizable monomer. A clad forming liquid (hereinafter referred to as a clad liquid) containing the MMA and a desired additive such as a reaction initiator, a chain transfer agent, and a dopant (refractive index adjusting agent) is prepared. This clad liquid is put into a cylindrical polymerization vessel having sufficient rigidity and having an inner diameter corresponding to the outer diameter of the desired preform. Next, it is preferable to perform prepolymerization while shaking the polymerization vessel in warm water to increase the viscosity of the clad liquid. Thereafter, the polymerization vessel is held in a horizontal direction (a state in which the height direction of the cylinder is horizontal), and rotational polymerization is performed while heating. In addition, the installation direction of the superposition | polymerization container at the time of performing rotation polymerization is not limited to a horizontal direction. For example, it may be installed and rotated in a vertical direction or an oblique direction substantially parallel to gravity. Thereby, it superposes | polymerizes so that a wall may be formed in the superposition | polymerization container inner surface, and the clad pipe 12 with thickness t1 substantially uniform can be obtained. In addition, it is preferable to deaerate a clad liquid by ultrasonication or a pressure reduction process after preparation. The polymerization is more preferably carried out in an inert gas atmosphere such as helium, argon or nitrogen. A commercially available pipe-shaped product can also be used for the clad pipe.

  In addition, the clad pipe used in the present invention may be formed of multiple layers in order to impart various functions such as improvement in mechanical strength and flame retardancy. By forming the clad pipe in multiple layers, the polymerizability and moisture resistance of the core portion can be provided in separate layers. For example, when a clad pipe is formed from two layers of a hollow tube inner wall portion that forms a core portion and an interface and a hollow tube outer wall portion that covers the hollow tube inner wall portion, the polymerizability of the core portion is determined by the inner wall of the hollow tube. The moisture resistance can also be provided at the outer wall of the hollow tube. The material that can be preferably used for providing the polymerizability of the core part is such that when the core part is generated by interfacial gel polymerization, no interface irregularity occurs between the inner wall part of the hollow tube and the core part. . In addition, when each layer consists of multiple layers, when the material and characteristics of the inner wall of the hollow tube are used as the outer layer of the core part, it may be referred to as the inner cladding when it is used as one constituent layer of the outer core and the cladding.

Specifically, the difference between the solubility parameter of the material (polymer) constituting the inner wall portion of the hollow tube and the solubility parameter of the material (polymer) constituting the core portion is 14000 (J / m ³ ) ^1/2 [= 7 (Cal / cm ³ ) ^1/2 ] or less, preferably 10,000 (J / m ³ ) ^1/2 [= 5 (cal / cm ³ ) ^1/2 ] or less, more preferably 6000 (J / m ³ ) ^{1 / 2} [= 3 (cal / cm ³ ) ^1/2 ] or less is preferably used. When the [outer] clad portion that provides moisture resistance is selected, the polymer with the core portion need not be considered. Therefore, in addition to the aforementioned materials, a polymer having a water absorption rate of less than 1.8% is arbitrarily selected. You can choose. In addition, the material that can be preferably used in the inner wall portion of the hollow tube in the multi-layer configuration only needs to consider at least the polymerizability of the core portion. If the difference in solubility parameter is within the above range, it can be preferably used.

  Below, the manufacturing method of the preform for plastic optical members formed from a clad (hollow pipe outer wall part), an outer core (hollow pipe inner wall part), and an inner core is demonstrated.

  Using the clad pipe 12 obtained by any one of the above methods, the outer core portion preparation pretreatment step 13 is performed. Various impurities remain in the clad pipe 12 during or after manufacture. As the first impurity, when the clad pipe 12 is manufactured, a polymerizable monomer that is a material of the clad pipe 12 and a decomposition product thereof can be used. Alternatively, an additive such as a polymerization initiator for initiating the polymerization reaction is also contained. Furthermore, the second impurity is moisture. Some water is taken into the polymer during the polymerization reaction, and some water in the atmosphere adheres while the clad pipe 12 is transported or stored. Moreover, these impurities usually evaporate more easily than the polymer that is the main component of the clad pipe 12. If the outer core polymerization step 14 and the inner core polymerization step 16 are performed with these impurities remaining, the impurities may volatilize and remain in the preform 17 as bubbles. When the optical fiber 19 is manufactured in the preform 17 in the stretching process 18, bubbles (also referred to as voids) are generated. Bubbles scatter the light being transmitted and cause transmission loss to deteriorate. Therefore, in the present invention, the processing step is performed before the core portion is formed. In addition, when the core part is formed of the outer core 31 and the inner core 30 as in the preform 17 shown in FIG. 2, bubbles are generated by performing a processing step before forming any of the core parts. However, it is most preferable to perform the treatment steps 13 and 15 before both the outer core polymerization step 14 and the inner core polymerization step 16 respectively.

  Any known method for removing impurities in the polymer can be applied to the outer core portion preparation pretreatment step 13. In particular, in order to obtain the effects of the present invention, it is preferable to perform the method described below.

  The first method includes a method of removing the volatile substance and water inside or on the surface by heating the clad pipe 12. The temperature is not particularly limited, but is preferably 40 ° C. or higher. Moreover, it is preferable that it is below the heat deformation temperature (degreeC) of the polymer of the main components of the clad pipe 12. When the heating temperature is less than 40 ° C., the volatile substance is hardly volatilized and a long time is required for removing the volatile substance. Further, when heated to a temperature higher than the thermal deformation temperature (° C.) of the polymer, volatilization of volatile substances and water occurs easily, but the clad pipe 12 starts to melt and the form of the clad pipe 12 may be disturbed. In addition, the main component polymer of the clad pipe 12 is likely to be thermally decomposed, which may cause impurities.

  The heat treatment time is not particularly limited, but is defined in consideration of the material of the main component polymer of the clad pipe 12 and its thickness t1. In the usual case, it is preferably in the range of 10 minutes to 48 hours, more preferably in the range of 1 hour to 36 hours, and most preferably in the range of 4 hours to 24 hours. If it is less than 10 minutes, the clad pipe 12 is not sufficiently heated, and the volatilization of the impurities hardly occurs, and it may be insufficient to reduce the impurities. In addition, if it exceeds 48 hours, the productivity is inferior, and a part of the main component polymer of the clad pipe 12 may be thermally decomposed to further generate impurities. In the present invention, this method is referred to as heat treatment.

  If the heat treatment of the clad pipe 12 is performed on the upper limit side, that is, the heat deformation temperature (° C.) or higher of the polymer, the clad pipe 12 may cause damage such as heat deformation. This often occurs because the clad pipe 12 is locally heated during heating. Therefore, the clad pipe 12 is inserted into a pipe formed of a metal having a high thermal conductivity (for example, stainless steel, copper, aluminum, etc.). And it becomes possible to heat the clad pipe 12 uniformly by setting the metal pipe to a desired temperature. Thereby, it becomes possible to perform the heat processing which heats to the heat deformation temperature (° C.) or higher of the polymer without damaging the clad pipe 12. In this case, it is more preferable to perform the heat treatment while rotating the metal pipe into which the clad pipe 12 is inserted.

  Specifically, when the clad pipe 12 is made of PMMA as a main component and the thickness t1 is 0.5 mm to 50 mm, the thermal deformation temperature of PMMA is 90 ° C. to 100 ° C. The heating time is preferably in the range of 10 minutes to 48 hours, more preferably in the range of 50 ° C. to 90 ° C., and 1 hour to 36 hours, most preferably The range is 60 ° C. to 80 ° C. and 4 hours to 24 hours. Further, when the clad pipe 12 is formed with PVDF as a main component, the PVDF has a heat deformation temperature (° C.) of 55 ° C. to 115 ° C. Therefore, the heating temperature is 40 ° C. to 115 ° C., and the heating time is The range is preferably 10 minutes to 48 hours, more preferably 50 ° C. to 115 ° C., and 1 hour to 36 hours, and most preferably 55 ° C. to 95 ° C., 4 hours to 24 hours. It is to be in the range.

  When the clad pipe 12 is formed from another polymer, the heat distortion temperature (° C.) is set as the upper limit value of the heating temperature. Examples of the heat distortion temperature (° C.) of the polymer include a melting point (Tm) and a glass transition temperature (Tg) which are constants specific to the material. If the melting point of the polymer varies, the lowest temperature is taken as a reference. In addition, when using a polymer having no melting point and only a decomposition temperature, the decomposition temperature is regarded as the melting point. Further, in the case where the clad pipe 12 is formed of the above-mentioned multi-layers, and when the main component polymer of each layer is different, the one having the lowest polymer melting point is used as a reference. . Or, a load deflection temperature (heat deformation temperature), a heat deterioration temperature, etc., which are usually referred to as heat resistant temperatures, can be used. The load deflection temperature is measured using a value measured by a test method defined in ASTM D-648, JIS K 7207, or the like. Moreover, the value measured by Vicat softening temperature prescribed | regulated by JISK7206, the softening temperature measurement by the TAM method prescribed | regulated by JISK7196, etc. can also be used. These measurements are all accelerated tests for measuring the deflection temperature under a constant load. In the present invention, the heat distortion temperature is usually based on the lowest temperature among these. However, depending on the application, a temperature other than the lowest temperature can be used as the heat distortion temperature, which is the reference temperature, and which value is used as the heat distortion temperature depending on the material and application of the optical fiber. select. The best determination method is a method in which only the temperature of the clad pipe is changed under heat treatment conditions, deformation such as warpage and fluctuations in the pipe thickness are examined, and the temperature immediately before the change occurs is set as the thermal deformation temperature.

  The second method is to place the clad pipe 12 under reduced pressure. Since the organic compound is usually more easily volatilized due to the reduced pressure, the heating is not necessary or the heating temperature may be maintained at about room temperature. Therefore, the heat given to the clad pipe 12 as compared with the first method is reduced. Damage can be minimized. In this case, the heating temperature is preferably 15 ° C. or higher. The upper limit temperature is preferably set to be equal to or lower than the heat distortion temperature (° C.) of the polymer, which is the same condition as in the first method.

  The pressure at which the pressure is reduced is not particularly limited, but if the clad pipe 12 is placed where the degree of vacuum is high (that is, the pressure is low), rapid volatilization may occur and the clad pipe 12 may be deformed. In addition, using such equipment causes high costs. Therefore, in the present invention, the pressure is preferably in the range of (atmospheric pressure−0.099) MPa to (atmospheric pressure−0.005) MPa. In the present invention, this method is referred to as a decompression process.

  Specifically, when the clad pipe 12 is formed mainly of PMMA, the temperature is preferably 15 ° C. to 100 ° C., and the time is preferably in the range of 10 minutes to 48 hours, more preferably 20 ° C. to It is 80 degreeC and it is set as the range of 1 hour-36 hours, Most preferably, it is set as the range of 25 degreeC-70 degreeC and 4 hours-24 hours. The pressure is preferably in the range of (atmospheric pressure−0.099) MPa or more (atmospheric pressure−0.005) MPa, more preferably (atmospheric pressure−0.095) MPa or more (atmospheric pressure− 0.02) MPa or less, and most preferably (atmospheric pressure−0.095) MPa or more (atmospheric pressure−0.05) MPa or less.

  When the clad pipe 12 is formed mainly of PVDF, the temperature is preferably 15 ° C. to 115 ° C., and the time is preferably 10 minutes to 48 hours, more preferably 20 ° C. to 105 ° C. , 30 minutes to 24 hours, and most preferably 25 ° C. to 95 ° C. and 1 hour to 16 hours. The pressure is preferably in the range of (atmospheric pressure−0.099) MPa or more (atmospheric pressure−0.005) MPa, more preferably (atmospheric pressure−0.095) MPa or more (atmospheric pressure− 0.02) MPa or less, and most preferably (atmospheric pressure−0.095) MPa or more (atmospheric pressure−0.05) MPa or less.

  Furthermore, in the present invention, it is also effective to clean the clad pipe 12 in the outer core portion preparation pretreatment step 13. Since washing uses water or a water-soluble organic solvent, washing is preferably performed before the heat treatment and the decompression treatment from the viewpoint of efficiency. The washing water used is water, particularly pure water and a water-soluble organic solvent. By using the water-soluble organic solvent, it is possible to efficiently wash the water attached to or contained in the clad pipe 12. Such organic solvents are not particularly limited, but include alcohols (for example, ethanol, methanol, isopropyl alcohol, etc.) and ketones (for example, acetone, methyl ethyl ketone, etc.) and have little influence on humans. In this respect, it is preferable to use ethanol.

  The outer core polymerization step 14 will be described. The outer core liquid is prepared, for example, by adding a desired additive (for example, a polymerization initiator, a chain transfer agent, a dopant, etc.) having a polymerizable monomer such as MMA as a main component. Thereafter, the liquid is poured into the clad pipe 12. 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. The rotation polymerization method is performed under the same conditions as the method for forming the clad pipe 12, and is formed on the inner surface of the clad pipe 12 as a hollow cylinder having a substantially uniform thickness t2. In addition, it is preferable to deaerate an outer core liquid by ultrasonication or a pressure reduction process after preparation.

  In general, a plastic optical fiber has a high ratio of an inner core and an outer core in its cross-sectional area. Further, when the incident light is highly excited, the light is transmitted so as to pass through the outer core portion. Therefore, it is preferable to sufficiently remove residual monomers and moisture in the outer core 31 before forming the inner core 30 so that the incident light is not scattered. For example, when the clad pipe is formed from PVDF (thermal deformation temperature; approximately 150 ° C.) and the outer core is formed from PMMA (thermal deformation temperature; 110 ° C.), the melting point of PVDF is generally high. Therefore, the heat treatment or the pressure reduction treatment is performed based on the melting point of PMMA so as not to cause thermal damage to the PMMA of the outer core. In this case, since the heat treatment or the pressure reduction treatment is performed at a relatively low temperature, the effect of removing foreign matter from the PVDF may be reduced. Therefore, it is effective to increase the processing time when the multilayer hollow tube is subjected to heat treatment or pressure reduction treatment. Furthermore, the removal of impurities from the multilayer hollow tube can suppress thermal damage to a layer formed of a polymer having a low melting point by applying a reduced pressure treatment.

  Next, the inner core polymerization step 16 will be described. Similarly to the outer core liquid, the inner core liquid is also prepared from a polymerizable monomer and a desired additive (for example, a polymerization initiator, a chain transfer agent, a dopant, etc.). After the inner core liquid is also prepared, it is preferable to deaerate by ultrasonic treatment or reduced pressure treatment. In addition, when forming the inner core 30, it is preferable to form by the GI type | mold which has a distribution from which the refractive index becomes low toward the radial direction from the center (refer FIG.2 (b)). The GI type can be easily formed by an interfacial gel polymerization method. In this case, the interface where polymerization starts is the inner surface of the outer core 31.

  The form of the preform manufactured by the preform manufacturing method according to the present invention is not limited to that shown in FIG. For example, the present invention can be applied to a preform composed of a core 41 and a clad pipe 42 as in the preform 40 shown in FIG. In this case, the core 41 may be a GI type having a refractive index distribution that continuously decreases from the center to the radial direction (see FIG. 3B). Alternatively, a step index type (SI type) or a single mode type (SM type) having no refractive index distribution may be used.

  4A shows a cross-section of the preform 50, and FIG. 4B shows a relationship between the radial direction and the refractive index. A large number of core layers having different refractive indexes are formed in the clad pipe 51. The multi-step index type (MSI type) may be used. In the MSI type preform 50, a large number of core layers 52, 53, 54, 55 and a core portion 56 are formed in the hollow portion of the clad pipe 51. In FIG. 4, the core layer is composed of four layers 52 to 55, but the number of core layers is not limited to four in the present invention. The refractive index of the core layers 52 to 55 and the core portion 56 is such that the core portion 56 has the maximum refractive index and gradually decreases toward the core layer 52 on the clad pipe 51 side. It is preferable to form the portion 56. Thereby, although it is inferior compared with GI type | mold, the preform 50 which suppresses mode dispersion and forms an optical fiber with a large aperture can be obtained.

  In the present invention, the method for manufacturing 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 30 of the preform 17 shown in FIG. In this case, after injecting the inner core liquid into the hollow of the clad pipe 12 in which the outer core 31 is formed, one end thereof is sealed and the horizontal state in the rotary polymerization apparatus (the height direction of the clad pipe is horizontal). Polymerization is carried out while rotating. At this time, the inner core liquid may be supplied all at once or sequentially or continuously. In the present invention, this polymerization method is referred to as a core rotation polymerization method. Also, the core part rotational polymerization method can be applied when forming the core 41 of the preform 40 shown in FIG. Furthermore, the core part rotational polymerization method can also be applied when manufacturing the preform 50 shown in FIG. In this case, it can be applied to each of the core layers 52 to 55, and can also be applied when forming the core portion 56 at the center.

  The core part rotational polymerization method can be obtained because the surface area of the core liquid can be increased compared to the interfacial gel polymerization method during the polymerization, and the bubbles generated from the core liquid can be easily degassed. It becomes possible to suppress the inclusion of bubbles in the preform. Moreover, 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 an 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.

  In addition, the preform 50 can be produced by a multilayer simultaneous melt extrusion method, but it is difficult to solidify the preform while maintaining the form at the time of extrusion by making the core layer multilayer. May occur. Therefore, the clad pipe 51 is produced by a rotation polymerization method or a melt extrusion method. After that, a method in which the core layers 52 to 55 are sequentially formed in the hollow portion in the clad pipe 51 by a rotational polymerization method and finally the core portion 56 is polymerized can be applied. In this case, it is preferable to apply the manufacturing method according to the present invention before forming each core layer. That is, after the clad pipe 51 is manufactured and before the core layer 52 is formed, the heat treatment or the decompression treatment is performed to suppress the generation of bubbles in the preform 50, and the preform 50 is stretched. Generation | occurrence | production of the bubble (henceforth an extending | stretching bubble) produced on the occasion can be suppressed. Hereinafter, similarly, after forming one core layer in the hollow, it is preferable to perform at least one of the heat treatment and the decompression treatment according to the present invention.

  An optical fiber 19 having a desired diameter, for example, 100 μm or more and 1000 μm or less can be obtained by stretching the preform produced by each of the above methods. There is no restriction | limiting in particular regarding the manufacturing method performed at the extending | stretching process 18, A known method can be applied equally. Although the amount of stretching is not particularly limited, it is possible to stretch so that an optical fiber having a length of 400 to 2000 times the length of the preform is obtained. Preferred for holding. Moreover, the residual monomer and water | moisture content in a preform can be reduced by drying the preform 17 under reduced pressure before performing the extending | stretching process 18. 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 18, the preform 17 is heated and melt stretched. The heating temperature can be appropriately determined according to the material of the preform 17 and the like. In general, it is preferably performed in an atmosphere at 180 ° C to 250 ° C. The stretching conditions (stretching temperature and the like) can be appropriately determined in consideration of the diameter of the preform 17, the diameter of the optical fiber 19, 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. For the optical fiber 19 obtained by the above method, the bending and lateral pressure characteristics of the optical fiber cable 21 described later can be improved by defining the breaking elongation and hardness as described in JP-A-7-244220. it can.

  The optical fiber 19 that is a bare wire can be used as it is, for example, as an optical transmission body such as an optical fiber. Usually, however, a protective layer is provided on the outer periphery of the optical fiber 19 to protect the optical fiber 19 and various types. Give function. 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, a coating process 20 for coating the surface of the optical fiber 19 with one or more protective layers is performed and used as the optical fiber cable 21. The material for the protective layer and the method for forming the protective layer on the optical fiber are not particularly limited.

  Common materials such as polyolefins such as polyethylene and polypropylene, polyvinyl chloride, polyvinyl alcohol, urethane resin, and nylon can be used as the material for forming the protective layer, but thermal damage to the coated optical fiber ( For example, materials that do not give deformation, modification, thermal decomposition, etc.) can be selected, and the following materials can be preferably used from the viewpoint of thermal damage and mechanical properties. 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 above listed polymers are not limited to the above materials as long as they can be molded at a glass transition temperature Tg (° C.) or lower of the polymer of the optical fiber strand. Combinations and mixed polymers 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.

  As a coating structure, a plastic optical fiber cable can be manufactured by coating an optical fiber. At that time, as a form of the coating, a contact type coating in which the interface between the coating material and the plastic optical fiber is in contact with the entire circumference, and a loose having a gap at the interface between the coating material and the plastic optical fiber There is a mold coating. In the loose type coating, for example, when the coating layer is peeled off at the connection portion with the connector or the like, moisture may enter from the gaps at the end face and diffuse in the longitudinal direction.

  However, in the case of a loose-type coating, since the coating and the strands are not in close contact, most of the damage such as stress and heat applied to the cable can be mitigated by the coating layer, and the damage to the strands can be reduced. Since it can be reduced, it can be preferably used depending on the purpose of use. As for the propagation of moisture, by filling the voids with fluid semi-solid or powdery particles, moisture propagation from the end face can be prevented, and heat and A coating with higher performance can be formed by having functions different from moisture propagation prevention such as improvement of mechanical functions. In order to produce a loose type coating, the void layer can be formed by adjusting the position of the extrusion nipple of the crosshead die and adjusting the pressure reducing device. The thickness of the gap layer can be adjusted by pressurizing / depressurizing the nipple thickness and the gap layer.

  Furthermore, you may provide a coating layer (secondary coating layer) further in the outer periphery of a coating layer (primary coating layer) as needed. Flame retardants, UV absorbers, antioxidants, radical scavengers, photosensitizers, lubricants, etc. may be introduced into the secondary coating layer, and as long as moisture permeation resistance is satisfied, Introduction is possible. In addition, some flame retardants contain halogen-containing resins such as bromine, additives, and phosphorous. However, metal hydroxides are becoming mainstream as flame retardants in terms of safety such as reduction of toxic gases. . Since the metal hydroxide has moisture as crystal water inside, and the attached water cannot be completely removed during the manufacturing process, the flame retardant coating by the metal hydroxide is the moisture-permeable coating of the present invention. It is desirable to provide as an outer layer coating (secondary coating layer) of (primary coating layer).

  Moreover, in order to provide a plurality of functions, coatings having various functions may be laminated. For example, in addition to flame retardant, it is possible to have a barrier layer for suppressing moisture absorption of strands and a moisture absorbing material for removing moisture, such as moisture absorbing tape and moisture absorbing gel in the coating layer or between the coating layers. A flexible material layer for relaxing stress during bending, 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, if the thermoplastic resin contains a fiber having a high elastic modulus (so-called tensile fiber) and / or a highly rigid metal wire, the mechanical strength of the resulting cable can be reinforced. It is preferable because it is possible. 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.

  In addition, depending on the type of use, the cable shape is a collective cable in which the strands 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.

  In addition, the cable using the optical fiber of the present invention has a higher tolerance than the conventional optical fiber with respect to the axis deviation, so it can be used for joining by butt, but an optical connector for connection is used at the end. It is preferable to securely fix the connecting portion. As the connector, various commercially available connectors such as PN type, SMA type, and SMI type that are generally known can be used.

  An optical fiber as an optical member 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 integrated circuits, optical transceiver modules, and the like. It is composed of an optical signal processing device including components. 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, pp. 476-480, “interconnection by optical sheet bus technology”, arrangement of light-emitting elements with respect to light guide surface described in JP 2003-152284 A, etc .; Optical buses described in JP-A-2002-90571, JP-A-2001-290055, etc .; JP-A-2001-74971, JP-A-2000-329962, JP-A-2001-74966, JP-A-2001-74968 Optical branching and coupling devices described in JP-A-2001-318263, JP-A-2001-31840, etc .; optical star described in JP-A-2000-241655, etc. Optical; optical signal transmission devices and optical data bus systems described in JP-A-2002-62457, JP-A-2002-101044, JP-A-2001-305395, etc .; optical described in JP-A-2002-23011 Signal processing apparatus; optical signal cross-connect system described in Japanese Patent Application Laid-Open No. 2001-86537; optical transmission system described in Japanese Patent Application Laid-Open No. 2002-26815; each of Japanese Patent Application Laid-Open Nos. 2001-339554 and 2001-339555 Multi-function system described in the official gazette; and various optical waveguides, optical splitters, optical couplers, optical multiplexers, optical demultiplexers, etc., combined with transmission / reception that is multiplexed, etc. A system can be constructed. In addition to the above optical transmission applications, it can also be used in the fields of illumination, energy transmission, illumination, and sensors.

  In Example 1, when the preform 17 and the optical fiber 19 were manufactured, (a) to (d) were observed and measured. The results are summarized in Table 1. (A) The number of voids was visually observed on the obtained preform 17. (B) During the stretching process 18, the number of bubbles (hereinafter referred to as stretched bubbles) generated in the stretched optical fiber 19 was visually observed. (C) The transmission loss of the obtained optical fiber 19 under the condition of a wavelength of 650 nm was measured. (D) From the tip of the obtained optical fiber 19, MINI Inc. Incidence of light from LWL-Fiberlight manufactured by the company was performed, and spots where light leaked from the middle part of the optical fiber were observed. When this portion was observed under a microscope under reflection conditions, small rugby ball-like bubbles (hereinafter referred to as microbubbles) having a size of about 0.5 mm to 2 mm were observed even in the longitudinal direction. The number of microbubbles per 50 m of the obtained optical fiber 19 was confirmed.

  In Experiment 1, a clad pipe 12 made of polyvinylidene fluoride (PVDF) having an outer diameter of 20 mm, an inner diameter of 19 mm, and a length of 60 cm produced by extrusion molding was used. The clad pipe 12 was inserted into a sufficiently rigid polymerization vessel having an inner diameter of 20 mm and a length of 60 cm. The clad pipe 12 was washed with pure water and dried at 90 ° C. Thereafter, using K850 pellets (manufactured by Kureha Chemical Co., Ltd.), bottoming was performed at 200 ° C. for 30 minutes on one end. Thereafter, an outer core part preparation pretreatment step 13 was performed. After the inner wall of the tube was washed with ethanol, a pressure reduction treatment was performed for 12 hours in a hot oven at 80 ° C. with a pressure (−0.08 MPa with respect to atmospheric pressure).

  Next, the outer core polymerization process 14 was performed. In the Erlenmeyer flask, 129.0 g of methyl methacrylate (manufactured by MMA Wako Pure Chemical Industries, Ltd.), 0.0645 g of 2,2′-azobis (isobutyric acid) dimethyl, 0.516 g of 1-dodecanethiol (lauryl mercaptan) The outer core liquid was obtained by weighing each. This outer core solution was subjected to ultrasonic irradiation for 10 minutes using an ultrasonic cleaning device USK-3 (38000 MHz, output 360 W) manufactured by Iuchi Seieido Co., Ltd. Next, after the outer core liquid was poured into the clad pipe 12, the inside of the clad pipe 12 was depressurized by 0.01 MPa with respect to atmospheric pressure using a vacuum filtration device. Ultrasonic treatment was performed for 5 minutes using the ultrasonic cleaning apparatus while degassing under reduced pressure.

  After the air at the tip of the clad pipe 12 was replaced with argon, the tip of the clad pipe 12 was sealed with a silicon stopper and a sealing tape. The entire clad pipe 12 containing the outer core solution was placed in a 60 ° C. hot water bath and preliminarily polymerized for 2 hours while being permeated. Thereafter, the prepolymerized clad pipe 12 is heated for 1 hour while being rotated at 3000 rpm while maintaining a temperature of 65 ° C. in a horizontal state (a state where the height direction of the clad pipe is horizontal) (rotational polymerization). Went. Thereafter, rotational polymerization was performed at a rotation speed of 3000 rpm for 70 hours at 70 ° C., and further at 3000 rpm for 90 hours at 90 ° C. A cylindrical tube having an outer core 31 made of PMMA inside the clad pipe 12 was obtained.

  Next, the inner core part preparation pretreatment process 15 was performed. The above-described clad pipe 12 on which the outer core 31 was formed was subjected to a decompression treatment for 3 hours in a 90 ° C. heat oven at a pressure (−0.08 MPa with respect to atmospheric pressure).

  Furthermore, the inner core polymerization process 16 was performed. In an Erlenmeyer flask, 60.0 g of deuterated methyl methacrylate (MMA-d8), 10 μL of di-tert-butyl peroxide, 0.165 g of 1-dodecanethiol, and 6.00 g of diphenyl sulfide as a dopant were weighed. An inner core solution was prepared. Thereafter, ultrasonic irradiation was performed for 10 minutes using an ultrasonic cleaning apparatus USK-3.

  The clad pipe 12 on which the outer core part was formed was kept at 80 ° C. for 20 minutes, and then the inner core liquid was injected into the hollow part. Cover one end of the clad pipe 12 with seal tape, and then set the clad pipe 12 by placing it in the autoclave (the bottom part is at the bottom and the part covered with the seal tape is at the top), then set the autoclave lid did. The air in the autoclave was replaced with argon gas, and the atmosphere was a pressure of 0.05 MPa. Heat polymerization was performed at 100 ° C. for 48 hours by an interfacial gel polymerization method. Thereafter, heat polymerization and heat treatment were further performed at 120 ° C. for 24 hours. Thereafter, the preform 17 was taken out of the autoclave. The obtained preform 17 was visually confirmed to be free of voids. In addition, the manufacturing method of the inner core 30 of the preform 17 by this experiment is called a core part static polymerization method.

  A stretching step 18 was performed by stretching the preform 17 to obtain an optical fiber 19. The preform 17 was melted by passing through an electric furnace (240 ° C., 220 ° C., 170 ° C. from the top, 140 ° C. at the bottom) having four temperature zones in the vertical direction. When the tip of the preform 17 became thin, stretching was continuously performed while adjusting stretching conditions (stretching speed and pulling conditions) to stabilize the diameter to 470 ± 10 μm. As a result, a 200 m optical fiber 19 was obtained. At the time of drawing, the tip portion of the preform 17 placed in an electric furnace and the obtained optical fiber 19 had no problem with visual observation. Further, when 650 nm LD light (laser diode light) was passed through the optical fiber 19 and the number of microbubbles observed as a bright spot was measured, 29 bubbles were observed per 50 m. The transmission loss of the optical fiber 19 was measured by a known method and found to be 153 dB / km.

  In Experiment 2, the experiment was performed under the same conditions as Experiment 1 except that the decompression process of the clad pipe on which the outer core 31 was formed was omitted in the inner core part preparation pretreatment step 15.

  In Experiment 3, the experiment was performed under the same conditions as Experiment 1 except that the decompression process was omitted in the outer core part preparation pretreatment step 13.

  In Experiment 4, the decompression process was omitted in the outer core part preparation pretreatment process 13. Furthermore, the experiment was performed under the same conditions as in Experiment 1 except that the decompression process of the clad pipe 12 on which the outer core 31 was formed was omitted in the inner core part preparation pretreatment step 15. However, since the number of microbubbles was large, the number of bright spots was large, and thus the number of fine bubbles was calculated by observing a 25 m long optical fiber per 50 m.

  Experiment 5 was performed under the same conditions as Experiment 1, except that the inner core part was manufactured by the following method. The clad pipe 12 on which the outer core part was formed was kept at 80 ° C. for 20 minutes, and then the inner core liquid was injected into the hollow part. One end of the clad pipe 12 is covered with a seal tape, and then the clad pipe 12 is rotated at 2500 rpm while maintaining a temperature of 45 ° C. in a horizontal state (a state in which the height direction of the clad pipe is horizontal) in the rotary polymerization apparatus. Then, heat polymerization (rotation polymerization) was performed for 2 hours. Thereafter, an inner core part was formed by a core part rotational polymerization method in which rotational polymerization was performed at 1000 rpm and 120 ° C. for 16 hours to obtain a preform. The experiment was conducted by replacing the inside of the rotary polymerization apparatus with nitrogen gas.

  In Experiment 6, the experiment was performed under the same conditions as Experiment 5 except that the decompression process of the clad pipe on which the outer core 31 was formed was omitted in the inner core part preparation pretreatment step 15.

  In Experiment 7, the experiment was performed under the same conditions as Experiment 5 except that the decompression process was omitted in the outer core part preparation pretreatment step 13.

  In Experiment 8, the decompression process was omitted in the outer core part preparation pretreatment process 13. Furthermore, an experiment was performed under the same conditions as in Experiment 5 except that the decompression process of the clad pipe 12 on which the outer core 31 was formed was omitted in the inner core part preparation pretreatment step 15. However, since the number of fine bubbles was large, the number of bright spots was observed with an optical fiber having a length of 10 m and converted to the number per 50 m.

  From Table 1, it turns out that generation | occurrence | production of a void and an extending | stretching bubble can be suppressed by performing a pressure reduction process in any case before outer core part and inner core part preparation. In addition, a reduction in transmission loss can be suppressed. In addition, from comparison between Experiment 2 and Experiment 3 in which the decompression process was performed once, it was found that a reduction in transmission loss can be further suppressed if the decompression process is performed before the outer core portion is manufactured.

  Further, comparing Table 1 with Experiments 1 to 3 according to the present invention in which the core portion static polymerization method was performed and Experiments 5 to 7 according to the present invention in which the core portion rotational polymerization method was performed, The number of bubbles is decreasing in any of the corresponding experiments. This is because when the core portion (in this embodiment, the inner core portion) is polymerized, the gas contained in the inner core liquid and the gas generated during the polymerization are efficiently defoamed by rotation. Conceivable. And it turns out that the deterioration of transmission loss is also suppressed with the reduction | decrease of microbubbles.

It is a manufacturing process figure of the preform concerning the present invention. It is sectional drawing of the preform which concerns on this invention. It is sectional drawing of the preform of other embodiment which concerns on this invention. It is sectional drawing of the preform of other embodiment which concerns on this invention.

Explanation of symbols

12 Clad pipe 17, 40, 50 Preform 19 Plastic optical fiber 30 Inner core 31 Outer core

Claims (12)

As a hollow tube made of polymer clad part,
In the method for producing a preform for a plastic optical member in which a polymerizable composition is injected into the hollow tube and polymerized to produce a core portion.
A method for producing a preform for a plastic optical member, wherein the hollow tube is heat-treated at a temperature not lower than 40 ° C. and not higher than a heat deformation temperature (° C.) of the polymer before producing the core portion. As a hollow tube made of polymer clad part,
In the method for producing a preform for a plastic optical member in which a polymerizable composition is injected into the hollow tube and polymerized to produce a core portion.
A method for producing a preform for a plastic optical member, wherein the hollow tube is subjected to a decompression treatment at a temperature not lower than 15 ° C. and not higher than a heat deformation temperature (° C.) of the polymer before producing the core portion.   The method for producing a preform for a plastic optical member according to claim 1 or 2, wherein the hollow tube is washed before the heat treatment or the decompression treatment.   The method for producing a preform for a plastic optical member according to any one of claims 1 to 3, further comprising a step of producing a hollow tube in which at least one layer made of a polymer is formed in the hollow tube.   A preform for a plastic optical member manufactured by the method for manufacturing a preform for a plastic optical member according to any one of claims 1 to 4. A clad formed from a hollow tube made of a polymer;
In a preform for a plastic optical member having a core portion produced by injecting and polymerizing a polymerizable composition into the hollow tube,
A preform for a plastic optical member, wherein the core portion has a refractive index distribution from a center to a radial direction.   The preform for a plastic optical member according to claim 6, wherein the core portion has a refractive index profile that continuously decreases from the center toward the radial direction.   The preform for a plastic optical member according to claim 6 or 7, wherein a refractive index of the clad portion is smaller than a refractive index of the core portion.   The preform for a plastic optical member according to any one of claims 6 to 8, wherein the clad portion is made of a fluorine-containing polymer.   A plastic optical fiber obtained by heating and stretching the preform for a plastic optical member according to any one of claims 6 to 9. As a hollow tube made of polymer clad part,
In a plastic optical member obtained by injecting a polymerizable composition into the hollow tube and polymerizing the preform for a plastic optical member in which a core portion is produced by heating and stretching,
The plastic optical member, wherein the stretched plastic optical member has less than 200 bubbles having a minor axis diameter of 10 μm or more per 100 m of the stretched plastic optical member. A plastic optical fiber obtained by cutting a predetermined length from the plastic optical member according to claim 11,
The plastic optical fiber, wherein the plastic optical fiber has less than 20 bubbles having a minor axis diameter of 10 μm or more per 10 m of the plastic optical fiber.

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