JP2006337808A - Method of manufacturing plastic optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a POF superior in transparency, ductility, strength, etc. <P>SOLUTION: A tubular first member 11 is manufactured from a polymer containing a crystalline structure. Inside a pipe 17 functioning also as the first member 11, a polymerizable compound is infused and forms an amorphous polymer. By repeating a polymerizing process, and superposing the layer successively concentrically, a second member 13 having a refractive index higher from the outside the diameter toward the center is formed. The inner diameter D1 (mm) of the first member 11 and the outer diameter D2 (mm) of the second member 13 are designed to satisfy the condition of 0.01<D1-D2<1.0. A preform 24 is made by combining the first and the second member 11, 13. The preform 24 is heated and drawn to obtain the POF having excellent transparency, breaking ductility, and knot strength. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plastic optical fiber that can be used for an optical fiber that is an optical transmission body or an optical waveguide having a curvature, and a method for manufacturing the same, and a plastic that is a base material of the plastic optical fiber. The present invention relates to an optical fiber preform.

  As an optical transmission body, for example, a plastic optical fiber (POF) used for an optical fiber is composed of an outer shell portion and an optical transmission portion having different refractive indexes. It is an optical transmission body that propagates light by making light incident at an angle and totally reflecting light at the interface between the outer shell portion and the optical transmission portion having different refractive indexes. Recently, among these POFs, a refractive index distribution type POF having a high and low refractive index distribution from the center toward the outside has attracted attention. In the gradient index POF, light passing through the center and light passing through the periphery are propagated almost simultaneously due to its unique refractive index distribution. Therefore, since distortion does not occur in the input signal, it is possible to realize a large transmission capacity by realizing a high transmission capacity.

  As the refractive index distribution type POF, for example, an amorphous fluorine-containing polymer is used as a main component, a substance having a refractive index different from that of the main component is added to this main component, and a concentration gradient is distributed in the radial direction. What is made to perform is known (for example, refer patent document 1). However, POF is very flexible due to its plastic characteristics, and therefore, deformation such as bending is likely to occur. When such deformation occurs, problems such as an increase in POF transmission loss occur.

Accordingly, the refractive index distribution type POF capable of suppressing an increase in transmission loss at the time of bending is formed by a fluoropolymer that forms an amorphous structure that is lower than the refractive index of the optical transmission part and is formed by the outer shell part. Has been proposed (see, for example, Patent Document 2).
JP-A-8-005848 JP 2002-071972 A

  In the refractive index distribution type POF of Patent Document 2, the outer shell portion is formed of a fluoropolymer having a low refractive index, and therefore, transmission loss is prevented by preventing light propagating through the optical transmission portion from being diffused to the outside. Can be suppressed. However, since the outer shell portion contains only an amorphous structure, such a refractive index distribution type POF has a problem that physical properties such as elongation and strength are inferior.

  The present invention relates to a plastic optical fiber element capable of manufacturing a refractive index distribution type POF which is excellent in both optical and physical characteristics, which suppresses an increase in transmission loss at the time of bending and has improved elongation and strength. A method of manufacturing a wire is provided.

In order to solve the above-mentioned problems, the method for producing a plastic optical fiber according to the present invention heats and melts a plastic optical fiber preform comprising a first member having a hollow portion and a second member different from the first member. In a manufacturing method in which a plastic optical fiber is drawn in the longitudinal direction, a first member forming step for forming the tubular first member made of a polymer containing a crystal structure and a polymer containing amorphous A second member forming step of forming the second member, and a combination step of combining the first member and the second member into a plastic optical fiber preform, wherein the refractive index of the first member is The refractive index of the surface of the second member in contact with the first member is lower by at least 5 × 10 ⁻³ or more.

  The second member preferably has a refractive index of 1.4 or more and 1.5 or less on a surface in contact with the first member. The first member is preferably a polymer containing fluorine atoms. When the inner diameter of the first member is D1 (mm) and the outer diameter of the outermost layer of the second member is D2 (mm), the condition of 0.01 <D1-D2 <1.0 is satisfied. Is preferred. The second member is columnar or cylindrical, and when the second member is cylindrical, it is preferable that the plastic optical fiber preform is heated and melted and stretched while the pressure is reduced. The second member preferably has a refractive index that gradually increases from the outside toward the center of the diameter.

  And the plastic optical fiber strand of this invention is manufactured with the manufacturing method of any one of the said plastic optical fiber strands, It is characterized by the above-mentioned. The plastic optical fiber preform of the present invention is a tubular first member made of a polymer containing a crystal structure, and a member inserted into the first member, and has an outer surface refractive index of 1.4 or more. And a second member made of a polymer containing amorphous that is 1.5 or less. The second member preferably has a refractive index that gradually increases from the outside toward the center of the diameter.

  According to the present invention, a refractive index distribution type POF having improved physical properties such as elongation and strength can be produced. For this reason, such a gradient index POF can suppress deformation such as bending, and can prevent an increase in transmission loss during bending. In addition, the present invention can be used not only as an optical fiber but also as an optical waveguide.

  Embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to this embodiment. FIG. 1 is a manufacturing process diagram of a POF in this embodiment. Here, only the process flow will be described.

  The manufacturing process of the POF 10 of the present invention includes a first member forming step 12 for forming the tubular first member 11 that becomes the outer shell portion, and a second member forming step 14 for forming the second member 13 that becomes the optical transmission portion. It has the combination process 15 and the extending | stretching process 16 which combine the 1st member 11 and the 2nd member 13. FIG.

  In the first member forming step 12, the first member 11 is formed. The first member 11 is made of a polymer containing a crystal structure. The crystal structure is superior in strength and the like compared to the amorphous structure. Therefore, the 1st member 11 formed from the polymer containing such a crystal structure shows physical properties, such as outstanding intensity and elongation. In the present embodiment, the first member 11 is formed by melt extrusion molding. However, the manufacturing method of the 1st member 11 is not specifically limited, As mentioned later, the polymer compound which produces | generates the 1st member 11 is inject | poured into the inside using a predetermined polymerization container, It superposes | polymerizes and is tubular. The first member 11 may be formed.

  In the second member forming step 14, the second member 13 is formed. In the present invention, a step of sequentially injecting and polymerizing a predetermined polysynthetic compound into a tubular member such as a pipe 17 manufactured in advance by melt extrusion molding or the like is repeated, and concentrically stacked sequentially from the outside. A cylindrical member showing a multilayer structure of layers is formed as the second member 13. The second member 13 is formed from a polymer containing amorphous. Here, the first layer to the nth layer forming steps 20 to 23 are continuously performed, so that the first layer, the second layer,... A multilayer structure composed of an n layer and an n layer is formed. In the present embodiment, the first member 11 and the pipe 17 are separately illustrated in FIG. 1 for convenience of explanation, but the first member 11 is used as the pipe 17. However, in the present invention, the first member 11 may be used as the pipe 17 as in the present embodiment, or the pipe 17 and the first member 11 manufactured separately may be used.

  Next, in the combining step 15, the tubular first member 11 and the second member 13 are combined to produce a preform 24 in which the first member 11 is provided on the outer periphery of the second member 13. At this time, when the second member 13 is directly formed in the tubular first member 11 as in the present embodiment, the manufacturing process of the second member 13 also serves as the combination process 15. In the stretching step 16, the preform 24 is heated and stretched in the longitudinal direction to form a POF 10 having a desired diameter. The second member 13 is a columnar or cylindrical member. When the cylindrical second member 13 is used, the preform 24 is heated and stretched while decompressing in the stretching step 16. Thereby, POF 10 can be obtained while suppressing the occurrence of firing inside the preform 24.

  The 2nd member formation process 21 is demonstrated in detail. FIG. 2 is a process diagram showing the flow of the second member forming process. In the present invention, the second member 13 having a multilayer structure is produced as described above. Accordingly, the second member forming step 14 includes the first layer forming step 20 for forming the first layer 31, the second layer forming step 21 for forming the second layer 32, and the (n-1) th layer 33 for forming the (n-1) layer 33. (N-1) It has the layer formation process 22 and the nth layer formation process 23 in which the nth layer 34 is formed.

  First, in the first injection step 35, a first polysynthetic compound that generates the first layer 31 is injected into the pipe 17. Then, as the first polymerization step 36, the first layer 31 is formed by polymerizing the first polysynthetic compound. Subsequently, as a second injection step 37, a second polymerization step 38 is performed by injecting the second polysynthetic compound into the first layer 31 and then polymerizing the second polysynthetic compound, and the second layer 32 is formed. In the present embodiment, such a layer forming process is repeated until a desired number of layers is obtained. When the (n-1) th layer 33 is formed, the (n-1) th polymerization step is performed after the (n-1) th injection step 39 for injecting the (n-1) th polymer compound. 40. Finally, as an n-th layer forming step 23, an n-th injection step 41 for injecting the n-th polymer compound into the (n-1) -th layer 33 is performed, and then the n-th polymer compound is added. An n-th polymerization step 42 for polymerization is performed.

  In the first to n-th layer forming steps 20 to 23, it is preferable to gradually reduce the amount of the polysynthetic compound injected into the polymerization tube toward the inner layer. Thereby, the thickness of each layer can be adjusted to a substantially constant or approximate value. This injection amount is not particularly limited, and may be adjusted in consideration of the thickness of the layer to be formed. In this embodiment, the pipe 17 is used as the first member 11 and the second member 13 is formed therein. For example, the first member 11 and the pipe 17 different from the first member 11 have a multilayer structure. After the structure is generated and the second member 13 is formed, the second member 13 may be directly inserted into the first member 11 after removing the pipe 17 of the second member 13. The second member 13 that does not remove the pipe 17 may be inserted directly into the inside.

  As described above, when the first to n-th layers 31 to 34 having different refractive indexes are formed inside the pipe 17, light can be propagated while suppressing dispersion of light. In the present embodiment, in each polymerization step, a rotational gel polymerization method is used in which a polysynthetic compound is polymerized by rotating a polymerization tube. Details of the rotating gel polymerization method will be described later.

  The combination process 22 will be described. FIG. 3 shows an explanatory diagram of the combination process. The 1st member 11 and the 2nd member 13 are shown with sectional drawing of radial direction. As described above, the first member 11 has a tubular shape, is formed of a polymer including a crystal structure, and is a pipe 17 in the present embodiment. And the 2nd member 13 has the core member 50 of the multilayer structure comprised by the 1st layer-the nth layers 31-34. Each layer has a tubular shape with a constant outer diameter and inner diameter in the longitudinal direction and a uniform thickness. In addition, a hollow portion 51 is provided at the center of the diameter. In addition, although the boundary of each layer is shown in FIG. 3, the clarity of the boundary differs depending on manufacturing conditions and the like, and it may not necessarily be confirmed. Similarly, the cavity 51 may disappear depending on manufacturing conditions, but the presence or absence is not limited in the present invention.

  When the inner diameter of the first member 11 is D1 (mm) and the outer diameter of the second member 13 is D2 (mm), the first member 11 satisfies the condition of 0.01 <D1-D2 <1.0. And the second member 12 are formed. When D1 and D2 are adjusted so as to satisfy such a range, for example, after the first member 11 and the second member 13 are formed separately, the second member 13 is inserted into the first member 11. When the two members 13 are combined, the second member 13 can be inserted into the first member 11 without the outermost layer of the second member 13 contacting the first member 11. Therefore, it is possible to prevent the first member 11 and the second member 13 from being lost, and it is possible to insert them easily.

In the present invention, the refractive index of the first member 11 is adjusted to be 5 × 10 ⁻³ or more lower than the refractive index of the surface of the second member 13 in contact with the first member 11. That is, in this embodiment, the refractive index of the pipe 17 corresponding to the first member 11 is 5 × 10 5 than the refractive index of the outermost layer of the second member 13 formed inside the pipe 17, that is, the first layer 31. It is adjusted to be lower than ^-3 . At this time, the refractive index of the first member 11 is also preferably adjusted to satisfy the above range. For example, when the pipe 17 is not present, the refractive index of the first member 11 may be adjusted so as to satisfy the above range. The refractive index of the outermost layer of the second member 13 is adjusted to be 1.4 or more and 1.5 or less. And the refractive index of the 2nd member 13 is designed so that it may become high gradually as it goes to the center of a diameter. Thereby, the 2nd member 13 which can propagate light, maintaining a low transmission loss can be obtained. However, the change in the refractive index of the first to n-th layers 31 to 34 may be stepwise or continuous.

  In the present embodiment, as a method for imparting a refractive index distribution in the radial direction to the second member 13, each layer is composed of at least two types of polysynthetic compounds that generate homopolymers having different refractive indexes, and these are mutually connected. A method is used in which copolymers are produced by copolymerization at different blending ratios. Thus, when it copolymerizes, adjusting the compounding ratio of the homopolymer which shows a different refractive index, a difference can be expressed in the refractive index of each layer. Moreover, since each layer is formed using the same polysynthetic compound, the affinity at the interface formed by the layers adjacent to each other can be improved. In order to increase the refractive index from the outside of the diameter toward the center as in this embodiment, the blending amount of the homopolymer having a higher refractive index is increased with respect to the homopolymer having a lower refractive index. That's fine. Thereby, the refractive index of the layer formed as it goes inside the diameter can be increased. In addition, the 1st member 11 consists of a polymer containing a crystal structure, and selects a polysynthetic compound so that it may further contain a fluorine atom. Thereby, an increase in transmission loss can be suppressed.

  The 2nd member 13 selects the polysynthetic compound which produces | generates the 2nd member 13 so that it may consist of a polymer containing an amorphous | non-crystalline substance. In the present embodiment, as a polysynthetic compound for generating the second member 13, 2,2,2 trifluoroethyl methacrylate (3FMd7) having a refractive index of 1.41 and a refractive index of the polymer of 1. 49, each of which is adjusted to have a different blending ratio using pentafluorophenyl methacrylate (PFPMAd5). In this way, when each layer is formed while changing the compounding ratio of the polysynthetic compounds having different refractive indexes, as described above, a desired high and low distribution of refractive index that gradually changes in the radial direction can be developed. Can do. In addition, it is preferable to use 3FMd7 and PFPAd5 in which hydrogen atoms are partially deuterium atoms because transmission loss can be reduced.

  In addition to the above, as a method of imparting a desired refractive index height distribution to the preform 24, a refractive index adjusting agent is added to the polymer compound for forming each layer 31 to 34, and each layer 31 to 34 is further added. A desired refractive index distribution can be imparted by adjusting the addition amount of the refractive index adjusting agent in the above so as to be different from each other. In this case, the refractive index can be gradually increased from the outside toward the center of the diameter by increasing the addition amount of the refractive index adjusting agent according to the inside of the diameter. Details of the refractive index adjusting agent will be described later.

  As described above, the tubular first member 11 made of a polymer containing a crystal structure is a polymer containing amorphous, and the second member 13 is adjusted so that the refractive index of the outer surface satisfies a predetermined range. By combining these, the preform 24 can be formed. By heating and stretching the preform 24 in the longitudinal direction, the POF 10 having a desired diameter can be obtained. FIG. 4 shows a cross-sectional view of the POF 10. The POF 10 is melt-stretched to a desired diameter while heating the preform 24. As a result, the first member 111 and the second member 113 are in close contact with each other, so that the cavity 58 existing in the preform 24 disappears. At this time, stretching under reduced pressure is preferable because POF 10 can be obtained without generating voids. Further, when the first member 11 and the second member 13 are separately manufactured and then the second member 13 is inserted into the first member 11 to form the preform 24, the first member 11 and the second member In some cases, a gap may be formed between the two. However, since the first member 11 and the second member 13 are brought into close contact with each other by heating and stretching the preform 24 as in the present invention, there is no problem because the gap disappears.

  The refractive index in the cross-sectional radial direction of the POF 10 is the lowest in the first layer 131 among the core members 150 constituting the second member 113, as in the preform 24, and the second layers 132,. n-1) The layer 133 and the n-th layer 134 gradually increase in order, and continuously increase toward the cross-sectional center of the POF 10. At this time, the refractive index distribution coefficient of the POF 10 shows almost the same value as that of the preform 24. The refractive index distribution of the preform 24 is as described above. Even if the preform 24 is not the POF 10, the preform 24 functions as an optical transmission body in this state.

  The material which produces | generates the 1st member 11 and the 2nd member 13 is demonstrated. The first member 11 is formed from a polymer including a crystal structure. As a result, physical properties such as elongation and strength can be improved, and the preform 24 and the POF 10 that do not undergo deformation during bending can be manufactured. The polymer compound that forms the first member 11 preferably includes a crystal structure and includes a fluorine atom from the viewpoint of realizing an improvement in physical strength and a low refractive index. For example, polyvinylidene fluoride (PVDF) resin, tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride terpolymer (THV) resin, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin, tetrafluoroethylene par A fluoro (alkyl vinyl ether (PFA) resin or the like is preferable, and a THV resin is particularly preferable in terms of low refractive index.

  Of the second member 13, the polymer compound forming the first layer to the n-th layers 31 to 33 is preferably an amorphous polymer so that light scattering does not occur, and is preferably excellent in adhesion to each other. More preferably, the polymer is excellent in mechanical properties and heat-and-moisture resistance. The pipe 17 may be a tubular member of the first member 11 or a tubular member that can be easily removed from the polymer compound formed in the pipe 17. In addition, when forming a tubular member, a polysynthetic compound may be used and you may form with a monomer instead of a polymer. And as a monomer for 1st layers, it is preferable that a refractive index is low among polymers.

  As monomers for the first layer to the n-th layer, for example, (meth) acrylic acid esters (fluorine-free (meth) acrylic acid ester (a), fluorine-containing (meth) acrylic acid ester (b)), styrene type Compound (c), vinyl esters (d), main chain cyclic fluorinated polymer forming monomers (e), amorphous fluororesin (for example, Teflon (registered trademark) AF), AVA resin, norbornene-based resin (for example, ZEONEX (registered trademark: manufactured by Nippon Zeon Co., Ltd.)), functional norbornene resin (for example, ARTON (registered trademark: manufactured by JSR), etc.) Polymerized using bisphenol A, which is a raw material of polycarbonates, as a polymerizable compound Can be. In selecting a monomer for each layer, it is preferable to consider the relationship between at least one of the refractive index and affinity.

  As the above (a) fluorine-free methacrylic acid ester and fluorine-free acrylic acid ester, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tert-butyl methacrylate, benzyl methacrylate, phenyl methacrylate, methacrylic acid Examples include cyclohexyl, diphenylmethyl methacrylate, adamantyl methacrylate, isobornyl methacrylate, norbornyl methacrylate, and methyl acrylate, ethyl acrylate, tert-butyl acrylate, and phenyl acrylate.

  (B) As fluorine-containing acrylic ester and fluorine-containing methacrylate ester, 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, Examples include 3,4,4-hexafluorobutyl methacrylate.

  (C) Styrene compounds include styrene, α-methylstyrene, chlorostyrene, bromostyrene, etc. (d) vinyl esters include vinyl acetate, vinyl benzoate, vinyl phenyl acetate, vinyl chloroacetate, etc. (E) As main chain cyclic fluorinated polymer forming monomers, a polymer having a cyclic structure as a monomer or forming a fluorinated polymer having a cyclic structure in an amorphous main chain by cyclopolymerization is formed. A monomer that forms a polymer having an alicyclic ring or a heterocyclic ring in the main chain exemplified by Cytop (registered trademark) polyperfluorobutanyl vinyl ether and JP-A-8-334634, and the like. Also exemplified in Japanese Patent Application No. 2004-186199 And the like. Of course, the present invention is not limited to these, and the refractive index of a polymer composed of a polymerizable compound alone or a copolymer may have a predetermined refractive index distribution in the molded body when molded into an optical transmission body. In addition, it is preferable to determine the type and composition ratio.

  Moreover, as a monomer for 1st layers, the following are mentioned other than said various compounds. For example, there is a copolymer of methyl methacrylate (MMA) and trifluoroethyl methacrylate (3FM), hexafluoroisopropyl methacrylate, pentafluorophenyl methacrylate fluoride (meth) acrylate, or the like. In addition, a copolymer of MMA and an alicyclic (meth) acrylate such as (meth) acrylate having a branch such as tert-butyl methacrylate, isobornyl methacrylate, norbornyl methacrylate, tricyclodecanyl methacrylate, etc. is there. Further, polycarbonate (PC), norbornene resin (for example, ZEONEX (registered trademark: manufactured by Nippon Zeon Co., Ltd.)), functional norbornene resin (for example, ARTON (registered trademark: manufactured by JSR)), fluorine resin ( For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or the like) can 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 may be used. it can.

  In addition, when these polymers contain a hydrogen atom (H), it is preferable that the hydrogen atom is substituted with a deuterium atom (D), thereby reducing transmission loss, particularly in the near infrared region. It is possible to reduce the transmission loss at the wavelength.

  In addition, in order to use POF10 for near infrared light, absorption loss due to C—H bonds constituting the polymer occurs, so that it is described in Japanese Patent No. 3332922 and Japanese Patent Application Laid-Open No. 2003-192708. By using a polymer in which C—H bond hydrogen atoms are replaced with deuterium atoms or fluorine, the wavelength range causing this transmission loss can be lengthened, and the loss of transmission signal light can be reduced. can do. Examples of such polymers include deuterated polymethyl methacrylate (PMMA-d8), polytrifluoroethyl methacrylate (P3FMA), polyhexafluoroisopropyl 2-fluoroacrylate (HFIP 2-FA), and the like. it can. In addition, in order not to impair the transparency after polymerization of the compound as a raw material, it is desirable that impurities and foreign substances serving as scattering sources are sufficiently removed before polymerization.

  In the present invention, a polymerization initiator is used when a polymerizable compound is polymerized to form a copolymer. As the polymerization initiator, for example, there are various types that generate radicals. For example, benzoyl peroxide (BPO), tert-butylperoxy-2-ethylhexanate (PBO), di-tert-butyl peroxide (PBD), tert-butylperoxyisopropyl carbonate (PBI) ) And peroxide compounds such as 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). The polymerization initiator is not limited to these. Two or more types may be used in combination.

  In order to keep various physical properties such as mechanical properties and thermophysical properties uniform when used as a copolymer, it is preferable to adjust the degree of polymerization. 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 (for example, n-butyl mercaptan, n-pentyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, tert-dodecyl mercaptan), thiophenols (thiophenol, m-bromothio). Phenol, 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.

  As a method for imparting a desired refractive index distribution, when a refractive index adjusting agent is added to the main component for forming each layer, it is preferable to use a non-polymerizable compound as the refractive index adjusting agent. When the refractive index adjuster is added when forming the core member 50 of the second member 13, the addition ratio may be 0.01 to 25 wt% with respect to the main component forming the core member 50. preferable. More preferably, the addition rate is 1 to 20% by weight. This makes it easier to control the refractive index distribution coefficient in the radial direction of the circular cross section within the preferred range as described above.

  As the refractive index adjuster, it is preferable to use a low molecular compound having a high refractive index, a large molecular volume, not participating in polymerization, and having a predetermined diffusion rate in a molten polymer. The refractive index adjusting agent is not limited to a monomer, and may be an oligomer (including a dimer, a trimer, etc.).

  Examples of the refractive index adjuster include benzyl benzoate (BEN), diphenyl sulfide (DPS), triphenyl phosphate (TPP), benzyl-n-butyl phthalate (BBP), diphenyl phthalate (DPP), Non-polymerizable low molecular weight compounds such as diphenyl (DP), diphenylmethane (DPM), tricresyl phosphate (TCP), diphenyl sulfoxide (DPSO) may be used, and among them, BEN, DPS, TPP, DPSO may be used. preferable. The refractive index of the second member 13 is controlled to a desired value by adding such a refractive index adjusting agent to the homopolymer for forming the core member 50 and further adjusting the concentration distribution of the refractive index adjusting agent. .

  The addition amount of the above-described polymerization initiator, chain transfer agent, and refractive index adjuster is appropriately determined in a preferable range according to the type of the polymerizable compound that is the monomer for the first layer to the n-th layer to be used. Can do. In this embodiment, the polymerization initiator is added so as to be 0.005 to 0.050% by mass with respect to the polymerizable compounds of the first layer to the nth layers 31 to 34. More preferably, the rate is 0.010 to 0.020 mass%. Moreover, although the said chain transfer agent is added so that it may become 0.10-0.40 mass% with respect to the polymeric compound of a 1st layer-n-th layer, this addition rate is 0.15- More preferably, it is 0.30 mass%.

  In addition, other additives can be added to a part of each layer constituting the core member 50 as long as the optical transmission performance is not deteriorated. For example, a stabilizer can be added to each layer constituting the core member 50 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 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 each of the layers 31 to 34 or a part of them by adding to the various polymerizable compounds as the raw material and then polymerizing.

  The manufacturing method of the 2nd member 13 is demonstrated in detail. However, this embodiment is an example as one aspect of the present invention and is not limited. FIG. 5 shows a cross-sectional view of a polymerization vessel used when the preform 24 is produced. The superposition | polymerization container 60 has the cylindrical tubular container main body 60a and the lid | cover 60b which each plugs up both ends of this container main body 60a, and is made from SUS in this embodiment. The polymerization vessel 60 has an inner diameter that is slightly larger than the outer diameter of the pipe 17 accommodated therein, so that the pipe 17 can rotate as the polymerization vessel 60 rotates. .

  First, the pipe 17 molded in advance by commercially available melt extrusion molding is accommodated in the polymerization container 60. Next, one end of the pipe 17 is closed with the stopper 61. The stopper 61 is made of a material that does not dissolve in the first to n-th layer monomers, and does not include a compound that elutes a plasticizer or the like. Examples of such a material include polytetrafluoroethylene (PTFE).

  After closing one end with the stopper 61, the first layer monomer 31 a for forming the first layer 31 is injected into the pipe 17. Then, after the other end is closed with the stopper 61, the first layer monomer 31 a is polymerized by rotating the polymerization container 60 to form the first layer 31. A support member that supports the pipe 17 may be provided on the inner surface of the polymerization vessel 60 or the like so that the pipe 17 can respond to the rotation of the polymerization vessel 60.

  When the polymerization vessel 60 is rotated as described above, a rotary polymerization apparatus is used. In FIG. 6, the schematic of the rotation superposition | polymerization apparatus 71 is shown. The rotation polymerization device 71 is a temperature controller for detecting the temperature in the plurality of rotating members 73, the drive unit 76, and the device main body 72 provided in the device main body 72 and controlling the internal temperature according to the detection result. 77.

  The rotating member 73 has a cylindrical shape, and the longitudinal directions thereof are substantially parallel to each other and substantially horizontal so that at least one polymerization vessel 60 can be supported by two peripheral surfaces. One end of each rotating member 73 is rotatably attached to the side surface of the apparatus main body 72 and is driven to rotate by the driving unit 76 under independent conditions. The drive unit 76 includes a controller (not shown) for controlling the drive of the drive unit 76.

  FIG. 7 is an explanatory diagram for the rotation method of the polymerization vessel. During the polymerization reaction, after the polymerization container 60 is set in a trough formed by the peripheral surfaces of adjacent rotating members 73, the polymerization container 60 is rotated according to the rotation of the rotating member 73. In FIG. 7, the rotation axis of the rotating member 73 is indicated by reference numeral 73a. Thus, the first layer monomer 31a can be polymerized by setting the polymerization vessel 60 in the rotation polymerization apparatus 71 and rotating it. In the present embodiment, the rotation of the polymerization vessel 60 is a surface drive type, but the rotation method of the polymerization vessel 60 is not particularly limited.

  Further, in the present embodiment, as shown in FIG. 7, the lid 60 b at both ends of the polymerization vessel 60 is provided with the magnet 60 c and the magnet 75 is provided below between the two adjacent rotating members 73. Thereby, it can prevent that the superposition | polymerization container 60 floats from the rotation member 73 at the time of rotation. However, the method for preventing the polymerization container 60 from floating from the rotating member 73 is not limited to this embodiment. For example, a rotation means similar to the rotation member 73 is provided so as to be in contact with the upper portion of the set polymerization vessel 60 and is rotated in the same manner to prevent the polymerization vessel 60 from being lifted or pressed above the polymerization vessel 60. Examples thereof include a method of preventing floating by providing a means and applying a predetermined load to the polymerization vessel 60. Note that the present invention does not depend on the floating prevention method, and any method can be applied.

  In addition, you may pre-polymerize the 1st layer 31 in the state which stood the pipe 17 before the rotation polymerization. When pre-polymerization is performed, the pipe 17 is rotated about the circular axis of the pipe 17 by a predetermined rotation mechanism as necessary. Thus, it is preferable to rotate the pipe 17 while keeping the longitudinal direction thereof substantially horizontal because the first layer 31 is easily generated on the entire inner surface of the pipe 17. In the present invention, when the first layer 31 is polymerized, it is most preferable that the longitudinal direction of the pipe 17 is horizontal in order to form the first layer 31 on the entire inner surface of the pipe 17. However, it may be substantially horizontal, and the allowable angle of the rotating shaft is generally within 5 ° with respect to the horizontal.

  In addition, it is preferable to use after removing a polymerization inhibitor, a water | moisture content, an impurity, etc. previously by performing filtration, distillation, etc. for the monomer for 1st layer-nth layer. In addition, after mixing a monomer and a polymerization initiator, it is preferable to ultrasonically treat this mixture to remove dissolved gas and volatile components. Furthermore, if necessary, the pipe 17 and the first layer monomer 31a may be subjected to a decompression process by a known decompression device before and after the first layer forming step.

  After the pipe 17 on which the first layer 31 is formed as described above is taken out from the rotary polymerization apparatus 71, in this embodiment, the heating process for a predetermined time is performed by a heating means such as a thermostatic bath set to a predetermined temperature. is doing.

  Next, the second layer 32 to the n-th layer 34 are sequentially generated. In FIG. 8, sectional drawing of the superposition | polymerization container 80 at the time of the production | generation start of each layer is shown. Since this polymerization container 60 is the same as that used when the first layer 31 is generated, the same reference numerals are used. First, the second layer monomer 32 a is injected into the hollow portion of the first layer 31. Then, the injection port is closed by the stopper 61, the longitudinal direction of the pipe 17 in which the first layer 31 is formed is set to a substantially horizontal state, and the reaction is started while rotating so that the center of the cross-sectional circle of the pipe 17 becomes the rotation axis. . Thus, the 2nd layer 32 is formed by advancing superposition | polymerization, rotating. When the monomers for the second layer to the n-th layer are polymerized, the rotational polymerization apparatus 71 (see FIG. 6) used when producing the first layer 31 is used. If necessary, the pipe 17 and the injected material may be decompressed by a known decompression device before and after the second to nth layer monomers including the second layer monomer 32a are injected. .

  At this time, when the second layer monomer 32a starts to polymerize, the inner wall of the first layer 31 is swollen by the second layer monomer 32a, and a swollen layer is formed in the initial stage of polymerization. Since this swelling layer is in a gel state, the polymerization rate is accelerated (referred to as a gel effect). From such a phenomenon, the present invention provides a reaction method in which a pre-fabricated tubular member is rotated and a swelling layer is formed by the reaction between the tubular member and the injected polymerizable compound to polymerize the polymerizable compound. This is called a rotational gel polymerization method. In addition, as for this polymerization reaction, it is more preferable that the longitudinal direction of a tubular member is horizontal like this embodiment.

  In addition, it is preferable that the reaction rate of each polymerization reaction is adjusted suitably. For example, the reaction rate is preferably adjusted so that the conversion rate representing the degree of reaction of each polysynthetic compound is 5 to 90% per hour. More preferably, the conversion rate per hour is adjusted to 10 to 85%, and more preferably 20 to 80%. This reaction rate can be controlled by adjusting the type of polymerization initiator and the polymerization temperature. In addition, the method of calculating | requiring the conversion rate of a polymeric compound should just use a well-known method, and is not specifically limited. For example, quantitative analysis of residual monomers by gas chromatography and visual evaluation may be performed to obtain a relationship between the two in advance, and evaluation may be performed by visual observation based on this relationship. In the rotating gel polymerization method as described above, the reaction temperature is preferably set to be equal to or lower than the boiling point of the polymerizable compound. Further, the conversion rate of each layer is controlled by appropriately adjusting the rotation speed.

  By the above method, the 2nd member 13 can be produced by forming the multilayer structure of the 1st layer-the n-th layers 31-34 produced | generated with the predetermined material inside the pipe 17. Then, the second member 13 is inserted into the separately manufactured tubular first member 11 to form a preform 24, and the preform 24 is melt-drawn to obtain a POF 10 having a desired diameter (for example, 200 to 1000 μm). Can be obtained. In addition, as the stretching method of the preform 24, various stretching methods described in JP-A-07-234322 can be applied.

  In the present embodiment, a grade index type (Graded Index: GI type) POF in which the refractive index of the second member 13 continuously increases as it goes toward the center of the diameter is shown. A step index type (SI type) POF in which the rate changes stepwise may be used. In the SI type POF, the second member 13 of the GI type POF has a multi-layer structure of the pipe 17 and the first layer to the n-th layers 31 to 34, whereas the pipe 17 and the first layer 31 have two layers. It has a layer structure. Since the manufacturing process of the SI type POF is the same as that of the GI type POF, the description thereof is omitted.

  POF10 has improved product value by bending, improving weather resistance, suppressing performance degradation due to moisture absorption, improving tensile strength, imparting stepping resistance, imparting flame resistance, protecting against chemical damage, preventing noise from external light, and coloring. For the purpose of improvement or the like, the surface is usually coated with one or more protective layers.

  When the outer periphery of the POF 10 thus obtained is covered with a coating material, a plastic optical fiber core or a plastic optical fiber cord (both Plastic Optical Code) can be obtained. Note that when the outer periphery of the POF 10 is coated with a coating material, a method of performing secondary coating after performing primary coating is generally used. However, the number of coating layers is not limited to one or two.

  Further, a plastic optical fiber cable (Plastic Optical Cable) can be obtained by bundling the plastic optical fiber cord. In the present invention, a single fiber cable is referred to as a single fiber cord that has only one fiber cord and is further coated as necessary. Further, a plurality of fiber cords combined with a tension member or the like and covered with a further covering material is referred to as a multi-fiber cable. The plastic optical fiber cable includes both the single fiber cable and the multi-fiber cable.

  When an optical cable is a single fiber cable, it may be used as an optical cable without passing through the second coating step, with the coating layer in the first coating step left as the outer surface. As the form of the coating when it is used as an optical cable, the interface between the single core wire and the coating material, or the outer periphery of the bundled optical fiber core wire and the coating material are all in contact with each other. There are a close-contact type coating and a loose type coating having a gap at the interface between the coating material and the optical fiber core. In loose type coating, for example, when the coating layer is peeled off at the connection portion with the connector, moisture may enter from the gaps at the end face and diffuse in the longitudinal direction.

  However, since the covering material and the optical fiber core wire are not in close contact with each other, there is an advantage that most of damage such as stress and heat applied to the optical cable can be alleviated by the covering layer. Therefore, the loose type coating can be preferably used depending on the purpose of use. About the propagation of moisture from the connector connection part in the case of loose type coating, by filling a gel-like semi-solid or granular material having fluidity in the gap part of the interface between the optical fiber core wire and the coating material, Can be prevented. Furthermore, an optical fiber cable in which a multifunctional coating layer is formed can be produced by imparting other different functions such as heat resistance and improvement of mechanical function to these semi-solids and granular materials. In order to obtain a loose-type coating, the layer having the voids can be formed by adjusting the position of the extrusion nipple of the crosshead die and adjusting the degree of pressure reduction by the pressure reducing device. The thickness of the void layer can be adjusted by pressurizing / depressurizing the nipple thickness and the void layer. Note that the coating materials provided in the first and second coating steps include flame retardants, ultraviolet absorbers, antioxidants, light-increasing agents, lubricants, etc. within a range of conditions that do not affect the light transmission characteristics. It may be added.

  Examples of the flame retardant include bromine and other halogen-containing resins and additives, and phosphorus-containing flame retardants. From the viewpoint of safety such as reduction of toxic gases during combustion, such as aluminum hydroxide and magnesium hydroxide. Metal hydroxides are becoming mainstream. However, such a metal hydroxide has moisture as crystal water therein. This moisture is caused by the adhering water in the process of producing these metal hydroxides and cannot be completely removed. Therefore, it is desirable that the flame resistance imparted by the metal hydroxide is not contained in the coating layer in contact with the POF 10 but only on the coating layer that is the outer surface of the cable.

  In addition, in order to impart a plurality of functions to the plastic optical fiber cable, a coating layer serving as a functional layer may be appropriately laminated. Examples of the functional layer other than the flame retardant layer include a barrier layer for suppressing moisture absorption of the POF 10 and a moisture absorbing material layer for removing moisture contained in the POF 10. As a method for applying the moisture absorbing material layer, for example, there is a method of providing a moisture absorbing tape or a moisture absorbing gel in a predetermined coating layer or between coating layers.

  In addition, as other functional layers, a flexible material layer for relaxing stress at the time of flexibility, a foam material layer that functions as a buffer material for buffering external stress, and a reinforcing layer for improving rigidity Etc. Moreover, as a structural material (coating material) for a plastic optical fiber cable, in addition to a resin, for example, a fiber having a high elastic modulus (so-called tensile fiber) and / or a wire material such as a highly rigid metal wire is used as a thermoplastic resin. What was contained is mentioned. Use of such a material is preferable because the mechanical strength of the plastic optical fiber cable can be reinforced.

  Examples of the tensile strength fibers include aramid fibers, polyester fibers, and polyamide fibers. And as said metal wire, a stainless steel wire, a zinc alloy wire, a copper wire, etc. are mentioned. However, the tensile strength fiber and the metal wire that can be applied to the present invention are not limited to these. In addition, it is also possible to incorporate a metal tube exterior to protect the plastic optical fiber cable, an aerial support line, a mechanism for improving workability during wiring, etc. into the outer periphery of the plastic optical fiber cable. it can.

  The shape of the plastic optical fiber cable depends on the type of use, such as a collective type in which plastic optical fiber cords are concentrically arranged, a tape type in which the optical fiber cords are arranged in a row, and a type in which they are gathered with a presser roll or wrap sheath Is mentioned. In addition, what is necessary is just to select these usage forms suitably according to a use.

  Since the plastic optical fiber cable obtained from the preform 24 of the present invention has a higher tolerance for axial deviation than the conventional product, it can be used even if it is joined by butt-joining. However, more preferably, the optical cable is provided with an optical connector for connection at the end of the optical cable, and the mutual connection parts are securely fixed. As the connector, various commercially available connectors such as PN type, SMA type and SMI type which are generally known can be used. Therefore, the plastic optical fiber cable of the present invention is suitably used in combination with various light emitting elements, light receiving elements, optical switches, optical isolators, optical integrated circuits, optical signal processing devices including optical components such as optical transceiver modules, and the like. It is done. At this time, it may be combined with other optical fibers as necessary. Any known technique can be applied as a technique related to them. For example, refer to the basics and actuality of plastic optical fibers (issued by NTS), Nikkei Electronics 2001.1.2.3, pages 110-127, "Optical components are mounted on printed circuit boards. be able to.

  In addition, by combining 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, Suitable for optical transmission systems suitable for short distances such as high-speed, large-capacity data communications such as optical LANs in apartments, factories, offices, hospitals, schools, etc., and control applications that are not affected by electromagnetic waves Can be used.

  Further, 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, which are described in “Interconnection by Optical Sheet Bus Technology”, and the arrangement of light emitting elements on the waveguide surface described in Japanese Patent Application Laid-Open No. 2003-152284; , JP-A-2002-90571, JP-A-2001-290055, and the like; JP-A-2001-74971, JP-A-2000-329962, JP-A-2001-74966, JP-A-2001-74968 , JP 2001-318263, JP 2001-31840, etc .; optical branch couplers described in JP 2000-241655, etc .; optical star couplers described in JP 2000-241655, etc .; Optical signals described in Japanese Patent Laid-Open Nos. 2002-101044 and 2001-305395 Optical signal bus system; optical signal processing apparatus described in JP-A No. 2002-23011; optical signal cross-connect system described in JP-A No. 2001-86537; optical described in JP-A No. 2002-26815 Multi-function system described in each publication such as JP 2001-339554 A and JP 2001-339555 A; various optical waveguides, optical splitters, optical couplers, optical multiplexers, optical demultiplexers, etc. By combining with, a more advanced optical transmission system using multiplexed transmission and reception can be constructed. In addition to the above optical transmission applications, it can also be used in the fields of illumination (light guide), energy transmission, illumination, lenses, and sensors.

  Examples of the present invention and comparative examples are shown below to specifically explain the present invention. In this example, POF was produced by the optical material and production method of the present invention, but the present invention is not limited to this. The manufacturing method and the like of the preform 24 will be described in detail in the first embodiment, and the description of the second embodiment and the first comparative example will be omitted when the same as the first embodiment.

  The POF 10 was manufactured according to the POF manufacturing process shown in FIG. A PVDF tube having an inner diameter of 19.5 mm and a length of 27 cm produced by melt extrusion molding is used as a pipe 17 that functions as the first member 11. The first layer monomer 31 a is placed in this hollow portion, and a PTFE membrane having a pore diameter of 0.2 μm. It inject | poured, filtering using a filter. As the first layer monomer 31a, 21.73 ml of 3FMd7 (hereinafter referred to as “a”) as a polysynthetic compound and 4.56 ml of PFPAd5 (hereinafter referred to as “b”) as a polysynthetic compound were mixed, and then a polymerization initiator. Were prepared by adding 0.1 mol% of 2,2 dimethylazobisisobutyrate and 0.05 mol% of dodecyl mercaptan.

  A PVDF tube having a refractive index of 1.41 into which the first layer monomer 31a has been injected is set in the polymerization vessel body 60a of the rotary polymerization apparatus 71 so that the longitudinal direction is horizontal, and is rotated at 2000 ° C. while rotating at 90 ° C. The heating polymerization was performed for 2 hours in the atmosphere. The polymerization vessel 60 was made of SUS. At this time, a non-grounded thermocouple was provided in the vicinity of the rotating polymerization vessel 60, specifically at a position 1 to 2 cm away, the temperature was measured, and this measured temperature was regarded as the temperature due to the polymerization reaction. Moreover, the temperature peak (exothermic peak) in the exotherm of the polymerization reaction measured by this method was determined. In Example 1, an exothermic peak of 67 ° C. was observed when about 1 hour and 20 minutes passed from the start of polymerization. Thus, the first layer 31 was formed on the inner surface of the pipe 17. The conversion rate of the obtained polymer was 90%.

  Next, the pipe 17 on which the first layer 31 was formed was taken out from the polymerization vessel 60, the second mixed solution was poured into the hollow portion, and the second layer 32 was formed by rotational polymerization. At this time, the same conditions and method as when the first layer 31 was formed were used. As the second layer monomer 32a, 7.57 ml of a and 1.99 ml of b are mixed, and then 0.1 mol% of 2,2dimethylazobisisobutyrate and 0.05 mol of dodecyl mercaptan are used as a polymerization initiator. % Mixed solution was used. And after forming the 2nd layer 32, as shown in Table 1, it uses the 3rd-11th mixed solution prepared so that b / a may differ as a compounding ratio, and the monomer for each layer as it goes to the center of a diameter The second member 13 made of PVDF is formed by repeatedly performing the same process as described above while reducing the amount of injection of Table 1 to form an 11-layer multi-layer structure inside the pipe 17 serving as the first member 11. Manufactured. The refractive index on the outer surface of the first layer 31 that is the outermost layer of the second member 13 was 1.432.

  After the 11th mixed solution was polymerized, the polysynthetic compound remaining for 6 hours while being heated to 90 ° C. was reacted. A preform 24 was obtained. At this time, the refractive index difference between the refractive index of the first member 11 and the outer surface of the second member 13 was 0.022. Then, while the cavity 58 of the preform 24 obtained is heated to 200 ° C. while being decompressed, the cavity 58 is closed by melting and stretching, and the first member 11 and the second member 13 are brought into close contact with each other. As a result, the gap 59 disappeared to obtain POF10 having an outer diameter of 470 μm. At this time, the fluctuation of the outer diameter of the POF 10 was ± 15 μm.

  When the obtained POF 10 was subjected to bending of 360 ° with a radius of curvature of 10 mm, the optical loss was 1.0 dB. In addition, as a result of measuring the elongation at break (%) and the knot strength (MPa) as physical properties of the obtained POF10 with a tensile tester (STROGRAPH-M1 manufactured by Toyo Seiki), the elongation at break was 20.0%. Yes, the knot strength was 423 MPa.

  Although the 2nd member 13 was formed using the same material and method as Example 1, in Example 2, the PVDF pipe used as pipe 17 which functions as the 1st member is removed, and the 1st member 11 is used beforehand. In the tubular first member 11 having an inner diameter of 20 mm, an outer diameter of 21 mm, and a refractive index of 1.36 manufactured by melt extrusion using a commercially available Dyneon (registered trademark: 3M) pellet, the first to eleventh layers are used. The configured second member 13 was inserted into a preform 24. At this time, the difference in refractive index between the first member 11 and the outer surface of the second member 13 was 0.072. Then, while the cavity 58 of the preform 24 obtained is heated to 200 ° C. while being decompressed, the cavity 58 is closed by melting and stretching, and the first member 11 and the second member 13 are brought into close contact with each other. As a result, the gap 59 disappeared to obtain POF10 having an outer diameter of 470 μm. At this time, the fluctuation of the outer diameter of the POF 10 was ± 15 μm.

  When the obtained POF 10 was subjected to bending of 360 ° with a radius of curvature of 10 mm, the optical loss was 0.2 dB, and the optical radiation loss due to bending was further reduced compared to Example 1. Moreover, as a result of measuring the elongation at break (%) and the knot strength (MPa) as physical properties of the obtained POF10 with a tensile tester (STROGRAPH-M1 manufactured by Toyo Seiki Co., Ltd.), the elongation at break was 6.0%. The nodule strength was 381 MPa.

[Comparative Example 1]
The second member 13 was formed using the same material and method as in Example 1. However, in Comparative Example 1, the first member 11 was not used, and only the second member 13 was used as the preform 24. Therefore, the pipe 17 is the outermost layer. The preform 24 was heated and stretched in the same manner as in Example 1 to produce POF 10 having an outer diameter of 470 μm. Further, when the obtained POF 10 was used to bend 360 ° with a curvature of 10 mm in the same manner as in Example 1, the optical loss was 2.2 dB. In addition, when the POF 10 was temporarily bent, it could be bent or broken. Furthermore, when a tensile test was performed using a tensile tester (manufactured by Toyo Seiki; STROGRAPH-M1), the elongation at break was 6.0% and the knot strength was 47 MPa.

  In Examples 1 and 2 and Comparative Example 1, regarding the second member forming material used when forming the second member 13, the mixing ratio (b / a) and total amount (a + b) of a and b in each mixed solution These are shown in Table 1.

Example 1 produced POF10 by forming the cylindrical 2nd member 13 in the inside of the tubular pipe 17 which consists of PVDF which functions as the 1st member 11, and heat-drawing this. In Example 2, the pipe 17 is used only as a polymerization pipe, and after the pipe 17 is removed, the tubular first member 11 and the cylindrical second member 13 are separately manufactured, and then the first member 11 The second member 13 was inserted into the preform 24, which was heated and stretched to produce POF10. On the other hand, in Comparative Example 1, the first member 11 was not used, and the preform 24 having the outermost layer of the second member 13 as the outer shell portion was produced, and this was heated and stretched to produce PO10.

  As a result, in Example 1, it was possible to obtain POF10 which was excellent in transparency without causing white turbidity and showed a large value in both elongation at break and knot strength. Further, in Example 2, it was possible to obtain POF having a large elongation at break and a very small loss due to bending as compared with Example 1. On the other hand, in Comparative Example 1, POF10 was obtained in which both the elongation at break and the knot strength were small, the physical properties were poor, and the loss increase due to bending was large. From the above, it was confirmed that in Example 1, a POF having excellent breaking strength and knot strength and showing low light loss can be produced. Therefore, after producing the tubular first member including the crystal structure and the second member including the amorphous structure, the second member is inserted into the hollow portion of the first member, and these are combined with each other to perform the preform. It was found that when this preform is heated and stretched, a POF that is excellent in elongation and strength and can suppress an increase in transmission loss during bending can be produced.

It is a manufacturing process figure of POF of this invention. It is process drawing which shows the flow of 2nd member formation of this invention. It is explanatory drawing of the combination process of this invention. It is sectional drawing of POF of this invention. It is sectional drawing of a superposition | polymerization container. It is the schematic of a rotation polymerization apparatus. It is explanatory drawing about the rotation method of a superposition | polymerization container. It is sectional drawing of the superposition | polymerization container after 1st layer formation.

Explanation of symbols

10 POF
DESCRIPTION OF SYMBOLS 11 1st member 12 1st member formation process 13 2nd member 14 2nd member formation process 15 Combining process 16 Stretching process 24 Preform 31 1st layer 32 2nd layer 33 (n-1) layer 34 nth layer

Claims (9)

In the manufacturing method in which the plastic optical fiber preform made of the second member different from the first member and the first member having the hollow portion is stretched in the longitudinal direction while being heated and melted to obtain the plastic optical fiber strand.
A first member forming step of forming the tubular first member made of a polymer containing a crystal structure;
A second member forming step of forming the second member made of a polymer containing amorphous;
A combination step of combining the first member and the second member into a plastic optical fiber preform,
The method of manufacturing a plastic optical fiber, wherein the refractive index of the first member is lower by at least 5 × 10 ⁻³ or more than the refractive index of the surface of the second member in contact with the first member.   2. The method of manufacturing a plastic optical fiber according to claim 1, wherein the second member has a refractive index of 1.4 or more and 1.5 or less on a surface in contact with the first member.   The method of manufacturing a plastic optical fiber according to claim 1 or 2, wherein the first member is a polymer containing a fluorine atom.   When the inner diameter of the first member is D1 (mm) and the outer diameter of the outermost layer of the second member is D2 (mm), the condition of 0.01 <D1-D2 <1.0 is satisfied. A method for producing a plastic optical fiber according to any one of claims 1 to 3. The second member is columnar or cylindrical,
The plastic optical fiber strand according to any one of claims 1 to 4, wherein when the second member is cylindrical, the plastic optical fiber preform is heated and melted while being decompressed and stretched. Production method.   The method of manufacturing a plastic optical fiber according to any one of claims 1 to 5, wherein the second member has a refractive index that gradually increases from the outside toward the center of the diameter.   A plastic optical fiber strand manufactured by the method for manufacturing a plastic optical fiber strand according to any one of claims 1 to 6.   A tubular first member made of a polymer containing a crystal structure, and a member inserted into the first member, and an amorphous material having an outer surface with a refractive index of 1.4 or more and 1.5 or less. A plastic optical fiber preform having a second member made of a unit. 9. The plastic optical fiber preform according to claim 8, wherein the refractive index of the second member gradually increases from the outside toward the center of the diameter.

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