JP2006058774A - Optical fiber cable and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a plastic optical fiber cable with which thermal contraction is suppressed. <P>SOLUTION: A preform is obtained by forming a core part having a GI type refractive index profile in a hollow cylindrical clad pipe. A GI type POF can be obtained by heating/fusion-drawing the preform. A GI type core wire 16 is obtained by covering the outer circumferential face of the GI type POF with polyethylene to form a protective layer 123. The GI type core wire 16 is arranged with a large number of aramid fibers on the outer circumference and covered with polyvinyl chloride to form the outermost layer 125, so that the plastic optical fiber cable 20 is obtained. The aramid fibers become a loose-type coating buffer layer 124, relaxing a stress imparted radially to the optical fiber cable 20. The optical fiber cable 20 is annealed at 60°C for 17 hours. Since the polymer of the outermost layer 124 is reoriented, longitudinal contraction is suppressed in the optical fiber cable 20 even when heat is applied thereto. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical fiber cable and a manufacturing method thereof.

  Plastic optical members have advantages such as easy manufacture and processing and low cost compared to quartz-based optical members having the same structure. Recently, optical fibers and optical lenses, Various applications such as waveguides have been attempted. Among these optical members, in particular, the plastic optical fiber has a disadvantage that the transmission loss is slightly larger than that of the quartz-based fiber because all the materials are made of plastic. However, it is advantageous in that it has good flexibility, light weight and good processability, and can be easily manufactured as an optical fiber having a large diameter as compared with a quartz optical fiber, and can be manufactured at a lower cost. Therefore, various studies have been made on optical communication transmission media for short distances where the magnitude of transmission loss is not a problem.

  A plastic optical fiber (hereinafter referred to as POF) generally has a refractive index different from that of a core (hereinafter referred to as a core or core portion) made of an organic compound having a polymer as a matrix (generally referred to as a core or core portion). Is composed of an outer shell (hereinafter referred to as a clad or a clad portion) made of an organic compound having a low refractive index. In particular, a refractive index distribution type plastic optical fiber having a core part having a distribution of refractive index from the center to the outside has a high transmission capacity because the band of an optical signal to be transmitted can be increased. It is attracting attention as an optical fiber. One of the methods for producing such a gradient index optical member is a method of producing an optical member base material (hereinafter referred to as a preform) using interfacial gel polymerization, and then stretching the preform. It has been proposed (see, for example, Patent Documents 1 and 2).

  POF is used as a plastic optical fiber core (hereinafter referred to as an optical fiber core or a core) by coating a polymer to form a protective layer in order to protect the outer peripheral surface and improve the mechanical strength. . An optical fiber core manufacturing method is also known in which a core portion, a cladding portion, and a protective layer are simultaneously composite-spun from a nozzle. Further, it is known that the optical fiber core wire is annealed to improve mechanical properties such as strength (see, for example, Patent Document 3).

JP 61-130904 A Japanese Patent No. 3332922 JP 2000-304942 A

  In recent years, a plastic optical fiber cable (hereinafter referred to as an optical fiber cable) in which one or more optical fiber cores are bundled and coated with a polymer to form a coating layer (hereinafter referred to as an outermost layer or a second coating layer). ) Is increasingly used. By bundling a plurality of optical fiber cores, a large amount of information can be transmitted and received with a single cable, which can be preferably used for a part of an optical transmission system. Moreover, what has waterproofness is used for the polymer which forms outermost layer. In general, the types of polymers forming the protective layer and the outermost layer are different from each other because the functions of the respective layers are different. Further, when the optical fiber cable is heated, the polymer may shrink. In this case, as described above, when different polymers are used for the protective layer and the covering layer, the shrinkage rate due to heat differs depending on each polymer, so that stress is applied to the optical fiber cable. Therefore, in order to relieve this stress, when bundling the optical fiber core wires, bundle the tensile strength fibers (for example, aramid fibers) together, and then form the outermost layer to form an optical fiber cable. Mitigating. Such a form of coating is referred to as loose-type coating. However, the conventional contraction in the longitudinal direction has not been particularly studied. Therefore, when attaching connectors to both ends of an optical fiber cable to form a part of an optical transmission system, if the thermal contraction rate of each layer is different in the longitudinal direction, it becomes difficult to connect the connectors, or connectors once attached There is a problem that comes off.

  An object of the present invention is to provide an optical fiber cable in which thermal contraction in the longitudinal direction is suppressed and a method for manufacturing the same.

  In the method of manufacturing an optical fiber cable according to the present invention, in the method of manufacturing an optical fiber cable by coating a polymer on an optical fiber composed of a core and a clad, the polymer is coated and then annealed. It is a case where at least one of the core or the clad is formed of a material having a glass transition temperature Tg (° C.), and the annealing temperature is at least one of the glass transition temperature Tg (of the core or the clad). C.) is preferable. The annealing temperature is preferably higher than 50 ° C. The annealing time is preferably longer than 8 hours and shorter than 100 hours.

  The method of manufacturing an optical fiber cable according to the present invention includes manufacturing an optical fiber having a first coating layer formed by coating an optical fiber composed of a core and a clad, and bundling one or more optical fibers. In the method of manufacturing an optical fiber cable in which the second coating layer is formed by coating with a polymer, the difference in thermal shrinkage between the first coating layer and the second coating layer after the formation of the second coating layer is 0. Annealing is performed so as to be less than 1%. The optical fiber is preferably a plastic optical fiber. The optical fiber is preferably a gradient index optical fiber. The core is preferably formed from deuterated polymethyl methacrylate. The coated polymer is preferably polyvinyl chloride.

  It is preferable that a buffer material is disposed around the optical fiber, and an outer peripheral portion of the optical fiber and the buffer material is covered with the polymer. The buffer material is preferably an aramid fiber.

  The optical fiber cable of the present invention is an optical fiber cable in which a polymer is coated on an optical fiber composed of a core and a clad, and the coated polymer is annealed. In the optical fiber cable of the present invention, one or more optical fiber cores having a first coating layer covering an optical fiber composed of a core and a clad are bundled and coated with a polymer to form a second coating layer. In the optical fiber cable, the second coating layer is annealed.

  It is preferable that the difference in thermal shrinkage between the first coating layer and the second coating layer is less than 0.1%. The optical fiber is preferably a plastic optical fiber. The optical fiber is preferably a gradient index optical fiber. The core is preferably formed from deuterated polymethyl methacrylate. The second coating layer is preferably polyvinyl chloride.

  It is preferable that a buffer material is disposed around the optical fiber core, and an outer peripheral portion of the optical fiber core and the buffer material is covered with the second coating layer. The buffer material is preferably an aramid fiber.

According to the method of manufacturing an optical fiber cable of the present invention, in the method of manufacturing an optical fiber cable by coating an optical fiber comprising a core and a clad, the optical fiber cable is annealed after coating the polymer. The thermal contraction of a polymer such as a protective layer formed on the cable is suppressed, and deformation of the optical fiber cable can be prevented when heat is applied to the optical fiber cable.

  According to the method for manufacturing an optical fiber cable of the present invention, an optical fiber having a first coating layer is manufactured by coating an optical fiber composed of a core and a cladding, and one or more optical fibers are formed. In the method of manufacturing an optical fiber cable in which the second coating layer is formed by bundling and coating with a polymer, there is a difference between thermal contraction between the first coating layer and the second coating layer after the second coating layer is formed. Since the annealing is performed so as to be less than 0.1%, the thermal contraction of the polymer forming the first and second coating layers is suppressed, and the heat is applied to the optical fiber cable. Deformation of the optical fiber cable due to the difference in thermal shrinkage between the coating layer and the second coating layer can be prevented. In addition, the manufacturing method of the optical fiber cable of this invention can acquire the effect of the thermal relaxation of a polymer more when the said optical fiber is a plastic optical fiber.

  According to the optical fiber cable of the present invention, in the optical fiber cable in which the polymer is coated on the optical fiber composed of the core and the clad, since the coated polymer is annealed, the optical fiber cable is formed on the optical fiber cable. The thermal contraction of the polymer such as the protective layer is suppressed, and deformation of the optical fiber cable can be prevented when heat is applied to the optical fiber cable.

  According to the optical fiber cable of the present invention, one or more optical fiber cores having a first coating layer that covers an optical fiber composed of a core and a clad are bundled and coated with a polymer to form a second coating layer. In the optical fiber cable, the second coating layer is annealed, and a difference in thermal shrinkage between the first coating layer and the second coating layer is less than 0.1%. The thermal contraction of the polymer forming the two coating layers is suppressed, and when the heat is applied to the optical fiber cable, the difference in the thermal shrinkage rate between the first coating layer and the second coating layer Deformation can be prevented. In addition, the manufacturing method of the optical fiber cable of this invention can acquire the effect of the thermal relaxation of a polymer more when the said optical fiber is a plastic optical fiber.

  One embodiment of a method for producing an optical fiber cable according to the present invention is shown in FIG. The preform production process 11 is performed using a polymer or the like as a raw material for the core part and the clad part to obtain a preform 12. The preform 12 is stretched (drawn) by a stretching step 13 to continuously obtain a plastic optical fiber (POF) 14 having a desired diameter (for example, 300 μm to 1000 μm). The POF 14 is usually wound on a take-up reel in a roll shape. When the stretching step 13 is performed, the POF 14 may be protected by continuously coating after the preform 12 is stretched. In the present invention, regardless of the presence or absence of coating, both are referred to as POF14. A protective layer is formed on the POF 14 in the first coating step 15 to form a plastic optical fiber core wire 16.

  The optical fiber core wire 16 can be used as an optical transmission body as it is. However, it normally has a function of suppressing tension / compression, lateral pressure / bending, water immersion, and the like. Therefore, the optical fiber core wire 16 is single-core or multi-core, and the buffer material 17 is disposed on the outer periphery thereof. The second coating step 18 is performed to bundle the optical fiber core wire 16 and the buffer material 17 together to form the outermost layer. A polymer is mainly used for the outermost layer. A plastic optical fiber cable original fabric (hereinafter referred to as a cable original fabric) 19 having an outermost layer formed in the second coating step 18 is obtained. Furthermore, thermal annealing is performed in the annealing step 20 to reorient the polymer forming the outermost layer of the cable original fabric 19. Through the above steps, a plastic optical fiber cable (hereinafter referred to as an optical fiber cable) 21 is obtained.

  In the following, as an embodiment of the present invention, an embodiment using a refractive index distribution type plastic optical fiber (hereinafter sometimes referred to as GI type POF) having a refractive index distribution in the core as POF is taken as an example. Although described, the present invention is not limited to the described contents.

[POF ingredients]
(Core part)
As the polymerizable monomer for the raw material of the core part, it is preferable to select a raw material that can be easily bulk-polymerized. Examples of raw materials that are highly light transmissive and easy to bulk polymerize include the following (meth) acrylic acid esters (fluorine-free (meth) acrylic acid ester (a), fluorine-containing (meth) acrylic acid ester (b) ), Styrenic compounds (c), vinyl esters (d), etc., and the core part is a homopolymer of these, or a copolymer comprising two or more of these monomers, and a homopolymer and / or It can be formed from a mixture of copolymers. Among these, a composition containing (meth) acrylic acid esters as a polymerizable monomer can be 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, include phenyl benzyl methacrylate (BzMA), methacrylate, cyclohexyl methacrylate, diphenylmethyl, tricyclo [5 · 2 · 1 · 0 ^2,6] decanyl methacrylate, adamantyl methacrylate, isobornyl methacrylate and And methyl acrylate, ethyl acrylate, tert-butyl acrylate, phenyl acrylate, and the like. Further, (b) the fluorine-containing acrylic ester and the fluorine-containing methacrylate ester are 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3. , 3-pentafluoropropyl methacrylate, 1-trifluoromethyl-2,2,2-trifluoroethyl methacrylate, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 2,2, 3,3,4,4-hexafluorobutyl methacrylate and the like. Furthermore, (c) styrene compounds include styrene, α-methylstyrene, chlorostyrene, bromostyrene, and the like. Furthermore, (d) vinyl esters include vinyl acetate, vinyl benzoate, vinyl phenyl acetate, vinyl chloroacetate and the like. Of course, it is not limited to these. The type and composition ratio of the constituent monomers are selected so that the refractive index of the polymer of the core portion made of a monomer alone or a copolymer is equal to or higher than that of the cladding portion. A particularly preferred polymer is polymethyl methacrylate (PMMA), which is a transparent resin.

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

(Clad part)
For the material of the clad part, it is preferable to use a material having a refractive index lower than the refractive index of the core part and having good adhesion to the core part because the light transmitted through the core part is totally reflected at the interface between them. Can do. However, in the case where irregularity of the interface between the core part and the clad part is likely to occur due to selection of the material or it is not preferable in terms of manufacturing suitability, a layer may be further provided between the core part and the clad part. For example, by forming an outer core layer made of a polymer having the same composition as the matrix of the core part at the interface with the core part (that is, the inner wall surface of the hollow tube), the interface state between the core part and the cladding part is corrected. can do. Details of the outer core layer will be described later. Of course, without forming the outer core layer, the cladding part itself can be formed of a polymer having the same composition as the matrix of the core part.

  As the material for the clad part, a material excellent in toughness and heat and heat resistance is preferably used. For example, it preferably comprises a homopolymer or copolymer of a fluorine-containing monomer. As the fluorine-containing monomer, vinylidene fluoride (PVDF) is preferable, and a fluororesin obtained by polymerizing one or more polymerizable monomers containing 10% by mass or more of vinylidene fluoride can be preferably used.

  Moreover, when forming a clad part by shape | molding a polymer with the below-mentioned melt extrusion method, it is necessary for the melt viscosity of a polymer to be suitable. As for the melt viscosity, molecular weight is used as a correlated physical property, and particularly, there is a correlation with the weight average molecular weight. In the present invention, the weight average molecular weight is suitably in the range of 10,000 to 1,000,000, more preferably in the range of 30,000 to 500,000.

  Furthermore, it is preferable to prevent moisture from entering the core as much as possible. For this purpose, a polymer having a low water absorption rate is used as a material (material) for the cladding. That is, it is preferable to produce a clad part using a polymer having a saturated water absorption rate (hereinafter referred to as a water absorption rate) of less than 1.8%. More preferably, the clad portion is formed using less than 1.5% polymer, and more preferably less than 1.0% polymer. Further, it is preferable to use a polymer having the same water absorption rate when the outer core layer is produced. The water absorption rate (%) can be calculated by immersing the test piece in water at 23 ° C. for 1 week according to the ASTM D 570 test method and measuring the water absorption rate at that time.

(Polymerization initiator)
When the core part and / or the clad part are made from a polymer polymerized from a polymerizable monomer, a polymerization initiator is used in the polymerization. As a polymerization initiator, it can select suitably according to the monomer and polymerization method to be used, for example, benzoyl peroxide (BPO), tert- butyl peroxy-2-ethyl hexanate (PBO), di-tert-butyl. Examples thereof include peroxide compounds such as 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′-azobis (2- And azo compounds such as methyl propionate). Of course, the polymerization initiator is not limited to these, and two or more kinds may be used in combination.

(Chain transfer agent)
The polymerizable composition for forming a core part and the polymerizable composition for forming a clad part preferably contain a chain transfer agent. The chain transfer agent is mainly used for adjusting the molecular weight of the polymer. When the polymerizable composition for forming the clad part and the core part contains a chain transfer agent, when the polymer is formed from the polymerizable monomer, the polymerization rate and the degree of polymerization are more controlled by the chain transfer agent. And the molecular weight of the polymer can be adjusted to a desired molecular weight. For example, when the obtained preform is drawn by drawing to make POF, the mechanical properties at the time of drawing can be adjusted to a desired range by adjusting the molecular weight, which contributes to improvement of productivity. .

  About the said 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 Masato Kinoshita, “Experimental Methods 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), 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 (D) or a fluorine atom (F) can also be used. Of course, the chain transfer agent is not limited to these, and two or more of these chain transfer agents may be used in combination.

(Refractive index modifier)
It is preferable to add a refractive index adjusting agent to the polymerizable composition for the core part. In some cases, the clad part polymerizable composition may contain a refractive index adjusting agent. By providing a distribution of the concentration of the refractive index adjusting agent, a refractive index distribution type core can be easily produced based on the concentration distribution. Even without using a refractive index adjusting agent, it is possible to introduce a refractive index distribution structure by using two or more polymerizable monomers for forming the core portion and having a distribution of the copolymerization ratio in the core portion. It is preferable to use a refractive index adjusting agent in view of the ease of production and the like as compared with the composition ratio control of copolymerization.

The refractive index adjusting agent is also called a dopant, and is a compound different from the refractive index of the polymerizable monomer used together. 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.

  Use 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 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 direction of the polymerization is controlled by the interfacial gel polymerization method, and the concentration of the dopant is given a gradient. A method of forming a refractive index distribution structure based on the dopant concentration distribution in the part is illustrated. Thus, the core portion having the refractive index distribution is referred to as a “refractive index distribution type core portion”. By forming the gradient index core portion, the obtained optical member becomes a gradient index plastic optical fiber having a wide transmission band. 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 compared to a polymer not containing this. Those having the property to Examples of such a copolymer include MMA-BzMA copolymer.

  Examples of the dopant include benzyl benzoate (BEN), diphenyl sulfide (DPS), triphenyl phosphate (TPP), and benzyl phthalate as described in Japanese Patent No. 3332922 and JP-A-11-142657. -N-butyl (BBP), diphenyl phthalate (DPP), diphenyl (DP), diphenylmethane (DPM), tricresyl phosphate (TCP), diphenyl sulfoxide (DPSO), sulfurized diphenyl derivatives, dithian derivatives and the like. Among them, BEN, DPS, TPP, DPSO, sulfurized diphenyl derivatives, and dithian derivatives are preferable. In addition, compounds obtained by substituting hydrogen atoms present in these compounds with deuterium atoms can also be used for the purpose of improving transparency in a wide wavelength region. Examples of the polymerizable compound include tribromophenyl methacrylate. When a polymerizable compound is used as the refractive index adjusting component, it is difficult to control various characteristics (particularly optical characteristics) because the polymerizable monomer and the polymerizable refractive index component are copolymerized when forming the matrix. However, it may be advantageous in terms of heat resistance.

  By adjusting the concentration and distribution of the refractive index adjusting agent, the refractive index of the optical member can be changed to a desired value. The addition amount is appropriately selected according to the use and the member to be combined. A plurality of types of refractive index adjusting agents may be added.

  Two or more types of dopants may be contained in the polymerizable composition used in the present invention. However, each has a benzene ring, and the Hammett value of the substituent (however, when there are a plurality of substituents, the weighted average of those Hammett values) is 0.04 or less and the SP value is 10.9 or less. It is preferable to use the compound which becomes.

(Other additives)
In addition, other additives can be added to the polymerizable composition for producing them in the core part, the clad part, or a part thereof, as long as the optical transmission performance is not deteriorated. 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 stimulated emission functional compound, the attenuated signal light can be amplified by the excitation light, and the transmission distance is improved. For example, it can be used as an optical 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.

[Preform manufacturing method]
Hereinafter, an embodiment in which the manufacturing method of the present invention is applied to a manufacturing method of a gradient index plastic preform having a core portion and a cladding portion will be described. Although there are mainly two types of this embodiment, it is not limited to the following embodiments.

  First, in the first embodiment, a hollow tube is produced by polymerizing a polymerizable composition for a cladding part. Alternatively, a hollow cylindrical tube serving as a clad portion is produced by melt extrusion molding of a thermoplastic resin (first step). The core portion-forming polymerizable composition is subjected to interfacial gel polymerization in the hollow portion of the hollow cylindrical tube to form a region that becomes a core portion, and a preform that includes regions corresponding respectively to the core portion and the cladding portion is produced ( Second step). The obtained preform is processed into a desired form (third step) by the manufacturing apparatus and the manufacturing method according to the present invention to obtain POF. In addition, the refractive index distribution type plastic optical fiber is obtained by polymerizing the polymerizable composition to which the dopant is added in the second step by the interfacial gel polymerization method.

  Next, in the second embodiment, after forming the hollow cylindrical tube corresponding to the cladding portion in the first embodiment, a layer called an outer core portion is further formed on the inner peripheral surface (first 'step). In the form having the outer core layer, the central core portion is also referred to as an inner core portion. In the following description, the term “core part” also means the “inner core part” depending on the form.

  For example, in the hollow portion of a hollow cylindrical tube made of a fluorine-containing resin such as polyvinylidene fluoride resin, the outer core layer is formed on the inner peripheral surface of the hollow cylindrical tube by polymerization of the polymerizable composition for the outer core by rotation polymerization. To form a hollow cylindrical tube having two layers (first 'step). An inner core portion is further formed in the hollow portion of the hollow cylindrical tube. The inner core portion is formed by interfacial gel polymerization of the polymerizable composition for forming the inner core portion (second step). Then, the obtained preform is processed into a desired form (third step) to produce an optical member.

  In the second embodiment, when a concentric hollow cylindrical tube composed of two layers is produced, the fluororesin serving as the cladding part and the polymer of the polymerization composition for the outer core are not melted stepwise as described above. A method of manufacturing in one step of the coextrusion method can be easily applied.

  In the first embodiment, the composition of the polymerizable monomers used in the polymerizable composition for forming the clad / core part and in the second embodiment for forming the outer core / inner core part is mutually different. Preferably equal. However, the composition ratio may not be the same, and the subcomponents may not be equal. By using the same type of polymerizable monomer, it is possible to improve light transmittance and adhesiveness at the cladding / core or outer core / inner core interface. In addition, when the resin forming the clad part or the outer core part is made of a copolymer and the refractive index of the copolymer component is different, the refractive index difference from the core part is increased by controlling the ratio of the copolymer component. As a result, the refractive index distribution structure can be easily formed.

  In the second embodiment, an outer core portion is formed between the clad portion and the core portion, thereby reducing a decrease in adhesiveness and a decrease in productivity due to a difference in material between the clad portion and the core portion. As a result, the range of selection of materials used for the clad part and the core part can be expanded. The cylindrical tube corresponding to the clad part can also be produced, for example, by molding a commercially available fluororesin into a pipe having a desired diameter and thickness by melt extrusion or rotational polymerization of a polymerizable composition. Furthermore, the outer core layer-forming polymerizable composition can be rotationally polymerized in the hollow portion of the obtained pipe to form an outer core layer on the inner peripheral surface thereof. In addition, a similar structure can be produced by co-extrusion of a polymer comprising the fluororesin and the polymerizable composition.

  When the POF according to the present invention is manufactured, the refractive index distribution type POF can also be manufactured by using a refractive index adjusting component and giving a gradient to the concentration. As a method of giving a gradient to the concentration of the refractive index adjusting component, an interfacial gel polymerization method or a rotational gel polymerization method described later can be applied.

  In the case where the clad part and the outer core part are made of a polymerizable composition, and in the polymerizable composition for forming a core part, the preferred range of the content ratio of each component differs depending on the type and cannot be unconditionally determined. In general, the polymerization initiator is preferably 0.005% by mass to 0.5% by mass and more preferably 0.01% by mass to 0.5% by mass with respect to the polymerizable monomer. preferable. The chain transfer agent is preferably 0.10% by mass to 0.40% by mass with respect to the polymerizable monomer, and more preferably 0.15% by mass to 0.30% by mass. Further, the refractive index adjusting component is preferably 1% by mass to 30% by mass, and more preferably 1% by mass to 25% by mass with respect to the polymerizable monomer.

  The molecular weight of the polymer obtained by polymerizing the clad part, the outer core part, and the polymer composition for forming the core part is in the range of 10,000 to 1,000,000 in terms of weight average molecular weight, because the preform is stretched. Is preferable, and it is more preferable that it is 30,000 to 500,000. Further, the molecular weight distribution (MWD: weight average molecular weight / number average molecular weight) is also influenced from the viewpoint of stretchability. If the MWD becomes large, even if there are a few components having an extremely high molecular weight, the stretchability is deteriorated, and in some cases, stretching may be impossible. Therefore, as a preferable range, MWD is preferably 4 or less, and more preferably 3 or less.

  Next, each step of the first and second modes (particularly the first embodiment) will be described in detail.

(First step)
In the first step, a hollow (for example, cylindrical) hollow cylindrical tube having one layer corresponding to the cladding part or two layers corresponding to the cladding part and the outer core part is manufactured. As a method for producing the hollow cylindrical tube, for example, it is produced by forming a hollow tube while polymerizing monomers. Examples of this method include a production method by rotational polymerization as described in Japanese Patent No. 3332922, and melt extrusion of a resin.

  When producing a hollow cylindrical tube from a polymerizable composition, it is carried out by a rotational polymerization method. For example, the polymerizable composition for forming a clad part is injected into a cylindrical polymerization container, or the polymerizable composition for forming an outer core part is injected into a hollow cylindrical tube made of a fluororesin that is a clad part. The polymerizable monomer is polymerized while rotating the polymerization vessel or the hollow cylindrical tube (preferably rotating with the cylinder axis kept horizontal). Thereby, a hollow cylindrical tube having an inner core portion formed on the clad portion or the inner peripheral surface of the clad portion can be produced.

  Before injecting any of the polymerizable compositions into the polymerization vessel or the hollow cylindrical tube, it is preferable to remove the dust contained in the composition by filtering the polymerizable composition through a filter. In addition, as long as it does not cause deterioration of performance or complication of the pre-process and post-process, adjustment of the viscosity and pre-polymerization are performed so that it is easy to handle like the viscosity adjustment of the raw material described in JP-A-10-293215. The polymerization time can be shortened by carrying out the process. Although the polymerization temperature and the polymerization time vary depending on the monomer and polymerization initiator used, in general, the polymerization temperature is preferably 60 ° C. to 150 ° C., and the polymerization time is preferably 5 hours to 24 hours. At this time, as described in JP-A-8-110419, the polymerization time required for molding may be shortened by prepolymerizing the raw material and increasing the raw material viscosity. Moreover, if the container used for polymerization is deformed by rotation, the resulting cylindrical tube is distorted. Therefore, it is desirable to use a metal tube / glass tube having sufficient rigidity.

  In addition, a pellet-like or powdery resin (preferably a fluororesin) is put into a cylindrical container, both ends are closed, and the container is rotated (preferably, rotating with the axis of the cylinder kept horizontal). And the hollow cylindrical tube which consists of a polymer can be produced by heating more than melting | fusing point of the said resin and melting resin. At this time, in order to prevent heat or oxidation of the resin due to melting and thermal oxidative decomposition, it is preferable to carry out the inside of the container in an inert gas atmosphere such as nitrogen, carbon dioxide, argon or the like. Moreover, it is preferable that the resin is sufficiently dried in advance.

  On the other hand, when a polymer is melt-extruded to form a clad portion, a desired shape (cylindrical shape in the present embodiment) is obtained by using a molding technique such as extrusion molding once the polymer is synthesized. A structure can also be obtained. There are mainly two types of melt-extrusion apparatuses used for these: an inner sizing die system and an outer die vacuum suction system.

  FIG. 2 shows an example of a cross-sectional view of an inner sizing die type melt extrusion apparatus, and an outline of inner sizing die type molding will be described. The raw material polymer 31 in the cladding part is extruded from the melt extrusion apparatus main body to the die main body 32 by a single screw extruder with a vent (not shown). The die body 32 is provided with a guide 33 that guides the raw polymer 31 into a cylindrical shape. The raw material polymer 31 passes through a flow path 34 a between the die body 32 and the inner rod 34 through a guide 33. The raw material polymer 31 is extruded from the die outlet 32a to form a clad 35 in the shape of a cylindrical hollow tube. The extrusion speed of the clad 35 is not particularly limited, but the extrusion speed is preferably in the range of 1 cm / min to 100 cm / min from the viewpoint of productivity while keeping the shape uniform.

  The die body 32 is preferably provided with a heating device (not shown) for heating the raw polymer 31. For example, even if one or more heating devices (for example, a device using steam, heat transfer oil, electric heater, etc.) are installed so as to cover the die body 32 along the traveling direction of the raw material polymer 31. Good. A thermometer 36 is attached in the vicinity of the die outlet 32a. It is preferable to adjust the temperature of the die body 32 by measuring the temperature of the clad 35 at the die outlet 32 a with the thermometer 36.

  It is preferable to set the heating temperature to 40 ° C. or higher because it is possible to suppress a change in shape due to a rapid temperature change. Further, the die body 32 may be provided with a cooling section. For controlling the temperature of the clad 35, for example, a temperature controller (for example, a liquid such as water, antifreeze liquid, oil, or a cooling device using electronic cooling) may be attached to the die body 32. You may cool by natural air cooling. When a heating device is installed in the die body 32, the cooling device is preferably attached downstream of the position of the heating device.

  Next, the outer die vacuum suction method will be described. FIG. 3 shows an example of the production line 40 of the melt extrusion apparatus, and FIG. 4 shows an example of a cross-sectional view of the forming die.

  The production line 40 shown in FIG. 3 includes a melt extrusion device 41, an extrusion die 42, a molding die 43, a cooling device 44, and a take-up device 45. The raw material polymer charged from the pellet charging hopper 46 is melted in the melt extrusion apparatus inside 41 a, extruded by the extrusion die 42, and sent to the molding die 43. A vacuum pump 47 is attached to the molding die 43. The extrusion speed S is preferably in the range of 0.1 ≦ S (m / min) ≦ 10, more preferably 0.3 ≦ S (m / min) ≦ 5.0, and most preferably 0.4 ≦ S. (M / min) ≦ 1.0. However, the extrusion speed S (m / min) is not limited to the above-described range.

  The forming die 43 in FIG. 4 includes a forming tube 50. By passing the raw material polymer 51 through the forming tube 50, the raw material polymer 51 is formed, and a cylindrical hollow clad 52 is obtained. The forming tube 50 is provided with a number of suction holes 50 a, and the decompression chamber 53 provided outside the forming tube 50 is decompressed by the vacuum pump 47, so that the outer wall surface of the clad 52 is formed on the forming tube 50. In order to adhere to the molding surface (inner wall surface) 50b, the cladding 52 is molded with a constant thickness. The pressure (absolute pressure) in the decompression chamber 53 is preferably in the range of 20 kPa to 50 kPa, but is not limited to this range. Further, it is preferable to attach a throat (outer diameter defining member) 54 for defining the outer diameter of the clad 52 to the inlet of the forming die 43.

  The clad 42 whose shape is adjusted by the molding die 43 is sent to the cooling device 44. The cooling device 44 is provided with a number of nozzles 60. Cooling water 61 is discharged from the nozzle 60 toward the clad 52. Thereby, the clad 52 is cooled and solidified. The cooling water 61 is collected by the receptacle 62 and discharged from the discharge port 62a. The clad 52 is drawn from the cooling device 44 by the take-up device 45. The take-up device 45 is provided with a drive roller 65 and a pressure roller 66. A motor 67 is attached to the drive roller 65 so that the take-up speed of the clad 52 can be adjusted. Further, it is possible to correct a minute position shift of the clad 52 by the pressure roller 66 arranged to face the driving roller 65 with the clad 52 interposed therebetween. By adjusting the take-up speed of the driving roller 65 and the extrusion speed of the melt extrusion device 41, or by finely adjusting the moving position of the clad by the pressure roller 66, the shape of the clad 52, particularly the wall thickness, can be made uniform. It becomes possible to do. If necessary, the driving roller 65 and the pressure roller 66 can be belt-shaped.

  The clad may be composed of multiple layers in order to give various functions such as mechanical strength improvement and flame retardancy, and after producing a hollow tube with an arithmetic average roughness of the inner wall in a specific range, The outer wall surface can be covered with a fluororesin or the like.

  The outer diameter D1 of the obtained cladding is preferably in the range of D1 ≦ 50 mm, more preferably in the range of 2 ≦ D1 (mm) ≦ 30, from the viewpoint of optical characteristics and productivity. Furthermore, the thickness t of the clad portion can be reduced as long as the shape can be maintained, but is preferably in the range of 2 ≦ t (mm) ≦ 20. However, in the present invention, these ranges are not limited to those described above.

  Specific examples of the polymerizable monomer or the like used as a raw material for the outer core layer are the same as the specific examples of the inner core portion. The outer core layer is provided mainly for the production of the inner core part, and the thickness thereof may be a thickness necessary for the bulk polymerization of the inner core part, and the inner layer having a refractive index by the progress of the bulk polymerization. It may be a simple core portion that is united with the core portion and does not exist as a single layer. Therefore, the thickness of the outer core provided before forming the core part may be 0.5 mm to 1 mm or more before the core part polymerization in order to perform bulk polymerization, and the upper limit remains a space where a sufficient refractive index distribution can be formed. Since it may be thickened to the extent, it can be selected according to the size of the preform.

  The single- or double-cylindrical polymer structure preferably has a bottom so that a polymerizable composition as a raw material for the core (inner core) can be injected. Moreover, it is preferable that the bottom part is made of a material that is rich in adhesiveness and adhesiveness with the polymer constituting the cylindrical tube. Further, the bottom can be made of the same polymer as the cylindrical tube. For example, before the polymerization is performed by rotating the polymerization vessel, or after forming the hollow tube by any method, the bottom portion made of the polymer is a small amount of polymerization in the polymerization vessel with the polymerization vessel left still vertically. It can be formed by injecting a polymerizable monomer and polymerizing it.

  After the rotational polymerization, the hollow tube obtained at a temperature higher than the polymerization temperature of the rotational polymerization may be subjected to heat treatment for the purpose of sufficiently reacting the remaining monomer and polymerization initiator. After the empty tube is obtained, the unpolymerized composition may be removed.

(Second step)
In the second step, the polymerizable monomer in the polymerizable composition filled in the hollow tube is polymerized to form the core part (or inner core part). In the interfacial gel polymerization method, the polymerization of the polymerizable monomer proceeds from the inner wall surface of the hollow tube toward the radial direction and the center of the cross section. When two or more kinds of polymerizable monomers are used, a monomer having a high affinity for the polymer constituting the hollow tube is unevenly distributed on the inner wall surface of the hollow tube and is mainly polymerized, A polymer with a high monomer ratio is formed. Towards the center, the ratio of the high affinity monomer in the formed polymer decreases and the ratio of other monomers increases. In this way, a distribution of the monomer composition occurs in the region that becomes the core portion, and as a result, a refractive index distribution is introduced. Further, when a refractive index adjuster is added to the polymerizable monomer for polymerization, as described in Japanese Patent No. 3332922, the core liquid dissolves the inner wall of the hollow tube, and the polymer constituting the inner wall surface is obtained. Polymerization proceeds while swelling to form a gel. At this time, a monomer having a high affinity for the polymer constituting the hollow tube is unevenly distributed on the surface of the hollow tube and polymerized, and a polymer having a low refractive index adjusting agent concentration is formed outside. The The ratio of the refractive index adjusting agent in the formed polymer increases toward the center. In this way, a concentration distribution of the refractive index adjusting agent is generated in the region that becomes the core portion, and as a result, a refractive index distribution is introduced.

  Further, the polymerization rate and degree of polymerization of the polymerizable monomer can be controlled by a polymerization initiator and a chain transfer agent added as required, and the molecular weight of the polymer can be adjusted to a desired molecular weight. For example, when the obtained polymer is drawn by stretching to obtain POF, the molecular weight of the polymer produced by the chain transfer agent (preferably 10,000 to 1,000,000, more preferably 30,000 to 500,000) If is adjusted, the mechanical properties at the time of stretching can be in a desired range, which contributes to the improvement of productivity.

  In this step, the refractive index distribution is introduced into the region to be the core portion to be formed, but the thermal behavior is different between the portions having different refractive indexes. Therefore, when the polymerization is performed at a constant temperature, the volume shrinkage responsiveness to the polymerization reaction changes in the region that becomes the core due to the difference in thermal behavior, and bubbles are mixed inside the preform. Alternatively, microscopic voids are generated, and there is a possibility that a large number of bubbles are generated when the obtained preform is heated and stretched. When the polymerization temperature is too low, the polymerization efficiency decreases. Further, the productivity is remarkably impaired, the polymerization is incomplete, the light transmittance is lowered, and the optical transmission performance of the produced optical member is impaired. On the other hand, if the initial polymerization temperature is too high, the initial polymerization rate is remarkably increased, the response to the shrinkage of the region that becomes the core portion cannot be relaxed, and the tendency of bubble generation becomes significant.

Therefore, it is preferable to maintain the initial polymerization temperature at a temperature T1 (° C.) that satisfies the following relational expression and to reduce the polymerization rate to improve the volume shrinkage response relaxation property in the initial polymerization.
Tb (° C.) − 10 ° C. ≦ T1 (° C.) ≦ Tg (° C.)
Tb (° C.) indicates the boiling point of the polymerizable monomer, and Tg (° C.) indicates the glass transition point (glass transition temperature) of the polymer of the polymerizable monomer. The temperature T1 (° C.) is referred to as the initial polymerization temperature. The same applies to the following description.

After carrying out the polymerization while maintaining the initial polymerization time T1 (° C.), the temperature is raised to a polymerization temperature T2 (° C.) that satisfies the following relational expression, and further polymerization is performed.
Tg (° C.) ≦ T 2 (° C.) ≦ T g (° C.) + 40 (° C.)
T1 (° C) <T2 (° C)
When the polymerization is completed by raising the temperature to the polymerization temperature T2 (° C.), it is possible to prevent the light transmittance from being lowered and to obtain a preform having a good light transmission capability. Further, it is possible to eliminate fluctuations in the density of the polymer existing in the interior and improve the transparency of the preform while suppressing the influence of thermal degradation and depolymerization of the preform. The polymerization temperature T2 (° C.) is more preferably Tg (° C.) or more and (Tg + 30) ° C. or less, and particularly preferably about (Tg + 10) ° C. If the polymerization temperature T2 (° C.) is less than Tg (° C.), this effect cannot be obtained. If the polymerization temperature T2 (° C.) exceeds (Tg + 40) ° C., the transparency of the preform decreases due to thermal degradation or depolymerization. Tend. Furthermore, when the refractive index distribution type core portion is formed, the refractive index distribution is lost, and the performance as an optical fiber is significantly reduced.

  The polymerization at the polymerization temperature T2 (° C.) is preferably performed until the polymerization is completed so that the polymerization initiator does not remain. If unreacted polymerization initiator remains in the preform, the heated unreacted polymerization initiator may be decomposed to generate bubbles during preform processing, particularly in melt stretching. It is preferable to terminate the reaction of the initiator. The preferred range of the holding time of the polymerization temperature T2 (° C.) varies depending on the type of the polymerization initiator used, and is preferably not less than the half-life time of the polymerization initiator at the polymerization temperature T2 (° C.).

  When the boiling point of the polymerizable monomer is Tb (° C.), a compound having a 10-hour half-life temperature of (Tb-20) ° C. or higher is preferably used as the polymerization initiator. It is also preferable from the same viewpoint that the polymerization is performed at an initial polymerization temperature T1 (° C.) satisfying the above relational expression for a time of 10% or more (preferably a time of 25%) of the half-life of the polymerization initiator. When a compound having a 10-hour half-life temperature of (Tb-20) ° C. or higher is used as a polymerization initiator and polymerized at the initial polymerization temperature T1 (° C.), the initial polymerization rate can be reduced. In addition, by polymerizing at the initial polymerization temperature T1 (° C.) to a time of 10% or more of the half-life time of the polymerization initiator, it is possible to quickly follow the volume shrinkage response in the initial polymerization by pressure. By setting the above conditions, it is possible to reduce the initial polymerization rate and improve the volume shrinkage responsiveness in the initial polymerization, and as a result, it is possible to reduce the mixing of bubbles due to the volume shrinkage in the preform and to improve the productivity. Can be improved. The 10-hour half-life temperature of the polymerization initiator refers to a temperature at which the number is reduced to 1/2 in 10 hours when the polymerization initiator is decomposed.

  When a polymerization initiator that satisfies the above conditions is used for polymerization for 10% or more of the half-life time of the initiator at the initial polymerization temperature T1 (° C.), the initial polymerization temperature T1 (° C.) is maintained until the polymerization is completed. May be. However, in order to obtain an optical member having high light transmittance, it is preferable to raise the polymerization temperature T2 (° C.) higher than the initial polymerization temperature T1 (° C.) to complete the polymerization. The temperature at the time of temperature rise is preferably the polymerization temperature T2 (° C.) satisfying the above relational expression, the more preferable temperature range is also as described above, and the preferable range of the holding time of the polymerization temperature T2 (° C.) is also as described above. It is.

  In this step, when methyl methacrylate (MMA) having a boiling point Tb (° C.) of 100 ° C. is used as the polymerizable monomer, the polymerization initiator having a 10-hour half-life temperature of (Tb-20) ° C. or higher is described above. Among them, PBD and PHV are applicable. For example, when MMA is used as the polymerizable monomer and PBD is used as the polymerization initiator, the initial polymerization temperature T1 (° C.) is maintained at 100 ° C. to 110 ° C. for 48 hours to 72 hours, and then the polymerization temperature T2 (° C. ) Is preferably heated to 120 to 140 ° C. and polymerized for 24 to 48 hours. When PHV is used as the polymerization initiator, the initial polymerization temperature T1 (° C) is maintained at 100 ° C to 110 ° C for 4 hours to 24 hours, and the polymerization temperature T2 (° C) is raised to 120 ° C to 140 ° C. The polymerization is preferably performed for 24 to 48 hours. In addition, although temperature rising may be performed in steps or continuously, it is better that the time required for temperature rising is short.

  In this step, the polymerization may be carried out under pressure as described in JP-A-9-269424 or under reduced pressure as described in Japanese Patent No. 3332922. May be changed. By these operations, it is possible to improve the polymerization efficiency of the polymerization at the initial polymerization temperature T1 (° C.) and the polymerization temperature T2 (° C.) satisfying the relational expression, which is a temperature in the vicinity of the boiling point Tb (° C.) of the polymerizable monomer. . When polymerization is performed in a pressurized state (hereinafter, polymerization performed in a pressurized state is referred to as “pressurized polymerization”), a hollow tube into which the polymerizable monomer has been injected is inserted into a hollow portion of a jig, and then cured. The polymerization is preferably carried out while being supported by the tool. Further, the generation of bubbles can be further reduced by dehydrating and degassing the polymerizable monomer before polymerization in a reduced-pressure atmosphere.

  The jig preferably has a hollow shape into which the hollow tube can be inserted, and the hollow portion preferably has a shape similar to the hollow tube. That is, the jig is also preferably cylindrical. The jig suppresses the deformation of the hollow tube during the pressure polymerization and supports the shrinkage of the region that becomes the core portion as the pressure polymerization progresses. Therefore, it is preferable that the hollow portion of the jig has a diameter larger than the outer diameter of the hollow tube and supports the hollow tube in a non-contact state. The hollow portion of the jig preferably has a diameter that is larger by 0.1% to 40% than the outer diameter of the hollow tube, and has a diameter that is larger by 10% to 20%. It is more preferable.

  The hollow tube can be placed in the polymerization vessel with the hollow tube inserted into the hollow portion of the jig. In the polymerization vessel, the hollow tube is preferably arranged with the height direction of the cylinder vertical. After the hollow tube is disposed in the polymerization vessel while being supported by the jig, the inside of the polymerization vessel can be pressurized. When pressurizing, it is preferable to pressurize the inside of a polymerization container with inert gas, such as nitrogen, and to advance pressurization polymerization in inert gas atmosphere. The preferred range of pressure during polymerization varies depending on the monomer used, but the pressure during polymerization (gauge pressure) is generally preferably about 0.05 MPa to 1.0 MPa.

  In the present invention, the method for producing the core portion is not limited to the above methods. For example, it can be formed by a rotational polymerization method in which interfacial gel polymerization is performed while rotating the inner core or the core. In addition, description is given in the example which forms an inner core. An inner core solution is injected into the hollow of the clad pipe where the outer core is formed. Thereafter, one end thereof is sealed, and polymerization is performed while rotating in a rotating polymerization apparatus in a horizontal state (a state in which the height direction of the clad pipe is horizontal). At this time, the inner core liquid may be supplied all at once or sequentially or continuously. By adjusting the supply amount, composition, and degree of polymerization of the polymerizable composition for the inner core, in addition to the graded index type (GI type) having a continuous refractive index distribution, a multi-layer having a stepped refractive index distribution The present invention can also be applied to a step type optical fiber manufacturing method. In the present invention, this polymerization method is referred to as a core part rotation polymerization method (core part rotation gel polymerization method).

  In the core part rotational polymerization method, the surface area of the core liquid can be increased as compared with the interfacial gel polymerization method during the polymerization, so that bubbles generated from the core liquid can be easily degassed. Therefore, inclusion of foam is suppressed in the obtained preform. Further, when the core part is formed by the core part rotational polymerization method, a preform having a hollow center part may be obtained. When the preform is used for a plastic optical member, particularly POF, the preform is melt-stretched. Since the hollow is stretched while being closed, no particular problem occurs. 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 at the center is closed by performing melt drawing so as to close the hollow of the preform. It is possible to produce a plastic lens or the like from this preform.

  In addition, at the time of completion | finish of a 2nd process, the bubble which generate | occur | produces after superposition | polymerization can be suppressed by performing cooling operation by the fixed cooling rate under control of a pressure. It is preferable for the pressure response of the core part to pressurize the inside of the polymerization vessel with an inert gas such as nitrogen at the time of the core part polymerization and advance the pressure polymerization in an inert gas atmosphere. However, it is basically impossible to completely remove the gas from the preform, and if the polymer contracts suddenly during the cooling process, etc., the gas aggregates in the voids and forms bubble nuclei, leading to the generation of bubbles. . In order to prevent this, it is preferable to control the cooling rate to about 0.001 ° C./min to 3 ° C./min in the cooling step, and more preferably to about 0.01 ° C./min to 1 ° C./min. This cooling operation may be performed in two or more stages according to the progress of the volume shrinkage of the polymer in the process of approaching the glass transition temperature Tg (° C.) of the polymer, particularly the glass transition temperature Tg (° C.) of the core region. In this case, it is preferable to increase the cooling rate immediately after the polymerization and gradually decrease it.

  The preform obtained by the above operation has a uniform refractive index distribution and sufficient light transmission, and the generation of bubbles and macro-spaces is suppressed. In addition, the smoothness of the interface between the cladding part or the outer core part and the core part that reflects light and confines in the POF is improved. Moreover, although the manufacturing method of the cylindrical preform which has a 1 layer outer core part was shown, an outer core part may be two or more layers. Further, after the outer core portion is formed into an optical fiber by interfacial gel polymerization, stretching, or the like, the outer core portion may be integrated with the inner core portion so that both cannot be identified.

  By processing the obtained preform into various forms, various plastic optical members can be produced. For example, if the preform is sliced perpendicular to the axial direction, a disk-shaped or columnar lens having a non-concave section can be produced. Moreover, POF can be produced by melt-drawing the preform. At this time, when the region to be the core portion of the preform has a refractive index distribution, a POF having a uniform optical transmission capability can be manufactured with high productivity and stably.

[Manufacture of plastic optical fiber by drawing]
(Third step)
In the third step, melt drawing, for example, the preform is heated by passing through the inside of a heating furnace (for example, a cylindrical heating furnace) and melted, and then continuously stretched and spun. Although heating temperature can be suitably determined according to the material etc. of preform, generally 180 to 250 degreeC is preferable. The stretching conditions (stretching temperature and the like) can be appropriately determined in consideration of the diameter of the obtained preform, the desired POF diameter, the material used, and the like. In particular, since the refractive index distribution type POF has a structure in which the refractive index changes from the center direction of the cross section toward the circumference, it is necessary to uniformly heat and stretch the fiber so as not to destroy this distribution. Therefore, it is preferable to use a cylindrical heating furnace or the like that can uniformly heat the preform in the cross-sectional direction for heating the preform. The heating furnace preferably has a temperature distribution in the direction of the drawing axis. A narrow melted portion is preferable because the shape of the refractive index profile is less likely to be distorted and the yield is increased. Specifically, preheating and gradual cooling are preferably performed before and after the melting region so that the region of the melting portion becomes narrow. Furthermore, the heat source used for the melting region is more preferably one that can supply high output energy even to a narrow region such as a laser.

  In order to maintain the linearity and its roundness, the drawing is preferably performed using a drawing spinning apparatus having an alignment mechanism that keeps the center position constant. By selecting the stretching conditions, the orientation of the polymer constituting the POF can be controlled, and the mechanical properties such as the bending performance of the POF obtained by drawing and the heat shrinkage can also be controlled.

  FIG. 5 shows a manufacturing facility 70 for manufacturing POF. The preform 12 is suspended on a preform vertical arm (hereinafter referred to as an arm) 73 via an XY aligning device 72. The arm 73 moves up and down in the vertical direction by rotation of a preform up / down screw (hereinafter referred to as a screw) 74. When the preform 12 is stretched, the screw 74 is rotated at a constant speed, and the arm 73 is slowly lowered (for example, from 1 mm / min to 20 mm / min). Thereby, the tip of the preform 12 is inserted into the hollow cylindrical heating furnace 75. The preform 12 is melted little by little from its tip, and a plastic optical fiber (POF) 14 is obtained. The entire preform 12 is preferably covered with a flexible cylinder 77. The flexible cylinder 77 keeps the atmosphere in the vicinity of the preform 12 before being heated by shielding dust from intrusion, adhesion prevention, and air flow from the outside. In addition, there is an effect of suppressing the generation of the rising airflow due to the heating of the atmospheric gas in the heating furnace 75 by making the upper portion of the flexible cylinder 77 a bag path.

  The heating furnace 75 is accommodated in a heating furnace outer cylinder 78. The stretched atmosphere is stabilized without being affected by the atmosphere outside the manufacturing facility 70. Furthermore, it is more preferable to attach a clean gas introduction device 79 in order to make the atmosphere in the heating furnace outer cylinder 78 clean.

  In order to prevent the polymer constituting the POF 14 from being deteriorated, the inside of the heating furnace 75 is preferably an inert gas atmosphere. The gas includes nitrogen gas (thermal conductivity 0.0242 W / (m · K)), helium gas (thermal conductivity 0.1415 W / (m · K)) which is a rare gas, and argon gas (thermal conductivity). 0.0015 W / (m · K)), neon gas or the like is preferably used. Nitrogen gas is preferably used from the viewpoint of cost, and helium gas is preferably used from the viewpoint of heat conduction efficiency. In addition, it is preferable to use a mixed gas in which several kinds of gases are mixed (for example, a mixed gas of helium gas and argon gas) because the purpose of obtaining a gas having a desired thermal conductivity and cost reduction can be achieved. . Since the inert gas is used to keep the inside of the heating furnace 75 in an inert state and adjust heat conduction, it may be circulated. Thereby, the gas medium cost can be reduced. The preferable supply amount of the inert gas varies depending on the heating conditions and the type of gas. For example, when helium gas is used, it is preferably 1 L / min to 10 L / min (converted value when the temperature is room temperature). .

  The preform inlet and POF outlet on the upper and lower surfaces of the heating furnace outer cylinder 78 should be shielded as much as possible so as not to be affected by the external environment. Therefore, it is preferable to attach shutters 80 and 81 to the preform inlet and the POF outlet. By controlling the opening and closing of the shutters 80 and 81, it is preferable to make the gap between the entrance and exit as small as possible. Or you may seal completely by the material which is excellent in sliding performance, heat resistance, etc.

  The wire diameter of the POF 14 is measured by the wire diameter measuring device 82. The descending speed of the arm 73, the heating temperature in the heating furnace 75, the take-off speed of the POF 14 and the like are controlled so that the wire diameter becomes a predetermined value. For the control, it is preferable to select a control system with good responsiveness in order to reduce loss due to the occurrence of wire diameter unevenness. In the manufacturing equipment 70 shown in FIG. 5, control is performed by changing the winding speed of the winding reel 83. In addition, depending on manufacturing equipment, you may perform control which suppresses a wire diameter fluctuation | variation by adjusting another location. For example, when the preform is heated by a method having good response such as laser heating, the amount of heat to be heated may be controlled.

  As described in JP-A-7-234322, the tension at the time of drawing is preferably 0.098 N or more in order to orient POF14. Further, as described in JP-A-7-234324, it is preferable that the pressure is 0.98 N or less so as not to leave distortion in the POF 14 after melt drawing. However, the tension at the time of drawing differs depending on the diameter of the POF to be obtained and the material constituting the POF, and is not limited to the above conditions. Further, as described in JP-A-8-106015, a method of performing a preheating step at the time of melt drawing can also be employed. The bending elongation and lateral pressure characteristics of the POF can be improved by defining the elongation at break and hardness of the POF obtained by the above method as described in JP-A-7-244220. Further, as in JP-A-8-54521, a transmission layer can be further improved by providing a low refractive index layer on the outer periphery to function as a reflective layer.

[Plastic optical fiber cord]
A plastic optical fiber cord can be obtained by directly coating POF. Forms of coating can be broadly divided into a method of continuously coating POF directly after the stretching step and a method of separately coating the obtained POF. The continuous method is preferable because the number of steps can be reduced when single-core fiber coating is performed because POF can be continuously coated. When the coating step is provided separately, Thick coating, multi-layer coating, creation of a cord composed of a plurality of fibers, etc. can be made easier, which is preferable.

[Coating structure]
A plastic optical fiber cable is obtained by covering the POF, the optical fiber, and the optical fiber. At that time, as a form of the coating, there is a gap at the interface between the outermost layer coating material and POF, etc., and the adhesion type coating in which the interface between the outermost layer coating material and POF is in contact with the entire circumference. There is a loose type coating. 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, in the case of a loose type coating, since the outermost layer coating material and POF or the like are not in close contact, the POF or the like in the coating may move. Most of the damage to be done can be mitigated by the void layer or the coating layer. Therefore, damage to the POF can be reduced, and 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, a void layer can be formed by adjusting the position of the extrusion nipple of the cross die head 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. Further, in this loose-type coating, when the shrinkage rates of the plastic optical fiber and the coating layer are different, the annealing process according to the present invention works particularly effectively.

  Specific examples of the coating material used for these coatings include the following materials. As a general covering material, a thermoplastic resin material is exemplified. Examples of these materials include polyethylene (PE) polypropylene (PP), vinyl chloride (PVC), ethylene vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), polyester, nylon and the like. Can be mentioned.

  Various elastomers can be used in addition to the above thermoplastic resins. Since these have high elasticity, they are also effective in terms of imparting mechanical properties such as bending. Examples of these elastomers include various rubbers such as isoprene-based rubber, butadiene-based rubber, and diene-based special rubber, and polydiene-based and polyolefin-based materials that exhibit fluidity at room temperature but lose their fluidity when heated. Examples of the liquid rubber include various thermoplastic elastomers (TPE) which are a group of substances that exhibit rubber elasticity at room temperature and are plasticized at a high temperature and can be easily molded.

  Moreover, what hardens the liquid which mixed the polymer precursor, the reactive agent, etc. can also be used. For example, a one-component thermosetting urethane composition comprising an NCO group-containing urethane prepolymer described in International Publication No. 95/26374 pamphlet and a solid amine of 20 μm or less can also be used.

  The materials listed above are not limited to the above materials as long as they can be molded at a glass transition temperature Tg (° C.) or less of the POF polymer, and are combined between the materials or as a copolymer or mixed polymer other than the above materials. 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. In addition, these materials may shrink due to the orientation that occurs during coating, and can be suppressed by the annealing process of the present invention.

  In the POF used in the present invention, the protective layer may be used as a primary coating layer, and a secondary (or multilayer) coating layer may be further provided on the outer periphery as necessary. When the primary coating has a sufficient thickness, thermal damage is reduced due to the presence of the primary coating, so the limit of the curing temperature of the material of the secondary coating layer is the case where the primary coating layer is coated. Compared to, it can be loosened. As described above, a flame retardant, an ultraviolet absorber, an antioxidant, a radical scavenger, a light raising agent, a lubricant and the like may be introduced into the secondary coating layer.

  Some flame retardants include halogen-containing resins such as bromine, additives, and phosphorus. However, aluminum hydroxide and magnesium hydroxide are used as flame retardants from the viewpoint of safety, such as reduction of toxic gases during combustion. A metal hydroxide such as can be preferably used. The metal hydroxide has water as crystal water inside, and the water adhering to the manufacturing process cannot be completely removed. Therefore, if the metal hydroxide is not a low-hygroscopic element wire or a lower coating layer, It is desirable that the flame retardant coating with an oxide is provided with a moisture resistant coating on the outer layer of the primary coating layer and further provided as a coating layer on the outer layer.

  As flame retardancy standards, UL (Underwriters Laboratory) has decided on several test methods. CMX (combustion test is generally referred to as VW-1 test), CM Grades such as (vertical tray combustion test), CMR (riser test), and CMP (plenum test) are set. In the case of the coating of the plastic optical fiber, since the plastic optical fiber as the core material is made of a flammable material, it is preferably a cord or cable having the VW-1 standard in order to prevent the spread of fire in the event of a fire.

  First, a method for directly coating POF will be described. The POF 14 is coated with a resin by a resin coating device 84. As the resin, a hot-melt resin is used. After the molten resin is coated on the POF 14, the molten resin is cured by the temperature controller 85. When a heat-meltable resin is used as the resin, a cooling device is used for the temperature controller 85. A thermosetting resin can also be used as the coating resin. In that case, the temperature controller 85 is provided with a heating device. Then, after the thermosetting resin is coated on the POF, it is solidified by heating with a heating device. When either the cooling device or the heating device is used for the temperature controller 85, a liquid or a gas can be used as the heat transfer medium. However, since liquid is more advantageous in terms of heat transfer efficiency, a water cooling method or a hot water method is preferable. In the manufacturing facility 70 of FIG. 5, a cooling device is used for the temperature controller 85, and a cooling gas introduction device 86 is attached and cooled by the cooling gas. Thus, the plastic optical fiber core wire (optical fiber core wire) 16 is obtained by covering the POF 14 with resin.

  The outer diameter of the optical fiber core wire 16 is measured by an outer diameter measuring device (hereinafter referred to as an upstream outer diameter measuring device) 88 immediately after application by the resin coating device 84. After the solidification by the temperature controller 85, the outer diameter of the optical fiber core wire 16 is measured by an outer diameter measuring device (hereinafter referred to as downstream outer diameter measuring device) 89. Temperature conditions and the like are adjusted based on the outer diameter value of the optical fiber core wire 16 measured by the upstream and downstream outer diameter measuring devices 88 and 89.

  When the stretching speed is increased (for example, 15 m / min or more), the POF 14 may be subjected to the viscosity resistance of a molten resin that is a liquid. In that case, the tension when the POF 14 is coated becomes excessive. As a result, transmission loss may increase, or POF 14 may be stretched to cause uneven wire diameter. For this reason, it is necessary to define experimental conditions in consideration of the POF wire diameter, coating speed (stretching speed), and the like. For example, curing a resin that does not require much heat, such as a polymerizable composition that cures at a relatively low temperature (50 ° C. to 90 ° C.), such as a thermosetting urethane elastomer having self-curing properties. In the case of heating, a heating gas may be supplied to the temperature controller 85 using a heating device. Clean air or an inert gas such as nitrogen or carbon dioxide is supplied from a heating gas introduction device. In addition, helium etc. can also be used when it is necessary to raise heat transfer efficiency using gas with a large specific heat.

  The atmosphere until the preform 12 is stretched and solidified as POF 14 needs to be kept clean. If there is dust in the atmosphere, the preform 12 cannot be stretched uniformly when it adheres, or sticks to the molten preform 12 to form a bump-like foreign material, and the uniformity of the POF 14 and thus optical The performance is adversely affected. For this reason, it is preferable to keep the atmosphere of the POF 14 clean by the clean box 90. A clean gas introduction device 91 is attached to the clean box 90. By introducing clean gas into the clean box 90 from the clean gas introduction device 91, the cleanliness in the clean box 90 is maintained at a predetermined value. The degree of cleanness is preferably class 10,000 or less, and more preferably 3000 or less. Although omitted in FIG. 5, it is preferable to provide a device for supplying and circulating clean air that has collected dust through a HEPA filter or the like in the clean gas introducing device 91.

  The optical fiber core wire 16 in which the resin is coated on the POF 14 is wound around the take-up reel 83. At this time, it is preferable that the tension of the coated optical fiber 16 is measured by the tension measuring device 92 and wound on the take-up reel 83 while the tension is controlled by the reel driving device 93. For example, in the case of the coated optical fiber core 16 having a cladding outer diameter of 316 μm, when the stretching tension is 0.98 N or more, the optical fiber core wire 16 being solidified is re-stretched by a high tension. Thereby, unevenness of the wire diameter of the POF 14 and / or the optical fiber core wire 16 may occur. When unevenness of the wire diameter occurs, the transmission loss is deteriorated and the mechanical strength is lowered.

  The method of coating the POF 14 can be carried out by an extrusion method in addition to the method of coating continuously after the stretching. The covering line 170 used for FIG. 6 is shown. A plastic optical fiber (POF) 171 is sent out from a transmitter 172. A plastic optical fiber core is formed by coating the POF 171 with a coating material (thermoplastic resin) by a coating device 174 having a die for extruding and coating the POF 171 running on the molten resin after the POF 171 is set to a desired temperature by the temperature controller 173. A wire (optical fiber core wire) 175 is obtained. The optical fiber core wire 175 is preferably cooled by cold water in the water tank 176 in order to reduce the heat damage of the heated molten resin. In this case, the moisture is removed by the moisture removing device 177 thereafter. The cooling of the optical fiber core wire 175 is not limited to the water tank, and other devices can be used. Then, the optical fiber core wire 175 is conveyed by the roller 178 and wound around the winder 179. Although FIG. 6 shows a form in which the POF 171 is supplied from the transmitter 172, the covering line used in the present invention is not limited to the form shown. For example, the coating line 170 may be a coating line similar to a conventionally known electric cable or quartz glass optical fiber, or a coating described in JP-A-2003-270453, JP-A-2004-29338, or the like. Equipment and coating methods can be applied.

[Plastic optical fiber cable manufacturing method]
In order to combine a plurality of fiber cords into one or to give a plurality of functions to the coating layer, it can be further processed into a cable in which coatings having various functions are laminated. For example, in addition to the above-described flame retardant, coloring for noise prevention and identification due to incident light from the outside, a barrier layer for suppressing moisture absorption, and a moisture absorbing material for removing moisture, such as moisture absorbing tape and moisture absorbing Gels can be contained in the coating layer or between the coating layers, depending on the application, such as a cushioning material such as a flexible material layer and foam layer for stress relaxation during flexing, and a reinforcing layer for improving rigidity It can be selected and provided. 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.

  The shape of the plastic optical cable depends on the type of use, and it is a collective type that concatenates POF or plastic optical fiber cores on a concentric circle, a tape type that is arranged in a row, and further, they are gathered together with a presser roll or wrap sheath. The usage form is selected according to the purpose of use. Even when a plurality of strands are used and processed into a cable shape, it can be manufactured using a line configuration of an independent coating process.

  FIG. 7 shows a coating line 100 used for a plastic optical fiber cable original fabric according to the present invention. Note that the coating line 100 can be directly connected to the manufacturing facility 70 of FIG. 5 to perform stretching and coating online.

  As the covering line 100, a covering line similar to a conventionally known electric cable or quartz glass optical fiber can be used. The plastic optical fiber core wire 16 is sent out from the sending machine 101. The buffer material 17 is wound around the delivery machine 104 in a reel shape. Examples of the buffer material include aramid fibers which are tensile strength fibers. A plurality of buffer materials 17 are usually provided on the outer peripheral surface of the optical fiber core wire 16 at the same time, but are omitted from FIG. It is also possible to provide a fiber or a filler as a waterproof material together with the tensile strength fiber on the outer peripheral portion of the optical fiber core wire 16.

  The buffer material 17 is disposed on the outer peripheral portion of the optical fiber core wire 16 by the disposing machine 105. Thereafter, the outermost layer is coated by the coating device 106. Hereinafter, the outermost layer coated core wire 107 is referred to. The outermost coated core wire 107 is cooled by cold water in the cooling water tank 108 and then moisture is removed by the moisture removing device 109. The cooling of the outermost coated core wire 107 is not limited to the water tank, and other devices can be used. Then, a plastic optical fiber cable original fabric (hereinafter referred to as a cable original fabric) 19 is conveyed by the roller 110 and taken up on the take-up reel 111.

(Annealing process)
In the present invention, an annealing step is performed to reduce the shrinkage of the coating after the coating layer is applied. The annealing process can be performed for both the optical fiber cord in which the POF is coated and the optical fiber cable obtained by processing the cord with a cable. Accordingly, an optical fiber cable annealing method will be described as an example. In the annealing step 20, the cable original fabric 19 is annealed to obtain a plastic optical fiber cable (optical fiber cable) 21. The annealing step 20 may be performed continuously by providing a heating furnace (not shown) between the moisture removing device 109 and the take-up reel 111 in FIG. 7 or after winding the cable original fabric 19. You may carry out by a batch type. In addition, it is preferable to perform this process after winding from a viewpoint of the response of shrinkage.

  The annealing temperature of the cable original fabric 19 in the annealing step 20 is not particularly limited. However, depending on the material constituting the POF 14, when the temperature condition is particularly high, the POF 14 may be deformed and its characteristics may change. In particular, these deformations and characteristic changes are remarkable when the POF 14 is made of a polymer, and particularly when the core is a polymer. Therefore, when the polymer has a glass transition temperature Tg (° C.) (for example, PMMA), the annealing temperature is preferably less than the glass transition temperature Tg (° C.). In the case where the polymer does not have a glass transition temperature Tg (° C.), or when it is approximately room temperature or lower (for example, PVDF (−40 # C) or the like), the melting point Tm (° C.) (for example, , PVDF is preferably less than about 190 ° C). Further, it is more preferably (Tg-5) ° C. or lower or (Tm−50) ° C. or lower, and most preferably (Tg−10) ° C. or lower or (Tm−100) ° C. or lower.

  The lower limit of the annealing temperature is not particularly limited. However, the temperature is preferably 40 ° C. or higher, more preferably higher than 50 ° C., for the purpose of thermally relaxing the polymer and smoothing the molecular orientation of the polymer molecules.

  The annealing time is not particularly limited, but it is preferably longer than 1 hour and shorter than 100 hours, more preferably longer than 5 hours and shorter than 50 hours, most preferably longer than 10 hours and longer than 24 hours. It is to make it shorter than time. For example, when PVC is used for the outermost layer, if it is 8 hours or less, thermal relaxation is not sufficiently performed, and the orientation control of PVC molecules may not be sufficiently performed. Further, if the annealing time is 100 hours or longer, the molecular orientation is sufficiently controlled even if annealing is performed for a longer time, so that time loss may occur and cause deterioration in productivity. Furthermore, a part of PVC that is a polymer for the outermost layer may be decomposed, resulting in deterioration of the characteristics of the PVC, for example, deterioration of mechanical strength.

  By performing the annealing step 20, the polymer constituting the outermost layer of the optical fiber cable 21 is thermally relaxed and has a desired orientation state. As a result, the difference in thermal shrinkage between the protective layer and the outermost layer due to the application of heat to the optical fiber cable 21 is extremely reduced, and variation in length due to the longitudinal direction can be suppressed during use due to environmental influences. . In the present invention, the value described in the following method is used as a preferable range for the difference in heat shrinkage rate. The optical fiber cable 21 is cut into a desired length (500 mm to 5000 mm), and the lengths of the optical fiber core wire 16 and the optical fiber cable 21 are measured. These lengths are the same when cut perpendicular to the longitudinal direction of the optical fiber cable. The optical fiber cable is placed in a heating furnace adjusted to a temperature of 70 ° C. and a humidity of 50% and left for a time. Thereafter, the temperature of the heating furnace is set to 40 ° C. and the humidity is set to 50%, and the mixture is further left for 2 hours. Repeat the above process for 2 cycles. Thereafter, the length of the optical fiber core wire 16 and the optical fiber cable 21 is measured to calculate the shrinkage rate. According to the present invention, it is possible to make the difference in shrinkage rate within 0.1%. Within this range, it is possible to suppress the occurrence of a failure of connector detachment when the connector is connected to the optical fiber cable 21 or when the connector is connected and used as a product. The test method is referred to as a heat cycle test in the present invention.

  A cross section of a plastic optical fiber cable 21 according to the present invention is shown in FIG. A core portion 121 is provided at the center of the optical fiber cable 21, and a cladding portion 122 covers the periphery thereof. Further, the outer peripheral portion of the cladding portion 122 is covered with a protective layer 123. The core portion 121, the cladding portion 122, and the protective layer 123 constitute a GI plastic optical fiber core wire (hereinafter referred to as GI core wire) 16. Although the GI type core wire 16 can be used as an optical transmission body as it is, a buffer layer 124 and an outermost layer 125 are formed in order to ensure strength assurance, loss stability, and the like. It is preferable to use a tensile body such as an aramid fiber described later for the buffer layer 124.

  The form of the plastic optical fiber cable 21 for performing the annealing under the annealing conditions of the annealing step 20 described above is a GI type core wire 16 having an outer diameter D11 of 0.1 mm to 1 mm and an outer diameter D12 of 0.5 mm to 5 mm, thickness. It is preferable that the outermost layer 125 having a t11 of 0.1 mm to 2 mm is formed, more preferably the outer diameter D12 is 0.75 mm to 3 mm, and the thickness t11 is 0.2 mm to 1.5 mm. That is, the outermost layer 125 having an outer diameter D12 of 1.2 mm to 2.2 mm and a thickness t11 of 0.2 mm to 1 mm is formed. The polymer forming the outermost layer 125 is preferably polyvinyl chloride, polyethylene, nylon, other polyamides, polyurethane, polyvinyl acetate, polyisoprene, or the like, more preferably polyvinyl chloride or polyethylene. The polymer forming the outermost layer 125 is not limited to a homopolymer, and a copolymer (copolymer) or a mixed polymer can also be used.

  FIG. 9 shows a schematic diagram of the refractive index distribution of the core 121 and the clad 122 constituting the optical waveguide of the GI type core wire 16. The refractive index of the core portion 121 has the highest refractive index at the center, and decreases in a substantially square distribution in the radial direction. The clad part 122 has a refractive index smaller than the refractive index distribution of the core part 121, so that light is transmitted through the core part 121. Note that PMMA or deuterated PMMA is preferably used for the core portion 121. Moreover, the GI type | mold core wire 16 which has such refractive index distribution can be manufactured from the preform manufactured by the 1st form of the manufacturing method of the said preform.

  Further, FIG. 10 shows a schematic diagram of a refractive index distribution shape of another POF having a refractive index distribution used in the plastic optical fiber cable of the present invention. The core portion 130 has an inner core portion 131 whose center has the highest refractive index and a refractive index that decreases in a substantially square distribution toward the radial direction, and an outer core portion 132 that serves as a wall surface for forming the inner core portion 131. Formed from. In addition, a clad portion 133 having a refractive index lower than that of the core portion is formed in the outer peripheral direction in order to totally reflect the light in the core portion. A POF having the form shown in FIG. 10 can also be used for the plastic optical fiber cable of the present invention. The POF having such a refractive index distribution can be manufactured from the preform manufactured by the second embodiment of the preform manufacturing method.

  FIG. 3 shows a cross-sectional view of another embodiment of a plastic optical fiber cable according to the present invention. A plastic optical fiber core wire (hereinafter referred to as SI-type core wire) 144 including a core portion 141 of the optical fiber cable 140, a cladding portion 142 that covers the outer periphery of the core portion 141, and a protective layer 143 that covers the outer periphery of the cladding portion 142 is used. ing. The optical fiber core 144 is covered with a buffer layer 145, and an outermost layer 146 is formed on the outer periphery thereof. The core 141 is preferably made of an acrylate polymer such as PMMA. The clad 142 is made of a fluorine-based polymer having a low refractive index. In addition, since the glass transition temperature Tg (° C.) of the fluorine-based polymer is approximately room temperature or lower, the annealing temperature described above is based on the glass transition temperature Tg (° C.) of the acrylate ester polymer that is the polymer of the core 141. It is preferable.

  In order to perform the annealing under the annealing conditions of the annealing step 20 described above, a specific form of the plastic optical fiber cable 140 is as follows: an SI type core wire 144 having an outer diameter D13 of 0.5 mm to 1 mm and an outer diameter D14 of 0.75 mm. It is preferable that an outermost layer 146 having a thickness of ˜5 mm and a thickness t13 of 0.1 mm to 2 mm is formed, more preferably an outer diameter D14 of 0.75 mm to 3 mm and a thickness t13 of 0.2 mm to 1.5 mm. Most preferably, an outermost layer 146 having an outer diameter D14 of 1.2 mm to 2.2 mm and a thickness t13 of 0.2 mm to 1 mm is formed. The polymer forming the outermost layer 146 is preferably polyvinyl chloride, polyethylene, nylon, other polyamides, polyurethane, polyvinyl acetate, polyisoprene, or the like, more preferably polyvinyl chloride or polyethylene. The polymer forming the outermost layer 146 is not limited to a homopolymer, and a copolymer (copolymer) or a mixed polymer can also be used.

  For the refractive index distribution of the core portion, the refractive index distribution having the highest center and a shape that gradually decreases in the radial direction can also be used. The form is called a multi-step index type. In addition, a step index type or a single mode type can be used for the optical transmission line of the optical fiber cable of the present invention.

  Another embodiment of the plastic optical fiber cable according to the present invention is shown in FIG. In the multi-core plastic optical fiber cable 150, a buffer layer 155 is formed on an SI-type optical fiber core 154 including a core portion 151, a cladding portion 152, and a protective layer 153. In addition, a buffer layer 160 is formed on a GI optical fiber core wire 159 including a core portion 156, a cladding portion 157, and a protective layer 158. The optical fiber core wires 154 and 159 on which the buffer layers 155 and 160 are formed are bundled, and the outermost layer 161 is further formed to form a multi-core optical fiber cable 150. In this case, the form of the transmission path of each optical fiber core wire is not particularly limited. The same form may be sufficient and a different form may be sufficient. Further, the number of the optical fiber cores constituting the optical fiber cable is not limited to two, and the optical fiber cable of the present invention is also used when manufacturing an optical fiber cable in which three or more optical fiber cores are bundled. The fiber cable manufacturing method (see FIG. 7) can be applied.

  The specific form of the multi-core plastic optical fiber cable for annealing under the annealing conditions of the annealing step 20 described above is preferably such that the width L15 is 1 mm to 10 mm and the thickness t15 is 0.1 mm to 2 mm. Preferably, the width L15 is 1.5 mm to 6 mm and the thickness t15 is 0.2 mm to 1.5 mm, and most preferably the width L15 is 2.4 mm to 4.4 mm and the thickness t15 is 0.2 mm to 1 mm. The polymer forming the outermost layer 161 is preferably polyvinyl chloride, polyethylene, nylon, other polyamides, polyurethane, polyvinyl acetate, polyisoprene, or the like, more preferably polyvinyl chloride or polyethylene. The polymer forming the outermost layer 161 is not limited to a homopolymer, and a copolymer (copolymer) or a mixed polymer can also be used. A preferred example of the preferred multi-core plastic optical fiber cable 150 is an example in which the width L15 is 4.4 mm and the width L16 is 2.2 mm.

  Moreover, it is preferable that the optical fiber cable according to the present invention obtained by the method described above is securely fixed to a connection portion with an optical member such as a light emitting element or a light receiving element using an optical connector for connection at the end. . As the connector, various commercially available connectors such as PN type, SMA type, and SMI type that are generally known can also be used.

[Optical transmission system]
The optical signal transmission system using the optical fiber cable according to the present invention includes an optical signal processing device including optical components such as various light emitting elements and light receiving elements, optical switches, optical isolators, optical integrated circuits, and optical transmission / reception modules. Consists of. 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, pp. 110-127 “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 to 480 described in “Interconnection by Optical Sheet Bus Technology”, and JP-A-10-123350, JP-A-2002-90571, JP-A-2001-290055, etc. Optical bus; described in JP-A-2001-74971, JP-A-2000-329962, JP-A-2001-74966, JP-A-2001-74968, JP-A-2001-318263, JP-A-2001-31840, etc. Optical star couplers described in JP 2000-241655 A, etc .; JP 2002-62457, JP 2002-101044, JP 20 Optical signal transmission device and optical data bus system described in each publication such as JP-A-305395; Optical signal processing apparatus described in JP-A-2002-23011; Optical signal cross-connect described in JP-A-2001-86537 System; optical transmission system described in JP-A-2002-26815; multi-function system described in JP-A-2001-339554, JP-A-2001-339555, etc .; and various optical waveguides, optical splitters, By combining with an optical coupler, optical multiplexer, optical demultiplexer, etc., a more advanced optical transmission system using multiplexed transmission / reception can be constructed. In addition to the above optical transmission applications, it can also be used in the fields of illumination, energy transmission, illumination, and sensors.

The present invention will be described more specifically with reference to the following examples. The types of materials, their proportions, operations and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

  In Example 1, an experiment was performed using a plastic optical fiber cable 21 using a GI type core wire (see FIG. 8) 16. The preform 12 was performed by a preform manufacturing step 11 described below. A clad pipe made of polyvinylidene fluoride (PVDF) having an outer diameter of 20 mm, an inner diameter of 19 mm, and a length of 600 mm produced by extrusion molding was used. This clad pipe was inserted into a sufficiently rigid polymerization vessel having an inner diameter of 20 mm and a length of 600 mm. The clad pipe was washed with pure water and dried at 90 ° C. Thereafter, the clad pipe was held vertically in a state where it was put in a polymerization vessel, and bottomed at 200 ° C. for 30 minutes using KF850 pellets (manufactured by Kureha Chemical Co., Ltd.). 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, outer core polymerization 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) Were measured to prepare an outer core solution. This outer core liquid was irradiated with ultrasonic waves 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 solution was poured into the clad pipe, the inside of the clad pipe was depressurized by 0.01 MPa with respect to atmospheric pressure using a vacuum filter. Ultrasonic treatment was performed for 5 minutes using the ultrasonic cleaning apparatus while degassing under reduced pressure.

  After replacing the air at the tip of the clad pipe with argon, the tip of the clad pipe was sealed with a silicon stopper and a seal tape. The clad pipe containing the outer core solution was placed in a 60 ° C. hot water bath and prepolymerized for 2 hours while shaking. Thereafter, the prepolymerized clad pipe is heated for 1 hour (rotational polymerization) while rotating at 3000 rpm while maintaining a temperature of 65 ° C. in a horizontal state (a state in which the length direction of the clad pipe is horizontal). 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 20 ° C. A cylindrical tube having an outer core layer made of PMMA inside the clad pipe was obtained.

  Next, an inner core part preparation pretreatment was performed. The above-described clad pipe on which the outer core was formed was subjected to a pressure reduction treatment for 3 hours in a 90 ° C. heat oven at a pressure (−0.08 MPa with respect to atmospheric pressure). Furthermore, inner core polymerization 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 on which the outer core portion was formed was kept at 80 ° C. for 20 minutes, and then the inner core liquid was injected into the hollow portion. One end of the clad pipe was covered with a seal tape, and then the clad pipe was set vertically in the autoclave (the bottom part was down and the part covered with the seal tape was up), and then the autoclave lid was set. The air in the autoclave was replaced with argon gas, and the atmosphere was a pressure of 0.05 MPa. Heat polymerization was carried out 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 12 was taken out of the autoclave.

  The preform 12 having an outer diameter of 20 mm was attached to the production facility 70 shown in FIG. 5 and was heated, melted and stretched to obtain POF 14 having an outer diameter target of 500 μm. And the protective layer 123 which has LDPE (low density polyethylene) as a main component was continuously formed with the resin application | coating apparatus 84 so that the coating diameter D11 might be 1.2 mm (refer FIG. 8). The refractive index distribution shape of the POF 14 was that shown in FIG. The heating furnace 55 was set to a temperature of 245 ° C.

  The take-up reel 83 controlled the POF 14 take-up speed by the reel driving device 93 so as to be 8 m / min. The take-up speed was changed by about ± 2% because it was adjusted while measuring the wire diameter of POF 14 with the wire diameter measuring device 82. The POF 14 was stretched with an outer diameter target of 500 μm. The outer diameter variation of the obtained POF was 500 μm ± 10 μm.

  And the cable original fabric 19 was manufactured using the coating line 100. FIG. As the buffer material 17, Kevlar (registered trademark) having an outer diameter of 10 μm was used as a tensile strength fiber. The buffer material 17 was disposed on the outer periphery of the optical fiber core wire 16 by the disposing machine 105. Then, the coating device 106 was used to coat the outermost layer forming polymer polyvinyl chloride. The polyvinyl chloride used was a black pigment containing 0.2% by weight of carbon. Thereafter, the inside of the cooling water tank 108 in which cooling water of about 10 ° C. is placed is transported for about 5 seconds to solidify the polyvinyl chloride, and after the moisture is removed by the moisture removing device 109, the winding reel 111 is used. It was wound up as a cable stock 19. The refractive index distribution of the POF 14 which is the optical transmission line of the cable original fabric 19 is shown in FIG.

[Annealing process]
The original cable 19 was unwound and cut so that the outermost layer was 198.0 cm and the GI core wire was 200.0 cm in the longitudinal direction. The cable blank 19 was wound around a ring having a diameter of about 30 cm in such a manner that no extra load was applied when the cable contracted. This ring was placed in an oven at a temperature of 70 ° C., a humidity of 50%, and an atmospheric atmosphere. In this state, the cable blank was annealed for 8 hours. After annealing, the optical fiber cable 21 was taken out from the heating furnace. When the shrinkage rate was calculated by measuring the length of the outermost layer and the core wire, the shrinkage rates were 0.32% and 0.21%, respectively.

[Heat cycle test]
The optical fiber cable 21 manufactured by the method described above was subjected to the heat cycle test. As temperature control conditions, the temperature was raised from 25 ° C. to 70 ° C. at 1 ° C./min, held at 70 ° C. for 2 hours, lowered to −40 ° C. at 1 ° C./min, held at −40 ° C. for 2 hours, and further The temperature was raised to 70 ° C. at 1 ° C./minute, held at 70 ° C. for 2 hours, lowered to −40 ° C. at 1 ° C./minute, held at −40 ° C. for 2 hours, and then raised to 25 ° C. at 1 ° C./minute. The cycle was done. Thereafter, the lengths of the outermost layer 125 and the optical fiber core wire 16 were measured to calculate the shrinkage ratios, which were 0.34% and 0.40%, respectively. The difference in shrinkage between the outermost layer and the optical fiber core wire (GI type) was 0.06%.

  In Example 2, an experiment was performed using a plastic optical fiber cable 140 using an SI-type core wire 144 (see FIG. 11). The plastic optical fiber cable 140 was produced using the SI type core wire 144. In the preform manufacturing step 11, a composite spinning nozzle was used. The preform 12 was manufactured by using PMMA for the core portion 141 and PVDF for the cladding portion 142 and having an outer diameter of 20 mm. The preform was manufactured so that the clad had a thickness of 0.5 mm.

  The preform 12 having an outer diameter of 20 mm was attached to the manufacturing facility 70 shown in FIG. And the protective layer 143 which has LDPE as a main component was continuously formed in the resin coating apparatus 84 so that the coating diameter might be 1.2 mm (refer FIG. 11). The temperature of the heating furnace 55 was set to 235 ° C.

  The take-up reel 83 controlled the POF 14 take-up speed by the reel driving device 93 so as to be 8 m / min. The take-up speed was changed by about ± 2% because it was adjusted while measuring the wire diameter of POF 14 with the wire diameter measuring device 82. POF14 was stretched with an outer diameter target of 750 μm. The outer diameter variation of the obtained POF (SI type) was 750 μm ± 15 μm.

  And the cable original fabric 19 was manufactured using the coating line 100. FIG. As the buffer material 17, Kevlar (registered trademark) having an outer diameter of 10 μm was used as a tensile strength fiber, and was adjusted so as to be evenly disposed on the outer peripheral portion of the POF. The buffer material 17 was disposed on the outer periphery of the optical fiber core 144 by the disposing machine 105. Then, the coating device 106 was used to coat the outermost layer forming polymer polyvinyl chloride. The polyvinyl chloride used was a black pigment containing 0.2% by weight of carbon. Thereafter, the inside of the cooling water tank 108 in which cooling water of about 10 ° C. is placed is transported for about 5 seconds to solidify the polyvinyl chloride, and after the moisture is removed by the moisture removing device 109, the winding reel 111 is used. It was wound up as a cable stock 19.

[Annealing process]
The original cable was unwound and cut so that the outermost layer was 198.0 cm and the SI-type core wire was 200.0 cm in the longitudinal direction. The cable blank 19 was wound around a ring having a diameter of about 30 cm in such a manner that no extra load was applied when the cable contracted. This ring was placed in an oven at a temperature of 50 ° C. and a humidity of 50% in an air atmosphere. In this state, the cable blank was annealed for 24 hours. After annealing, the optical fiber cable 140 was taken out from the heating furnace. When the contraction rate was calculated by measuring the length of the outermost layer and the core wire (SI type), the contraction rates were 0.31% and 0.12%, respectively. When the heat cycle test was performed, the shrinkage rates were calculated by measuring the lengths of the outermost layer 146 and the optical fiber core 144 and found to be 0.31% and 0.22%, respectively. The difference in shrinkage between the outermost layer and the optical fiber core wire (SI type) was 0.09%.

  In Example 3, an experiment was conducted using a multi-core plastic optical fiber cable 150. In addition, it conducted in detail in Experiment 3-1, and about Experiment 3-2 thru | or Experiment 3-5, an experimental result is put together in Table 1 thru | or Table 3, and is shown.

  In Experiment 3-1, an SI type core wire 154 and a GI type core wire 159 were used. The SI type core wire 154 was manufactured by the same method as the manufacturing method of the SI type core wire described in Example 2. The GI type core wire 159 has a POF with an outer diameter target of 316 μm. The protective layer 158 was formed so that the coating diameter of LDPE (black) was 1.2 mm.

  And the cable original fabric was manufactured using the covering line 100. FIG. As the buffer material, Kevlar (registered trademark) having an outer diameter of 10 μm was used as a tensile strength fiber, and was adjusted so as to be evenly disposed on the outer periphery of the POF. The buffer material was disposed on the outer periphery of the optical fiber core wires 154 and 159 by the disposing machine 105. Then, the coating device 106 was used to coat the outermost layer forming polymer polyvinyl chloride. The polyvinyl chloride used was a white pigment containing 1.3% by weight of titanium oxide. Thereafter, the inside of the cooling water tank 108 in which cooling water of about 10 ° C. is put is transported for about 5 seconds to solidify the polyvinyl chloride, and after the moisture is removed by the moisture removing device 109, the winding reel 111 It was wound up as a cable stock.

[Annealing process]
The original cable was unwound and cut so that the outermost layer was 198.0 cm in the longitudinal direction, and the SI core wire 154 and GI core wire 159 were both 200.0 cm. The cable was wound around a ring having a diameter of about 30 cm in such a manner that no extra load was applied when the cable contracted. This ring was placed in an oven at a temperature of 60 ° C., a humidity of 50%, and an atmospheric atmosphere. In this state, the cable blank was annealed for 17 hours. After annealing, it was taken out from the heating furnace as a multi-core plastic optical fiber cable 150. When the contraction rate was calculated by measuring the lengths of the outermost layer 161, the SI-type core wire 154, and the GI-type core wire 159, the contraction rates were 0.20%, 0.00%, and 0.00%, respectively. It was. Moreover, the average value of five times of experiments (3-1 to 3-5) was 0.27%, −0.11%, and 0.12%. When the heat cycle test was performed, the shrinkage rate was calculated by measuring the lengths of the outermost layer 161, the SI-type core wire 154, and the GI-type core wire 159. 15% and 0.55%. Moreover, the average value of five times of experiments (3-1 to 3-5) was 0.37%, 0.29%, and 0.41%. The average shrinkage difference between the outermost layer 161 and the SI core wire 154 was 0.08%, and the average shrinkage difference between the outermost layer 161 and the GI core wire 154 was 0.04%. .

  In Example 4, the experiment was performed under the same conditions as in Example 3 except for the experimental conditions described below. The GI type core wire 159 obtained POF with an outer diameter target of 750 μm. The protective layer 158 was formed so that the coating diameter of LDPE (not including coloring components such as pigments) was 1.2 mm. Coated with polyvinyl chloride. The polyvinyl chloride used was a black pigment containing 0.2% by weight of carbon. The cable was wound around a ring having a diameter of about 30 cm in such a manner that no extra load was applied when the cable contracted. This ring was placed in an oven at a temperature of 70 ° C. and a humidity of 50% under an atmospheric atmosphere. In this state, the cable blank was annealed for 10 hours. After annealing, it was taken out from the heating furnace as a multi-core plastic optical fiber cable 150. When the shrinkage rates were calculated by measuring the lengths of the outermost layer 161, the SI-type core wire 154, and the GI-type core wire 159, the shrinkage rates were 0.35%, 0.13%, and 0.21%, respectively. It was. When the heat cycle test was performed, the shrinkage rate was calculated by measuring the lengths of the outermost layer 161, the SI-type core wire 154, and the GI-type core wire 159. 21% and 0.29%. The difference in shrinkage rate between the outermost layer 161 and the SI type core wire 154 was 0.07%, and the difference in shrinkage rate between the outermost layer 161 and the GI type core wire 154 was 0.01%.

  In Example 5, for the SI type core wire and the GI type core wire, POF having an outer diameter target of 750 μm was obtained by heating melt drawing. A protective layer 158 was formed so that the coating diameter of linear low density polyethylene (LLDPE) (using black pigment containing 0.2 wt% carbon) was 1.2 mm. It was further coated with low density polyethylene (LDPE) in a structure in which two cores of GI type and SI type were joined with a width of 1 mm. For the low density polyethylene, a white pigment containing 1.3% by weight of titanium oxide was used. The cable was wound around a ring having a diameter of about 30 cm in such a manner that no extra load was applied when the cable contracted. This ring was placed in an oven at a temperature of 70 ° C. and a humidity of 50% under an atmospheric atmosphere. In this state, the cable blank was annealed for 10 hours. After annealing, it was taken out from the heating furnace as a multi-core plastic optical fiber cable 150. When the shrinkage rate was calculated by measuring the lengths of the outermost layer 161, the SI-type core wire 154, and the GI-type core wire 159, the shrinkage rates were 0.35%, 0.22%, and 0.21%, respectively. It was. Further, when the heat cycle test was conducted, the shrinkage rate was calculated by measuring the length of the outermost layer 161 and 1542 SI type core wires, and the shrinkage rates were 0.18%, 0.11%, 0, respectively. 19%. The difference in shrinkage between the outermost layer 161, the SI type core wire 154, and the GI type core wire 159 was 0.07% and 0.01%.

  In Example 6, the GI type core wire obtained POF having an outer diameter target of 750 μm by heat-melt stretching. A protective layer 158 was formed so that the coating diameter of linear low density polyethylene (LLDPE) (using black pigment containing 0.2 wt% carbon) was 1.2 mm. The two cores of the two GI type core wires were joined with a width of 1 mm, and further coated with low density polyethylene (LDPE). For the low density polyethylene, a white pigment containing 1.3% by weight of titanium oxide was used. The cable was wound around a ring having a diameter of about 30 cm in such a manner that no extra load was applied when the cable contracted. This ring was placed in an oven at a temperature of 70 ° C. and a humidity of 50% under an atmospheric atmosphere. In this state, the cable blank was annealed for 10 hours. After annealing, it was taken out from the heating furnace as a multi-core plastic optical fiber cable 150. When the lengths of the outermost layer 161 and the GI core wire 159 were measured to calculate the shrinkage rate, the shrinkage rates were 0.32%, 0.27%, and 0.26%, respectively. Further, when the heat cycle test was performed, the shrinkage rates were calculated by measuring the lengths of the outermost layer and the two GI core wires, and the shrinkage rates were 0.22%, 0.15%,. 13%. The difference in shrinkage between the outermost layer and the two GI type core wires was 0.07% and 0.09%. When this cable was compared with a commercially available two-core cable in accordance with JIS C 6851 such as a tensile test, a bending rigidity, a bending test and the like, the performance was equivalent, and the handleability of the cable was also equivalent.

  In the comparative experiment, the experiment was performed using the multi-core plastic optical fiber cable used in Example 3. The description will be made in detail in Experiment 5-1, and the results of Experiments 5-2 to 5-5 are summarized in Tables 4 and 5.

  In Experiment 5-1, the SI core 154 and the GI core 159 of Experiment 3-1 were used. And the cable original fabric was produced on the same conditions as the experiment 11 using the coating line 100. FIG. After the heat cycle test, the shrinkage rates were calculated by measuring the lengths of the outermost layer, the SI-type core wire, and the GI-type core wire, and the shrinkage rates were 0.53%, 0.15%,. 55%. The average values of the five experiments (5-1 to 5-5) were 0.64%, 0.19%, and 0.53%. The average shrinkage difference between the outermost layer 161 and the SI core wire 154 is 0.45%, and the average shrinkage difference between the outermost layer 161 and the GI core wire 154 is 0.11%. there were.

  The method for manufacturing an optical fiber cable of the present invention is not limited to a plastic optical fiber formed from a polymer, and can also be applied when manufacturing an optical fiber cable from a silica-based optical fiber or a silica-polymer optical fiber. .

It is process drawing for manufacturing the plastic optical fiber cable which concerns on this invention. 1 is a schematic view of an embodiment for producing a preform for producing a plastic optical fiber cable according to the present invention. FIG. FIG. 6 is a schematic view of another embodiment for producing a preform for producing a plastic optical fiber cable according to the present invention. It is a principal part enlarged view of FIG. It is the schematic of embodiment which manufactures the plastic optical fiber core wire for manufacturing the plastic optical fiber cable which concerns on this invention. It is the schematic of other embodiment which manufactures the plastic optical fiber core wire for manufacturing the plastic optical fiber cable which concerns on this invention. It is the schematic of embodiment which manufactures the cable original fabric for manufacturing the plastic optical fiber cable which concerns on this invention. It is sectional drawing of the plastic optical fiber cable which concerns on this invention. It is the schematic which shows the shape of the refractive index distribution of the optical transmission line of the plastic optical fiber cable which concerns on this invention. It is the schematic which shows the other shape of the refractive index distribution of the optical transmission line of the plastic optical fiber cable which concerns on this invention. It is sectional drawing of other embodiment of the plastic optical fiber cable which concerns on this invention. It is sectional drawing of other embodiment of the plastic optical fiber cable which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 Plastic optical fiber 16 Plastic optical fiber core wire 20 Annealing process 21,140,144 Plastic optical fiber cable 100 Coated line 150 Multi-core type plastic optical fiber cable

Claims (20)

In a method of manufacturing an optical fiber cable by coating a polymer on an optical fiber composed of a core and a cladding,
An optical fiber cable manufacturing method comprising annealing after coating the polymer. In the case where at least one of the core and the clad is formed from one having a glass transition temperature Tg (° C.),
2. The method of manufacturing an optical fiber cable according to claim 1, wherein the annealing temperature is lower than a glass transition temperature Tg (° C.) of at least one of the core and the clad.   The method for manufacturing an optical fiber cable according to claim 2, wherein the annealing temperature is higher than 50 ° C.   The method for manufacturing an optical fiber cable according to any one of claims 1 to 3, wherein the annealing time is longer than 8 hours and shorter than 100 hours. An optical fiber having a first coating layer formed by coating an optical fiber composed of a core and a clad is manufactured,
In the method of manufacturing an optical fiber cable in which one or more optical fiber cores are bundled and coated with a polymer to form a second coating layer,
A method of manufacturing a plastic optical fiber cable, wherein annealing is performed so that a difference in thermal shrinkage between the first coating layer and the second coating layer is less than 0.1% after the second coating layer is formed. .   6. The method of manufacturing an optical fiber cable according to claim 1, wherein the optical fiber is a plastic optical fiber.   7. The method of manufacturing an optical fiber cable according to claim 1, wherein the optical fiber is a gradient index optical fiber.   8. The method for manufacturing an optical fiber cable according to claim 1, wherein the core is made of deuterated polymethyl methacrylate.   9. The method of manufacturing an optical fiber cable according to claim 1, wherein the coated polymer is polyvinyl chloride. A buffer material is disposed around the optical fiber,
The method for manufacturing an optical fiber cable according to any one of claims 1 to 9, wherein an outer peripheral portion of the optical fiber and the buffer material is coated with the polymer.   The method for manufacturing an optical fiber cable according to claim 10, wherein the buffer material is an aramid fiber. In an optical fiber cable in which a polymer is coated on an optical fiber consisting of a core and a cladding,
An optical fiber cable, wherein the coated polymer is annealed. In an optical fiber cable in which one or more optical fiber cores having a first coating layer covering an optical fiber composed of a core and a clad are bundled and coated with a polymer to form a second coating layer.
The optical fiber cable, wherein the second coating layer is annealed.   The optical fiber cable according to claim 13, wherein a difference in thermal shrinkage between the first covering layer and the second covering layer is less than 0.1%.   The optical fiber cable according to claim 12, wherein the optical fiber is a plastic optical fiber.   16. The optical fiber cable according to claim 12, wherein the optical fiber is a gradient index optical fiber.   The optical fiber cable according to any one of claims 12 to 16, wherein the core is made of deuterated polymethyl methacrylate.   The optical fiber cable according to any one of claims 13 to 17, wherein the second covering layer is polyvinyl chloride. A buffer material is disposed around the optical fiber core wire,
The optical fiber cable according to any one of claims 13 to 18, wherein an outer peripheral portion of the optical fiber core wire and the buffer material is covered with the second coating layer. 20. The optical fiber cable according to claim 19, wherein the buffer material is an aramid fiber.

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