JP2006163030A - Manufacturing method of plastic optical member and continuous manufacturing equipment thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continuously manufacture a plastic optical fiber in which the deterioration in transmission loss is suppressed. <P>SOLUTION: Filters 16, 17 are disposed on breaker plate parts of extrusion parts 11a, 12a of core part extrusion equipment 11 and a clad part extrusion equipment 12. Therein, the filters 16, 17 of a powder-sintered type made of stainless steel are used. Filtration precision of the filters 16, 17 is made to be 0.5μm. Materials for the core part and the clad part are heated and melted at 220°C and 250°C. The materials are respectively supplied to a bilayer coextrusion die 13 and is extruded as raw fiber 20 for optical fiber. By heating the raw fiber with a heating furnace 24 and performing re-drawing, the optical fiber 25 in which the deterioration in transmission loss is suppressed may be continuously obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a plastic optical member and a plastic optical fiber, and a continuous manufacturing apparatus used in the manufacturing method.

  In recent years, with the development of the communication industry, the demand for plastic optical transmission bodies has increased, transmission loss is small, and low cost is required. The plastic optical transmission body has advantages such as easy manufacture and processing and low cost compared to the quartz optical transmission body having the same structure. Among plastic optical transmission bodies, plastic optical fibers (hereinafter also referred to as POF) have the disadvantage that the transmission loss is slightly larger than that of quartz optical fibers because the materials are all made of plastic. However, it has the advantages of having good flexibility, light weight, good processability, and easy production of an optical fiber having a large diameter as compared with a quartz optical fiber. Further, it has an advantage that it can be manufactured at low cost. Therefore, various studies have been made on optical fibers for short distances in which the magnitude of transmission loss is not a problem (see, for example, Patent Document 1).

  The plastic optical fiber is composed of a plastic core (hereinafter referred to as a core or a core portion) and an outer shell (hereinafter referred to as a cladding or a cladding portion) made of plastic having a lower refractive index than the core portion. As one method for producing a plastic optical fiber, a method is known in which a pipe-shaped clad portion (hereinafter referred to as a clad pipe) is formed by a melt extrusion method, and a core portion is formed in the clad pipe. In particular, a refractive index distribution type (graded index type, hereinafter referred to as GI type) plastic optical fiber including a core portion having a distribution of refractive index from the center to the outside is used for an optical signal transmitted. Since it is possible to increase the bandwidth, it has recently attracted attention as an optical transmission body having a high transmission capacity. As one of the manufacturing methods of such GI type POF, a preform (base material) is produced using an interfacial gel polymerization method. Thereafter, a method is known in which the preform is fed into a heating furnace and heated, melted and stretched (see, for example, Patent Document 2).

  As another manufacturing method of GI-type POF, there is known a method of forming a refractive index distribution by co-extruding a core and a clad and diffusing a dopant in the core portion. In this method, a composite fiber composite spinning method can be applied, and productivity can be increased by increasing the number of cores. Furthermore, it has the advantage that clean fibers can be produced continuously and efficiently. That is, POF can be obtained continuously by extruding and stretching the core and the clad simultaneously (for example, see Patent Document 3).

When POF manufactured continuously contains foreign matter in its optical transmission path, transmission loss increases due to light scattering. Therefore, a filter is used to remove foreign substances in the raw material constituting the POF. When forming from a molten resin, a wire mesh type filter is often used as a filter. However, a soft material such as a resin gel is deformed by the eyes of the filter and is not sufficiently removed. It is known to use a long metal fiber sintered filter for such poor filtration (see, for example, Patent Document 4).
JP-A-61-130904 Japanese Patent No. 3332922 Japanese Patent No. 34471015 JP-A-6-59138

  However, even if a long metal fiber sintered filter is used, a soft material such as a resin gel-like material contained in the molten material which is a POF raw material is deformed by the eyes of the filter and is not sufficiently removed. There is a problem. For this reason, a method using a filter having a low filtration accuracy (for example, 3 μm) is also used, but it is not sufficient.

  An object of this invention is to provide the manufacturing method of the plastic optical member which can remove the foreign material contained in the raw material of a plastic optical member efficiently and continuously, and the continuous manufacturing apparatus of a plastic optical fiber.

  As a result of diligent study, the present inventor has used a metal powder sintered type filter in which metal powder is sintered in a laminated state for filtration of a material in a molten state, regarding the production of a plastic optical fiber formed by melting an optical fiber material. Found that it was effective. For hard foreign substances, they are collected according to the filtration accuracy shown in JIS-B8356, but for soft gel-like foreign substances that are thought to pass while deforming, the diameter is larger than the filtration accuracy. I also found out that it would pass through deformation. Since the metal powder sintered filter is sintered in a state in which the metal powder is tightly packed, the resin passage length is longer than that of metal long fiber sintering, and the collection of gel-like foreign matters is higher than that of metal fiber sintering.

  The method for producing a plastic optical member of the present invention is a method for producing a long plastic optical member by melt-extruding a polymer, and using a filter in which at least a polymer forming a core portion is melted and a metal powder is sintered. After filtration, it is melt extruded. The polymer may be supplied from the resin polymerization tank to the extrusion apparatus in a molten state, or may be supplied in the form of pellets. The long plastic optical member is preferably a plastic optical fiber having a core part and a clad part.

  The filtration accuracy of the filter is preferably in the range of 0.3 μm or more and 5 μm or less. The filtration accuracy is a value defined by the method described in JIS-B8356. It is preferable that the polymer is continuously melt-extruded to continuously produce the plastic optical member. The plastic optical fiber is not limited to a two-layer structure of a core and a clad, and may be a multi-layer structure having three or more layers. Furthermore, the core portion is preferably a multi-step index type or a graded index type having a refractive index distribution in the radial direction.

  The plastic optical fiber continuous manufacturing apparatus according to the present invention has a plurality of resin supply units each including a melt extruder and a pipe connecting the melt extruder and the extrusion die, and the plurality of resin supply units are connected to the extrusion die. In an apparatus for continuously producing a plastic optical fiber having a core part and a clad part, a filter obtained by sintering a metal powder is provided at the outlet of the melt extruder.

  The plastic optical fiber continuous manufacturing apparatus according to the present invention has a plurality of resin supply units each including a melt extruder and a pipe connecting the melt extruder and the extrusion die, and the plurality of resin supply units are connected to the extrusion die. In an apparatus for continuously producing a plastic optical fiber having a core portion and a cladding portion, a filter in which metal powder is sintered is provided on the tube.

  The filtration accuracy of the filter is preferably in the range of 0.3 μm or more and 5 μm or less. When the filtration accuracy exceeds 5 μm, the foreign matter collecting ability is lowered, which is insufficient for suppressing an increase in transmission loss of the plastic optical fiber. On the other hand, since a differential pressure becomes large in a filter medium with high filtration accuracy, discharge of collected foreign matters and durability of the filter become problems. The filter can be installed in the form of a breaker plate installed at the outlet of the extruder or in the form of a filter housing loaded with a large number of leaf disk-shaped filters in order to increase the filtration area in order to reduce the differential pressure. In order to obtain a uniform plastic optical fiber diameter, a filter pump can be installed between the extruder and the gear pump or after the gear pump in the case where a gear pump for quantitative discharge is installed after the extruder. Moreover, although the pressure difference of a filter can be lowered | hung by raising the extrusion temperature of each material and raising resin temperature and reducing the viscosity of resin, it is preferable to adjust temperature suitably because resin thermal decomposition arises. In addition, the said continuous manufacturing apparatus can also be preferably used for the continuous manufacturing apparatus of a plastic optical member.

  According to the method for producing a plastic optical member of the present invention, in a method of producing a long plastic optical member by melt-extruding a polymer, the metal powder is sintered in a molten state at least in the polymer forming the core portion. Since it is melt-extruded after being filtered by a filter, the optical transmission loss can be remarkably improved by removing foreign substances in the optical transmission path that cause light scattering in the plastic optical member. In particular, the plastic optical member is a plastic optical fiber. If there is, the effect appears remarkably.

Hereinafter, the present invention will be described in detail. The preferred embodiment describes a preferred application example of the present invention, and does not limit the present invention.

(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 monomers 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, phenyl methacrylate benzyl (BzMA), methacrylate, cyclohexyl methacrylate, diphenylmethyl, tricyclo [5 · 2 · 1 · 0 ^2,6] decanyl methacrylate, adamantyl methacrylate, isobornyl methacrylate, norbornene Nyl methacrylate and the like, and methyl acrylate, ethyl acrylate, tert-butyl acrylate, phenyl acrylate, and the like. In addition, (b) fluorine-containing acrylic acid ester and fluorine-containing methacrylate ester include 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3 , 3-Pentafluoropropyl methacrylate, 1-trifluoromethyl-2,2,2-trifluoroethyl methacrylate, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 2,2, 3,3,4,4-hexafluorobutyl methacrylate and the like. Furthermore, (c) styrene compounds include styrene, α-methylstyrene, chlorostyrene, bromostyrene, and the like. Furthermore, (d) vinyl esters include vinyl acetate, vinyl benzoate, vinyl phenyl acetate, vinyl chloroacetate and the like. Of course, it is not limited to these. The type and composition ratio of the constituent monomers are selected so that the refractive index of the polymer of the core portion made of a monomer alone or a copolymer is equal to or higher than that of the cladding portion. A particularly preferred polymer is polymethyl methacrylate (PMMA), which is a transparent resin.

  Furthermore, when a plastic optical fiber, which is a kind of optical member to be produced, is used for near-infrared applications, absorption loss due to the C—H bond constituting the polymer of the core portion occurs, and therefore, in Japanese Patent No. 3332922 C—H, including deuterated polymethyl methacrylate (PMMA-d8), polytrifluoroethyl methacrylate (P3FMA), polyhexafluoroisopropyl 2-fluoroacrylate (HFIP 2-FA) and the like as described By using a polymer in which the hydrogen atom (H) of the bond is substituted with a deuterium atom (D), fluorine (F), or the like, the wavelength region causing this transmission loss can be lengthened, and the transmission signal light Loss 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 50,000 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). In addition, 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. 3333292 and Japanese Patent Laid-Open No. 5-173026. ) Within ^1/2 , and 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 to the additive-free polymer. Any of those which can stably 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.

  The dopant may be a polymerizable compound. When a dopant of the polymerizable compound is used, the copolymer containing this as a copolymerization component has a property of increasing the refractive index as compared with a polymer not containing the copolymer. Use what has. Examples of such a copolymer include MMA-BzMA copolymer.

  Examples of the dopant include benzyl benzoate (BEN), diphenyl sulfide (DPS), triphenyl phosphate (TPP), and phthalic acid as described in Japanese Patent No. 3333292 and JP-A-11-142657. Examples include benzyl-n-butyl (BBP), diphenyl phthalate (DPP), diphenyl (DP), diphenylmethane (DPM), tricresyl phosphate (TCP), diphenyl sulfoxide (DPSO), diphenyl sulfide derivatives, and dithian derivatives. 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 POF that is 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.

(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.

[Protective layer forming material]
By forming a protective layer on the POF manufactured according to the present invention to form an optical fiber cord, the mechanical strength increases and handling becomes easy. As the protective layer forming material used, a material that does not cause thermal damage (for example, deformation, modification, thermal decomposition, etc.) to the POF is selected. Therefore, it is preferable to use a polymer that can be cured at a glass transition temperature Tg (° C.) or lower and (Tg-50) ° C. or higher of the polymer that forms POF. Further, in order to reduce production cost, it is more preferable to use a molding time (time for curing the material) of 1 second to 10 minutes, preferably 1 second to 5 minutes. When the POF is formed from a plurality of polymers, the glass transition temperature at the lowest temperature among the glass transition temperatures of each polymer is regarded as Tg (° C.). In the case where the glass transition temperature Tg (° C.) is not higher than room temperature (for example, about −40 ° C. for PVDF) such as PVDF, or in the case of a polymer having no glass transition temperature, other phase transition temperatures such as The melting point is taken as the reference temperature.

  In addition to general olefin polymers such as polyethylene (PE) and polypropylene (PP), and highly versatile polymers such as vinyl chloride and nylon, specific materials for protective layer formation include: Can be mentioned. Since these have high elasticity, they are also effective from the viewpoint of imparting mechanical properties such as bending. First, rubber which is one form of the polymer can be mentioned. Specifically, isoprene-based rubber (for example, natural rubber, isoprene rubber, etc.), butadiene-based rubber (for example, styrene-butadiene copolymer rubber, butadiene rubber), diene special rubber (for example, nitrile rubber, chloroprene rubber, etc.) ), Olefin rubber (for example, ethylene-propylene rubber, acrylic rubber, butyl rubber, halogenated butyl rubber, etc.), ether rubber, polysulfide rubber, urethane rubber and the like.

  As the material for forming the protective layer, it is possible to use a liquid rubber that exhibits fluidity at room temperature and is cured by heating when the fluidity disappears. Specifically, polydiene-based (for example, basic structure is polyisoprene, polybutadiene, butadiene-acrylonitrile copolymer, polychloroprene, etc.), polyolefin-based (for example, basic structure is polyolefin, polyisobutylene, etc.), polyether-based (for example, , Basic structure is poly (oxypropylene), etc., polysulfide type (eg, basic structure is poly (oxyalkylene disulfide), etc.), polysiloxane type (eg, basic structure is poly (dimethylsiloxane), etc.) Can do.

  Examples of the resin (including the base resin of the masterbatch) used in the present invention include thermoplastic resins such as ethylene, propylene or α-olefin polymers. Examples of these polymers include ethylene homopolymers, ethylene-α-olefin copolymers, and ethylene-propylene copolymers.

  A master batch containing a metal hydrate or phosphorus and nitrogen and a flame retardant material as a colorant is used together with these thermoplastic resins. A masterbatch is a product obtained by mixing a functional additive in a resin at a high concentration and kneading. Since the additive is kneaded with the bulk resin, an inorganic compound that is stable against heat is often selected, and its functionality includes an antistatic conductive material, a flame retardant material, a coloring dye, Pigments, and the like, and is often used particularly when a colorant is used as an additive. Further, in order to disperse at a high concentration when preparing a masterbatch, it may be produced by adding a dispersant or a lubricant or modifying the additive.

  Inorganic fine particles as additives used in the present invention are preferably fine in particle size. In particular, it is not preferable that coarse particles are mixed in the innermost layer and the outermost layer in contact with the plastic optical fiber, because the optical fiber is damaged or workability is deteriorated.

  Although it is not specifically limited as an additive, for example, as a conductive substance, noble metal fine particles such as tin, zinc alloy powder and silver, and as a flame retardant substance, metal water such as magnesium hydroxide and aluminum hydroxide is used. Examples of the coloring pigment include carbon black, titanium oxide, and zirconium oxide. Carbon black is low-cost, and when used as a coating material for optical fibers, it has antistatic properties in addition to coloring, making it difficult to be charged with static electricity. It is particularly preferable because it has many advantages such as being restrained from being returned to the outside of the optical fiber due to bending or the like.

  The concentration of the additive contained in the master batch is in the range of 30.0% by weight or less, preferably in the range of 5% by weight or more and 20.0% by weight or less, more preferably 10.0% by weight or more. It is in the range of 15.0% by weight or less. When there are too few additives, there is no effect as a masterbatch, and when it contains more than 30% by weight, the masterbatch becomes brittle or the dispersibility decreases.

  The concentration of the preferred additive contained in the polymer obtained by mixing the masterbatch and the bulk resin is 0.10 wt% or more and 10.0 wt% or less, more preferably 0.15 wt% or more and 5.0 wt%. % Or less, more preferably 0.20% by weight or more and 3.0% by weight or less. When the amount is less than 0.10% by weight, the additive effect of the additive is not substantially exhibited. When the amount exceeds 10%, the fluidity and toughness of the resin are impaired, and troubles such as resin breakage and outer diameter fluctuation occur during coating. appear.

  Further, the molecular weight (for example, number average molecular weight, weight average molecular weight, etc.), molecular weight distribution, melting point, melt flow rate and the like of the thermoplastic resin and masterbatch used in the present invention are not particularly limited. As for the melt flow rate, the melt flow rate (MFR) obtained by the thermoplastic flow test method (JIS K 7210 1916) is an indicator of the fluidity of the resin. The closer the value of MFR, the more uniform the extrusion.

  If the resin melting temperature of the bulk resin and the master batch are different, the flow in the extrusion device becomes non-uniform (the amount of extrusion with the screw varies), resulting in large fluctuations in discharge, and the outer diameter after coating also varies. End up. Therefore, it is preferable that the temperature difference between the melting point of these resins, the bulk resin melting point Ta (° C.) and the master batch melting point Tb (° C.) is small.

In the present invention, the difference between the melting point Ta (° C.) of the thermoplastic resin and the melting point Tb (° C.) of the master batch is preferably | Ta−Tb | ° C ≦ 25 ° C., more preferably | Ta−Tb | ° C. ≦ 10 ° C., and most preferably | Ta−Tb | ° C. ≦ 5 ° C.
When Ta is higher than Tb by 20 ° C., melting of the thermoplastic resin proceeds, but formation of a protective layer becomes difficult because melting of the masterbatch does not proceed. On the other hand, when the difference is larger than 20 ° C., it is necessary to increase the temperature in order to dissolve the thermoplastic resin or the master batch. In this case, the base resin (base resin) constituting the master batch may be decomposed.

In the present invention, the ratio of the melt flow rate M1 (g / 10 min) of the thermoplastic resin to the melt flow rate M2 (g / 10 min) of the master batch is set to (1/4) ≦ (M2 / M1) ≦ ( 4/1), more preferably (1/2) ≦ (M2 / M1) ≦ (2/1), and most preferably (1 / 1.5) ≦ (M2 / M1) ≦. (1.5 / 1).
When the ratio is smaller than 1/4 or when the ratio is larger than 4/1, the coating material has poor compatibility between the thermoplastic resin and the master batch, and it is difficult to form a uniform protective layer. This may cause a problem in dispersion of the additive or lose the flexibility of the protective layer.

In the present invention, the content x (wt%) of the colored fine particles in the coating material is preferably 0.05 ≦ x (wt%) ≦ 20, more preferably 0.07 ≦ x (wt%) ≦ 10. And most preferably 0.1 ≦ x (wt%) ≦ 5.
If it is less than 0.05 wt%, the function of the additive may not be sufficiently exhibited. Moreover, when it exceeds 20 wt%, there exists a possibility that the flexibility of the polymer of a protective layer may be lost.

  As a material for the protective layer, thermoplastic elastomer (TPE) can also be used. Thermoplastic elastomers are a group of substances that exhibit rubber elasticity at room temperature, are plasticized at high temperatures, and are easy to mold. Specific examples include styrene TPE, olefin TPE, vinyl chloride TPE, urethane TPE, ester TPE, amide TPE, and the like. The listed polymers are not particularly 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, particularly the polymer of the core portion. Copolymers and mixed polymers can also be used.

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

  FIG. 1 is a schematic view of a plastic optical fiber continuous manufacturing apparatus (hereinafter referred to as a continuous manufacturing apparatus) 10 and other apparatuses according to the present invention. The continuous manufacturing apparatus 10 includes a core part forming material extruding apparatus 11, a cladding part forming material extruding apparatus 12, and a two-layer coextrusion die 13. The extrusion apparatuses 11 and 12 and the two-layer coextrusion die 13 are connected by pipes 14 and 15. Breaker plates 16 and 17 are provided in the extrusion portions 11a and 12a of the extrusion apparatuses 11 and 12, respectively. The pipes 14 and 15 are also provided with filter plates 18 and 19, respectively.

  The core forming material and the clad forming material are fed from the extrusion apparatuses 11 and 12 to the two-layer coextrusion die 13 through the pipes 14 and 15. Each material melted at this time passes through the breaker plates 16 and 17 and the filter plates 18 and 19 to remove impurities. This point will be described in detail later. Each material becomes a fiber (hereinafter referred to as an optical fiber yarn) 20 by the two-layer coextrusion die 13, and is drawn from the two-layer coextrusion die 13 by the first roller 21. The drawn optical fiber yarn 20 is conveyed into the water tank 22. Cooling water of −5 ° C. to 30 ° C. is placed in the water tank 22 and the optical fiber yarn 20 is cooled. In the present invention, this cooling step can be omitted.

  An optical fiber is formed by changing the refractive indexes of the core portion and the clad portion. In this case, a compound that increases the refractive index of the refractive index adjusting agent (dopant) in the core portion forming material (for example, DPS (diphenyl sulfide), BEN (benzyl benzoate), TPP (triphenyl phosphate), etc.) It is made to contain. In addition, a material for reducing the refractive index (for example, a copolymerized fluororesin, a cyclic fluororesin, or the like) is included in the cladding portion forming material. As a result, a difference in refractive index occurs between the core portion and the clad portion of the optical fiber yarn 20, and the core portion becomes an optical waveguide.

  In the case of a graded index type (GI type) that has the highest refractive index in the cross section of the core portion and continuously decreases toward the outer periphery (radial direction), a polymerizable monomer (for example, MMA) and By mixing a dopant (for example, DPS) and an additive such as a polymerization initiator and feeding them to the two-layer coextrusion die 13, the MMA becomes PMMA while polymerizing, and its central portion has the highest refractive index and is in the radial direction. Thus, an optical fiber having a form in which the refractive index continuously decreases can be obtained. The core portion forming material may be a material containing a dopant in PMMA that has been polymerized in advance.

  The optical fiber yarn 20 is conveyed through the heating furnace 24 while being drawn by the second roller 23. Although the temperature of the heating furnace 24 is not specifically limited, It is preferable to set it as 120 to 180 degreeC. In addition, by making the take-up speed of the second roller 23 faster than the take-up speed of the first roller 21, the optical fiber raw yarn 20 is further drawn into a plastic optical fiber (hereinafter referred to as an optical fiber) 25. it can. By redrawing the optical fiber yarn 20 thus melt-extruded, a higher-strength optical fiber 25 can be obtained. Finally, the optical fiber 25 is wound into a roll by a winder 26 and stored as an optical fiber roll 27.

  FIG. 2 shows an enlarged view of the two-layer coextrusion die 13 used in the present invention. The two-layer coextrusion die 13 includes a core part die 30 and a clad part die 31. In addition, temperature controllers 33 and 34 are provided to adjust the temperatures of the dies 30 and 31, respectively. The core part die 30 is connected to the pipe 14 for supplying the core part forming material 35. Further, the pipe 15 for supplying the clad part forming material 36 is connected to the clad part die 31.

  The core portion forming material 35 is sent from the tube 14 to the core portion die 30 to form a rod-shaped core portion 37. The core portion 37 diffuses the dopant into a desired state while passing through the diffusion portion 38 of the core portion die 30. Thereby, the core part 37 which has a refractive index profile of a step index type or a graded index type is obtained.

  The cladding portion forming material 36 is supplied to the pocket 40 through the tube 15 and the liquid flow path 39. The pressure distribution of the cladding portion forming material 36 is relaxed by the pocket 40, and the thickness thereof becomes substantially uniform when the outer peripheral surface of the core portion 37 is covered. The clad part forming material 36 is coated so as to cover the outer peripheral surface of the core part 37 and is sent out from the two-layer coextrusion die 13 as the optical fiber raw yarn 20.

  By making the surface roughness (maximum height) Ry of the inner surfaces of the pipes 14 and 15, the diffusion part 38, the liquid flow path 39, and the pocket 40 serving as supply paths for the materials 35 and 36 to be 0.8 S or less, each material Adhesion to the inner surfaces of 35 and 36 is suppressed. Therefore, it is possible to prevent defects such as thermal deterioration and seizure of the materials 35 and 36 due to stagnation accompanying adhesion.

  The viscosity ratio between the core portion forming material 35 and the cladding portion forming material 36 is preferably 50 or less. By setting the viscosity ratio to 50 or less, the interface between the core portion forming material 35 and the cladding portion forming material 36 is stabilized, and the core portion and the cladding portion are stably formed. Therefore, deterioration of mechanical properties and optical properties associated with interface instability can be suppressed. The viscosity ratio means a value calculated by (large value) / (small value) of the viscosity value measured according to the capillary method under the condition of the resin temperature at which the resin layers join together. The viscosity ratio is adjusted by adjusting the extrusion temperature, containing the additive, the type of polymer and the degree of polymerization.

  In the present invention, the core portion forming material 35 and the clad portion forming material 36 are filtered by the breaker plates (perforated plates) 16 and 17 and the filter plates 18 and 19 so as to be contained in the respective materials 35 and 36. The mechanical properties (maintenance of mechanical strength) and optical properties (suppression of deterioration of transmission loss) of the optical fiber 25 obtained by removing foreign matters are made suitable. In the present invention, the effect of the present invention can be obtained by using at least one of the breaker plates 16 and 17 or the filter plates 18 and 19. In the following description, the breaker plates 16 and 17 and the filter plates 18 and 19 are referred to as filters.

  In the present invention, a filter obtained by sintering metal powder (hereinafter referred to as a metal powder sintered mold) is used for the filter. Sintered metal long fibers (hereinafter referred to as “metal long fiber sintered mold”) are formed in a form in which the fibers are stacked. Since the positions of continuous fiber gaps coincide with each other in the thickness direction (flow direction), there is a portion through which the polymer easily passes. Therefore, polymer gel-like foreign matters (hereinafter referred to as gel-like foreign matters) may pass through the filter due to deformation even if they are within the range of filtration accuracy due to their ease of deformation. However, since the metal powder sintered type used in the filter of the present invention has a liquid flow path that sews the gap between the closely packed fusion powders, the flow path length is long, and the local large openings and shorts are short. Since the path and the like are suppressed, the possibility of passing through the filter is extremely small even if the gel-like foreign material is deformed. Therefore, the metal powder sintered type is considered to have a higher foreign matter collecting ability even with the same filtration accuracy.

  The material for the metal powder sintered filter is not particularly limited. However, it is preferable to use a steel material because it is used under high temperature and pressure. Of the steel materials used, stainless steel, steel, etc. are particularly preferred from the viewpoint of corrosivity, and stainless steel is particularly preferred.

  The metal powder sintered filter can be produced by a known method (for example, see JP-A-58-71361). In addition, it can replace with the atomized powder used as the raw material of a powder sintered filter, and can also use a short fiber powder.

In the present invention, the filtration accuracy of the filter is preferably from 0.3 μm to 5 μm, more preferably from 0.5 μm to 5 μm, and most preferably from 0.5 μm to 1 μm. If the filtration accuracy is less than 0.3 μm, the pressure for supplying the core portion forming material 35 and the cladding portion forming material 36 becomes high, and it becomes necessary to increase the pressure resistance of the continuous manufacturing apparatus 10, which causes high costs. Further, the clogging of the filter frequently occurs, and the continuous manufacturing apparatus 10 is stopped along with the replacement of the filter, and it may be difficult to continuously manufacture the optical fiber 25. Moreover, when the thing whose filtration precision exceeds 5 micrometers is used, there exists a possibility that a gel-like foreign material may pass a filter and may be supplied to the two-layer coextrusion die 13. If the optical fiber 25 is manufactured while containing the gel-like foreign matter, the mechanical properties and optical properties may be adversely affected.

  The thickness of the filter is not particularly limited. However, in consideration of maintaining filtration accuracy and pressure resistance of the continuous manufacturing apparatus 10, it is preferably in the range of 1 mm to 2 mm. The filtration pressure is also preferably in the range of 2 MPa to 8 MPa. If the filtration pressure is less than 1 MPa, the supply pressure of the materials 35 and 36 is too low, and the extrusion pressure in the two-layer coextrusion die 13 may be insufficient. In this case, the clad portion may not be uniformly formed on the outer peripheral surface of the core portion 37, and the optical fiber 25 having excellent mechanical properties and optical properties may not be manufactured. Further, if the filtration pressure is higher than 15 MPa, the pressure resistance of the continuous production apparatus 10 needs to be increased, resulting in an increase in cost. In addition, a part of the filter may be damaged, and the damaged material may be mixed into the materials 35 and 36. Furthermore, the materials 35 and 36 may be denatured.

  FIG. 3 is a cross-sectional view of 25 of a plastic optical fiber (optical fiber) according to the present invention. The optical fiber 23 includes a core part 50 serving as a light waveguide and a clad part 51 having a lower refractive index than that of the core part 50 and totally reflecting the transmitted light at the interface. The diameter and thickness of each of these parts are not particularly limited, but when the core diameter D1 is 100 μm to 500 μm, the cladding outer diameter D2 is preferably 110 μm to 800 μm.

  Moreover, the continuous manufacturing apparatus 10 used for this invention is not limited to what is shown by FIG. For example, the thing using the 3 layer coextrusion die | dye which extrudes an inner core, an outer core, and a clad simultaneously simultaneously is mentioned. Alternatively, a plastic optical fiber cord (plastic optical fiber core wire) can be obtained by simultaneously melting and extruding the core portion, the clad portion, and the protective layer.

  An optical fiber according to the present invention, an optical fiber core manufactured using the optical fiber, and a system for transmitting an optical signal using an optical fiber cable include various light emitting elements, light receiving elements, optical switches, optical isolators, An optical signal processing device including optical components such as an optical integrated circuit and an optical transceiver module is used. Moreover, you may combine with another optical fiber etc. as needed. Any known technique can be applied as a technique related to them. For example, the basic and actual of plastic optical fiber (published by NTS Corporation), Nikkei Electronics 2001.1.2.3, 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 A, JP 2002-101044 A, JP Optical signal transmission apparatus and optical data bus system described in each publication such as 001-305395; Optical signal processing apparatus disclosed 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.

  Hereinafter, the manufacturing method of the plastic optical fiber according to the present invention will be described more specifically with reference to Experiments 1 to 4 and Comparative Examples 5 to 7 according to the present invention. The description will be made in detail in Experiment 1, and only the points different from Experiment 1 will be described in other experiments. The following types of materials, their proportions, operations and the like can be appropriately changed without departing from the spirit of the present invention. Accordingly, the scope of the present invention is not limited to the following examples.

<Experiment 1>
The continuous production apparatus 10 provided with two screw extrusion apparatuses (manufactured by Randcastle) 11 and 12 having a diameter of 16 mm was used. Breaker plates 16 and 17 incorporating filters with a metal powder sintering type, manufactured by Nippon Seisen Co., Ltd., and a filtration accuracy of 5 μm were attached to the extrusion portions 11a and 12a of the extrusion apparatuses 11 and 12, respectively. A fiber with an outer diameter of 1 mmφ is extruded. The materials 35 and 36 were selected so that the core 50 was deuterated polymethyl methacrylate (PMMA-d8) + DPS (15 wt%) and the cladding 51 was deuterated polymethyl methacrylate (PMMA-d8). PMMA-d8 used was a pellet that had been dried. The extrusion temperature was adjusted by temperature controllers 33 and 34 so that the core was 200 ° C. and the clad was 220 ° C. A two-layer coextrusion die 13 having an outer diameter of the optical fiber yarn 20 of φ1 mm was used. At this time, the filtration pressure of the core portion forming material 35 was 4 MPa or less, and the filtration pressure of the cladding portion forming material 36 was 6 MPa or less.

  The extruded optical fiber yarn 20 was cooled in a water bath 22 at 15 ° C. and taken up at a speed of 4 m / min by the first roller 21. And it was taken up at a speed of 7 m / min with the second roller 23 while being heated in a heating furnace 24 having a length of 1 m and 120 ° C. An optical fiber 25 having an outer diameter D1 of about φ750 μm was manufactured and wound as an optical fiber roll 27 by a winder 26. The outer diameter D1 of the core part at this time was about φ500 μm. The wound optical fiber 25 was heated in a constant temperature bath at 170 ° C. for 10 minutes and naturally cooled at room temperature to obtain a gradient index plastic optical fiber. Each material 35 and 36 was extruded continuously for 1 hour, and the optical fiber 25 was manufactured. Transmission loss was measured using the optical fiber 25 after 1 hour as a sample (50 m long). The transmission loss of the manufactured optical fiber 25 was measured at a light source wavelength of 650 nm, and the transmission loss per 1 km (dB / km) was measured. The transmission loss of the optical fiber manufactured in Experiment 1 was about 140 dB / km, which was good.

<Experiment 2>
A metal powder sintered filter having a filtration accuracy of 0.5 μm was used. Further, the temperature was adjusted by the temperature controllers 33 and 34 so that the core was 220 ° C. and the clad was 250 ° C. Otherwise, the experiment was performed under the same conditions as in Experiment 1. At this time, the filtration pressure of the core portion forming material 35 was 8 MPa or less, and the filtration pressure of the cladding portion forming material 36 was 8 MPa or less. The transmission loss value of the obtained optical fiber 25 was 125 dB / km, which was good.

<Experiment 3>
The experiment was conducted under the same conditions as in Experiment 2, except that the filtration accuracy of the sintered metal powder filter was 0.3 μm, and a filter housing loaded with two 7-inch leaf disks was attached to the outlet of the extruder. The obtained optical fiber 25 had a good transmission loss value of 120 dB / km.

<Experiment 4>
The experiment was performed under the same conditions as in Experiment 1, except that a sintered metal fiber filter with a filtration accuracy of 5 μm and a sintered metal powder filter with a filtration accuracy of 10 μm were assembled in a breaker plate. The transmission loss value of the obtained optical fiber was 145 dB / km.

<Experiment 5>
The experiment was performed under the same conditions as Experiment 1 except that the filter was not attached to the breaker plate. The obtained optical fiber had a transmission loss value of 800 dB / km or more, which is a measurement limit because scattered light was generated from the side surface of the optical fiber.

<Experiment 6>
The experiment was performed under the same conditions as Experiment 1 except that a metal fiber sintered filter with a filtration accuracy of 5 μm was used. The transmission loss value of the obtained optical fiber was 165 dB / km.

<Experiment 7>
The experiment was performed under the same conditions as in Experiment 2 except that a metal fiber sintered filter having a filtration accuracy of 0.5 μm was used. The transmission loss value of the obtained optical fiber was 155 dB / km.

It is the schematic of the continuous manufacturing apparatus of the plastic optical fiber which concerns on this invention. It is a principal part enlarged view of FIG. It is a cross-sectional view of the plastic optical fiber according to the present invention.

Explanation of symbols

10 Plastic Optical Fiber Continuous Manufacturing Equipment 16, 17 Breaker Plates 18, 19 Filter Plate 25 Plastic Optical Fiber

Claims (7)

In a method for producing a long plastic optical member by melt-extruding a polymer,
A method for producing a plastic optical member, wherein at least a polymer forming a core portion is melted and extruded after being filtered through a filter obtained by sintering a metal powder in a molten state.   2. The method of manufacturing a plastic optical member according to claim 1, wherein the long plastic optical member is a plastic optical fiber having a core portion and a cladding portion.   The method for producing a plastic optical member according to claim 1 or 2, wherein a filtration accuracy of the filter is in a range of 0.3 µm to 5 µm.   4. The method for producing a plastic optical member according to claim 1, wherein the polymer is continuously melt-extruded to continuously produce the plastic optical member. A plastic light having a plurality of resin supply parts composed of a melt extruder and a tube connecting the melt extruder and an extrusion die, the plurality of resin supply parts being connected to the extrusion die, and having a core part and a clad part In an apparatus for continuously producing fibers,
An apparatus for continuously producing a plastic optical fiber, wherein a filter obtained by sintering metal powder is provided at the outlet of the melt extruder. A plastic light having a plurality of resin supply parts composed of a melt extruder and a tube connecting the melt extruder and an extrusion die, the plurality of resin supply parts being connected to the extrusion die, and having a core part and a clad part In an apparatus for continuously producing fibers,
An apparatus for continuously producing a plastic optical fiber, wherein a filter in which metal powder is sintered is provided on the tube. 7. The plastic optical fiber continuous manufacturing apparatus according to claim 5, wherein the filtration accuracy of the filter is in the range of 0.3 to 5 [mu] m.

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