JP2005258218A - Method and apparatus for manufacturing clad pipe for plastic optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a clad pipe in which appearance of a wrinkle and a streak can be suppressed. <P>SOLUTION: Molten PVDF (poly(vinylidene fluoride)) is extruded at ejection flow rate c (mm<SP>3</SP>/second) from a resin flow passage which is a clearance between an inner lip 70 and an outer lip 71. An inner lip outer peripheral surface radius is denoted by (a) (mm) and an outer lip inner peripheral surface radius is denoted by (b) (mm). The molten PVDF is sent to a sizing die 45 as a molten pipe 44. The molten pipe 44 solidifies while being molded to become a clad pipe in a cooling vacuum device 46. The clad pipe is taken out from the cooling vacuum device 46 at a taking-out speed (e) (mm/second). Arrangement is performed so that distance (d) (mm) between an extrusion die exit 43a and a sizing die entrance 45a satisfies a relation : [eäπ(b<SP>2</SP>-a<SP>2</SP>)}/c]-1≥0.1d. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

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

  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) optical fiber having a core part having a distribution of refractive index from the center toward the outside has a bandwidth of an optical signal to be transmitted. Since it can be made large, it has recently attracted attention as an optical fiber having a high transmission capacity. As one of the manufacturing methods of such a GI type plastic optical fiber, there has been proposed a method of producing a preform (base material) using an interfacial gel polymerization method and then stretching the preform. (For example, refer to Patent Document 2).

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

  When manufacturing a clad pipe by the melt extrusion method, it is necessary to adjust the inner and outer lip diameters and lip clearance of the extrusion die, the distance from the extrusion die to the sizing die, the molding speed, and the like. By selecting optimum molding conditions from these conditions, a clad pipe having a desired diameter and thickness can be manufactured. Conventionally, however, these relationships have not been clarified, and the molding conditions are searched according to the diameter and thickness of the clad pipe to be manufactured, and the production of the extrusion die and the distance between the extrusion die and the sizing die as necessary. Adjustments have to be made and time and cost are wasted.

  In particular, it is known that the distance from the extrusion die to the sizing die is related to the generation of streaks and wrinkles on the outer peripheral surface of the clad pipe to be formed. By making this distance appropriate, the generation of streaks and wrinkles can be suppressed. It is known that there are scratches on the inner lip surface and streaks are also generated on the inner peripheral surface of the clad pipe depending on the structure of the extrusion die. It is also known that the streaks on the inner peripheral surface can be made thinner or the generation can be suppressed depending on the distance and positional relationship from the extrusion die to the sizing die. Thus, the distance between the extrusion die and the sizing die is a very important experimental condition that affects the quality of the clad pipe molded product. However, conventionally, the operator repeatedly made fine adjustments according to the target clad pipe diameter and wall thickness to search for optimum conditions, which is a cause of wasting time and cost.

  An object of the present invention is to produce a clad pipe in which the generation of streaks and wrinkles on the pipe surface and fluctuations in the wall thickness of the pipe are suppressed.

  The present invention relates to the production of clad pipes for plastic optical fibers, and has found that the optimum molding conditions are expressed by one relational expression according to the diameter and thickness of the pipe studied from a rheological viewpoint. According to this, even when manufacturing pipes with new diameters and thicknesses, it is possible to form with the existing extrusion die, and if it is not possible, you can know the optimal inner and outer diameters of the extrusion die, etc. You can know the optimal take-up speed and the distance between the extrusion die and the sizing die.

The method for producing a clad pipe for plastic optical fiber according to the present invention melts a polymer, extrudes it from a lip clear lath of an extrusion die having an inner lip and an outer lip, puts it into a sizing die, and molds it. In the method of manufacturing a clad pipe taken as a pipe, the radius of the outer peripheral surface of the inner lip is a (mm), the radius of the inner peripheral surface of the outer lip is b (mm), and the discharge flow rate of the molten polymer is c (mm ³ / sec), when the distance between the pipe outlet of the extrusion die and the pipe inlet of the sizing die is d (mm), and the take-up speed of the pipe is e (mm / sec), e {π (b ² −a ² )} / c] −1 ≧ 0.1d is satisfied.

  The polymer is preferably a fluororesin. The melt flow rate of the polymer is preferably in the range of 2 g / 10 min to 30 g / min. The melting temperature of the polymer is preferably in the range of 170 ° C. or higher and 240 ° C. or lower. The present invention also includes a plastic optical fiber, a plastic optical fiber strand, a plastic optical fiber core, and a plastic optical fiber cable manufactured using the plastic optical fiber clad pipe.

  A plastic optical fiber clad pipe manufacturing apparatus of the present invention is a plastic optical fiber clad pipe manufacturing apparatus including an extrusion die having an inner lip and an outer lip. Means for extruding the molten polymer into a pipe shape from the clearance between the inner lip and the outer lip, a sizing die for adjusting the outer diameter of the polymer extruded into the pipe shape, and fixing the shape by cooling the pipe polymer A cooling means for forming a pipe, a means for taking up the pipe, and a means for changing the take-up speed of the pipe.

According to the method of manufacturing a clad pipe for plastic optical fiber of the present invention, selection and molding of a stable extrusion die that does not cause wrinkles or streaks in the clad pipe according to various specifications of the clad pipe for plastic optical fiber of interest. Conditions can be easily set. For this reason, conventionally, for example, when a pipe having a small diameter and a pipe having a large diameter are manufactured, it is considered from experience that the exchange of the extrusion die is necessary, and the extrusion die is replaced. However, if the relational expression [e {π (b ² −a ² )} / c] −1 ≧ 0.1d shown in the present invention is used, it is possible to form small and large diameter pipes with the same extrusion die. Therefore, when molding is possible, time and labor required for exchanging the extrusion die and adjusting the distance between the extrusion die and the sizing die can be eliminated.

  According to the plastic optical fiber clad pipe manufacturing apparatus of the present invention, in the plastic optical fiber clad pipe manufacturing apparatus including an extrusion die having an inner lip and an outer lip, the discharge flow rate of the molten polymer is controlled, A means for extruding the molten polymer into a pipe shape from the clearance between the inner lip and the outer lip of the extrusion die, a sizing die for adjusting the outer diameter of the polymer extruded into the pipe shape, and cooling the pipe-shaped polymer to form a shape Since it comprises a cooling means to be fixed and a pipe, a means for taking up the pipe, and a means for varying the take-up speed of the pipe, the experimental conditions can be adjusted when the diameter of the pipe to be manufactured is different. It becomes easy.

  FIG. 1 shows a method for manufacturing a plastic optical fiber cable (hereinafter referred to as an optical fiber cable) manufactured using the clad pipe according to the present invention. In the clad pipe production step 11, the clad pipe 12 is produced by melt-extruding the raw material polymer. A method for manufacturing the clad pipe 12 will be described later in detail. Next, a liquid for forming an outer core containing a polymerizable composition (hereinafter referred to as an outer core liquid) is prepared, and the outer core polymerization step 13 is performed using the liquid, and the outer core is attached to the hollow portion of the clad pipe 12. Form. Further, a liquid for forming an inner core (hereinafter referred to as an inner core liquid) is prepared, an inner core polymerization step 14 is performed to form an inner core, and a preform 15 is obtained. The preform 15 is heated, melted and stretched in a stretching step 16 to obtain a plastic optical fiber (hereinafter referred to as POF) 17.

  The POF 17 can be used as an optical transmission body such as an optical fiber as it is. However, it is preferable to form a protective layer in order to facilitate handling and to prevent damage to the outer surface of the POF 17. The protective layer is formed by the coating step 18, and a plastic optical fiber core wire (hereinafter referred to as an optical fiber core wire) 19 in which a coating material is formed as a protective layer on the outer peripheral surface of the POF 17 can be obtained. Furthermore, it is preferable that the optical fiber cable 21 is formed by performing a covering step 20 for covering the optical fiber core wire 19 with nylon or the like. The POF 17 and / or the optical fiber core wire 19 can be used as an optical fiber cable 21 in which one or a plurality of bundles are bundled.

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

  A fluororesin is preferably used as a clad of an optical member because it has a low refractive index, excellent transparency, flexibility, and excellent mechanical strength. In addition, since the fluororesin is generally poorly soluble in an organic solvent, the molding is mainly performed by melt molding at a high temperature. Below, the specific example of the fluorine resin used preferably is given. Examples thereof include polyvinylidene fluoride (PVDF: melting temperature 160 ° C. to 180 ° C.), polyvinyl fluoride (PVF: melting temperature 206 ° C.), polychlorotrifluoroethylene (PCTFE: melting temperature 210 ° C.), and the like. In the present invention, the melting temperature means a temperature at which the polymer starts to melt when heated and heated. The melt flow rate indicating the thermal properties of the molten resin is preferably selected from the range of 2 g / 10 min to 30 g / 10 min at the melting temperature, preferably 4 g / 10 min to 20 g / 10 min. It is more preferable to select a certain one.

  Among the fluorine-based resins, polyvinylidene fluoride (PVDF) is preferably used, and a copolymer thereof is also preferably used. For example, a vinylidene fluoride-tetrafluoroethylene copolymer (preferably containing 50% by weight or more of vinylidene fluoride, more preferably containing 70% by weight or more and 90% by weight or less), vinylidene fluoride-hexafluoro Propylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride-trifluoroethylene copolymer, and a ternary or more copolymer of vinylidene fluoride. Note that the raw material of the clad pipe 12 according to the present invention is not limited to the fluororesin.

FIG. 3 shows an embodiment of a production line 40 used in the method for producing the clad pipe 12 according to the present invention. In addition, the manufacturing method which uses PVDF as a cladding pipe raw material is illustrated. A hopper 42 for charging PVDF, which is a raw material polymer, is attached to the extruder 41. The extrusion part 41a of the extruder 41 is heated to a range of 170 ° C. to 240 ° C. to melt the charged PVDF. The molten PVDF is extruded into a pipe shape from the extrusion die 43 using a screw (not shown) provided in the extrusion portion 41a. The discharge flow rate of molten PVDF is c (mm ³ / sec). Hereinafter, this pipe is referred to as a melting pipe 44. The melting pipe 44 is passed through a sizing die 45 that molds its outer shape. The forms of the extrusion die 43 and the sizing die 45 will be described in detail later.

  The sizing die 45 is provided in the cooling vacuum device 46. The cooling vacuum device 46 includes a water supply device for supplying and discharging cooling water, a drainage device, and a vacuum device for reducing the pressure to a desired pressure. A vacuum seal 47 is provided at the pipe outlet of the cooling vacuum device 46, and the pressure in the cooling vacuum device 46 is adjusted to be within a desired pressure range. The degree of vacuum and the temperature of the cooling water are not particularly limited, but are preferably 60 kPa to 95 kPa in absolute pressure and the temperature is 1 ° C. to 20 ° C. The pipe thickness (outer diameter) of the cooled pipe (hereinafter referred to as a cooling pipe) 48 sent out from the cooling vacuum device 46 is measured by a wall thickness / outer diameter measuring device 49.

  The cooling pipe 48 is changed to a pipe 51 by the take-up machine 50. The take-up machine 50 is provided with a pair or a plurality of pairs of rollers composed of drive rollers 54 and 55 and nip rollers 56 and 57 to which motors 52 and 53 are connected. By conveying the cooling pipe 48 with a pair of rollers, tension can be applied to the cooling pipe 48. Then, the obtained pipe 51 is cut into a desired length and used as the clad pipe 12. In addition, let the taking-up speed of the pipe 51 be e (mm / sec).

  FIG. 4 shows a cross-sectional view of the extrusion die 43 taken along line IV-IV. Moreover, the principal part enlarged view of the manufacturing line 40 is shown in FIG. In the extrusion die 43, an inner lip 70 and an outer lip 71 are inserted into a cylinder 72. The radius of the outer peripheral surface 70a of the inner lip 70 is assumed to be a (mm). In addition, the radius of the inner peripheral surface 71a of the outer lip 71 is b (mm). The clearance between the inner lip outer peripheral surface 70 a and the outer lip inner peripheral surface 71 a becomes the resin flow path 73.

  As shown in FIG. 5, molten PVDF flows through the resin flow path 73. The molten PVDF is extruded from the outlet 43 a of the extrusion die 43 and enters the sizing die 45 from the inlet 45 a of the sizing die 45 as a molten pipe 44. The distance from the extrusion die outlet 43a to the sizing die inlet 45a is defined as d (mm). The melting pipe 44 is brought into close contact with the inner surface that is the molding surface by the suction hole 45 b of the sizing die 45. The outer peripheral surface of the melting pipe 44 is smoothed by the molding surface. Moreover, it cools with cooling water and solidifies.

In the present invention, regardless of the diameter and wall thickness of the pipe 51, the conditions under which the inner and outer surfaces of the pipe 51 can be stably molded without generation of streaks or wrinkles should satisfy the following formula (1).
[E {π (b ² −a ² )} / c] −1 ≧ 0.1d (1)
Note that a to e are as described above.
a: Radius (mm) of the outer peripheral surface 70a of the lip in the extrusion die
b: Radius (mm) of the outer peripheral surface 71a of the extrusion die outer lip
c: Discharge flow rate of molten resin (mm ³ / sec)
d: Distance (mm) between the extrusion die outlet 43a and the sizing die inlet 45a
e: Pipe 51 take-up speed (mm / sec)
It is.

By satisfying the formula (1), stable molding conditions can be quickly established when a pipe having a new diameter and thickness is manufactured. In particular, the distance d (mm) from the extrusion die outlet 43a to the sizing die inlet 45a includes the inner lip outer peripheral surface radius a (mm), the outer lip inner peripheral surface radius b (mm), and the molten resin discharge flow rate c ( mm) It can be easily calculated from the take-up speed e (mm / sec) of the pipe 51. Each numerical value can be arbitrarily selected as long as the above formula is satisfied. Preferably, a is 5 mm to 45 mm, b is 1 mm to 50 mm, c is 100 mm ³ / second to 5000 mm ³ / second, d is preferably in the range of 0.5 mm to 50 mm, and e is preferably in the range of 1 mm / second to 40 mm / second.

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

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

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

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

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

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

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

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

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

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

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

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

  The pipe 51 obtained by the above method is used as the clad pipe 12. The outer core polymerization step 13 for forming the outer core 31 in the hollow will be described. The outer core liquid is prepared by adding a desired additive (for example, a polymerization initiator, a chain transfer agent, a dopant, etc.) with methyl methacrylate (hereinafter referred to as MMA) as a main component as a main component. The outer core 31 is formed on the inner surface of the clad pipe 12 by a rotational polymerization method so as to form a hollow cylinder for forming an inner core. In the rotation polymerization method, the outer core liquid is put into the hollow portion of the clad pipe 12. The clad pipe 12 is preferably preliminarily polymerized with shaking in warm water to increase the viscosity of the outer core liquid. Thereafter, the clad pipe 12 is held in a horizontal direction (a state in which the height direction of the clad pipe is horizontal), and rotational polymerization is performed while heating.

  Next, the inner core polymerization step 14 for forming the inner core 30 will be described. The inner core liquid is prepared by adding a polymerization initiator, a chain transfer agent, a dopant and the like to MMA which is a polymerizable monomer. And using this inner core liquid, the method described in the international publication 93/08488 pamphlet and patent 3332922 is applied, the GI type (graded index type) inner core 30 is formed, A reform 15 is obtained (see FIG. 2). The form of the preform 15 is not particularly limited, but after forming the outer core 31 with the thickness t2 of 2 mm to 10 mm using the thickness t1 of the clad pipe 12 of 0.2 mm to 15 mm, the diameter D1 is It is preferable to form an inner core 30 of 3 mm to 25 mm. When the stretching step 16 is performed using the preform 15 of this form, a POF 17 having excellent optical characteristics and mechanical strength can be obtained.

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

  In the present invention, the method for producing the core portion is not limited to the above method. For example, it can be formed by a rotational polymerization method in which interfacial gel polymerization is performed while rotating the inner core 30 shown in FIG. In this case, after injecting the inner core liquid into the hollow of the clad pipe 12 in which the outer core 31 is formed, one end thereof is sealed and the horizontal state in the rotary polymerization apparatus (the height direction of the clad pipe is horizontal). Polymerization is carried out while rotating. At this time, the inner core liquid may be supplied all at once or sequentially or continuously. At this time, by adjusting the supply amount, composition and degree of polymerization of the polymerizable composition for the inner core, in addition to the GI type having a continuous refractive index distribution, a multi-step type light having a stepped refractive index distribution It can also be applied to fiber production. In the present invention, this polymerization method is referred to as a core part rotation polymerization method (core part rotation gel polymerization method).

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

  By stretching the preform 15, a POF 17 having a desired diameter, for example, 100 μm or more and 1000 μm or less can be obtained. There is no restriction | limiting in particular regarding the manufacturing method performed at the extending | stretching process 16, A known method can be applied equally. In addition, the residual monomer and water | moisture content in a preform can be reduced by drying the preform 15 under reduced pressure before performing the extending | stretching process 16. FIG. Thereby, the generation | occurrence | production of the extending | stretching bubble which arises by the residual monomer and water | moisture content at the time of melt-heating extending | stretching volatilizing and foaming can be suppressed.

  In the stretching step 16, the preform 15 is heated and melted and stretched. The heating temperature can be appropriately determined according to the material of the preform 15 and the like. In general, it is preferably performed in an atmosphere at 180 ° C to 250 ° C. The stretching conditions (stretching temperature and the like) can be appropriately determined in consideration of the diameter of the preform 15, the diameter of the POF 17, the material used, and the like. For example, as described in JP-A-7-234322, the drawing tension is set to 0.1 N or more in order to orient the molten polymer, or described in JP-A-7-234324. Thus, in order not to leave distortion after melt drawing, it is preferable to be 1N or less. Further, as described in JP-A-8-106015, a method of providing preheating at the time of stretching can be used. Regarding the POF 17 obtained by the above method, the bending elongation and lateral pressure characteristics of the optical fiber cable described later can be improved by defining the breaking elongation and hardness as described in JP-A-7-244220.

  The POF 17 can be used as it is, for example, as an optical transmission body such as an optical fiber. Normally, a protective layer is provided on the outer periphery of the POF 17 to form the optical fiber core wire 19 to protect the POF 17 and various types. To have special functions. For example, products with improved bending and weather resistance of optical fibers, suppression of performance degradation due to moisture absorption, improved tensile strength, imparting stepping resistance, imparting flame resistance, protection from chemical damage, prevention of noise from external light, coloring, etc. A coating process 18 for coating the surface of the POF 17 with a protective layer is performed for the purpose of improving the value and the optical fiber core wire 19 is obtained. Moreover, it is preferable to use the optical fiber cable 21 in which the optical fiber core wire 19 is coated with a resin such as nylon because the strength can be improved. The material for the protective layer and the method for forming the protective layer on the optical fiber are not particularly limited. Alternatively, a plurality of POFs 17 and / or optical fiber core wires 19 may be bundled and used as an optical fiber cable 21 covered with resin.

  As a material for forming the protective layer, general materials such as polyolefins such as polyethylene and polypropylene, polyvinyl chloride, polyvinyl alcohol, urethane resin, and nylon can be used, but thermal damage to the POF 17 during coating (for example, Those which do not give deformation, modification, thermal decomposition, etc.) can be selected, and the following materials can be preferably used from the viewpoint of thermal damage and mechanical characteristics. Specific examples include the following materials. Since these have high elasticity, they are also effective in terms of imparting mechanical properties such as bending. First, rubber which is one form of polymer can be used. Specifically, isoprene rubber (for example, natural rubber, isoprene rubber, etc.), butadiene rubber (for example, styrene-butadiene copolymer rubber, butadiene rubber, etc.), diene special rubber (for example, nitrile rubber, chloroprene rubber, etc.) ), Olefin rubber (for example, ethylene-propylene rubber, acrylic rubber, butyl rubber, halogenated butyl rubber, etc.), ether rubber, polysulfide rubber, urethane rubber and the like.

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

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

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

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

  Moreover, in order to provide a plurality of functions, the optical fiber cable 21 may be manufactured by laminating coatings having various functions on the optical fiber core wire 19. For example, in addition to the above-mentioned flame retardancy, a barrier layer for suppressing moisture absorption of POF 17 and a moisture absorbing material for removing moisture, for example, a moisture absorbing tape and a moisture absorbing gel can be included in the coating layer or between the coating layers. A flexible material layer for relaxing stress at the time of flexibility, a cushioning material such as a foam layer, a reinforcing layer for increasing rigidity, and the like can be selected and provided depending on the application. An optical fiber cable in which the mechanical strength of the POF 17 is reinforced when a fiber such as a high elastic modulus fiber (so-called tensile fiber) and / or a highly rigid metal wire is contained as a structural material in addition to the resin. 21 is preferable. Examples of the tensile strength fiber include aramid fiber, polyester fiber, and polyamide fiber. Examples of the metal wire include stainless steel wire, zinc alloy wire, copper wire and the like. None of these are limited to those described above. In addition, a metal tube exterior for protection, an aerial support line, and a mechanism for improving workability during wiring can be incorporated.

  Also, the shape of the plastic optical fiber cable depends on the form of use, and is a collective cable in which the optical fiber cables 21 are concentrically arranged, an aspect called a tape core wire arranged in a row, and further, a press winding or a wrap sheath. The form can be selected according to the application such as the assembled cable.

  In addition, the optical transmission body using the POF 17, the optical fiber core wire 19, the optical fiber cable 21 and the like manufactured using the clad pipe 12 according to the present invention uses the connection optical connector at the end to securely connect the connection portion. It is preferable to fix to. As the connector, it is possible to use various commercially available connectors such as PN type, SMA type, SMI type, F05 type, MU type, FC type, and SC type that are generally known.

  The system for transmitting an optical signal using the POF 17, the optical fiber core wire (optical fiber cord) 19, and the optical fiber cable 21 as optical members manufactured using the clad pipe 12 of the present invention includes various light emitting elements, An optical signal processing device including optical components such as a light receiving element, an optical switch, an optical isolator, 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, pages 110 to 127, “Printed Wiring You can refer to "This time, optical components are mounted on the board." Combined with various technologies described in the above documents, internal wiring in computers and various digital devices, internal wiring in vehicles and ships, optical terminals and digital devices, optical links between digital devices, general households and housing complexes・ Suitable for optical transmission systems suitable for short distances such as high-speed, large-capacity data communications and control applications that are not affected by electromagnetic waves, including optical LANs in factories, offices, hospitals, schools, etc. Can be used.

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

Hereinafter, the present invention will be described more specifically with reference to Example 1. The types of materials, their proportions, operations, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. The description will be made in detail in Experiment 1 according to the present invention, and in Experiments 2 and 3, descriptions of the same conditions are omitted. Further, in the experiments 4 and 5 which are comparative examples, the description of the same conditions as in the experiment 1 is omitted. The outer peripheral surface radius a (mm) of the extrusion die inner lip, the outer peripheral surface radius b (mm), the molten PVDF discharge flow rate c (mm ³ / second), the pipe take-up speed e (mm / second), and the extrusion die Table 1 summarizes the distance d (mm) between the outlet and the sizing die inlet. Table 2 summarizes the outer diameter, target wall thickness, wall thickness, presence / absence of wrinkles and lines, and molding stability of the clad pipe 12. Further, Table 2 also shows the transmission loss values at 650 nm of the optical fiber core 19 manufactured from the clad pipe 12 obtained in each experiment.

In experiment 1, PVDF (polyvinylidene fluoride; KF polymer # 850 manufactured by Kureha Chemical Industry Co., Ltd .; melt flow rate 20 g / 10 min) was discharged at a single screw extruder 41 (plastic engineering research laboratory, screw diameter φ50 mm) 41. the 510 mm ³ / sec outer diameter at an extrusion temperature 180 ° C. as φ35mm (a = 17.5mm) of the inner lip 70, using an extrusion die 43 having an outer lip 71 with an inner diameter of 36.5mm (b = 18.25mm). The melted pipe 44 was extruded from the extrusion die 43 into a pipe shape. Using a sizing die 45 having an inner diameter of about 20 mm, a pipe 51 having an outer diameter of 20 mm and an inner diameter of 19 mm was formed at a take-up speed (= e) of 17 mm / sec. The distance d between the extrusion die outlet 43a and the sizing die inlet 45a was 10 mm.

  The formed pipe 51 was cut with a long cross section, and the pipe wall thickness distribution of the cross section was measured at 8 points with a digital micrometer of both spherical surfaces, and the average value was calculated. The measurement result was 0.512 mm, and the difference from the target wall thickness of 0.500 mm was 0.012 mm. Moreover, when the pipe 51 was observed visually, generation | occurrence | production of wrinkles and a stripe was not seen ((circle)). Further, the stability during molding of the pipe 51 was also good (◯).

  The pipe 51 was cut into 600 mm to form a clad pipe 12. The clad pipe 12 was inserted into a sufficiently rigid polymerization vessel having an inner diameter of 20 mm and a length of 600 mm. The clad pipe 12 was washed with pure water and dried at 90 ° C. Thereafter, using the same PVDF as that of the clad pipe, bottoming was performed on one end at 230 ° C. for 20 minutes.

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

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

  A stretching step 16 was performed by stretching the preform 15 to form POF 17. The preform 15 was placed in a heater having four temperature zones in the vertical direction. In addition, the temperature zone was adjusted to 250 degreeC, 220 degreeC, 160 degreeC, and 130 degreeC in order from the top. POF17 obtained by stretching the preform 15 was placed in a 25 ° C. water bath and cooled and solidified. The stretching speed was 5 m / min, and the film was taken up by a take-up roller. In the take-up roller, a tension of 0.2 N was applied to the POF 17. 1000 m of POF 17 was obtained. A coating step 18 was performed so that the average film thickness of the POF 17 with a polyolefin resin was about 200 μm, and an optical fiber core wire 19 was obtained. When the transmission loss value of the optical fiber core wire 19 was measured by a known method, it was 160 dB / km at a wavelength of 650 nm.

In Experiment 2, an extrusion die having an inner lip outer peripheral surface of 22 mm (a = 11 mm) and an outer lip inner peripheral surface of 26 mm (b = 13 mm) was used. The experiment was performed under the same conditions as in Experiment 1 except that the molten resin discharge flow rate c was 1500 mm ³ / sec and the distance d between the extrusion die outlet and the sizing die inlet was 5 mm.

In Experiment 3, an extrusion die having an inner lip outer peripheral surface of 55 mm (a = 27.5 mm) and an outer lip inner peripheral surface of 60 mm (b = 30 mm) was used. The experiment was conducted with the molten resin discharge flow rate c being 2740 mm ³ / sec, the distance d between the extrusion die outlet and the sizing die inlet being 5 mm, and the take-up speed e being 12 mm / sec.

  In Experiment 4 as a comparative example, the experiment was performed under the same conditions as Experiment 1 except that the distance d between the extrusion die outlet and the sizing die inlet was 20 mm. In Experiment 5 as a comparative example, the experiment was performed under the same conditions as Experiment 3 except that the distance d between the extrusion die outlet and the sizing die inlet was 20 mm.

  In Experiment 1, the generation of streaks on the inner peripheral surface was suppressed and stable molding was possible. In Experiment 2, a pipe close to the target wall thickness could be stably formed while suppressing the generation of streaks on the outer peripheral surface. In Experiment 3, the generation of streaks on the outer peripheral surface was suppressed and molding was stable. In Experiment 4 as a comparative example, a pipe close to the target thickness could be formed, but thin streaks were intermittently generated on the inner peripheral surface. In Experiment 5, which is a comparative example, large streaks occurred on the outer peripheral surface, and the wall thickness fluctuated and was very unstable.

  From Table 2, it can be seen that the optical fiber manufactured using the clad pipe according to the present invention suppresses the deterioration of the transmission loss value. This is because the generation of streaks and the like is suppressed in the manufactured clad pipe, and therefore the generation of streaks that cause deterioration in transmission loss when a core is formed in the pipe and drawing is also suppressed. .

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

Explanation of symbols

12 Clad Pipe 40 Production Line 43 Extrusion Die 45 Sizing Die 70 Inner Lip 71 Outer Lip

Claims (6)

In a method for producing a clad pipe for plastic optical fiber, in which a polymer is melted and extruded from a lip clear lath of an extrusion die having an inner lip and an outer lip into a pipe shape, put into a sizing die, and taken as a pipe,
The radius of the outer peripheral surface of the inner lip is a (mm),
The radius of the inner peripheral surface of the outer lip is b (mm),
The molten polymer discharge flow rate is c (mm ³ / sec),
The distance between the pipe outlet of the extrusion die and the pipe inlet of the sizing die is d (mm),
When the pipe take-up speed is e (mm / second),
A method for producing a clad pipe for plastic optical fiber, which satisfies the relationship [e {π (b ² −a ² )} / c] −1 ≧ 0.1 d.   The method for producing a clad pipe for plastic optical fiber according to claim 1, wherein the polymer is a fluororesin.   The method for producing a clad pipe for plastic optical fiber according to claim 1 or 2, wherein the melt flow rate of the polymer is in the range of 2 g / 10 min to 30 g / min.   The method for producing a clad pipe for plastic optical fiber according to any one of claims 1 to 3, wherein a melting temperature of the polymer is in a range of 170 ° C or higher and 240 ° C or lower.   A plastic optical fiber manufactured using the plastic optical fiber clad pipe manufactured by the plastic optical fiber clad pipe manufacturing method according to any one of claims 1 to 4. In an apparatus for producing a clad pipe for plastic optical fiber comprising an extrusion die having an inner lip and an outer lip,
Means for controlling the discharge flow rate of the molten polymer and extruding the molten polymer in a pipe shape from the clearance between the inner lip and the outer lip of the extrusion die;
A sizing die for adjusting the outer diameter of the polymer extruded into a pipe shape;
Cooling means for cooling the pipe-shaped polymer and fixing the shape to form a pipe;
Means for pulling the pipe;
Means for varying the take-up speed of the pipe;
An apparatus for producing a clad for plastic optical fiber, comprising:

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