JP2006126703A - Manufacturing method of plastic optical member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continuously manufacture a plastic optical member that is superior in optical characteristics and also in mechanical strength. <P>SOLUTION: Materials 35, 36, 37 for forming an inner core, an outer core and a clad respectively are supplied to the three-layer co-extruding die of continuous extruding equipment. The viscosity ratio between the inner core and the outer core forming materials 35, 36 is set at 20; the viscosity ratio between the outer core and the clad-forming materials 36, 37 is set at 10; and the viscosity ratio between the adjacent materials 35-37 is set at 50 or smaller. As a result, instability between the boundaries of respective materials is suppressed, enabling the plastic optical member to be obtained that is superior in optical characteristics, as well as in mechanical strength. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a plastic optical member.

  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 having a core part having a distribution of refractive index from the center toward the outside is a band of an optical signal to be transmitted. Therefore, it has recently been attracting attention as an optical transmission body having a high transmission capacity. As one of the manufacturing methods of such a GI type plastic optical fiber, a preform (base material) is manufactured by 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).

Another method for producing POF is a melt continuous extrusion method (see, for example, Patent Documents 3 to 6). 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 an 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. Furthermore, a core, a clad, and an outermost layer (usually functioning as a protective layer) are simultaneously extruded and stretched to perform a plastic optical fiber cord (also referred to as a plastic optical fiber core, hereinafter referred to as an optical fiber cord). ) Can be obtained continuously.
JP-A-61-130904 Japanese Patent No. 3332922 JP 2000-356716 A JP 2003-531394 A Japanese Patent No. 34471015 JP-A-8-334635

  The continuous extrusion method of POF described in Patent Document 3 is a continuous production method of GI-type POF in which a molten resin layer in which a layer including a layer including a dopant is laminated concentrically is passed through a diffusion region. In this method, when a resin layer having a large viscosity difference in the diffusion region co-extrusion flows for a long time, disturbance due to flow instability at each layer interface may occur. If this disturbance occurs, the refractive index distribution in the core portion may be disturbed, leading to a deterioration in transmission loss.

  In the method described in Patent Document 4, after each layer is extruded with a multilayer die, it is heated at a temperature not higher than the glass transition temperature Tg of the polymer forming the outermost layer, and the diffusible additive in the inner layer is thermally diffused to give GI. Make a structure. Similarly to the method described in Patent Document 3, in this method, when a resin layer having a large viscosity difference co-extrusion flows for a long time, disturbance due to flow instability at each layer interface may occur. Due to this disturbance, the refractive index distribution may be disturbed, and transmission loss may be deteriorated. Patent Document 5 describes a method in which a dopant is allowed to flow concentrically through a diffusible polymer and diffused within a predetermined time. However, this method does not specifically mention the multilayer flow conditions of each layer.

  In Patent Document 6, two or more kinds of polymers containing a non-polymerizable compound forming an optical transmission body are flowed concentrically in a die to produce a POF. A production method using a highly viscous resin is described. Moreover, although the wraparound phenomenon of the resin at the time of co-extrusion is mentioned, the instability of the interface due to the viscosity difference (interface stress difference) of each layer is not mentioned. As described above, the instability of the interface may disturb the refractive index distribution and cause a deterioration in transmission loss.

  In the case of continuous extrusion production of POF, the resin forms a multilayer flow in a coextrusion die or a diffusion zone (such as a pipe), but in order to produce POF with little light scattering, the interface may be smooth. is necessary. However, it is known that when the viscosity difference between resin layers flowing adjacent to each other is large, the shear stress at the interface increases and an unstable phenomenon occurs at the interface (Multiphase Flow in Polymer Processing by Chang Dae Han). Chapter 8 P419-448). When the interface is in an unstable state, the thermal diffusion of the refractive index adjusting agent may not be performed uniformly in a concentric manner. As a result, there may be obtained a distorted refractive index profile at the core of the obtained POF. Further, there is a possibility that interface irregularity (microbending) may occur due to a change in the orientation state of the polymer at the interface. Loss of material results in deterioration of productivity due to changes in the mechanical properties of POF obtained by the occurrence of these defects (for example, reduction in mechanical strength) and optical changes (for example, deterioration in transmission loss). The problem causing the increase is occurring.

  An object of the present invention is to provide a method of manufacturing a plastic optical member that can suppress instability of an interface in multilayer extrusion, maintain mechanical strength, and suppress deterioration of transmission loss.

  As a result of intensive studies, the present inventor has suppressed the instability phenomenon at the interface by regulating the viscosity ratio of adjacent molten materials (molten polymer) in the POF continuous manufacturing method, and has low light scattering loss at the interface and low transmission. It has been found that a plastic optical fiber having a loss and excellent mechanical strength can be continuously produced. In this case, it has been found that the method for adjusting the viscosity between adjacent molten materials varies depending on the configuration of the adjacent molten materials.

(1) When the polymer matrix constituting the molten material is (almost) equal When the refractive index distribution is formed in the POF, the viscosity change due to the concentration difference of the refractive index adjusting agent (for example, DPS (diphenyl sulfide)) is used. It is preferable. This is because the addition of a low molecular compound serving as a refractive index adjusting agent breaks the uniformity of the polymer matrix, and this low molecular compound provides an effect as a plasticizer. An example is shown in FIG. As shown in FIG. 4, when PMMA is used as a polymer matrix, it can be seen that the viscosity is lowered by increasing the content of DPS, which is a low molecular compound, from 10 wt% to 20 wt%.

  In order to reduce the shear stress due to the difference in viscosity between adjacent molten materials and to obtain a desired refractive index distribution, it is necessary to determine how much the viscosity change due to the added refractive index adjusting agent affects. When using a polymer matrix whose viscosity varies greatly depending on the refractive index adjusting agent, it is possible to adjust the viscosity of the adjacent molten material by increasing the number of coextrusion layers and adjusting the content of the refractive index adjusting agent in each layer. I found it preferable. When examining the difference in viscosity, the difference in viscosity between molten materials due to changes in concentration tends to decrease during the process of thermal diffusion of the refractive index modifier. It is preferable to do.

(2) When the polymer matrix constituting the molten material is different In many cases, the physical properties of the polymer matrix itself are different between the molten materials, and there is also a difference in the influence of the composition change due to the refractive index adjusting agent as described above. Therefore, it has been found that it is necessary to grasp in advance the change in viscosity due to the combination of the polymer matrix and the refractive index adjusting agent. In addition, unlike the case of the same polymer matrix, the degree of thermal diffusion of the refractive index modifier varies depending on the matrix configuration, so if the optical and mechanical properties of the polymer matrix can be adjusted, the viewpoint of adjusting the refractive index profile Then, it discovered that it was one of the effective control methods.

(3) Others When the viscosities differ between molten materials, the viscosity difference can be reduced by adjusting the extrusion temperature. However, when the residence time after joining is long, the temperature difference between the melted materials is relaxed and the viscosity difference becomes large, and the instability phenomenon at the interface or the layer inversion (replacement) due to the wraparound phenomenon occurs. It was. In this case, it has been found that it is effective to increase the take-up speed of the formed POF in order to shorten the residence time.

  The present inventor adjusts the viscosity ratio (VR) of adjacent molten materials to 50 or less and extrudes, thereby reducing the shear stress difference at the interface between adjacent molten materials. It has been found that the generation of unstable flow at the substrate can be suppressed. Thereby, the thickness of each layer is uniform, the smoothness of the interface is high, light scattering at the interface is suppressed, and a plastic optical fiber with good optical characteristics can be obtained.

  The method for producing a plastic optical member according to the present invention is a method for producing a plastic optical member formed by laminating a plurality of molten materials to form a viscosity ratio of adjacent molten materials when performing the melt extrusion. 50 or less. More preferably, it is 30 or less, and most preferably 20 or less. It is preferable that adjacent layers are arranged concentrically.

  It is preferable to adjust the temperature of each molten material. It is preferable that at least one of the molten materials has a polymer composed of (meth) acrylic acid ester as a main component. It is preferable that at least one of the molten materials has polymethyl methacrylate as a main component. The polymerization degree of the polymethyl methacrylate is preferably 100 or more and 5000 or less. In the case of extruding three or more types of the molten material, it is preferable that a refractive index distribution type optical waveguide is formed by the refractive index of each of the molten materials being different.

  According to the method for manufacturing a plastic optical member of the present invention, in the method for manufacturing a plastic optical member formed by laminating a plurality of molten materials, the viscosity of the adjacent molten materials is used when performing the melt extrusion. Since the ratio of the ratio is 50 or less, each molten material interface during co-extrusion flow becomes stable, and thus a plastic optical member, particularly a plastic optical fiber, which has a smooth interface and little increase in transmission loss due to interface irregularity can be obtained. . Moreover, when the co-extrusion flow is stabilized, fluctuations in the outer diameter of the extruded plastic optical member can be suppressed. Furthermore, since fluctuations in the outer diameter are suppressed, troubles during production, such as the plastic optical member being cut, are reduced, making it suitable for a continuous production method.

  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), main chain cyclic fluorinated polymer-forming monomers (e), etc., and the core is a homopolymer of these, or two of these monomers It can form from the copolymer which consists of the above, and the mixture of a homopolymer and / or a copolymer. 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. Further, (c) styrene compounds include styrene, α-methylstyrene, chlorostyrene, bromostyrene, and (d) vinyl esters include vinyl acetate, vinyl benzoate, vinyl phenyl acetate, vinyl chloroacetate. (E) As the main chain cyclic fluorinated monomers, a polymer having a cyclic structure as a monomer or forming a fluorinated polymer having a cyclic structure in an amorphous main chain by cyclopolymerization is formed. A monomer that forms a polymer having an alicyclic ring or a heterocyclic ring in the main chain exemplified in polyperfluorobutanyl vinyl ether and JP-A-8-334634, and Japanese Patent Application No. 2004-186199. Examples thereof are exemplified. 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.

  Use the above-mentioned properties as a dopant that can stably coexist with the polymer and is stable under the polymerization conditions (polymerization conditions such as heating and pressurization) of the above-described polymerizable monomer. Can do. In the present embodiment, the core portion-forming polymerizable composition contains a dopant, and in the step of forming the core portion, the concentration distribution is controlled by the content and thermal diffusion in the layer, and the concentration of the dopant is inclined, A method of forming a refractive index distribution structure based on the dopant concentration distribution in the core portion will be exemplified. Thus, the core portion having the refractive index distribution is referred to as a “refractive index distribution type core portion”. By forming the gradient index core part, the obtained optical member becomes a gradient index plastic optical fiber (GI POF) having a wide transmission band.

  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.

  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. 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, 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 shows a schematic view of a continuous extrusion apparatus 10 and other apparatuses used in the method for continuously producing a plastic optical fiber of the present invention. The continuous extrusion apparatus 10 includes an inner core part forming material extrusion apparatus 11, an outer core part forming material extrusion apparatus 12, a cladding part forming material extrusion apparatus 13, and a three-layer coextrusion die 14. Each extrusion apparatus 11, 12, 13 and the three-layer coextrusion die 14 are connected by pipes 15, 16, and 17. Each material is sent from each of the extrusion apparatuses 11 to 13 to the three-layer coextrusion die 14 through the pipes 15 to 17. Each material becomes a fiber (hereinafter referred to as an optical fiber yarn) 18 by a three-layer coextrusion die 14 and is drawn by a first roller 19. The drawn optical fiber yarn 18 is conveyed into the water tank 20. Cooling water of −5 ° C. to 30 ° C. is placed in the water tank 20, and the optical fiber yarn 18 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 (for example, DPS (diphenyl sulfide), BEN (benzyl benzoate), TPP) that increases the refractive index of the refractive index adjusting agent (dopant) in the core portion forming material or the inner core portion forming material. (Triphenyl phosphate, etc.). 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 18, 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 further an additive such as a polymerization initiator and feeding it to the three-layer coextrusion die 14, 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. Further, instead of the polymerizable monomer, the dopant, and the polymerization initiator, the polymer and the dopant may be fed into the three-layer coextrusion die 14 in a molten state.

  The optical fiber yarn 18 is conveyed through the heating furnace 22 while being drawn by the second roller 21. Although the temperature of the heating furnace 22 is not specifically limited, It is preferable to set it as 120 to 180 degreeC. Further, the optical fiber yarn 18 is further drawn into a plastic optical fiber (hereinafter referred to as an optical fiber) 23 by making the take-up speed of the second roller 21 faster than the take-up speed of the first roller 19. it can. By redrawing the melt-extruded optical fiber yarn 18 in this way, a higher-strength optical fiber 23 can be obtained. Finally, the optical fiber 23 is wound into a roll by a winder 24 and stored as an optical fiber roll 25. By forming a protective layer on the optical fiber roll 25 to obtain a plastic optical fiber cord (plastic optical fiber core wire), an optical transmission body having further improved mechanical strength can be obtained.

  The principal part enlarged view of the continuous extrusion apparatus 10 used for FIG. 2 at this invention is shown. The three-layer coextrusion die 14 includes a core part die 30, a clad part die 31, and a heat insulating plate 32 that insulates them. 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 15 for supplying the inner core part forming material 35 and the pipe 16 for supplying the outer core part forming material 36. Further, a pipe 17 for supplying a clad part forming material 37 is connected to the clad part die 31.

  The inner core portion forming material 35 is sent from the tube 15 to the inner core portion forming portion 38 of the core die 30 to form a rod-shaped inner core (hereinafter referred to as a rod-shaped inner core portion). The outer core portion forming material 36 is supplied from the tube 16 to the pocket 40 through the liquid flow path 39. The pressure distribution of the outer core portion forming material 36 is relaxed in the pocket 40, and the outer core portion is formed with a substantially uniform thickness on the outer peripheral surface of the rod-shaped inner core portion. The outer core portion forming material 36 is covered from the pocket 40 so as to cover the outer peripheral surface of the rod-shaped inner core portion, thereby forming the outer core portion. The core part 41 in which the outer core is formed passes through the diffusion part 42 of the core part die 30. While passing through the diffusion part 42, the dopant is diffused to a desired state. Thereby, the core part which has a refractive index profile of a step index type or a graded index type is obtained. The cladding portion forming material 37 is supplied to the pocket 44 through the tube 17 and the liquid flow path 43. The pressure distribution of the cladding portion forming material 37 is relaxed by the pockets 44, and the thickness becomes substantially uniform when the outer peripheral surface of the core portion 41 is covered. The clad part forming material 37 is coated so as to cover the outer peripheral surface of the core part 41 and is sent out from the three-layer coextrusion die 14 as the optical fiber raw yarn 18.

  Moreover, the surface roughness (maximum height) of the inner surfaces of the pipes 15 to 17 serving as supply paths for the materials 35 to 37, the inner core portion forming portion 38, the liquid flow passages 39 and 43, the pockets 40 and 44, and the diffusion portion 42. By setting Ry to 0.8 S or less, adhesion of each material 35 to 37 to each inner surface is suppressed. Therefore, defects such as thermal deterioration and seizure of the respective materials 35 to 37 due to stay due to adhesion can be prevented.

  In the present invention, the viscosity ratio between adjacent materials (in the above description, the inner core portion forming material 35 and the outer core portion forming material 36, and the outer core portion forming material 36 and the cladding portion forming material 37) It is preferably 50 or less, more preferably 30 or less, and most preferably 20 or less. By setting the viscosity ratio in the above range, the interface between the materials 35, 36, and 37 is stabilized, and each part is stably formed. Therefore, deterioration of mechanical properties and optical properties associated with interface instability can be suppressed. In the present invention, the viscosity ratio means a value calculated by (large value) / (small value) of the shear viscosity value measured with a capillary rheometer or the like under the conditions of the molding temperature.

  In the present invention, the viscosity of each of the materials 35 to 37 is adjusted so that the viscosity ratio between the materials 35 to 37 is 50 or less. The method for adjusting the viscosity is not particularly limited. For example, the temperature at which the materials 35 to 37 are extruded to the three-layer coextrusion die 14 is adjusted. Furthermore, the viscosity ratio can be adjusted by selecting the degree of polymerization of the polymers of the materials 35 to 37. Among the materials 35 to 37, it is preferable to use a polymer raw material or polymer made of (meth) acrylic acid ester for the materials 35 and 36 forming the core part. In particular, it is preferable to use polymethyl methacrylate because deterioration of transmission loss can be suppressed. In this case, the polymerization degree of polymethyl methacrylate is preferably 100 or more and 5000 or less. When the degree of polymerization is less than 100, POF in which sufficient mechanical strength cannot be obtained may be produced. On the other hand, if it exceeds 5000, the viscosity becomes so high that it may be difficult to adjust the viscosity ratio between adjacent molten materials.

  In the present invention, the viscosity of each of the materials 35 to 37 is not particularly limited. However, in order to obtain an optical fiber yarn 18 having ease of extrusion, ease of processing, and desired mechanical strength, as a specific example, the viscosity of the inner core portion forming material 35 is set to 30 Pa · s to 300 Pa. When s (200 ° C. to 170 ° C.) is set, the viscosity of the outer core portion forming material 36 is 30 Pa · s to 300 Pa · s (240 ° C. to 210 ° C.), and the viscosity of the cladding portion forming material 37 is 1000 Pa · The example made into s-10000Pa * s (250 to 190 degreeC) is mentioned.

  FIG. 3 shows a cross-sectional view of 23 of a plastic optical fiber (optical fiber) according to the present invention. The optical fiber 23 includes an inner core 50 and an outer core 51 that serve as light waveguides, and a clad 52 that totally reflects transmission light at its interface with a lower refractive index than the outer core 51. The diameter and thickness of each part are not particularly limited, but when the inner core diameter D1 is 100 μm to 500 μm, the outer core diameter D2 is preferably 200 μm to 700 μm, and the cladding outer diameter D3 is preferably 300 μm to 1000 μm.

  Moreover, the continuous manufacturing apparatus 10 used for this invention is not limited to what is shown by FIG. For example, a two-layer coextrusion die that continuously extrudes a core and a clad at the same time, or a die that can coextrude more layers can be used. 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. In addition, the flat plastic molding obtained by controlling the take-off speed and extruding to a desired diameter and cutting it in the direction perpendicular to the longitudinal direction has a different refractive index between the central part and the outer peripheral part. It can be used as a so-called GRIN lens.

  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 according to the present invention and Experiments 5 and 6 as comparative examples. 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>
A continuous extruder 10 equipped with three φ16 mm diameter screw extruders (manufactured by Randcastle) 11, 12, 13 was used. The materials 35 to 37 were selected so that the inner core 50 was PMMA (degree of polymerization 1000) + DPS (20 wt%), the outer core 51 was PMMA (degree of polymerization 1000), and the clad 52 was PVDF. The extrusion temperature was adjusted with temperature controllers 34 and 35 so that the inner core was 210 ° C, the outer core was 240 ° C, and the clad was 230 ° C. When the viscosities of the materials 35 to 37 at these temperatures were measured with a flow tester manufactured by Toyo Seiki Co., Ltd., the ratio of the inner core portion forming material viscosity / outer core portion forming material viscosity (hereinafter referred to as VR1). Was about 20, and the ratio of the material viscosity for forming the outer core portion / the material viscosity for forming the cladding portion (hereinafter referred to as VR2) was about 10. Each material 35 to 37 was extruded from the three-layer coextrusion die 14 so as to be an optical fiber yarn 18 having an outer diameter of 1 mm. The outer diameter of the outer core portion of the optical fiber yarn 18 was φ952 μm, and the outer diameter of the inner core portion was φ580 μm.

  The extruded optical fiber yarn 18 was cooled in a water bath 20 at 15 ° C. and taken up at a speed of 5 m / min by a low speed godet roll 19. Then, while heating in the heating furnace 22 at 150 ° C., the high-speed godet roll 21 was taken up at a speed of 9 m / min. An optical fiber 23 having a diameter of about φ750 μm was manufactured and wound as an optical fiber roll 25 by a winder 24. At this time, the outer core portion outer diameter D2 was about 714 μm, and the inner core portion outer diameter D1 was about 435 μm. The wound optical fiber 23 was heated in a thermostatic chamber at 190 ° C. for 5 minutes and naturally cooled at room temperature to obtain a gradient index plastic optical fiber. Each material 35-37 was extruded continuously for 1 hour, and the optical fiber 23 was manufactured. Transmission loss was measured using the optical fiber 23 after 1 hour as a sample (30 m long). Ten samples were prepared each. The transmission loss of the manufactured optical fiber 23 was measured at a transmission loss per 1 km (dB / km). The transmission loss of the optical fiber manufactured under the conditions of Experiment 1 was 140 dB / km to 160 dB / km, which was good.

<Experiment 2>
The experiment was performed under the same conditions as Experiment 1 except that the extrusion temperature of the inner core portion forming material 35 was set to 230 ° C. In addition, VR1 at this time was about 50, and VR2 was about 10. The obtained optical fiber had a good transmission loss in the range of 180 dB / km to 190 dB / km.

<Experiment 3>
A continuous extruder 10 equipped with three φ16 mm screw extruders (manufactured by Randcastle) 11, 12, 13 was used. The materials 35 to 37 were selected so that the inner core 50 was PMMA (degree of polymerization 1000) + DPS (20 wt%), the outer core 51 was PMMA (degree of polymerization 1000), and the clad 52 was PVDF. The extrusion temperature was adjusted with temperature controllers 34 and 35 so that the inner core was 210 ° C, the outer core was 240 ° C, and the clad was 230 ° C. The viscosity ratio VR1 was about 20, and VR2 was about 10. Each material was extruded from the three-layer coextrusion die 14 so that 35 to 37 became an optical fiber yarn 18 having an outer diameter of 1 mm. A three-layer coextrusion die 14 having an inner diameter of φ1 mm was used. The outer cladding portion outer diameter of the optical fiber yarn 18 was φ952 μm, and the inner core portion outer diameter was 580 μm.

  The extruded optical fiber yarn 18 was cooled in a water bath 20 at 15 ° C. and taken up at a speed of 50 m / min by a low speed godet roll 19. And it heated at the speed of 90 m / min with the high-speed godet roll 21, heating with the heating furnace 22 of 150 degreeC. An optical fiber 23 having a diameter of about φ750 μm was manufactured and wound as an optical fiber roll 25 by a winder 24. The outer diameter D2 of the outer core portion was about 714 μm, and the outer diameter D1 of the inner core portion was about 435 μm. The wound optical fiber was heated in a thermostat at 190 ° C. for 5 minutes and then naturally cooled at room temperature to obtain a gradient index plastic optical fiber. Each material 35-37 was extruded continuously for 1 hour, and the optical fiber 23 was manufactured. Transmission loss was measured using the optical fiber 23 after 1 hour as a sample (30 m long). Ten samples were prepared each. The transmission loss of the optical fiber manufactured under the conditions of Experiment 2 was 145 to 165 dB / km, and the optical fiber 23 having excellent optical characteristics could be obtained even under the experimental conditions where the extrusion speed (take-off speed) was increased.

<Experiment 4>
The experiment was performed under the same conditions as in Experiment 3 except that the extrusion temperature of the inner core portion forming material 35 was set to 230 ° C. At this time, VR1 was about 50 and VR2 was about 10. The transmission loss of the obtained optical fiber was 200 dB / km, which was a little worse than Experiment 3, but an optical fiber with excellent optical characteristics was obtained.

<Experiment 5>
The test was performed under the same conditions as in Experiment 1 except that the extrusion temperature of the inner core portion forming material 35 was 240 ° C. At this time, VR1 was about 100 and VR2 was about 10. The transmission loss of the obtained optical fiber was as large as 300 dB / km to 350 dB / km.

<Experiment 6>
The experiment was performed under the same conditions as in Experiment 3 except that the extrusion temperature of the inner core portion forming material 35 was 240 ° C. At this time, VR1 was about 100 and VR2 was about 10. The transmission loss of the obtained optical fiber was as large as 400 dB / km to 450 dB / km.

It is the schematic of the apparatus used for the continuous manufacturing method of the plastic optical fiber of 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. It is a graph for demonstrating the correlation of the temperature and viscosity of a polymer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Continuous extrusion apparatus 14 3 layer coextrusion die 23 Optical fiber 35 Inner core part forming material 36 Outer core part forming material 37 Clad part forming material

Claims (7)

In the manufacturing method of the plastic optical member formed by laminating a plurality of molten materials,
A method for producing a plastic optical member, wherein, when performing the melt extrusion, the viscosity ratio of the adjacent molten materials is 50 or less.   The method for producing a plastic optical member according to claim 1, wherein adjacent layers are arranged concentrically.   3. The method of manufacturing a plastic optical member according to claim 1, wherein the temperature of each molten material is adjusted.   The method for producing a plastic optical member according to any one of claims 1 to 3, wherein at least one of the molten materials contains a polymer composed of (meth) acrylic acid ester as a main component.   The method for producing a plastic optical member according to any one of claims 1 to 4, wherein at least one of the molten materials contains polymethyl methacrylate as a main component.   6. The method for producing a plastic optical member according to claim 5, wherein the degree of polymerization of the polymethyl methacrylate is 100 or more and 5000 or less. When extruding three or more of the molten materials,
7. The method of manufacturing a plastic optical member according to claim 1, wherein a refractive index distribution type optical waveguide is formed by changing a refractive index of each of the molten materials.

Images