JP2007094148A - Method of manufacturing plastic optical transmission member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical transmission member having a desired cross sectional shape by using a melt-extruding method. <P>SOLUTION: Using an extruder, there is extruded to a common extruding die 14 a fused body of a core forming material 26, a clad forming material 27 and a protective layer forming material 28. The core forming material 26 extruded to the common extruding die 14 is formed into a rod-like core 46 in the core forming part 43. In the clad forming part 49, a clad is formed on the outer circumference of the core 46 and, in the protective layer forming part 53, a protective layer is formed on the outer circumference of the clad. The common extruding die 14 extrudes an optical transmission member precursor 18 for which the clad and the protective layer are successively formed on the outer circumference of the core 46. The cross sectional shape of the core, the clad and the protective layer constituting the cross section of this optical transmission member precursor 18 is formed bearing a rough resemblance to the cross sectional shape of the diffusing part 45, the clad forming part 49 and the protective layer forming part 53. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  In recent years, with the development of the communication industry, demand for optical transmission members has increased, transmission loss is small, and low cost is required. Examples of the optical transmission member include a quartz optical transmission member and a plastic optical transmission member. In particular, the plastic optical transmission member has advantages such as easy manufacture and processing and low cost compared to the quartz optical transmission body. A typical example of the plastic optical transmission member is a plastic optical fiber (hereinafter referred to as POF).

  Since POF is made entirely of plastic, POF has a disadvantage that transmission loss is slightly larger than that of silica-based optical fiber. 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).

  In fields such as parallel signal transmission, image capture and image output, a plurality of POFs are often bundled and used as a multi-fiber optical transmission member. As a method of manufacturing this multi-core optical transmission member, a method of thermocompression bonding a plurality of optical transmission members in a parallel state (for example, refer to Patent Document 2) or a method of covering a plurality of optical transmission members in a parallel state ( For example, see Patent Document 3). In addition, as a multi-core transmission material, a method using a photoresist or etching (for example, see Patent Document 4) for an optical transmission line has been proposed.

  In many applications, a protective layer is formed on the outer periphery of the POF. This protective layer can protect the POF from scratches and damages during handling and use in a poor environment, structural irregularities such as microbending, or deterioration of optical properties. Such a protective layer is formed by coating the peripheral surface of the POF. Further, when POF is coated with a polymer such as a thermoplastic resin, various functionalities can be imparted to the protective layer by adding an additive to the polymer. The POF on which the protective layer is formed is referred to as a plastic optical fiber core or a plastic optical fiber cord (hereinafter referred to as an optical fiber cord).

An example of such a POF production method is a melt extrusion method (for example, see Patent Document 5). 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 performing extrusion stretching simultaneously on the core part and the clad part. Furthermore, the optical fiber cord can be continuously obtained by simultaneously extruding and stretching the core portion, the clad portion, and the outermost layer (usually functioning as a protective layer).
JP-A-61-130904 JP-A-6-317716 JP 2000-338377 A JP 2001-166165 A Japanese Patent No. 34471015

  By the way, in fields such as optical communication and optical measurement, the POF and the optical fiber cord are used in connection with a planar optical waveguide. The connection work between the POF or optical fiber cord and the planar optical waveguide is performed on the substrate on which the planar optical waveguide optical transmission line is formed. In general, since the cross section of the POF and the optical fiber cord is often circular, it is difficult to accurately arrange the POF and the optical fiber cord at predetermined positions in this connection operation. In order to obtain highly efficient optical coupling at the connection portion with the planar optical waveguide, it is desirable that the core portion of the optical fiber has the same shape as the cross section of the planar optical waveguide. In general, since the cross section of the core portion of the planar optical waveguide is often a quadrangular shape, the cross section of the core portion of the POF and the optical fiber cord is also preferably a quadrangular shape. However, the melt extrusion method disclosed in Patent Document 5 described above does not specify a method for manufacturing POF and optical fiber cords having a quadrangular cross section. Moreover, it is not specified about the method of batch-forming the multi-fiber optical transmission member by the melt extrusion method.

  In view of the above problems, an object of the present invention is to provide a method for producing an optical transmission material having a desired cross-sectional shape using a melt extrusion method. Moreover, it aims at providing the manufacturing method of the multi-core optical transmission member using a melt extrusion method.

  The present invention relates to a method for producing a plastic optical transmission member, which is formed by a melt extrusion method of extruding a resin melt from a die, and a melt-extruded core portion has a clad portion having a lower refractive index than the core portion by melt extrusion. The clad portion whose cross section is any one of a polygon, a closed curve, or a figure combining straight lines and curves is formed around the core portion. Moreover, it is preferable that the said cross section of the said core part and the said cladding part is formed in a different shape.

  Further, the melt of the protective layer forming material is extruded from the die, and a protective layer whose cross section is a polygon, a closed curve, or a figure combining straight lines and curves is formed around the clad portion. It is preferable. Moreover, it is preferable that the said cross section of the said cladding part and the said protective layer are formed in a different shape.

  It is preferable that the cross section of the core portion is formed in a circular shape or a rectangular shape.

  It is preferable that the core portion is formed in a refractive index distribution type in which the refractive index increases continuously or stepwise as it goes toward the center of the cross section.

  It is preferable that the core portion has light scattering particles.

  It is preferable that the core portion is formed with (meth) acrylic acid ester as a main component and the clad portion is formed with a fluororesin as a main component.

The cross-sectional area is preferably 1 × 10 ⁴ μm ² or more.

  It is preferable that the plurality of core portions are formed inside the clad or the plurality of cores and clad portions are formed inside the protective layer. Moreover, it is preferable that the said several core part is formed in a clad inside by a sea island structure.

  It is preferable that a light-shielding material is used for at least one of the clad part or the protective layer.

  It is preferable that the cross sections of the plurality of core portions are formed from different shapes. Moreover, it is preferable that the said several core part is formed from a different material.

  According to the method for producing a plastic optical transmission member of the present invention, the clad part whose cross section is any one of a polygon, a closed curve, or a figure combining a straight line and a curve is melted and extruded around the core part. Therefore, a plastic optical transmission member having a desired cross-sectional shape can be manufactured.

  Further, the melt of the protective layer forming material is extruded from the die, and a protective layer whose cross section is a polygon, a closed curve, or a figure combining straight lines and curves is formed around the cladding portion. Therefore, an optical transmission member with a protective layer having a desired cross-sectional shape can be manufactured.

  Since the cross section of the core part and the clad part are formed in different shapes, and the cross section of the core part is formed in a circle or a rectangle, the connection work with the planar optical waveguide is improved while improving the connection workability. An optical transmission member having a cross-sectional shape corresponding to the above planar optical waveguide can be manufactured. The same applies to the optical transmission member with a protective layer, and the cross-sectional shape of each of the core part, the clad part, and the protective layer is set to a desired shape according to the usage form of the optical transmission member and the optical transmission member with the protective layer. Can be manufactured.

  Since the core portion is formed in a refractive index distribution type in which the refractive index continuously increases toward the center of the cross section, a GI (graded index) type optical transmission member can be manufactured. Further, since the core portion is formed in a refractive index distribution type in which the refractive index increases stepwise toward the center of the cross section, an MSI (multi-step index) type or SI (step index) A mold type optical transmission member can be manufactured.

  Since the core part has light scattering particles, it can be used for optical interconnection technology, light guide members such as a diffusion sheet and a reflector.

Since the core part is formed with (meth) acrylic acid ester as a main component and the cladding part is formed with a fluororesin as a main component, a plastic optical transmission member with low transmission loss can be manufactured. Moreover, since the area of the said cross section is formed in 1 * 10 < ⁴ > micrometer < ² > or more, the workability | operativity about a plastic optical transmission member improves.

  Since a plurality of core parts are formed, it can be used as a multi-core plastic optical transmission member.

  Since the plurality of core portions are formed inside the cladding, or because the plurality of cores and cladding portions are formed inside the protective layer, and the plurality of core portions are formed in a sea-island structure inside the cladding, the inter-core distance Is possible.

  Since a light-shielding material is used for at least one of the cladding portion forming material or the protective layer, it is possible to suppress the influence on the optical transmission path from the outside and to prevent the crosstalk of each core portion.

  Since the cross sections of the plurality of core portions are formed from different shapes, high-efficiency optical coupling can be obtained at the connection portions of all planar optical waveguides. Further, since the cross sections of the plurality of core portions are formed of different materials, multi-core optical transmission materials having different transmission characteristics and physical characteristics can be manufactured.

  Next, a first embodiment of the present invention will be described. FIG. 1 shows a schematic view of a melt extrusion apparatus 10 and other apparatuses used in a method for producing a plastic optical transmission member with a protective layer (hereinafter referred to as an optical transmission member) of the present invention. The melt extrusion apparatus 10 includes a core part forming material extruding apparatus 11, a cladding part forming material extruding apparatus 12, a protective layer forming material extruding apparatus 13, and a coextrusion die 14. Each extrusion apparatus 11-13 and the coextrusion die 14 are connected with the pipe | tubes 15-17. Each material stored in each of the extrusion apparatuses 11 to 13 is sent to the coextrusion die 14 through the pipes 15 to 17. Each material becomes an optical transmission member precursor 18 by the coextrusion die 14 and is drawn out by the first roller 19. The drawn optical transmission member precursor 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 transmission member precursor 18 is cooled. In the present invention, this cooling step can be omitted.

  The optical transmission member precursor 18 is further transported through the heating furnace 22 while being taken up by the second roller 21. Further, by increasing the take-up speed of the second roller 21 relative to the take-up speed of the first roller 19, the light transmission member precursor 18 can be further extended to form the light transmission member 23. By re-stretching the optical transmission member precursor 18 that has been melt-extruded in this way, a higher-strength optical transmission member 23 can be obtained. Finally, the optical transmission member 23 is wound into a roll by the winder 24 and stored as the optical transmission member 25.

  The core part forming material extruding device 11, the clad part forming material extruding device 12 and the protective layer forming material extruding device 13 have a lower refractive index than the core part forming material 26 and the core part forming material 26, respectively. The part forming material 27 and the protective layer forming material 28 are stored as a melt. The melt of the core part forming material 26 and the clad part forming material 27 becomes a precursor of the plastic optical transmission member having the core part and the clad part in the coextrusion die 14. The protective layer forming material 28 is formed in the coextrusion die 14 so as to cover the outer periphery of the precursor of the optical transmission path, and is extruded from the coextrusion die 14 as the optical transmission member precursor 18.

  As the core portion forming material 26, an amorphous polymer described later, preferably a polymer mainly composed of (meth) acrylic acid ester, is used. In the case of a graded index type (GI type) in which the refractive index continuously increases toward the center of the cross section of the core portion, a polymerizable monomer (for example, MMA), a dopant (for example, DPS), and further When an additive such as a polymerization initiator is mixed and fed into the coextrusion die 14, the MMA is polymerized to become PMMA, the central portion of which has the highest refractive index, and the refractive index continuously decreases in the radial direction. An optical transmission member of the form is obtained. As the cladding part forming material 27, PVDF having a refractive index lower than that of the core part and having good adhesion with the core part is used. PVDF is excellent in toughness and heat and heat resistance. The protective layer forming material 28 is also made of PVDF or the like that does not cause thermal damage (for example, deformation, modification, thermal decomposition, etc.) during manufacturing. Details of these materials will be described later.

  FIG. 2 shows an enlarged view of a main part of the coextrusion die 14 used in the present invention. The co-extrusion die 14 includes a core part die 30, a clad part die 31, a protective layer die 32, and heat insulating plates 33 and 34 that insulate them. Moreover, in order to adjust the temperature of each die | dye 30-32, the temperature regulators 35-37 are provided. The pipe 15 for supplying the core part forming material 26 to the core part die 30, the pipe 16 for supplying the cladding part forming material 27 to the cladding part die 31, and the protective layer forming material 28 to the protective layer die 32. Is connected to the pipe 17.

  The core part forming material 26 is sent from the tube 15 to the core part forming part 43 of the core part die 30 to form a rod-shaped core precursor 44. The core precursor 44 passes through the diffusion part 45 of the core part die 30. While the core precursor 44 passes through the diffusion portion 45, the dopant contained in the core portion forming material 26 is diffused to a desired state, and the core portion 46 having a GI type refractive index distribution is obtained. The cross-sectional shape of the core portion 46 is formed in a shape corresponding to the cross-sectional shapes of the core portion forming portion 43 and the diffusing portion 45. Thus, by appropriately selecting the cross-sectional shapes of the core portion forming portion 43 and the diffusing portion 45, the core portion 46 having a desired cross-sectional shape can be obtained.

  The cladding portion forming material 27 is supplied from the pipe 16 through the liquid flow path 47 to the pocket 48. Within the pocket 48, the pressure distribution of the cladding portion forming material 27 is relaxed. The clad part forming material 27 extruded from the pocket 48 covers the outer peripheral surface of the core part 46 in the clad part forming part 49. In this manner, the optical transmission line precursor 50 having the clad portion having a substantially uniform thickness on the outer peripheral surface of the core portion 46 is formed. Further, the cross-sectional shape of the optical transmission line precursor 50 is formed in a shape corresponding to the cross-sectional shape of the cladding portion forming portion 49. Thus, by appropriately selecting the cross-sectional shape of the cladding portion forming portion 49, the optical transmission line precursor 50 having a desired cross-sectional shape can be obtained.

  The protective layer forming material 28 is supplied from the pipe 17 through the liquid flow path 51 to the pocket 52. In the pocket 52, the pressure distribution of the protective layer forming material 28 is relaxed. The protective layer forming material 28 extruded from the pocket 52 covers the outer peripheral surface of the optical transmission line precursor 50 in the protective layer forming portion 53. Further, the cross-sectional shape of the optical transmission line precursor 50 is formed in a shape corresponding to the cross-sectional shape of the protective layer forming portion 53. In this manner, the optical transmission member precursor 18 having the protective layer with a substantially uniform thickness on the outer peripheral surface of the optical transmission path precursor 50 is formed. The optical transmission member precursor 18 is composed of a core part 46, a clad part covering the core part 46, and a protective layer covering the clad part. These cross-sectional shapes are the core part forming part 43, the clad part. The shape reflects the cross-sectional shape of the forming portion 49 and the protective layer forming portion 53. By subjecting the optical transmission member precursor 18 to a predetermined treatment, an optical transmission member 23 having a cross-sectional shape substantially similar to the optical transmission member precursor 18 is obtained.

  In order to form such a cross section of the core portion, the clad portion, and the protective layer, the core portion forming material 26, the clad portion forming material 27, and the protective layer forming material are used by using temperature controllers 35-37. It is preferable to extrude at an appropriate temperature according to 28.

  In FIG. 3, the example of the cross section of the optical transmission members 23a-23d which can be produced using the melt extrusion apparatus 10 mentioned above is described. In the optical transmission member 23a, a clad portion 61a and a protective layer 62a are sequentially formed on the outer periphery of a core portion 60a having a circular cross section, and the cross sections of the clad portion 61a and the protective layer 62a are circular. Is formed. The outer peripheries of the cross sections of the core portion 60a, the clad portion 61a, and the protective layer 62a are substantially similar to each other (FIG. 3A). In the optical transmission members 23b to 23d shown in FIGS. 3B to 3D, the outer peripheries of the cross sections of the core portion 60b and the clad portion 61b are formed in a square shape and a circular shape, respectively. The outer peripheral shape of the cross section of the protective layer 62a of the optical transmission member 23b is formed in a circular shape that is substantially similar to the cladding portion 61b, and the outer peripheral shape of the protective layer 62c of the optical transmission member 23c is substantially similar to that of the core portion 60b. The outer peripheral shape of the cross section of the protective layer 62d of the optical transmission member 23d is a hexagon.

  In the said embodiment, although it described that the cross-sectional shape of the core part 46 was determined by the cross-sectional shape of the core part formation part 43 or the spreading | diffusion part 45, it is also about the cross-sectional shape of the optical transmission line precursor 50. Although it has been described that it is determined by the cross-sectional shape of the core part forming part 43 and the diffusion part 45, the cross-sectional shape of each of the core part, the clad part and the protective layer is formed into a circular, quadrangular or hexagonal shape. However, the present invention is not limited to this, and can be formed in any shape of a polygon, a closed curve, or a combination of a straight line and a curve, such as another polygon or an ellipse.

  In the above embodiment, the GI type optical transmission line in which the refractive index continuously increases toward the center of the cross section of the core portion is described. However, the present invention is not limited to this, and the type of dopant and the refractive index are different. A step index (SI) in which the refractive index increases stepwise toward the center of the cross section of the core portion by appropriately selecting the composition ratio of the copolymerization of the monomer or more and the temperature of the temperature controller 35. ) Type or multi-step index (MSI) type optical transmission line can be manufactured.

  In addition, by using the core part forming material 26 containing light scattering particles, it can be used for optical interconnection technology applications, light guide member applications such as diffusion sheets and reflectors, and the like.

  Next, the second embodiment of the present invention will be described with a focus on portions different from the above-described embodiment, and detailed description of the same portions will be omitted. FIG. 4 shows a schematic view of the melt extrusion apparatus 70 and other apparatuses used in the production method of the present invention. The melt extrusion apparatus 70 includes a core part forming material extruding apparatus 11, a clad part forming material extruding apparatus 12, and a coextrusion die 71. The extrusion apparatuses 11 and 12 and the coextrusion die 71 are connected by pipes 15 and 16. The melt of the core part forming material 26 and the clad part forming material 27 stored in each of the extrusion apparatuses 11 and 12 is extruded to the coextrusion die 71 via the pipes 15 and 16. By the coextrusion die 71, an optical transmission member precursor 72 including a rod-shaped core portion and a clad portion covering the outer periphery of the core portion with a uniform thickness is formed. The optical transmission member precursor 72 is drawn from the coextrusion die 71 by the first roller 19. The drawn optical transmission member precursor 72 is conveyed into the water tank 20. The optical transmission member precursor 72 is further transported through the heating furnace 22 while being taken up by the second roller 21. In this way, the light transmission member precursor 72 can be further stretched to obtain the light transmission member 73. Finally, the optical transmission member 73 is wound into a roll shape by the winder 24 and stored as the optical transmission member roll 74.

  The core portion forming material extrusion device 11 and the cladding portion forming material extrusion device 12 include a core portion forming material 26 and a cladding portion forming material 27 having a lower refractive index than the core portion forming material 26, respectively. Stored as a melt. The melt of the core part forming material 26 and the clad part forming material 27 becomes a precursor of an optical transmission line having the core part and the clad part in the coextrusion die 14. The precursor of this optical transmission path becomes an optical transmission member precursor 72 and is extruded from the coextrusion die 71.

  FIG. 5 shows an enlarged view of a main part of a coextrusion die 71 used in the present invention. The coextrusion die 71 includes a core part die 30, a clad part die 31, and a heat insulating plate 33 that insulates them. In addition, temperature controllers 35 and 36 are provided to adjust the temperatures of the dies 30 and 31, respectively. A tube 15 for supplying the core portion forming material 26 is connected to the core portion die 30, and a tube 16 for supplying the cladding portion forming material 27 is connected to the cladding portion die 31.

  The core part forming material 26 is sent from the tube 15 to the core part forming part 43 of the core part die 30 to form a rod-shaped core precursor 44. The core precursor 44 passes through the diffusion part 45 of the core part die 30. While passing through the diffusion portion 45, the dopant contained in the core portion forming material 26 is diffused to a desired state, and the core portion 46 having a GI type refractive index distribution is obtained. The cross-sectional shape of the core portion 46 is formed in a shape corresponding to the cross-sectional shapes of the core portion forming portion 43 and the diffusing portion 45. Thus, by appropriately selecting the cross-sectional shapes of the core portion forming portion 43 and the diffusing portion 45, the core portion 46 having a desired cross-sectional shape can be obtained.

  The cladding portion forming material 27 is supplied from the pipe 16 through the liquid flow path 47 to the pocket 48. The clad part forming material 27 extruded from the pocket 48 covers the outer peripheral surface of the core part 46 in the clad part forming part 49. In this way, the optical transmission member precursor 72 having a clad portion having a substantially uniform thickness on the outer peripheral surface of the core portion 46 is extruded from the coextrusion die 71.

  FIG. 6 shows cross sections of optical transmission members 73a to 73d that can be manufactured using the melt extrusion apparatus 70 described above. In the optical transmission member 73a, the clad portion 76a is formed uniformly in the thickness direction on the outer periphery of the core portion 75a, and the outer peripheral shape of each cross section is formed in a circular shape (FIG. 6A). In the optical transmission member 73b, the clad portion 76b is formed uniformly in the thickness direction on the outer periphery of the core portion 75b, and the outer peripheral shape of the cross section is formed in a square shape, which are substantially similar to each other (see FIG. 6 (B)). The optical transmission member 73c includes a core part 75a having a circular cross section and a clad part 76c formed around the core part 75a (FIG. 6C). The outer peripheral shape of the cross section of the clad portion 76c is formed in a square shape. The optical transmission member 73d includes a core part 75b having a square cross section and a clad part 76d formed around the core part 75b (FIG. 6D). The outer peripheral shape of the cross section of the clad portion 76d is circular.

  It is also possible to heat-stretch the optical transmission member precursor 72 created by the melt extrusion apparatus 70 to form an optical transmission member having a cross-sectional shape substantially similar to that of the optical transmission member precursor 72.

  Next, a third embodiment of the present invention will be described. Description of the same parts as those in the first and second embodiments described above will be omitted. FIG. 7 shows a schematic view of a melt extrusion apparatus 80 used in the method for producing a multi-core optical transmission member with a protective layer of the present invention. The melt extrusion device 80 includes a plurality of extrusion devices and a coextrusion die 81. The extrusion apparatus included in the melt extrusion apparatus 80 includes five pairs of first and second extrusion apparatuses 82a and 82b and a third extrusion apparatus 82c. Each of the first to third extrusion devices 82a to 82c includes a core part forming material, a clad part forming material having a lower refractive index than the core part forming material, and a protective layer forming material containing a light shielding member. Stored as a melt.

  Each extrusion apparatus 82a-82c and the coextrusion die 81 are connected by a pipe, and each material extruded from each extrusion apparatus 82a-82c is sent to the coextrusion die 81 via the pipe. The coextrusion die 81 forms the multi-core optical transmission member precursor 84 using each material from each of these extrusion apparatuses 82a to 82c. The multi-core light transmission member precursor 84 pushed out from the coextrusion die 81 is drawn out by a roller. The multi-core optical transmission member precursor 84 drawn out by the roller becomes a multi-core optical transmission member 85 through a predetermined cooling process, a heating process by the heating furnace 22, and a stretching process. Finally, the multi-core optical transmission member 85 is wound into a roll by the winder 24 and stored as a multi-core optical transmission member roll 87.

  The multi-core optical transmission member 85 includes five optical transmission lines and a protective layer formed around the optical transmission lines. This optical transmission line is composed of a core part and a clad part formed around the core part.

  FIG. 8 shows a cross section of a multi-core optical transmission member 85 that can be produced using the melt extrusion apparatus 80 described above. The multi-core optical transmission member 85 includes a five-core optical transmission path composed of a core portion 85a and a clad section 85b, and a protective layer 85c formed so as to surround the outer periphery of the five-core optical transmission path. The cross section of the core part 85a and the clad part 85b is formed in a circle, and the cross section of the protective layer 85c is formed in a rectangle. Further, the optical transmission lines are arranged at a constant interval on the cross section of the protective layer 85c. The cross-sectional shape of the core portion 85a, the cladding portion 85b, and the protective layer 85c and the arrangement position of the optical transmission path in the multi-core optical transmission member 85 are determined by the coextrusion die 81. By selecting the coextrusion die 81 capable of forming the core portion 85a, the clad portion 85b, and the protective layer 85c having a desired cross-sectional shape, the multi-core optical transmission member 85 having the desired cross-sectional shape can be formed. .

  Since such a multi-core optical transmission member 85 has five independent optical transmission paths, it can be used for parallel signal transmission and the like. Further, since the protective layer 85c formed so as to surround the optical transmission path contains a light shielding member, it is possible to prevent crosstalk between the optical transmission paths.

  In the coextrusion die 81 shown in FIG. 7, the first extrusion device 82a for storing the core portion forming material and the third extrusion device 82c having a refractive index lower than that of the core portion formation material for storage are used. It is also possible to form a multi-core optical transmission member 90 as shown in FIG. The multi-core optical transmission member 90 having a rectangular cross section has five core portions 90a having a circular cross section. Further, these core portions 90 a are arranged at equal intervals in the cross section of the multi-core optical transmission member 90. Since this multi-core optical transmission member 90 has five core portions 90a which are independent optical transmission paths, it can be used for parallel signal transmission and the like. Further, since the clad portion 90b formed so as to surround the core portion 90a contains a light shielding member, it is possible to prevent crosstalk between the core portions 90a.

  In the above embodiment, it has been described that the multi-core optical transmission member 85 and the multi-core optical transmission member 90 have five optical transmission paths. However, the present invention is not limited to this, and the first, further the first depending on the number of optical transmission paths. By adding two extrusion devices and using a coextrusion die corresponding to this, a multi-core optical transmission member having more optical transmission paths can be formed.

  In the said embodiment, in the same multi-core optical transmission member, an optical transmission line may be formed with a different material. Moreover, the multi-core optical transmission member from which the cross section of each optical transmission path differs can also be formed.

(Core forming material)
As the polymerizable monomer for the core material, it is preferable to select an amorphous thermoplastic material having high light transmittance. Examples of these raw materials include the following (meth) acrylic acid esters (fluorine-free (meth) acrylic acid ester (a), fluorine-containing (meth) acrylic acid ester (b)), styrene-based compounds (c ), Vinyl esters (d), main chain cyclic fluorinated polymer-forming monomers (e), etc., and the core part is a homopolymer of these, or a copolymer comprising two or more of these monomers, And mixtures of homopolymers and / or copolymers. Among these, a composition containing (meth) acrylic acid esters as a polymerizable monomer can be preferably used.

  Specific examples of the polymerizable monomer listed above include (a) fluorine-free methacrylic acid ester and fluorine-free acrylic acid ester: methyl methacrylate (MMA), ethyl methacrylate, isopropyl methacrylate, methacrylic acid-tert -Butyl, benzyl methacrylate (BzMA), phenyl methacrylate, cyclohexyl methacrylate, diphenylmethyl methacrylate, tricyclo [5.2.1.0.6] decanyl methacrylate, adamantyl methacrylate, isobornyl methacrylate, norbornyl Examples thereof include methacrylate, and examples thereof include 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. 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 transmission member, which is a kind of optical member to be produced, 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 Japanese Patent No. 3332922 and the like are used. Deuterated polymethyl methacrylate (PMMA-d8), polytrifluoroethyl methacrylate (P3FMA), polyhexafluoroisopropyl 2-fluoroacrylate (HFIP 2-FA), etc. By using a polymer in which an H-bonded hydrogen atom (H) 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 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. Therefore, a solvent is used as a method for obtaining a polymer from the monomer. Preferred is a method obtained by bulk polymerization.

(Clad part forming material)
For the material of the cladding part, it is necessary 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. preferable. However, in the case where irregularities of the interface between the core part and the clad part are likely to occur due to the selection of the material or it is not preferable in production, a layer may be further provided between the core part and the clad part. For example, by forming a clad layer (inner clad 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 core part It is possible to correct the interface state between the clad part and the clad part. Of course, without forming the inner clad layer, the clad part itself can be made 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 fluorine resin obtained by polymerizing one or more polymerizable monomers containing 10% by mass or more of vinylidene fluoride can be preferably used.

  In addition, when a polymer is formed by melt extrusion to produce a clad part, it is necessary that the polymer has an appropriate melt viscosity. As for the melt viscosity, the molecular weight is used as a correlated physical property, and particularly has 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, since absorption loss also occurs due to moisture, 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. Moreover, when producing an inner clad layer, it is preferable to use a polymer having the same water absorption rate. 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 for obtaining a raw material resin. As a polymerization initiator, it can select suitably according to the monomer and polymerization method to be used, for example, benzoyl peroxide (BPO), tert- butyl peroxy-2-ethyl hexanate (PBO), di-tert-butyl. Examples thereof include peroxide compounds such as peroxide (PBD), tert-butyl peroxyisopropyl carbonate (PBI), and n-butyl-4,4-bis (tert-butylperoxy) valerate (PHV). 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2-methylpropane), 2,2′-azobis (2-methylbutane), 2,2′-azobis (2-methylpentane), 2,2′-azobis (2,3-dimethylbutane), 2,2 '-Azobis (2-methylhexane), 2,2'-azobis (2,4-dimethylpentane), 2,2'-azobis (2,3,3-trimethylbutane), 2,2'-azobis (2 , 4,4-trimethylpentane), 3,3′-azobis (3-methylpentane), 3,3′-azobis (3-methylhexane), 3,3′-azobis (3,4-dimethylpentane), 3,3′-azobis (3-ethylpentane , Dimethyl-2,2′-azobis (2-methylpropionate), diethyl-2,2′-azobis (2-methylpropionate), di-tert-butyl-2,2′-azobis (2- And azo compounds such as methyl propionate). Of course, the polymerization initiator is not limited to these, and two or more kinds may be used in combination.

(Chain transfer agent)
The polymerizable composition for forming a core part and the polymerizable composition for forming a clad part preferably contain a chain transfer agent. The chain transfer agent is mainly used for adjusting the molecular weight of the polymer. When the polymerizable composition for forming the clad part and the core part contains a chain transfer agent, the polymerization rate and the degree of polymerization are more controlled by the chain transfer agent when forming a polymer from the polymerizable monomer. And the molecular weight of the polymer can be adjusted to a desired molecular weight. For example, when the obtained preform is drawn by stretching to obtain an optical transmission member, the mechanical properties at the time of stretching can be adjusted to a desired range by adjusting the molecular weight, which also improves productivity. Contribute.

  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 (J. BRANDRUP and EH IMMERGUT edition, 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)
A refractive index adjusting agent may be contained in the core portion forming material or the clad portion forming material. By providing a distribution in 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-described 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 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. 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 member 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. 3332922 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 optical transmission line, which is an optical member, can be changed to a desired value. The amount added 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. As a method for imparting the refractive index distribution, it can be obtained by thermal diffusion or multilayer coextrusion as described above.

(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, it is possible to amplify the attenuated signal light with the excitation light and improve the transmission distance. For example, it can be used as an optical 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)
An optical transmission member having a protective layer around the optical transmission member has higher mechanical strength and is easier to handle than an optical transmission member that does not have a protective layer. As the protective layer forming material used for the optical transmission member, a material that does not cause thermal damage (for example, deformation, modification, thermal decomposition, etc.) to the optical transmission member to be coated is selected. Therefore, it is preferable to use a polymer that can be cured at a temperature not higher than the glass transition temperature Tg (° C.) of the polymer forming the optical transmission member and not lower than (Tg−50) ° C. 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 light transmission member is formed of 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, for example, 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.

  Moreover, the liquid rubber which lose | disappears the fluidity | liquidity and hardens | cures by showing fluidity | liquidity at room temperature and heating can be used as a protective layer formation material. 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.

  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 polymers listed above are not particularly limited to the above materials as long as they can be molded at a glass transition temperature Tg (° C.) or lower of the polymer of the optical transmission member, particularly the polymer of the core portion. Copolymers and mixed polymers other than these can also be used.

(Functional additives)
In some cases, a functional additive is added to the material for forming the core portion, the clad portion, and the protective layer. Examples of the additive include a conductive material for preventing static charge, a flame retardant material, and a coloring dye or pigment. Although the specific example of an additive is given to the following, it is not limited to this. Examples of the conductive substance include noble metal fine particles such as tin, zinc alloy powder and silver, and examples of the flame retardant substance include metal hydroxides such as magnesium hydroxide and aluminum hydroxide. As a coloring pigment added for identification, carbon black, titanium oxide, zirconium oxide or the like is preferably used. Carbon black is low-cost, and when used as a coating material for optical transmission members, it has antistatic properties in addition to coloring, making it difficult to be charged with static electricity and absorbing in the near-infrared region, thereby blocking ambient light. It is particularly preferable because it has many advantages such as being excellent in closeness and suppressing the light released to the outside of the optical transmission path from being returned again by bending or the like.

  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 or the outermost layer in contact with the core portion, because the core portion is damaged or workability is deteriorated. In order to improve the dispersion workability of the fine particle additive, it is preferable to knead the master batch and the base resin for the coating material using a master batch in which the additive is filled in the resin at a high concentration.

  A multi-core optical transmission member 85 was created using the melt extrusion apparatus 80 of FIG. PMMA was used for the core portion forming material 26, PVDF was used for the cladding portion forming material 27, and PVDF with carbon black added to the protective layer forming material 28 was used. As the extrusion apparatus, five first and second extrusion apparatuses 82a and 82b, and one third extrusion apparatus 83c and coextrusion die 81 were used. The co-extrusion die 81 can form a core part having a circular cross-sectional shape and five pairs of clad parts covering the core part with a uniform thickness, and further surround the five pairs of core parts and the clad part. In addition, a protective layer having a rectangular cross-sectional shape can be formed. The melt of the core part forming material 26, the cladding part forming material 27, and the protective layer forming material 28 stored in the first to third extrusion apparatuses 82 a to 82 c was extruded into the coextrusion die 81. The multi-core optical transmission member precursor 84 extruded from the co-extrusion die 81 was subjected to a cooling process, a heating process of the heating furnace 22 and a stretching process to obtain a multi-core optical transmission member 85 (FIG. 8). The cross-sectional shape of the multi-core optical transmission member 85 was a rectangle having a length of 200 μm and a width of 1000 μm. The five optical transmission lines composed of the core part 85a and the clad part 85b are arranged at equal intervals on the cross section of the multi-core optical transmission member 85, and the cross-sectional shape of the core part is formed in a circular shape, and its diameter is It was 100 μm. Further, the cross-sectional shape of the clad portion 85b was a circle substantially similar to the core portion 85a. The transmission loss of the multi-core optical transmission member 85 in the light source with a wavelength of 850 nm was 0.02 dB / cm.

  A multi-fiber optical transmission member 90 was produced using the melt extrusion apparatus 80 of FIG. PMMA was used as the core portion forming material 26, and five first extruders 81a and one third extruder 83c were used as the extruder. As the co-extrusion die 81, a co-extrusion die 81 capable of forming the cross-sectional shape of the core portion in a circular shape and the cross-sectional shape of a clad portion in a rectangular shape was used. The melt of the core part forming material 26 and the clad part forming material stored in the first and third extrusion apparatuses 82 a and 82 c was extruded to the coextrusion die 81. The multi-core optical transmission member precursor extruded from the co-extrusion die 81 is subjected to a cooling process, a heating process and a stretching process, and a multi-core optical transmission member 90 comprising a clad portion 90b and five core portions 90a (FIG. 9). Got. The cross-sectional shape of the clad portion 90b was a rectangle having a length of 200 μm and a width of 1000 μm. Moreover, the core part 90a was arrange | positioned at equal intervals inside the clad part 90b, and each cross-sectional shape was a circle | round | yen with a diameter of 100 micrometers. In addition, the transmission loss of the multi-core optical transmission member 90 in the light source with a wavelength of 850 nm was 0.03 dB / cm.

It is the schematic of the optical transmission member manufacturing apparatus used for the melt extrusion method of this invention. It is an enlarged view of the coextrusion die of FIG. It is a cross-sectional view of the optical transmission member manufactured by the optical transmission member manufacturing apparatus. It is the schematic of the optical transmission member manufacturing apparatus used for the melt extrusion method of this invention. It is an enlarged view of the coextrusion die of FIG. It is a cross-sectional view of the optical transmission member manufactured by the optical transmission member manufacturing apparatus. It is the schematic of the multi-fiber optical transmission member manufacturing apparatus used for the melt extrusion method of this invention. It is a cross-sectional view of the multi-core optical transmission member manufactured by the multi-core optical transmission member manufacturing apparatus. It is a cross-sectional view of the multi-core optical transmission member manufactured by the multi-core optical transmission member manufacturing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 70, 80 Melt extrusion apparatus 11 Core part formation material extrusion apparatus 12 Cladding part formation material extrusion apparatus 13 Protective layer formation material extrusion apparatus 14, 71, 81 Coextrusion die 18 Optical transmission member precursor 23 Optical transmission member 26 Core part forming material 27 Clad part forming material 28 Protective layer part forming material 30 Core part die 31 Clad part die 32 Protective layer die 35 to 37 Temperature controller 43 Core part forming part 49 Clad part forming part 53 Protective layer Formation part 72 Optical transmission member precursor 73, 73a-73d Optical transmission member 82a-82c 1st-3rd extrusion apparatus 84 Multi-fiber optical transmission member precursor 85 Multi-fiber optical transmission member 90 Multi-fiber optical transmission member

Claims (16)

In a method for producing a plastic optical transmission member, which is formed by a melt extrusion method for extruding a resin melt from a die, and a melt-extruded core part outer periphery is formed by melt extrusion with a clad part having a lower refractive index than the core part,
A method for producing a plastic optical transmission member, characterized in that the clad portion having a cross section of any one of a polygon, a closed curve, or a figure combining straight lines and curves is formed around the core portion.   2. The method of manufacturing a plastic optical transmission member according to claim 1, wherein the cross sections of the core portion and the clad portion are formed in different shapes. Extruding the melt of the protective layer forming material from the die,
3. The plastic optical transmission member according to claim 1, wherein a protective layer whose cross section is a polygon, a closed curve, or a figure combining straight lines and curves is formed around the clad portion. Manufacturing method.   4. The method for manufacturing a plastic optical transmission member according to claim 3, wherein the cross section of the clad portion and the protective layer are formed in different shapes.   5. The method for manufacturing a plastic optical transmission member according to claim 1, wherein the cross section of the core portion is formed in a circular shape.   5. The method for manufacturing a plastic optical transmission member according to claim 1, wherein the cross section of the core portion is formed in a rectangular shape.   The plastic optical transmission member according to any one of claims 1 to 6, wherein the core portion is formed in a refractive index distribution type in which the refractive index continuously increases toward a center of a transverse section thereof. Manufacturing method.   7. The plastic optical transmission member according to claim 1, wherein the core portion is formed in a refractive index distribution type in which the refractive index increases stepwise toward the center of the transverse section. Manufacturing method.   The method of manufacturing a plastic optical transmission member according to claim 1, wherein the core portion includes light scattering particles.   The plastic light according to any one of claims 1 to 9, wherein the core portion is formed with (meth) acrylic acid ester as a main component, and the cladding portion is formed with a fluororesin as a main component. A method for manufacturing a transmission member. The method for producing a plastic optical transmission member according to any one of claims 1 to 10, wherein the cross-sectional area is 1 x 10 ⁴ µm ² or more.   The method of manufacturing a plastic optical transmission member according to claim 1, wherein the plurality of core portions are formed inside the clad or the plurality of cores and clad portions are formed inside the protective layer.   The method of manufacturing a plastic optical transmission member according to claim 12, wherein the plurality of core portions are formed in a clad structure with a sea-island structure.   The method for producing a plastic optical transmission member according to claim 1, wherein a light-shielding material is used for at least one of the clad part and the protective layer.   15. The method for manufacturing a plastic optical transmission member according to claim 12, wherein the cross sections of the plurality of core portions are formed in different shapes. The method of manufacturing a plastic optical transmission member according to any one of claims 12 to 15, wherein the plurality of core portions are formed of different materials.

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