JP2007127882A - Method of manufacturing plastic optical member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing plastic optical member capable of easily and precisely manufacturing a plastic optical member in which a core and a protective layer have rectangular cross-sectional shapes. <P>SOLUTION: The bar-shaped core 20 having a polygonal cross-section is formed. A clad 21 having a fitting hole 21a is formed. The core 20 is fitted into the fitting hole 21a. The protective layer 22 made of an angular bar having a round fitting hole 22a is formed on the center. The clad 21 having the core is fitted into the fitting hole 22a of the protective layer 22 and a preform 23 is formed. The preform 23 is heat-stretched in a heating furnace. In the heat-stretching, heating conditions are controlled such that a cross-sectional outline of the optical member after the stretching comes to substantially similar to the cross-sectional outline of the preform 23. By the heat-stretching, the optical member 27 in which the core and the protective layer have rectangular cross-sectional shapes can be easily and precisely formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  Conventionally, optical members for propagating light have high hardness and are chemically stable, have low transmission loss, and have advantages such as excellent transparency and moldability. in use. Examples of the quartz-based optical member include an optical fiber, an optical waveguide, a lens, and an electronic component depending on the use and shape. Recently, however, plastic optical members have been attracting attention because they have advantages such as excellent workability and transparency comparable to quartz optical members, and can be reduced in weight. This plastic optical member has the disadvantage that the transmission loss is slightly larger than that of the quartz-based material because all of the material is a polymer, but in addition to the above-mentioned advantages, it exhibits good flexibility and is also more flexible than the quartz-based material. Since it has the advantage that a large aperture is possible, the use as an optical member for a short distance, in which the magnitude of transmission loss is not a serious problem, is being studied (see, for example, Patent Document 1). .

  The plastic optical member has a core made of plastic and used as an optical transmission path, and a clad made of plastic having a refractive index lower than that of the core. Furthermore, a protective layer for the purpose of improving thermal damage, water resistance, etc. with respect to the core and the clad is formed on the outer periphery of the clad as needed.

  A core having a refractive index distribution in which the refractive index gradually changes from the center of the diameter toward the outside is preferably used. Then, it is classified into a graded index (GI) type, a step index (SI) type, a multi-step index (MSI) type, etc., depending on the difference in refractive index distribution. The GI type plastic optical member has a refractive index that continuously decreases from the center of the diameter toward the outside, and the SI type plastic optical member has a constant refractive index without distribution. The MSI type plastic optical member has a stepwise refractive index distribution intermediate between the GI type and the SI type.

  Regardless of the difference in refractive index distribution, a plastic optical member is produced by, for example, forming a pipe-like clad (hereinafter referred to as a clad pipe) by a melt extrusion method, and then forming a core in the clad pipe. A method is mentioned. And as a manufacturing method of a GI type plastic optical member, after polymerizing the polymer which comprises an optical member by a polymerization method and producing preform (base material), this preform is heat-melt-stretched with a heating furnace, for example. A method (for example, refer to Patent Document 2) is known. In general, many plastic optical members have a circular outer diameter cross section. However, depending on the application, it may be desirable that the outer shape is not a circle but a rectangle or an ellipse. Thus, as a method of manufacturing an optical member having a non-circular outer shape as described above, for example, after manufacturing an optical member having a circular cross-sectional outer shape, this is processed to manufacture a plastic optical member having an elliptical cross-section. A method has been proposed (see, for example, Patent Document 3).

In addition, plastic optical members can be used as they are, but in applications such as parallel signal transmission, image capture, and image output, a plurality of plastic optical members are closely arranged or bound in a cylindrical or prismatic shape. Often used. As a method of forming an aggregate using a plurality of such single optical members, a method of thermocompression bonding a plurality of optical members in a parallel state (for example, see Patent Document 4), a photoresist or etching is used. In addition, a method for manufacturing an optical member (see Patent Document 5), and a method for manufacturing an optical member by inserting a plurality of cores into a clad in which a plurality of hollow portions are formed in parallel (for example, Patent Document 6). And a method of manufacturing a plurality of MSI type plastic optical members by fusing and integrating them in the outermost layer (for example, see Patent Document 7).
JP-A-61-130904 Japanese Patent No. 3332922 Japanese Patent Application No. 2004-019968 JP-A-6-317716 JP 2001-166165 A JP 2005-003899 A Japanese Patent Laid-Open No. 11-52147

  However, among the patent documents listed above, Patent Document 6 is a method for producing a quartz-based optical member, and is not a description regarding a plastic optical member. In any of the above methods, there is a problem in that, when an optical member is manufactured, a special device is required for processing, resulting in an increase in equipment cost. In addition, when a processing apparatus is used corresponding to various optical members, the manufacturing time is increased and the manufacturing cost is increased. In addition, as in Patent Document 3, when an optical member having a desired cross section is formed, fine processing is required, so that it is difficult to ensure the accuracy and the manufacturing efficiency is reduced. Have the problem of In addition, any of the above methods has a problem that it takes time and labor to accumulate a plurality of optical members at a high density and is not suitable for mass production.

  In addition, the conventional optical fiber has a round cross-sectional shape, and is easy to roll and bend when connecting to a planar waveguide, connecting and arranging on a substrate, arranging on a matrix, etc. There is a problem that connection work becomes difficult.

  An object of the present invention is to provide a manufacturing method capable of mass-producing a plastic optical member, which can be easily connected and arranged, with high accuracy and at low cost.

  The plastic optical member manufacturing method of the present invention includes a core having a polygonal cross-sectional shape and serving as an optical transmission part, a clad disposed on the outer periphery of the core and having a lower refractive index than the core, and an outer periphery of the clad A first step of forming a plastic first preform including a protective layer having a polygonal cross-sectional shape, wherein the first preform is heated and stretched in a direction perpendicular to the cross-section, It has the 2nd process of forming the 1st extending body which has the cross-sectional shape of a substantially similar shape with the cross section of 1 preform. The first step is characterized in that the first preform is formed with a polygonal cross-sectional shape of the clad. Further, the first step is characterized in that the first preform is formed with a cross-sectional shape including an outer periphery of the clad being substantially circular or substantially elliptical. Further, the first step is characterized in that the first preform is formed by arranging a plurality of the cores in a line in the transverse section. The core is composed of a plurality of types of materials or shapes. Further, the clad is composed of a plurality of types of materials or shapes. The protective layer is composed of a plurality of types of materials or shapes. Furthermore, a plurality of the protective layers are formed.

In addition, the present invention includes a third step of heating and stretching the first stretched body to form a second stretched body having a cross-sectional shape substantially similar to the cross section of the first stretched body. To do. Furthermore, the present invention provides a fourth step of forming a second preform by bundling a plurality of the first stretched bodies or the second stretched bodies, and heat-stretching the second preform, and a cross section of the second preform. And a fifth step of forming a third stretched body having a substantially similar cross-sectional shape. Further, the refractive index distribution is such that the refractive index gradually decreases from the center of the cross section of the core toward the outside. Moreover, the cross-sectional area in the cross section of the said core is 400 micrometers ² or more, It is characterized by the above-mentioned.

  According to the method for producing a plastic optical member of the present invention, the preform is formed with the cross-sectional shape of the core and the protective layer being polygonal, and the shape of the cross-section of the plastic optical member which is the final product form is the shape of the preform. Since it is heated and stretched so that it has a shape that is almost similar to the cross-sectional shape, plastic optical members with a polygonal cross-sectional shape of the core and protective layer can be manufactured easily and without using special manufacturing equipment. can do. Therefore, when connecting or arranging to an optical waveguide or a substrate, connection or arrangement can be easily performed. In the case of a multi-core structure, a high-density multi-core plastic optical member can be easily and inexpensively manufactured by changing the draw ratio or by heating and drawing in multiple steps.

  In addition, since the protective layer covering the cladding is provided on the outer periphery of the cladding, it is not necessary to form the protective layer after heating and stretching, thereby simplifying the production. By providing the protective layer with a multilayer structure, water resistance, scratch resistance and the like can be imparted according to the usage pattern. Furthermore, a wide variety of optical members can be easily manufactured by configuring the core or the clad from the same type or a plurality of types of optical materials. In addition, a graded index type in which the refractive index continuously decreases from the center to the outside in the cross section of the core, or a multi-step index type in which the refractive index gradually decreases from the center to the outside in the cross section of the core. By using this, an optical member having excellent transmission characteristics can be manufactured.

  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.

  As shown in FIG. 1, the method for producing a plastic optical member of the present invention is roughly composed of a preform forming step 11 and a heat stretching step 12. The preform forming process 11 includes a core forming process 13, a cladding forming process 14, a protective layer forming process 15, and an assembly process 16.

  First, the core 20 is formed in the core formation step 13. Further, the clad 21 is formed in the clad forming step 14. Then, in the protective layer forming step 15, the protective layer 22 is formed. Next, in the assembly step 16, the core 20, the clad 21, and the protective layer 22 are fitted to obtain a preform 23.

  In the heating and stretching step 12, the preform 23 is placed in the heating furnace 30 as shown in FIG. Then, after the preform 23 is heated by the heating furnace 30 to soften a part of the preform 23, the optical member 27 is drawn (stretched) in the longitudinal direction starting from the tip 23a of the softened portion. Get. Here, the longitudinal direction is a direction perpendicular to a plane in which the cross sections of the core and the clad are the same or similar, that is, an axial direction. Although the said softening temperature is not specifically limited, It is preferable that it is a temperature of 80-500 degreeC, More preferably, it is 180-240 degreeC, Most preferably, it is 190-220 degreeC. The wire diameter monitor 32 monitors the outer diameter of the optical member 27. In accordance with the monitoring result, the position of the preform 23 in the heating furnace 30, the temperature of the heating furnace 30, the winding speed of the winding device 33, and the like are adjusted as appropriate so that the outer diameter of the optical member 27 is always constant. To. The winding device 33 winds the drawn optical member 27 around the core material 33a. Thus, the optical member 27 wound up and stored in a roll shape is obtained.

  The softening in the heat stretching in the present invention refers to a state in which a substantially similar cross section is obtained when the non-circular preform 23 is heat stretched, and the melting in the heat stretching in the present invention means When the non-circular preform is stretched by heating, the substantially similar shape is not maintained and the cross-section is substantially circular. Since the temperature at which the preform softens depends on the temperature characteristics of the polymer and cannot be specified unconditionally, the temperature at which the preform softens at the time of heating and stretching is determined for each polymer by experiments, etc. Heat stretching is performed.

  Thereby, an optical member 27 having a shape substantially similar to the cross section of the preform 23 is obtained. The obtained optical member 27 may be coated with a resin in order to protect the outer peripheral surface, and a coating layer may be further formed. This coating layer may be formed by applying radiation after application of the radiation curable resin, or may be formed by extrusion molding of a thermoplastic resin. In addition, when forming a coating layer, you may carry out as a separate line from the manufacturing process of an optical member, and you may incorporate in the manufacturing process of an optical member by performing after a heating extending process.

  FIG. 3A shows an example of a change in cross-sectional shape in the optical member manufacturing process. The core 20 is a member serving as a light transmission path, and is composed of a square bar. The clad 21 has a lower refractive index than the core 20 and is a hollow member that totally reflects light at the interface with the core 20, and is made of a round bar having a fitting hole 21a formed of a square hole as a center. The protective layer 22 is composed of a square bar having a fitting hole 22a formed of a round hole as a center. Each of these preform pieces is obtained by melt extrusion.

  Next, after inserting the core 20 into the fitting hole 21a and fitting the core 20 and the clad 21 together, the core 20 and the clad 21 are fitted into the fitting hole 22a of the protective layer 22, and FIG. A preform 23 as shown in FIG.

  Next, either one of the ends of the preform 23 is fixed. This fixed end portion becomes an end portion on the stretching side during heating and stretching. As a result, the clad 21 is not dropped from the protective layer 22, the core 20 is not dropped from the clad, and the fitting position is not shifted, and the preform 23 can be stretched in the heating furnace 30. . The end is fixed by a fixing member provided at one end of the fitting holes 21a and 22a. Examples of the fixing member include commercially available heat-resistant tapes and adhesives. However, it is preferable to select in consideration of the affinity with the polymer material forming the preform 23 because excellent adhesiveness at the interface can be obtained. In addition, instead of using a fixing member, one end of the preform 23 may be heat-sealed. Any heating device may be used as long as the fixed end portion can be directly heated and fused. For example, a hot plate or an electric heater is used. In this way, a single-core type preform 23 having the protective layer 22 as the outermost layer is obtained. By optically stretching the preform 23 in a heating furnace, an optical member 27 having a shape substantially similar to the preform 23 is obtained.

  In addition, the manufacturing method of the core 20, the clad 21, and the protective layer 22 is not specifically limited. For example, the core 20 may be formed by injecting PMMA into a clad 21 made of a clad pipe formed by melt extrusion using PMMA or PVDF and then radical polymerization. Then, the preform 23 is formed by putting the clad 21 on which the core 20 is formed in the protective layer 22. Further, a melt extrusion apparatus equipped with a composite type nozzle capable of coextrusion is used to form a core 20 provided with a clad 21 on the outer periphery, and this is placed in a protective layer 22 to form a preform 23. May be. Further, the preform 23 may be formed almost simultaneously by co-extrusion of the core 20, the clad 21 and the protective layer 22 by a melt extrusion apparatus.

  In this embodiment, an example in which the refractive index distribution is made uniform in the radial direction of the core has been shown, but instead of this, the GI type in which the refractive index gradually decreases from the center of the core toward the outside, An SI type having no distribution of the rate or an MSI type having a stepwise refractive index distribution between the GI type and the SI type may be used. Further, when the core portion has a refractive index distribution in which the refractive index increases continuously or stepwise as it goes to the center of the cross section, the distribution shape is not limited. As a specific example of the refractive index distribution shape of the core portion, there is one that changes continuously or stepwise from the center of the cross section of the core portion to a concentric circle shape or a concentric polygon shape. In this case, a refractive index adjusting agent is added to the polymer for forming the core 20, the dispersion degree and concentration thereof are adjusted, and layers having different refractive indexes that express a desired refractive index distribution are laminated. It is obtained by a diffusion method or the like. Specific examples include a production method by radical polymerization described in Japanese Patent No. 3332922 and a melt extrusion method described in Japanese Patent Application No. 2004-354786.

  Note that the cross-sectional shape of the fitting hole 21 a of the clad 21 only needs to substantially match the outer shape of the cross-section of the core 20. The cross-sectional shape of the core 20 is a polygon other than a square, such as a rectangle, a triangle, a pentagon, and a hexagon, but a square is preferably used. Similarly, the cross-sectional shape of the fitting hole 22a of the protective layer 22 only needs to substantially match the outer shape of the cross-sectional surface of the clad 21, and either a polygon, a closed curve, or a figure composed of a straight line and a curve is adopted. Is done.

  As shown in FIGS. 3B and 3C, in addition to heating and stretching the optical member 27 from the preform 23, the preform 23 shown in FIG. An intermediate preform 40 as shown in the figure may be formed, and the intermediate preforms 40 may be assembled to form a preform aggregate 41 as shown in FIG. Then, by heating and stretching the preform aggregate 41 as a preform, as shown in FIG. 4C, an optical member 42 having a plurality of cores 42a and clads 42b in one protective layer 42c is obtained. . The number of the cores 42a and the clads 42b disposed in the optical member 42 may be plural, and the arrangement direction is not limited to a linear one-dimensional direction in a direction going straight in the stretching direction, but also a two-dimensional planar shape. It may be a direction. The heat stretching for reducing the size of the intermediate preform 40 is not limited to one time, and may be performed a plurality of times.

  When the preform aggregate 41 is configured, the intermediate preforms 40 are joined by heating, for example. Heating may be performed before heat stretching or may be performed by heat fusion during heat stretching. When heat-sealing at the time of heat stretching, each intermediate preform 40 is held with a clamp or an adhesive tape.

  Each of the core, the clad, and the protective layer may be configured not only by one but also by combining a plurality. For example, FIG. 5 shows an example of a preform 56 in which four protective rods 51 to 54 are combined to form the protective layer 55. First, as shown to (A), the clad 57 which consists of a square pipe, and the square bars 51-54 used as a protective layer are obtained by the melt extrusion method. Next, as shown in (B), a polymer is injected into the clad 57 and polymerized to form the core 58. The core may also be formed by melt extrusion and fitted. Next, as shown in (C), the preform 56 is configured by combining the clad 57 and the square bars 51 to 54. This preform 56 is heated and stretched to obtain an optical member 60 as shown in (D).

  In addition, when a plurality of cores and claddings are formed in one protective layer, the interval between the cores when the optical member is a product is arbitrarily set by appropriately changing the size of the protective layer. be able to. Moreover, you may arrange | position a square bar etc. as a core space | interval adjustment material between each protective layer instead of changing the size of a protective layer. The spacing adjusting material is preferably the same material as the protective layer. An optical member capable of arbitrarily changing the interval between the cores is obtained by heating and stretching the preform thus configured. Further, a plurality of protective layers may be formed.

  Details of the manufacturing conditions in the embodiment according to the present invention will be described below. In the present invention, when a preform is produced using a plurality of preform pieces such as a core, a clad, and a protective layer, the number of preform pieces is not particularly limited, but two or more and 100 pieces. The number is preferably 2 or less, more preferably 2 or more and 50 or less, and most preferably 2 or more and 10 or less. Further, the arrangement is not particularly limited, and they may be arranged adjacent to each other or bound together.

  Further, the preform piece or the intermediate preform piece used for forming the preform is joined by welding or adhesion. When a plurality of preform pieces are arranged or bundled, an adhesive (for example, urethane compound, epoxy compound, acrylic compound, etc.) may be used at the interface. However, the interfaces and the like may be bonded using a heating and pressing method, an ultrasonic welding method, a vibration welding method, or the like. In addition, welding or adhesion may be performed by heat at the time of heat stretching in addition to being performed before heat stretching.

  When a plurality of preform pieces or intermediate preform pieces constituting the preform are bundled, the preform may be stretched while being aligned without bonding. In this case, the surfaces of the plurality of preform pieces or intermediate preform pieces are bonded to each other at the stage of heat softening in the heating and stretching step performed when forming the optical member, and are substantially similar to the cross section of the preform. An optical member having a cross-sectional shape can be obtained. This method has the advantage that the bonding step can be omitted.

  Further, the preform pieces may be used in a mixture of different shapes or different optical characteristics. As a method of manufacturing preform pieces having different optical characteristics, the constituent materials can be changed, the refractive index distribution can be changed using a refractive index adjusting agent described later, and additives can be selected. Although there is a method of developing the optical characteristics, it is not particularly limited.

A core is demonstrated among the optical members of this invention. The cross-sectional area in the cross section of the core is preferably 400 μm ² or more. In this case, multimode transmission is possible, and connection work and the like are facilitated. As the polymerizable monomer that becomes the raw material of the core, 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) ), Styrene compounds (c), vinyl esters (d), fluoropolymers (e) containing a cyclic structure in the main chain, bisphenol A, which is a raw material for polycarbonates, and the like, and polymerized as a polymerizable compound And a norbornene-based resin can be exemplified, and the core can be formed from these homopolymers, a copolymer composed of two or more of these monomers, and a mixture 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 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, benzyl methacrylate (BzMA), phenyl methacrylate, cyclohexyl methacrylate, diphenylmethyl methacrylate, tricyclo [5.2.1.0.2,6] decanyl methacrylate, adamantyl methacrylate, isobornyl methacrylate, nor Examples include bornyl methacrylate, and examples 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, Examples include 3,3,4,4-hexafluorobutyl methacrylate. Furthermore, (c) styrene compounds include styrene, α-methylstyrene, chlorostyrene, bromostyrene, and the like. (D) Examples of vinyl esters include vinyl acetate, vinyl benzoate, vinyl phenyl acetate, vinyl chloroacetate, etc. As a polymer having a cyclic structure in the main chain as shown in (e), originally has a cyclic structure. Examples thereof include polymers obtained by polymerizing monomers, polymers having a cyclic structure formed in the main chain of an amorphous structure by cyclopolymerization, and examples thereof include polyperfluorobutanyl vinyl ether and JP-A-8-334634. From the viewpoint of transmission characteristics, polymers having an alicyclic or heterocyclic ring in the main chain described in JP-A No. 2002-1972, and those described in JP-A No. 2002-71972 and Japanese Patent Application No. 2004-186199 are preferable. 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 core polymer consisting of a monomer alone or a copolymer is equal to or higher than that of the cladding. A particularly preferred polymer is polymethyl methacrylate (PMMA), which is a transparent resin.

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

  Of the optical member of the present invention, the cladding will be described. As the cladding material, it is preferable to use a material having a lower refractive index than that of the core and having excellent adhesion to the core because light transmitted through the core is totally reflected at the interface between them. However, if irregularities are likely to occur at the interface between the core and the clad due to the selection of the material, or if it is not preferable in terms of manufacturing suitability, an additional layer is provided between the core and the clad to ensure consistency. May be improved. In this case, for example, when an inner cladding layer made of a polymer having the same composition as the matrix of the core is formed at the interface with the core (that is, the inner wall surface of the hollow tube), the interface state between the core and the cladding can be corrected. it can. The details of the inner cladding layer will be described later. Of course, the clad itself may be formed of a polymer having the same composition as the core matrix without forming the inner clad layer.

  As the clad material, a material excellent in toughness and heat-and-moisture resistance is preferably used. For example, suitable materials include homopolymers or copolymers of fluorine-containing monomers. 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 is preferably used.

  In addition, when a polymer is formed by melt extrusion to produce a clad, 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 1 to 1,000,000, more preferably in the range of 5 to 500,000.

  Furthermore, it is preferable to prevent moisture from entering the core. For this purpose, it is preferable to use a polymer having a low water absorption rate as a material for the cladding. That is, it is preferable to produce a clad 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 cladding is formed using less than 1.5% polymer, more preferably less than 1.0% polymer. Moreover, it is preferable to use a polymer having the same water absorption rate when the inner clad layer is formed. 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.

  When the core and / or cladding is made from a polymer polymerized from a polymerizable monomer, a polymerization initiator is used during the polymerization. As a polymerization initiator, it can select suitably according to the monomer and polymerization method to be used, for example, benzoyl peroxide (BPO), tert- butyl peroxy-2-ethyl hexanate (PBO), di-tert-butyl. Examples thereof include peroxide compounds such as peroxide (PBD), tert-butyl peroxyisopropyl carbonate (PBI), and n-butyl-4,4-bis (tert-butylperoxy) valerate (PHV). 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2-methylpropane), 2,2′-azobis (2-methylbutane), 2,2′-azobis (2-methylpentane), 2,2′-azobis (2,3-dimethylbutane), 2,2 '-Azobis (2-methylhexane), 2,2'-azobis (2,4-dimethylpentane), 2,2'-azobis (2,3,3-trimethylbutane), 2,2'-azobis (2 , 4,4-trimethylpentane), 3,3′-azobis (3-methylpentane), 3,3′-azobis (3-methylhexane), 3,3′-azobis (3,4-dimethylpentane), 3,3'-azobis 3-ethylpentane), dimethyl-2,2′-azobis (2-methylpropionate), diethyl-2,2′-azobis (2-methylpropionate), di-tert-butyl-2,2 ′ -Azo compounds such as azobis (2-methylpropionate). In addition, a polymerization initiator is not limited to these, Furthermore, you may use 2 or more types together.

  The core-forming polymerizable composition and the clad-forming polymerizable composition preferably contain a chain transfer agent. Chain transfer agents are mainly used to adjust the molecular weight of the polymer. When the polymerizable composition for forming the cladding and the core each contains a chain transfer agent, the polymerization rate and the degree of polymerization can be more controlled by the chain transfer agent when forming the polymer from the polymerizable monomer, The molecular weight of the polymer can be adjusted to a desired molecular weight. For example, when forming the optical member by drawing the obtained preform by stretching, 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 a chain transfer agent, according to the kind of polymerizable monomer used together, a kind and addition amount can be selected suitably. The chain transfer constant of the chain transfer agent for each monomer can be referred to, for example, Polymer Handbook 3rd Edition (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 the chain transfer agent include alkyl mercaptans (eg, n-butyl mercaptan, n-pentyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, tert-dodecyl mercaptan), thiophenols (eg, thiophenol, m- Bromothiophenol, p-bromothiophenol, m-toluenethiol, p-toluenethiol, etc.) are preferably used. In particular, it is preferable to use an alkyl mercaptan such as n-octyl mercaptan, n-lauryl mercaptan, and tert-dodecyl mercaptan. A chain transfer agent in which a hydrogen atom of a C—H bond is substituted with a deuterium atom (D) or a fluorine atom (F) can also be used. Of course, the chain transfer agent is not limited to these, and two or more of these chain transfer agents may be used in combination.

  The core polymerizable composition preferably contains a refractive index adjusting agent. 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. In addition, you may make a clad polymerizable composition contain a refractive index regulator as needed. 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. At this time, the difference in refractive index is preferably 0.005 or more. However, a refractive index distribution structure can also be introduced by using two or more kinds of polymerizable monomers for forming the core and having a distribution of the copolymerization ratio in the core without using a refractive index adjusting agent. .

The dopant has the property that the polymer containing it has a higher refractive index than the additive-free polymer. These have a difference in solubility parameter of 7 (cal / cm ^{3) in} comparison with a polymer produced by monomer synthesis as described in Japanese Patent No. 3332922 and Japanese Patent Laid-Open No. 5-173026. ) Within ^1/2 , the difference in refractive index is 0.001 or more, and the polymer containing this has the property that the refractive index changes compared to the additive-free polymer. Any one that can stably coexist and is stable under the polymerization conditions (polymerization conditions such as heating and pressurization) of the polymerizable monomer that is the above-described raw material can be used.

  Using the above-mentioned properties as a dopant that can stably coexist with a 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. For example, a dopant is contained in the core-forming polymerizable composition, the progress of polymerization is controlled by radical polymerization in the step of forming the core, the dopant concentration is inclined, and the core is refracted based on the dopant concentration distribution. A method of forming a rate distribution structure is mentioned. This refractive index distribution structure includes a GI type and an MSI type, and these GI type and MSI type optical members have a wide transmission band.

  The dopant may be a polymerizable compound, and when a dopant of the polymerizable compound is used, a copolymer containing this as a copolymerization component has a higher refractive index than a polymer not containing this. Use those with properties. Examples of such a copolymer include MMA-BzMA copolymer.

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

  By adjusting the concentration and distribution of the dopant, the refractive index of the 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 dopants may be added.

  In addition to the dopant and the like, the core, the clad, or part of them may contain an additive in the polymerizable composition constituting the core as long as the optical transmission performance is not deteriorated. For example, a stabilizer can be added to the core or a part thereof for the purpose of improving the weather resistance and durability. In addition, for the purpose of improving optical transmission performance, a stimulated emission functional compound for optical signal amplification can also be added. By adding the 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 added to the core monomer, the cladding, or a part thereof by polymerizing after being added to the raw material monomer.

  A coating layer is preferably provided on the outer periphery of the heat-stretched protective layer by extrusion molding of a molten resin or the like for the purpose of improving waterproofness and durability. The material of the coating layer is not particularly limited, and for example, a thermoplastic resin is used. Particularly, a polyolefin-based resin is preferably used because it has good chemical resistance and flexibility. Examples of the polyolefin-based resin include polymers such as ethylene, propylene, and α-olefin. Examples of the α-olefin include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-peptene, and 1-octene. Examples of these polymers include polyethylene. And copolymers of ethylene and propylene, copolymers of ethylene and α-olefin, polypropylene, copolymers of propylene and α-olefin, polybutene, polyisoprene and the like. In addition, the polyolefin resin may be blended in an appropriate combination in consideration of the physical properties to be obtained. In addition, although the molecular weight and molecular weight distribution of polyolefin resin are not specifically limited, The weight average molecular weight is 5000-5 million normally, Preferably it is 20000-300000. And the molecular weight distribution shown by weight average molecular weight Mw / number average molecular weight Mn is 2-80, Preferably it is set to 2-40.

  Further, after applying a radiation curable resin or a thermosetting resin, it may be cured by irradiating with radiation or applying heat to form a coating material. Examples of the radiation curable resin include acrylic-modified unsaturated polyester, epoxy resin, and polyurethane, and examples of the thermosetting resin include phenol resin, melamine resin, and diacryl phthalate resin. The coating layer may be not only a single layer but also a multilayer. In the case of multiple layers, tensile strength fibers or the like may be disposed between them.

  In each of the embodiments described above, the core may contain light scattering particles in advance. The size of the light scattering particles is not particularly limited, but those having an average particle diameter of 1 μm or more and 2 μm or less are preferably used. The material is not particularly limited, but silicon particles, silica particles, polystyrene particles, zirconia beads, melamine particles, and the like are preferably used, and silicon particles are particularly preferably used. By containing light scattering particles in the core, optical interconnection technology applications such as an optical bus (sheet bus) disclosed in JP-A-10-186184, and different light scattering particle concentration units are patterned. The optical member of the present invention can be used for a light guide member application such as a light guide plate, a diffusion sheet, and a reflector plate, which are disposed in the region and whose light scattering ability is locally changed.

  The optical transmission material of the present invention is used in an optical signal processing apparatus including optical components such as various light emitting elements, light receiving elements, optical switches, optical isolators, optical integrated circuits, and optical transmission / reception modules. Alternatively, it may be combined with a plastic fiber or optical waveguide. Any known technique can be applied as a technique related to them. For example, the basics and actuality of plastic optical fiber (issued by NTS), Nikkei Electronics No. 2001.1.12.3, pp. 110-127 “ You can refer to "This time, optical components are mounted on the printed circuit board." By combining with various techniques described in the above-mentioned documents, the optical member of the present invention is used for internal wiring in computers and various digital devices, internal wiring for vehicles and ships, optical transmission systems, and the like. The optical transmission system is used for high-speed and large-capacity data communication and control applications that are not affected by electromagnetic waves, and particularly preferably for short-distance applications. Specific examples of this optical transmission system include data communication optical terminals and digital devices, optical links between digital devices, and indoor or regional optical LANs in ordinary homes, apartment houses, factories, offices, hospitals, schools, etc. .

  Further, IEICE TRANS. ELECTRON. , VOL. E84-C, no. 3, MARCH 2001, p. 339-344 “High Uniformity Star Coupler Using Diffused Light Transmission”, Journal of Japan Institute of Electronics Packaging, Vol. 3, no. 6, 2000, pages 476 to 480, as described in "Interconnection by Optical Sheet Bus Technology", and JP-A-10-123350, JP-A-2002-90571, JP-A-2001-290055, etc. Optical buses described: Japanese Patent Laid-Open Nos. 2001-74971, 2000-329962, 2001-74966, 2001-74968, 2001-318263, 2001-31840, etc. Optical star couplers described in JP 2000-241655 A, etc .; JP 2002-624457, JP 2002-101044, JP 2001-305395 A, etc. Optical signal transmission apparatus and optical bus system; optical signals described in JP-A-2002-23011, etc. Processing apparatus; optical signal cross-connect system described in JP-A-2001-86537; optical transmission system described in JP-A-2002-26815; various publications such as JP-A-2001-339554 and JP-A-2001-339555 Multi-function system as described in the above; and various optical waveguides, optical splitters, optical couplers, optical multiplexers, optical demultiplexers, etc., combined with transmission / reception, etc., for more advanced optical transmission A system can be constructed. In addition to the above optical transmission applications, the plastic optical member of the present invention can be used in the fields of illumination, energy transmission, illumination, and sensors.

  Hereinafter, the manufacturing method of the optical member which concerns on this invention is given and mentioned about Examples 1-3. It should be noted that the types of materials, ratios thereof, prescriptions, and the like shown in the following examples may 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.

  In Example 1, a clad 21 made of a PVDF pipe having a circular cross section having a diameter of 15 mm as shown in FIG. 3A and having a square hole of 10 mm square at the center is formed. Then, a core 20 made of a 10 mm square PMMA square bar is fitted, and this cladding 21 is fitted to a protective layer 22 made of a 17 mm square PMMA square bar having a round hole with a diameter of 15 mm. 23 was produced. This preform 23 was heated and stretched to produce an optical member 27 as shown in FIG. This optical member 27 has an outer dimension of 200 μm square in the cross section, and the cross section of the core 27 a corresponding to the core 20, the clad 27 b corresponding to the clad 21, and the protective film 27 c corresponding to the protective layer 22 has a preform shape. The core 20, the clad 21, and the protective layer 22 of FIG. The optical member having a rectangular cross-sectional shape of the protective film 27c can be easily attached to the optical waveguide or the substrate as compared with the circular optical member.

  Using the preform formed in Example 1, an intermediate preform 40 as shown in FIG. 4A is formed, and five intermediate preforms 40 are arranged in one line to form a preform assembly 41. This preform assembly 41 was heated and stretched as a preform. The obtained optical member 42 had a cross-sectional shape substantially similar to the preform assembly 41 and could be easily connected to an optical waveguide or a substrate as in Example 1.

  In Example 3, as shown in FIG. 5, a square pipe made of PVDF having an inner side of 10 mm square and an outer side of 12 mm square is used as a clad 57, and a deuterated MMA monomer solution is put into the clad 57 and radical polymerization is performed. A core 58 was produced. Also, 12 mm square PMMA square bars 52 and 53 for PMMA protective layer and 36 mm × 6 mm square bars 51 and 54 for PMMA protective layer are formed by melt extrusion molding. A preform 56 was formed by surrounding the clad 57 therebetween. By heating and stretching this, an optical member 60 having a rectangular cross section of 100 × 200 μm and substantially similar to the cross sectional shape of the preform 56 was obtained. This optical member 60 could also be easily connected to an optical waveguide or a substrate as in Example 1.

It is process drawing which shows the manufacturing method of the optical member which concerns on this invention. It is the schematic which shows the heating extending process of this invention. It is sectional drawing which shows the cross-sectional shape of the core in a manufacturing process, a clad, a protective layer, a preform, and an optical member. It is sectional drawing which shows the cross-sectional shape of the intermediate | middle preform in another embodiment, a preform assembly, and an optical member. It is sectional drawing which shows the cross-sectional shape of the core in another embodiment, a clad, a protective layer, a preform, and an optical member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Preform formation process 12 Heat drawing process 20, 58 Core 21, 57 Clad 22, 55 Protective layer 23, 56 Preform 27, 42, 60 Optical member 40 Intermediate preform 41 Preform assembly

Claims (12)

A core having a polygonal cross-sectional shape and serving as an optical transmission part, a clad disposed on the outer periphery of the core and having a refractive index lower than that of the core, and a polygonal cross-sectional shape disposed on the outer periphery of the clad A first step of forming a plastic first preform including a protective layer;
The method includes a second step of heating and stretching the first preform in a direction perpendicular to the cross section to form a first stretched body having a cross section substantially similar to the cross section of the first preform. A method for producing a plastic optical member.   2. The method of manufacturing a plastic optical member according to claim 1, wherein in the first step, the first preform is formed with a polygonal cross-sectional shape of the clad.   2. The method of manufacturing a plastic optical member according to claim 1, wherein in the first step, the first preform is formed with a cross-sectional shape including an outer periphery of the clad having a substantially circular or substantially elliptical shape.   4. The method of manufacturing a plastic optical member according to claim 1, wherein the first step forms the first preform by arranging a plurality of the cores in a row in the transverse section. 5.   5. The method of manufacturing a plastic optical member according to claim 4, wherein the core is made of a plurality of types of materials or shapes.   6. The method of manufacturing a plastic optical member according to claim 1, wherein the clad is made of a plurality of types of materials or shapes.   The method for producing a plastic optical member according to any one of claims 1 to 6, wherein the protective layer is composed of a plurality of types of materials or shapes.   The method for producing a plastic optical member according to claim 7, wherein a plurality of the protective layers are formed.   9. The method according to claim 1, further comprising a third step of heating and stretching the first stretched body to form a second stretched body having a cross-sectional shape substantially similar to a cross section of the first stretched body. The manufacturing method of the plastic optical member of any one of Claims 1.   A fourth step of forming a second preform by bundling a plurality of the first stretched body or the second stretched body, and heat-stretching the second preform to cross a cross section substantially similar to a transverse section of the second preform. The method for producing a plastic optical member according to claim 1, further comprising a fifth step of forming a third stretched body having a surface shape.   The method for producing a plastic optical member according to any one of claims 1 to 10, wherein the plastic optical member has a refractive index distribution in which a refractive index gradually decreases outward from the center of the cross section of the core. The method for producing a plastic optical member according to claim 1, wherein a cross-sectional area of the core in a cross section is 400 μm ² or more.

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