JP2007121381A - Method for manufacturing plastic optical member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a plastic optical member with ease and precision in which cores are arranged in a matrix form. <P>SOLUTION: A rod-like core part 20 is formed. An outer shell part 21 with a fitting hole 21a is formed. The core part 20 is fitted in the fitting hole 21a to form a preform element piece 23. The preform element pieces 23 are arranged in a 3x3 matrix to form a preform 25. The preform 25 is drawn by heating in a heating furnace to obtain an optical transmission body 27 with 9 pieces of cores. In the heat drawing, heating conditions are controlled so that the cross-sectional form of the optical transmission body after drawn is almost similar to that of the preform 25. The optical transmission body of a multi-core structure can be formed with ease and precision by the heat-drawing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  Conventionally, as an optical transmission body for propagating light, it has high hardness and is chemically stable, but has low transmission loss, and also has advantages such as excellent transparency and moldability. The body is used. Examples of the silica-based optical transmission body 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 attracted attention because they have advantages such as excellent workability and transparency comparable to quartz-based optical transmission bodies, 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 an advantage that a large aperture is possible, use as an optical transmission body 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 includes a core made of plastic and serving as an optical transmission line (sometimes referred to as a core portion), and a clad made of plastic having a lower refractive index than the core (sometimes referred to as a clad portion). Yes. In the following description, a member including a core is referred to as a core portion, and a member that is disposed on the outer periphery of the core portion and is intended to improve thermal damage, water resistance, and the like on the core portion is referred to as an outer shell portion. . The outer shell includes a protective layer that protects the cladding and the core.

  As the core, particularly the core, one 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. The SI type plastic optical member has a refractive index that decreases stepwise from the center of the diameter toward the outside. It will be. The MSI plastic optical member has an intermediate refractive index distribution between the GI type and the SI type.

  Regardless of the difference in the refractive index distribution, a plastic optical member can be produced by, for example, forming a pipe-shaped clad portion (hereinafter referred to as a clad pipe) by a melt extrusion method, and then placing a core portion in the clad pipe. The method of forming is mentioned. As a method for producing a GI type plastic optical member, for example, a polymer constituting an optical transmission body is polymerized by a polymerization method to prepare a preform (base material), and then the preform is heated and melt stretched in a heating furnace. There is a known method (for example, see Patent Document 2). 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. Therefore, as a method of manufacturing an optical transmission body having a non-circular outer shape as described above, for example, after manufacturing an optical transmission body having a circular cross-sectional outer shape, a plastic optical member having an elliptical cross-section is processed. A manufacturing 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 for forming an aggregate using a plurality of such single optical transmission bodies, a method of thermocompression bonding a plurality of optical transmission bodies in a parallel state (for example, see Patent Document 4), photoresist or etching For manufacturing an optical transmission body using a laser (see Patent Document 5), and further, a method for manufacturing an optical transmission body by inserting a plurality of core parts into a clad part in which a plurality of hollow parts are formed in parallel (For example, refer to Patent Document 6), and a method of manufacturing a plurality of MI-type plastic optical members by fusing and integrating them in the outermost layer (for example, refer to 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 each of the patent documents listed above, Patent Document 6 is a method for manufacturing a quartz-based optical transmission body, and is not a description regarding a plastic optical member. In any of the above methods, there is a problem that, when manufacturing an optical transmission body, a special device is required for processing, resulting in an increase in equipment cost. In addition, when a processing device is used corresponding to various optical transmission bodies, the manufacturing time is increased and the manufacturing cost is increased. In addition, as in Patent Document 3, when an optical transmission body 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 to integrate a plurality of optical transmission bodies at a high density and is not suitable for mass production.

  An object of the present invention is to provide a manufacturing method capable of mass-producing a plastic optical member in which a plurality of cores serving as optical transmission paths are arranged in a two-dimensional direction with high accuracy and low cost.

  The method for producing a plastic optical member of the present invention includes a plastic optical member formed by stretching an optical member preform comprising a core portion serving as an optical transmission portion and an outer shell portion disposed on the outer periphery of the core portion in the longitudinal direction. In the manufacturing method, an optical member preform forming step for forming the optical member preform by arranging a plurality of the core portions in a direction orthogonal to the longitudinal direction, and heating and stretching the optical member preform to form the optical member preform. It has a heating and drawing step for obtaining the plastic optical member having a cross-sectional shape substantially similar to the cross-sectional shape of the reform. In addition, it is preferable that the said core part is arrange | positioned regularly. Moreover, it is preferable that the outer periphery of the core portion has a clad having a refractive index lower than that of the optical transmission portion, or the outer shell portion has a clad having a refractive index lower than that of the optical transmission portion on the surface in contact with the core portion.

  In the optical member preform forming step, it is preferable that a plurality of the optical member preforms are bundled to form a preform assembly, and in the heating and stretching step, the preform assembly is stretched. Alternatively, in the optical member preform forming step, it is preferable to form the optical member preform by accumulating the preform pieces made of the core portion and the preform pieces made of the outer shell portion.

  In the optical member preform forming step, it is preferable that a plurality of the optical member preforms are bundled to form a preform assembly, and in the heating and stretching step, the preform assembly is stretched. Moreover, it is preferable that the said outer shell part is connected by the side surface.

  It is preferable that the core portion is composed of a plurality of types. Moreover, it is preferable that the said outer shell part is comprised from multiple types of material or shape. Moreover, it is preferable to have a refractive index distribution in which the refractive index gradually decreases from the center of the cross section of the core toward the outside. Furthermore, it is preferable that the cross-sectional shape of the core portion is circular, and the cross-sectional shape of the clad portion is a polygon, particularly a square, a rectangle, or a regular hexagon.

  According to the method for producing a plastic optical member of the present invention, an optical member preform is formed by arranging a plurality of core portions in a direction perpendicular to the longitudinal direction, and the optical member preform is heated and stretched to form the optical member preform. Since the plastic optical member having a cross-sectional shape substantially similar to the cross-sectional shape is created, the plastic optical member having a plurality of core parts can be easily manufactured with high accuracy without using a special manufacturing apparatus. be able to. Moreover, a high-density multi-core plastic optical member can be easily manufactured by changing the draw ratio or by heating and drawing in multiple steps.

  By having a clad having a refractive index lower than that of the optical transmission part on the outer periphery of the core part, or having a clad having a refractive index lower than that of the optical transmission part on the surface in contact with the core part of the outer shell part, light is transmitted at the interface between them. It is totally reflected and transmitted through the core.

  In the optical member preform formation step, the optical element preform is formed by accumulating the preform pieces including the core portion and the outer shell portion, or from the preform piece and outer shell portion including the core portion. A plastic optical member having a wide variety of cross-sectional shapes can be easily manufactured by accumulating the preform pieces to form the optical member preform. Further, in the optical member preform forming step, a plurality of optical member preforms are bundled to form a preform assembly, and in the heating and stretching step, the preform assembly is stretched to increase the draw ratio. Thus, a plastic optical member having a more precise cross-sectional shape can be obtained.

  In addition, by configuring the core portion from a plurality of types and forming the outer shell portion from a plurality of types of materials or shapes, plastic optical members of a wider variety of forms can be obtained. By having a refractive index distribution in which the refractive index gradually decreases from the center of the cross section of the core portion toward the outside, an optical transmission body excellent in 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 step 11 includes a core portion forming step 13, an outer shell portion forming step 14, a fitting step 15, and an assembly step 16.

  First, the core part 20 is formed in the core part forming step 13. Further, the outer shell portion 21 is formed in the outer shell portion forming step 14. Next, in the fitting step 15, the core portion 20 and the outer shell portion 21 are fitted to obtain a preform piece 23. Next, in the assembly step 16, a plurality of preform pieces 23 are combined and bundled to form a preform 25.

  In the heating and stretching step 12, the preform 25 is placed in the heating furnace 30 as shown in FIG. Then, the preform 25 is heated by the heating furnace 30 to soften a part of the preform 25, and then drawn (stretched) in the longitudinal direction starting from the leading end 25 a of the softened portion. Get 27. Here, the longitudinal direction is a direction perpendicular to a plane in which the cross sections of the core portion and the outer shell portion are the same or similar, that is, an axial direction. Although this 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 transmission body 27. The outer diameter of the optical transmission body 27 is always constant by appropriately adjusting the position of the preform 25 in the heating furnace 30, the temperature of the heating furnace 30, the winding speed of the winding device 33 and the like according to the monitoring result. Like that. The winding device 33 winds the drawn optical transmission body 27 around the core material 33a. Thus, the optical transmission body 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 25 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 transmission body 27 having a shape substantially similar to the cross section of the preform 25 is obtained. In order to protect the outer peripheral surface of the obtained optical transmission body 27, a protective film may be formed by covering with resin. The protective film by this coating may be formed by irradiating radiation after application of the radiation curable resin, or may be formed by extrusion molding of a thermoplastic resin. In addition, when forming a protective film, you may carry out as a separate line from the manufacturing process of an optical transmission body, and you may incorporate in the manufacturing process of an optical transmission body by performing after a heating extending process.

  As shown in FIG. 3A, the core part 20 has a core 20a and a clad 20b. The core 20a is a member that becomes a light transmission path, and the clad 20b is a hollow member that has a lower refractive index than the core 20a and totally reflects light at the interface with the core 20a. In this embodiment, the refractive index distribution of the core 20a is adjusted so that the refractive index gradually decreases from the center of the diameter toward the outside. The core portion 20 having such a refractive index distribution is configured in the same manner as a preform for a GI type plastic optical fiber (POF).

  The manufacturing method of the core 20a and the clad 20b is not particularly limited. For example, there is a method of radical polymerization after injecting PMMA for forming the core 20a into a clad pipe formed by melt extrusion using PVDF, and this method is applied in this embodiment. In addition, the core part 20 in which the clad 20b is provided on the outer periphery of the core 20a may be formed by using a melt extrusion apparatus equipped with a composite type nozzle capable of co-extrusion. It should be noted that a desired refractive index distribution can be expressed by adding a refractive index adjusting agent to the polymer for forming the core 20a and adjusting the dispersion and concentration. 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, and these descriptions also apply to the present invention. Can do.

  As shown in FIG. 3A, the outer shell portion 21 is a member having a fitting hole 21a. The manufacturing method of the outer shell portion 21 is not particularly limited, and examples thereof include a melt extrusion molding method using a material (for example, PMMA, PVDF, etc.) that forms the outer shell portion 21. In the present embodiment, molding is performed by melt extrusion using PMMA. The cross-sectional shape of the fitting hole 21a only needs to substantially match the cross-sectional shape of the core portion 20. Therefore, when the cross-sectional shape of the core part 20 is composed of a polygon other than a circle, such as an ellipse or a rectangle, or a combination of a straight line and a curve, an arc, or an ellipse, it substantially coincides with this. Shaped. Instead of forming the clad 20b on the outer periphery of the core 20a, the clad 20b may be formed in the fitting hole 21a of the outer shell portion 21.

  And the core part 20 is inserted and fitted in the fitting hole 21a, and the preform piece 23 as shown in FIG.3 (B) is formed. At this time, the sizes of the core portion 20 and the fitting hole 21a are adjusted so that the gap 24 is formed during fitting. In the present invention, the clearance X (mm) of the air gap 24 satisfies 0 <X ≦ 8. Thereby, the core part 20 and the outer shell part 21 can be easily fitted. However, in the case of 8 <X, since the clearance is too large, when the optical transmission body is used, the consistency between the core portion and the fitting portion may be lowered.

  Next, either one of the ends of the preform piece 23 is fixed. This fixed end portion becomes an end portion on the stretching side during heating and stretching. As a result, the preform piece 23 can be stretched in the heating furnace 30 without dropping the core portion 20 from the outer shell portion 21 or shifting the fitting position. The end is fixed by a fixing member provided at one end of the fitting hole 21a. 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 piece 23 because excellent adhesiveness at the interface can be obtained. In addition to this, instead of using the fixing member, one end of the preform piece 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.

  As shown in FIG. 3C, the preform pieces 23 are arranged in a 3 × 3 matrix, for example, and a preform 25 is formed. The joining of the preform pieces 23 is performed by heating, for example. Heating may be performed before heat stretching or may be performed by heat fusion during heat stretching. When joining beforehand, you may carry out simultaneously with fixation of the core part 20 and the outer shell part 21. FIG. Further, when heat fusion is performed at the time of heating and stretching, the preform piece 23 is held by a clamp or the like. In addition, the example of arrangement | positioning of the preform piece 23 is not restricted to 3x3, NxM and NxN (N is an integer greater than or equal to 2 and M is an integer greater than or equal to 3) may be sufficient.

  In the present embodiment, the GI type is shown in which the refractive index gradually decreases from the center of the diameter toward the outside. However, the refractive index distribution may be any form that gradually decreases from the center of the diameter toward the outside. It is not limited. In addition to the GI type, for example, an SI type in which the refractive index decreases stepwise as it goes from the center of the diameter to the outside, or an MSI type that exhibits characteristics approximately halfway between the GI type and the SI type can be used. .

  In the above embodiment, the single core type preform piece 23 having one core portion 20 is formed in one outer shell portion 21, but instead of this, as shown in FIG. A multi-core preform piece 35 having a plurality of core portions 20 may be formed on each outer shell portion 34. In each of the following embodiments, the same components as those in the above embodiment are denoted by the same reference numerals, and redundant description is omitted. In the case of this embodiment, three fitting holes 34a are provided side by side in one outer shell portion 34, and the cross section is formed in a rectangular shape. The core portion 20 is fitted into each fitting hole 34a of the outer shell portion 34 to form a preform piece 35 as shown in FIG. Next, as shown in FIG. 4C, three preform pieces 35 are stacked to form a preform 36 in which the core portions 20 are arranged in a 3 × 3 matrix. By heating and stretching the preform 36, an optical transmission body similar to the optical transmission body 27 shown in FIG. 1 can be obtained.

  Further, as shown in FIG. 5, when the preform 37 is combined to form the preform 37, the interval adjusting member 38 is disposed between the outer shell portions 21 to adjust the interval between the core portions 20. May be. The spacing adjusting member 38 is preferably made of the same material as that of the outer shell portion 21. By heating and stretching such a preform 37, an optical transmission body 39 capable of arbitrarily changing the interval between the core portions 20 is obtained.

  FIG. 6 is a cross-sectional view showing a preform 40 in another embodiment. In this preform 40, as shown in (A), a cylindrical pipe is used as an outer shell portion 41, and a core portion 42 is provided inside to form a preform piece 43. As the preform piece 43, the core portion 20 itself shown in FIG. 1 may be used, or the core portion 42 may be fitted in the outer shell portion 41. In the assembly process, the preform pieces 43 are arranged in a 2 × 4 matrix, and the preform pieces 43 are bonded together to form the preform 40. The preform piece 43 may be bonded by heating or the like in addition to using an adhesive. The preform 40 is heat-stretched in a heat-stretching step, whereby an optical transmission body 44 having a cross-sectional shape substantially similar to the preform 40 is obtained.

  As shown in FIG. 6B, instead of the preform 40 in which the preform pieces 43 are joined in the vertical and horizontal directions, the upper and lower preform pieces 43 are staggered as shown in FIG. Alternatively, the preform 45 may be arranged and bonded to each other. In the optical transmission body 44 obtained from the preform 40 shown in FIG. 6, the separability of each core when the core is joined to a terminal or the like is improved, and the connection work is facilitated. Moreover, in the optical transmission body 46 obtained from the preform 45 shown in FIG. 7, each core can be bundled with high density, and the optical transmission body 46 can be made compact.

  In the above embodiment, the preform and the outer shell are formed by fitting the core and the outer shell in the fitting step. In addition to this, the pipe-shaped outer shell is filled with a polymer that becomes the core. For example, the preform piece may be constituted by radical polymerization. Moreover, you may comprise a core part and an outer shell part combining several element pieces.

  In addition, as shown in FIG. 8, in the preform forming step 49, the preform piece 23 is heated and stretched in the first heating and drawing step 50 to reduce the cross section size of the intermediate preform piece 51. In the assembly step 16, the preform 53 may be formed by combining the intermediate preform pieces 51. In this case, the heat transmission body 55 is obtained by performing heat stretching in the second heat stretching process 54. The heating and stretching for reducing the size of the preform piece 23 is not limited to one time, and may be performed a plurality of times.

  Further, as shown in FIG. 10, the preform 72 may be configured by combining a plurality of core portions 70 and an outer shell portion 71. In this case, the core part 70 is comprised from the square bar made from PMMA, and the outer shell part 71 for a clad is comprised from the square bar made from PVDF. Then, the four outer shell portions 71 are arranged so as to cover the side surface of the core portion 70 to constitute the preform 72. In addition, as shown in FIG. 11, a preform 75 may be configured by arranging a square bar 73 made of PMMA so as to cover the side surface of the outer shell portion 71. In this case, the outer shell portion made of the square bar 73 has the function of a protective layer.

  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, the number of preform pieces is not particularly limited, but is preferably 2 or more and 100 or less, more Preferably they are 2 or more and 50 or less, Most preferably, they are 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 pieces or the intermediate preform pieces used for forming the preform are joined together by welding or adhesion to form an integrated preform. 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.

  Moreover, you may coat | cover the outer periphery with respect to a preform. Thereby, water resistance and toughness can be improved. In addition, when a plurality of preform pieces or intermediate preform pieces constituting the preform are bundled, the preform may be stretched in an aligned state 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 heating and softening in the heating and stretching step performed when forming the optical transmission body, and the cross section of the preform is substantially the same. An optical transmission body having a similar cross-sectional shape can be obtained. This method is particularly suitable when the number of preform pieces constituting the preform is small, and has an 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. The outer peripheral shape of the cross section of the preform piece is not limited to a substantially circular shape, and may be any shape that is a combination of a substantially elliptical shape, a polygonal shape, a straight line and a curved line. In addition, as a method of manufacturing preform pieces having different optical characteristics, the constituent materials are changed, the refractive index distribution is changed using a refractive index adjusting agent described later, or additives are selected. However, it is not particularly limited to a method of developing desired optical characteristics.

  A core part is demonstrated among the optical transmission bodies of this invention. As the polymerizable monomer that is a raw material for the core part, it is preferable to select a raw material that is easily bulk-polymerized. Examples of raw materials that are highly light transmissive and easy to bulk polymerize include the following (meth) acrylic acid esters (fluorine-free (meth) acrylic acid ester (a), fluorine-containing (meth) acrylic acid ester (b) ), Styrenic compounds (c), vinyl esters (d), etc., and the core part is a homopolymer of these, or a copolymer comprising two or more of these monomers, and a homopolymer and / or It can be formed from a mixture of copolymers. Among these, a composition containing (meth) acrylic acid esters as a polymerizable monomer can be preferably used.

  Specific examples of the polymerizable monomers listed above include (a) fluorine-free methacrylic acid ester and fluorine-free acrylic acid ester: methyl methacrylate (MMA), ethyl methacrylate, isopropyl methacrylate, methacrylic acid. -Tert-butyl, 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. Examples of (d) vinyl esters include vinyl acetate, vinyl benzoate, vinyl phenyl acetate, and vinyl chloroacetate. 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.

  Further, when the optical transmission body is used for near-infrared applications, absorption loss due to the C—H bond constituting the polymer of the core portion occurs, so deuterium as described in Japanese Patent No. 3332922 and the like. Hydrogen atoms (H) of C—H bonds, including polymethyl methacrylate (PMMA-d8), polytrifluoroethyl methacrylate (P3FMA), polyhexafluoroisopropyl 2-fluoroacrylate (HFIP 2-FA), etc. A polymer substituted with a deuterium atom (D), fluorine (F), or the like 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 transmission body of the present invention, the cladding portion will be described. As the material of the clad part, it is preferable to use a material having a lower refractive index than that of the core part and having excellent adhesion to the core part, because light transmitted through the core part is totally reflected at the interface between them. However, if irregularities are likely to occur at the interface between the core part and the clad part due to the selection of the material, or it is not preferable in terms of manufacturing suitability, an additional layer is provided between the core part and the clad part. The consistency may be improved. In this case, for example, when an outer core layer made of a polymer having the same composition as the matrix of the core part is formed on the interface with the core part (that is, the inner wall surface of the hollow tube), the interface state between the core part and the cladding part is changed. It can be corrected. Of course, the clad part itself may be formed from a polymer having the same composition as the matrix of the core part without forming the outer core layer.

  As the material for the clad part, 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 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 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 portion. For this purpose, a polymer having a low water absorption rate is used as a material (material) for the cladding portion. That is, it is preferable to produce a clad part using a polymer having a saturated water absorption rate (hereinafter referred to as a water absorption rate) of less than 1.8%. More preferably, the clad portion is formed using less than 1.5% polymer, and more preferably less than 1.0% polymer. Further, it is preferable to use a polymer having the same water absorption rate when the outer core layer is produced. The water absorption rate (%) can be calculated by immersing the test piece in water at 23 ° C. for 1 week according to the ASTM D 570 test method and measuring the water absorption rate at that time.

  When the core part and / or the clad part are made from a polymer polymerized from a polymerizable monomer, a polymerization initiator is used in the polymerization. As a polymerization initiator, it can select suitably according to the monomer and polymerization method to be used, for example, benzoyl peroxide (BPO), tert- butyl peroxy-2-ethyl hexanate (PBO), di-tert-butyl. Examples thereof include peroxide compounds such as peroxide (PBD), tert-butyl peroxyisopropyl carbonate (PBI), and n-butyl-4,4-bis (tert-butylperoxy) valerate (PHV). 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 polymerizable composition for forming a core part and the polymerizable composition for forming a clad part 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 part and the core part 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 an optical transmission body by drawing the obtained preform by stretching, the mechanical properties at the time of stretching can be set to a desired range by adjusting the molecular weight, thereby improving productivity. Also 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 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.

  The core part 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 part polymeric composition contain a refractive index adjusting agent 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, it is possible to introduce a refractive index distribution structure by using two or more kinds of polymerizable monomers for forming the core portion and providing a distribution of the copolymerization ratio in the core portion without using a refractive index adjusting agent. However, 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 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, the core portion-forming polymerizable composition contains a dopant, and in the step of forming the core portion, the polymerization progress direction is controlled by radical polymerization, the dopant concentration is inclined, and the dopant concentration distribution in the core portion. And a method of forming a refractive index distribution structure based on the above. This refractive index distribution structure includes a GI type and an MSI type, and these GI type and MSI type optical transmitters 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 transmission body 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 part, the clad part, or a part thereof 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 portion or a part thereof for the purpose of improving weather resistance, durability, and the like. In addition, for the purpose of improving optical transmission performance, a stimulated emission functional compound for optical signal amplification can also be added. By adding the stimulated emission functional compound, the attenuated signal light can be amplified by the excitation light, and the transmission distance is improved. For example, it can be used as an optical fiber amplifier in a part of the optical transmission link. . These additives can also be contained in the core part, the clad part or a part of them by adding to the raw material monomer and then polymerizing.

  It is preferable to provide a coating layer on the outer periphery of the clad portion after heat-stretching 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 molecular weight distribution shown by weight average molecular weight Mw / number average molecular weight Mn is 2-80, Preferably it is set to 3-40.

  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 light transmission body of the present invention can be used for a light guide member application such as a light guide plate, a diffusion sheet, and a reflection plate that are arranged 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 basic and actual of plastic optical fiber (published by NTS Corporation), Nikkei Electronics 2001.1.2.3, pp. 110-127 “Printed Wiring You can refer to "This time, optical components are mounted on the board." By combining with various techniques described in the above documents, the optical transmission body of the present invention is used for in-device 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 transmission body 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 PMMA square pipe (corresponding to the outer shell portion 21) having a 10 mm square square cross section as shown in FIG. Into the hollow portion having a circular cross section, a mixed solution in which DPS as a refractive index adjusting agent is added to 7% by weight and added to the MMA monomer solution is formed to form the core portion 20 by radical polymerization, and the preform piece 23 is produced. did. The preform pieces 23 were arranged in a 3 × 3 matrix in the assembling process to obtain a preform 25 as shown in FIG. This preform 25 was heated and stretched to produce an optical transmission body 27 as shown in FIG. The optical transmission body 27 had a 600 μm square outer dimension in a cross section, a 9 × 3 × 3 core with a core diameter of 100 μm. Further, when the transmission loss of the optical transmission body 27 was measured, it was 0.03 dB / cm at a wavelength of 850 nm, indicating a low transmission loss.

  In Example 2, the optical transmission body 55 was manufactured according to the process shown in FIG. First, as shown in FIG. 9, a deuterated MMA monomer solution was added to a PVDF pipe 60 having an inner diameter of 9 mm and an outer diameter of 10 mm, and a core portion 61 was produced by radical polymerization. Further, an outer shell portion 62 made of a PMMA rod having a rectangular shape with a cross section of 20 mm × 30 mm and having a diameter of 10 mm at the center is manufactured, and the core portion 20 is fitted into the round hole 62a. A reforming piece 23a was produced. This preform piece 23a was heated and stretched in the first heating and stretching step 50 to produce an intermediate preform piece 51 having a rectangular cross section of 6 mm × 9 mm. Next, a PMMA square bar of 6 mm × 6 mm was placed between the intermediate preform pieces 51 as a spacing adjusting member 63 to prepare a preform 53 having 2 × 2 four cores. The preform 53 was heated and stretched to produce a four-core optical transmission body 55a having a rectangular shape with a cross section of 400 μm × 500 μm and a core diameter of 180 μm. The obtained optical transmission body 55a was 0.02 dB / cm at the wavelength of 850 nm for all the four cores, indicating a low transmission loss.

  In Example 3, as shown in FIG. 6, a PVDF round pipe having an inner diameter of 9 mm and an outer diameter of 10 mm was used as an outer shell portion 41, and a mixed liquid of MMA monomer solution was added into the outer shell portion 41 by radical polymerization. The core part 42 was formed and the preform piece 43 was produced. The preform segments 43 are arranged in a 2 × 4 matrix to produce a preform 40. The preform 40 is heated and stretched, and each preform segment 43 is fused by stretching heat to 400 μm × 800 μm. The optical transmission body 44 was produced. The obtained optical transmission body 44 was 0.03 dB / cm at the wavelength of 850 nm for all the 8 cores, indicating a low transmission loss.

It is process drawing which shows the manufacturing method of the optical transmission body which concerns on this invention. It is explanatory drawing of the heating extending process of this invention. It is sectional drawing which shows the cross-sectional shape of the core part, outer shell part, preform piece, preform, and optical transmission body in a manufacturing process. It is sectional drawing which shows the cross-sectional shape of the core part, outer shell part, preform piece, and preform in other embodiment. It is sectional drawing which shows the cross-sectional shape of the preform in other embodiment. It is sectional drawing which shows the preform piece, preform, and optical transmission body in other embodiment. It is sectional drawing which shows the preform piece, preform, and optical transmission body in other embodiment. It is the schematic which shows the manufacturing process of the optical transmission body in other embodiment. FIG. 4 is a cross-sectional view showing a preform piece and a preform of Example 2. It is sectional drawing which shows the cross-sectional shape of the preform in other embodiment. It is sectional drawing which shows the cross-sectional shape of the preform in other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Preform formation process 12 Heat drawing process 20 Core part 21 Outer shell part 27,37,44,46,55 Optical transmission body 23,31,43,47 Preform piece 25,32,37,40,45 Preform 27, 39, 44, 46, 55 Optical transmission body

Claims (10)

In a method for producing a plastic optical member by stretching an optical member preform composed of a core portion serving as an optical transmission portion and an outer shell portion disposed on the outer periphery of the core portion in the longitudinal direction,
An optical member preform forming step of forming the optical member preform by arranging a plurality of the core portions in a direction orthogonal to the longitudinal direction;
A method for producing a plastic optical member, comprising the step of heating and stretching the optical member preform to obtain the plastic optical member having a cross-sectional shape substantially similar to the cross-sectional shape of the optical member preform. .   The method of manufacturing a plastic optical member according to claim 1, wherein the core portions are regularly arranged.   The method for producing a plastic optical member according to claim 1, wherein a clad having a refractive index lower than that of the light transmission portion is provided on an outer periphery of the core portion.   The method for producing a plastic optical member according to claim 1, wherein a clad having a refractive index lower than that of the optical transmission portion is provided on a surface of the outer shell portion that contacts the core portion.   5. The optical member preform forming step includes forming the optical member preform by accumulating preform pieces including the core portion and the outer shell portion. 6. A method for producing a plastic optical member.   5. The optical member preform forming step includes forming the optical member preform by accumulating the preform pieces made of the core portion and the preform pieces made of an outer shell portion. The manufacturing method of the plastic optical member of any one of Claims 1.   The plastic optical according to any one of claims 1 to 6, wherein in the heating and stretching step, a plurality of optical member preforms are bundled to form a preform assembly, and the preform assembly is stretched. Manufacturing method of member.   The method of manufacturing a plastic optical member according to any one of claims 1 to 7, wherein the core portion includes a plurality of types.   9. The method of manufacturing a plastic optical member according to claim 1, wherein the outer shell portion is made of a plurality of types of materials or shapes.   10. The method for manufacturing a plastic optical member according to claim 1, wherein the plastic optical member has a refractive index distribution in which the refractive index gradually decreases from the center of the cross section of the core toward the outside.

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