JP6545074B2 - Method of manufacturing multi-core plastic fiber and multi-core plastic fiber manufacturing apparatus - Google Patents

Description

  The present invention relates to a method and an apparatus for producing a multi-core fiber, and more particularly to a method for producing a plastic image fiber and an apparatus for producing a plastic image fiber.

  In medical applications such as an endoscope, an image fiber for transmitting an image is used by being inserted into a catheter tube or the like. The image fiber is a multicore fiber (multi-core fiber) having a plurality of cores corresponding to the number of pixels of the image to be transmitted. In the above applications, the image fiber is required to have a small outer diameter, to be easily inserted into a catheter tube or the like, to have good flexibility (flexibility), and to have safety that does not easily break. In the above applications, as the image fiber, plastic is more preferably used than glass. (Hereafter, plastic image fibers are referred to as "plastic image fibers" or "PIF".) PIF is not limited to medical applications, and is also used for other image transmission applications such as industrial fiberscopes. .

  PIF has a sea-island structure in which a plurality of cores (core portions) exist in an island shape in a sea portion formed of a clad (sheath portion) in a cross-sectional shape.

  Heretofore, as a method of manufacturing the above-mentioned sea-island structure PIF, there is known a method of simultaneously extruding a plurality of single-core fibers in which one core is covered with a cladding layer from a composite spinneret having a plurality of nozzle holes corresponding to the number of pixels (For example, patent document 1 grade | etc.,).

  In this method, product specifications such as the pixel diameter (core diameter), the number of pixels (number of cores), and the core area ratio (aperture ratio) are fixed by the composite cap used. Therefore, when the product specification is changed, it is necessary to remake the composite cap, which may increase the cost due to the change of the product specification or the diversification of the product specification.

  On the other hand, multicore fibers including PIF have a problem of crosstalk in which optical signals leaked from each core interfere with each other.

  Generally, if the pixel diameter (core diameter) and the number of pixels (number of cores) are the same condition, both the average brightness of the lit pixels and the degree of blurring of the image due to crosstalk are both core areas in the cross section of the fiber Correlate with the ratio. (In this specification, “average brightness of the lit pixels” indicates the average brightness of the lit core and the clad layer covering the lit core.) The larger the core area ratio, the Since the ratio decreases, the average brightness of the lit pixels is improved, but the degree of blurring of the image is increased due to the crosstalk, and the image quality tends to be degraded. On the other hand, the smaller the core area ratio, the larger the proportion of the cladding layer, so crosstalk is suppressed and the degree of blurring of the image is reduced and the image quality is improved, but the average brightness of the lit pixels tends to be reduced. There is.

  Patent Document 2 proposes the following method as a method for solving the above problem (see FIG. 5). In Patent Document 2, a plurality of single-core fiber strands corresponding to the number of pixels are bundled and inserted into a hollow portion of a clad pipe to obtain a bundle preform. Then, the tip portion of the obtained bundle preform is heated and drawn in a reduced pressure atmosphere, thereby producing a PIF made of a multi-core fiber having a plurality of cores corresponding to the number of pixels. In this method, since it is not necessary to use a composite cap, it is possible to flexibly cope with changes in product specifications such as the pixel diameter, the number of pixels (the number of cores), and the core area ratio.

  In the method described in Patent Document 2, when bundling a plurality of single-core fiber strands, there is a problem that individual single-core fiber strands are damaged. Each single-core fiber strand is thin and is made of plastic, so it is weak against rubbing, and the friction between multiple single-core fiber strands is large. When bundling fiber strands, they may rub against each other and be damaged. Then, when a bundle preform including a flawed single-core fiber strand is drawn, the transmittance of the flawed core may be reduced to cause a dark defect in which the lit pixel is displayed blackish.

  In addition, when bundling a plurality of single-core fiber strands, if they rub against each other to form a flaw, foreign matter may be mixed into the interior of the single-core fiber strand through the flaw. This can also be a factor of dark defects.

  In PIF, in order to transmit an image with high accuracy, it is preferable that a plurality of pixels be aligned in order. For this purpose, it is preferable to arrange a plurality of single-core fiber strands in order at the time of forming a bundle preform. For example, it is preferable that a plurality of single-core fiber strands be arranged in a hexagonal close-packed arrangement.

  However, as described above, the individual single-core fiber strands are thin and made of plastic, so they are susceptible to rubbing. In addition, considering the manufacturing efficiency, it is not possible to unnecessarily spend time and labor in the process of forming the bundle preform. In the conventional method, it is difficult to efficiently and easily arrange a plurality of single-core fiber strands in order without damage. This problem is particularly noticeable in high definition PIFs in which the pixel diameter (core diameter) is small and the number of pixels (core number) is large.

Unexamined-Japanese-Patent No. 1-18108 gazette Unexamined-Japanese-Patent No. 63-143510 (patent 2519699)

  The present invention has been made to solve such a problem, and can flexibly cope with changes in product specifications such as pixel diameter (core diameter), pixel number (core number), and core area ratio, and An object of the present invention is to prevent surfactant or foreign matter from mixing between single-core fiber strands, and to reduce dark defects in which an image can not be transmitted.

  A method of manufacturing a multi-core fiber according to the present invention is a method of manufacturing a multi-core fiber having a cladding and a plurality of cores formed in the cladding, wherein the core is covered with a cladding layer. Is inserted into the hollow portion of a clad pipe made of the same material as the clad layer to form a bundle preform, and a bundle preform forming step; and heating and drawing the tip of the bundle preform under a reduced pressure atmosphere. A multi-core fiber forming step of forming the multi-core fiber having a clad and a plurality of cores formed in the clad; The manufacturing method includes: the plurality of single-core fibers in the bundle preform between the bundle preform forming step and the multi-core fiber forming step Having a cleaning process in the space between the line and the cladding pipe for cleaning fluid out pressure pumping.

  In the method of manufacturing a multi-core fiber according to the present invention, preferably, in the bundle preform forming step, the plurality of single-core fiber strands are inserted into the hollow portion of the cladding pipe in a solution containing a surfactant Get a preform.

  In the method of manufacturing a multi-core fiber according to the present invention, preferably, in the cleaning step, the liquid is pressurized and delivered, and then the delivery and the evacuation of gas are alternately repeated twice or more in the bundle preform. More preferably, it is repeated 10 times or more, more preferably 1000 times or more.

  According to these configurations, the surfactant or single core used when bundling single-core fiber strands is carried out by sending a cleaning solution between single-core fiber strands in the formed bundle preform for cleaning. Foreign matter between fiber strands can be removed, and variations in optical signals between cores can be reduced.

  The multi-core fiber manufacturing apparatus of the present invention inserts a plurality of single-core fiber strands, the core of which is coated with a cladding layer, into the hollow portion of a cladding pipe made of the same material as the cladding layer to obtain a bundle preform. A multi-core fiber manufacturing apparatus comprising: a bundle preform forming part; and a multi-core fiber forming part for heating and drawing the tip of the bundle preform in a reduced pressure atmosphere to form the multi-core fiber. The multi-core fiber manufacturing apparatus press-feeds a liquid into a space (gap) between the plurality of single-core fiber strands in the bundle preform formed in the bundle preform forming portion and the cladding pipe. The multicore fiber forming part includes the bundle preform cleaned in the cleaning part, and the multicore fiber forming part includes the cleaning part for cleaning. Is a multi-core fiber manufacturing apparatus characterized by forming.

  In the multicore fiber manufacturing apparatus of the present invention, preferably, in the bundle preform forming portion, the plurality of single core fiber strands are inserted into the hollow portion of the cladding pipe in a solution containing a surfactant, Get a reform.

  In the multi-fiber manufacturing apparatus of the present invention, preferably, the delivery and the exhaust of the gas are alternately repeated two or more times in the bundle preform in the cleaning section. More preferably, it is repeated 10 times or more, more preferably 1000 times or more.

  According to these configurations, the surfactant or single core used when bundling single-core fiber strands is carried out by sending a cleaning solution between single-core fiber strands in the formed bundle preform for cleaning. Foreign matter between fiber strands can be removed, and variations in optical signals between cores can be reduced.

  According to the present invention, it is possible to flexibly cope with changes in product specifications such as the pixel diameter (core diameter), the number of pixels (number of cores), and the core area ratio, and reduce variations in optical signals between cores. . Further, according to the present invention, it is possible to flexibly cope with changes in product specifications such as the pixel diameter (core diameter), the number of pixels (number of cores), and the core area ratio, and dark defects are suppressed, and a plurality of pixels are It is possible to provide a plastic image fiber that can be aligned in order and transmit an image with high accuracy.

FIG. 1 is a flow chart showing an example of a method of manufacturing a multi-core fiber according to the present embodiment. FIG. 2 is a cross-sectional view showing an example of a single-core fiber. FIG. 3 is a perspective view showing an example of a single-core fiber. FIG. 4 is a schematic view showing an example of a single-core fiber forming device in the present embodiment. FIG. 5 is a cross-sectional view of a bundle preform. FIG. 6 is a perspective view showing an example of a fiber strand bundle. FIG. 7 is a perspective view showing an example of a bundle preform. FIG. 8 is a schematic view showing an example of the cleaning apparatus in the present embodiment. FIG. 9 is a schematic view showing an example of a multi-core fiber manufacturing apparatus according to the present embodiment. FIG. 10 is a cross-sectional view of a multicore fiber. FIG. 11 is a block diagram showing the configuration of the multi-core fiber manufacturing apparatus of the present embodiment. 12 is a cross-sectional photograph of the optical microscope of Example 1. FIG. FIG. 13 is a cross-sectional photograph of the optical microscope of Example 2. FIG. 14 is a cross-sectional photograph of the optical microscope of Example 3. FIG. 15 is a cross-sectional photograph of the optical microscope of Comparative Example 1. FIG. 16 is a cross-sectional photograph of the optical microscope of Comparative Example 2. FIG. 17 is a cross-sectional photograph of the optical microscope of Comparative Example 3.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart showing an example of a method of manufacturing a multi-core fiber according to the present embodiment. As shown in FIG. 1, in the method of manufacturing a multicore fiber according to the present embodiment, step S11 in which a single core fiber is formed, step S12 in which a bundle preform is formed, and the bundle preform are cleaned. It comprises step S13 and step S14 in which a multi-core fiber is formed. Each step will be described in order.

  First, in step S11 of FIG. 1, a single-core fiber is formed. FIG. 2 is a cross-sectional view showing an example of a single-core fiber. As shown in FIG. 2, one core rod 21 made of a core material (a translucent polymer with a relatively high refractive index) and one first clad material made of a cladding material (a translucent polymer with a relatively low refractive index) A clad pipe 22 is prepared. In the present specification, the “rod” is a cylindrical member having no hollow portion inside, and the “pipe” is a tubular member having a hollow portion inside. The outer diameter of the core rod 21 is designed to be slightly smaller than the inner diameter of the first clad pipe 22.

  The core rod 21 and the first cladding pipe 22 are manufactured by a known method. For example, the core rod 21 is manufactured by polymerizing one or more monomers in the presence of a solvent in a bottomed cylindrical container such as a glass ampoule. In this method, the inner diameter of the container used for manufacturing is the outer diameter of the core rod 21.

  For example, the first clad pipe 22 is produced by polymerizing one or more monomers in the presence of a solvent by centrifugal casting in a bottomed cylindrical container such as a glass ampoule. In the production of the first clad pipe 22, the container containing one or more monomers is rotated around the central axis, and the action of centrifugal force causes the one or more monomers to be applied to the inner wall surface of the container. The polymer is produced in the form of a pipe by polymerizing in a state of heat. In this method, the inner diameter of the container used for manufacturing is the outer diameter of the first clad pipe 22. The thickness of the first cladding pipe 22 is adjusted by the amount of material such as monomers contained in the vessel and the centrifugal force.

  In addition, the manufacturing method of the 2nd clad pipe 43 mentioned later changes the internal diameter of the bottomed cylindrical container to be used, and changes the quantity of material and a centrifugal force as needed, and it is a 1st clad pipe. It can be carried out in the same manner as the production method of 22. Further, as the second clad pipe 43, an extruded pipe may be applied.

  Next, as shown in FIG. 3, the core rod 21 is inserted into the hollow portion of the first clad pipe 22 to obtain a single core clad / core composite material 23. FIG. 3 is a perspective view showing an example of a single-core fiber.

  FIG. 3 shows a distribution example of the refractive index nd in one direction (x direction) from the central axis toward the outer periphery in the single-core clad / core composite material 23. In this example, the refractive index nd in the core rod 21 is uniform in the x direction, and its value is n2. The refractive index nd of the first cladding pipe 22 is uniform in the x direction, and its value is n1. Here, n2> n1.

  The refractive index n1 of the core rod 21 and the refractive index n2 of the cladding pipe 22 can be adjusted by the monomer composition, molecular weight and the like. The core rod 21 may have a refractive index distribution in the x direction. Similarly, the first cladding pipe 22 may have a refractive index distribution in the x direction.

  Then, the core rod 21 and the cladding pipe 22 are integrated by heating the core rod 21 and the cladding pipe 22 of the obtained single core clad / core composite material 23 in a reduced pressure atmosphere, preferably in a vacuum atmosphere. After being processed, it is subjected to the step of drawing. The pressure in the reduced pressure atmosphere, preferably the vacuum atmosphere, and the heating temperature are the same as in the known method.

  FIG. 4 is a schematic view showing an example of a single-core fiber forming device in the present embodiment. In FIG. 4, the single-core fiber forming device 30 includes a heating unit 31, a drawing unit 32, a cutting unit 33, and a vacuum pump 34.

  The heating means 31 is a circular heater disposed opposite to each other with the tip of the single-core clad / core composite material 23 interposed therebetween. The heating means 31 heats the tip of the single-core clad / core composite material 23 whose position has been adjusted by the holding means (not shown).

  The wire drawing means 32 is a pair of pressure rollers for pressing and holding the tip of the heated single-core clad / core composite material 23. The drawing means 32 draws the tip of the heated single-core clad / core composite material 23.

  The cutting means 33 is a cutter. The cutting means 33 cuts the manufactured single-core fiber strand 35 into a predetermined length.

  The vacuum pump 34 evacuates through a tube to make the space between the core rod 21 and the cladding pipe 22 a reduced pressure atmosphere or a vacuum atmosphere.

  The single-core fiber strand 35 is manufactured from the single-core clad / core composite material 23 using the single-core fiber forming device 30 having the above configuration.

  The single-core fiber forming apparatus 30 is configured such that the inside of the chamber 34 is in a reduced pressure atmosphere, preferably in a vacuum atmosphere, and the single-core fiber strand 35 is formed to form the core 41 of the single-core fiber strand 35 and the cladding. It is suppressed that gas such as air, impurities, and foreign matter remain with the layer 42.

  Specifically, the single-core fiber forming apparatus 30 heats the tip of the single-core clad / core composite material 23 by the heating means 31 in a reduced pressure atmosphere, preferably in a vacuum atmosphere, and then draws the wire by the drawing means 32. And cut into a predetermined length by the cutting means 33. A single-core fiber strand 35 of a predetermined length is manufactured by these series of processes. In the step of drawing, the pressure in the reduced pressure atmosphere, preferably the vacuum atmosphere and the heating temperature are the same as in the known method.

  Next, in step S12 of FIG. 1, a bundle preform is formed. Specifically, as shown in FIG. 2, the number of single-core fiber strands 35 corresponding to the number N of pixels of PIF is prepared. The single-core fiber strand 35 is obtained by coating one core rod 21 with a clad pipe 22 in step S11. In step S12, in order to equalize the core diameter of the PIF and the core pitch indicating the distance between the cores, it is preferable to prepare a plurality of single-core fiber strands 35 of the same specification. Also, in the single-core fiber strand 35, the core rod 21 is made of the same material (a translucent polymer with a relatively high refractive index) as the core of PIF, and the cladding pipe 22 is the same material (a relatively low refractive index) Of the transparent polymer). That is, the refractive index of the core rod 21 is higher than the refractive index of the cladding pipe 22.

  Thus, in step S12 of FIG. 1, a bundle preform is formed. FIG. 5 is a perspective view showing an example of a bundle preform. As shown in FIG. 5, in the bundle preform 40, single-core fiber strands 35 in a number corresponding to the number N of pixels of the PIF 70 are inserted into the hollow portion of the second cladding pipe 43 made of cladding material.

  In FIG. 5, the fiber strand bundle 45 indicates a bundle of a plurality of single-core fiber strands 35 (fiber strand bundle). The inner diameter of the second clad pipe 43 is designed to be slightly larger than the fiber bundle 45. Also, the second cladding pipe 43 mainly serves as an outer edge portion of the PIF 70.

  FIG. 5 is a cross-sectional view of a bundle preform. In FIG. 5, the bundle preform 40 is inserted into the hollow portion of the second clad pipe 43 by bundling a plurality of single-core fiber strands 35 consisting of one core 41 and the clad layer 42 covering the core 41. It is done.

  At the time of forming the bundle preform, in the bundle preform 40, a plurality of single-core fiber strands 35 located between each other and among the plurality of single-core fiber strands 35 at the outermost periphery. An air gap 44 exists between the fiber strand 35 and the second clad pipe 43. At this point of time, the cladding layers 42 of the plurality of single-core fiber strands 35 and the second cladding pipe 43 are not integrated with each other, and are distinguishable.

  In FIG. 5, the core diameter sa of the single-core fiber strand 35, the separation distance 2 × st of the cores 41 of two single-core fiber strands 35 adjacent to each other (corresponding to twice the cladding layer thickness st), The outer diameter sd of the single-core fiber strand 35 is defined.

  The core pitch in the bundle preform 40 matches the outer diameter sd of the single-core fiber strand 35.

  In step S12 of FIG. 1, when bundling a plurality of single-core fiber strands 35, a solution containing a surfactant is used to form a bundle preform by arranging the single-core fiber strands in order without damage. be able to. For example, a plurality of single-core fiber strands 35 can be stacked in a solution containing a surfactant to obtain the fiber strand 45 of FIG. FIG. 6 is a perspective view showing an example of a fiber strand bundle. Then, the fiber strand bundle 45 is inserted into the hollow portion of the clad pipe 43 to obtain a bundle preform 40. FIG. 7 is a perspective view showing an example of a bundle preform.

  In step S12 of FIG. 1, instead of the step of bundling a plurality of single-core fiber strands 35 in a solution containing a surfactant and the step of inserting the fiber strand 45 into the hollow portion of the clad pipe 43, The bundle preform 40 may be obtained by inserting a plurality of single-core fiber strands 35 into the hollow portion of the clad pipe 43 while bundling them in a solution containing a surfactant.

  The surfactant used in step S12 of FIG. 1 may be either an anionic surfactant, a nonionic surfactant or an amphoteric surfactant, or a combination thereof.

As anionic surfactants, fatty acid systems such as sodium fatty acid and sodium alpha sulfonated fatty acid ester;
Linear alkyl benzenes such as linear alkyl benzene sulfonic acid sodium (LAS);
Sodium alkyl sulfate such as sodium lauryl sulfate (SLS) (AS), and higher alcohol such as sodium alkyl ether sulfate (AES);
Alpha olefins such as alpha olefin sulfonate sodium (AOS);
Examples thereof include normal paraffins such as sodium alkyl sulfonate and the like.
Examples of the cationic surfactant include alkyl trimethyl ammonium salts, dialkyl dimethyl ammonium salts, and alkyl benzyl dimethyl ammonium salts.

As a nonionic surfactant,
Higher alcohols such as polyoxyethylene alkyl ether (AE);
Alkylphenols such as polyoxyethylene alkylphenyl ether (APE);
Sucrose fatty acid salt esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene fatty acid esters, and fatty acids such as alkanolamides and the like can be mentioned.

  Amphoteric surfactants include alkyl dimethyl amine oxide and alkyl carboxy betaine. Among the above, anionic surfactants are preferable because they are easily available at low cost and hard to remain, and higher alcohol anionic surfactants such as sodium lauryl sulfate (SLS) are particularly preferable.

  The surfactant is preferably used in the form of an aqueous solution to facilitate removal in a later step. The concentration of the surfactant in the aqueous solution is not particularly limited as long as it is equal to or higher than the critical micelle concentration, and for example, about 0.3 to 0.7% by mass is preferable. Moreover, surfactant can use 1 type, or 2 or more types of well-known things.

  Moreover, a temporary adhesive can be added to the solution (preferably aqueous solution) containing surfactant as needed. As the temporary adhesive, a water-soluble polymer such as polyvinyl alcohol (PVA) is preferable because it can be easily removed by water washing or the like in a later step.

  By using the temporary adhesive, the fiber strand bundle 45 to which a plurality of single-core fiber strands 35 are temporarily bonded is obtained, and the handleability at the time of being subjected to the later process is improved. In addition, you may add another arbitrary component to the solution (preferably aqueous solution) containing surfactant as needed. In addition, water-soluble substances are preferable because other optional components can be easily removed by water washing or the like in a later step.

Next, in step S13 of FIG. 1, the bundle preform 40 is cleaned.
As described above, in the present embodiment, the bundle preform is formed in the surfactant to prevent the single-core fiber strand 35 from being damaged. On the other hand, when the surfactant used when bundling core fiber strands is not completely removed, the remaining component such as surfactant precipitates and squeezes the core to increase the optical loss in the core. There is a fear that it may occur and the light signal between the cores may vary. In addition, when foreign matter is mixed between single-core fiber strands when bundling single-core fibers, similarly, there is a fear that optical signals between cores may vary.

  Therefore, in the present embodiment, components of the solution used in step S12 of FIG. 1 attached to the bundle preform 40 by cleaning the bundle preform (surfactant and temporary adhesive used as needed) Etc.) and foreign substances mixed in during preforming.

  FIG. 8 is a schematic view showing an example of the cleaning apparatus in the present embodiment. In FIG. 8, the cleaning device 50 includes an ultrapure water tank 51, a pressure line 52, a water injection pump 53, an electromagnetic valve 54, a hollow fiber filter 55, a pressure gauge 56, an electromagnetic valve 57, and submicrons. A pore filter 58, a solenoid valve 59, a strength holding member 60, a solenoid valve 61, a pressure gauge 62, a solenoid valve 63, and an aspirator 64 are provided.

  The ultrapure water tank 51 is a tank for storing ultrapure water. The ultrapure water tank 51 is always filled with ultrapure water.

  The water injection pump 53 is connected to the ultrapure water tank 51 and the solenoid valve 54 via a pipe, pressurizes the ultrapure water tank 51, and sends it to the solenoid valve 54.

  The solenoid valve 54 is connected to the water injection pump 53 and the hollow fiber filter 55 through a pipe, and the ultra pure water supplied from the water injection pump 53 is circulated or blocked to the hollow fiber filter 55.

  One of the hollow fiber filters 55 is connected to the solenoid valve 54 by piping, and the other is connected to the pressure gauge 56 and the solenoid valve 57 by piping. The hollow fiber filter 55 also removes impurities from the ultrapure water fed from the water injection pump 53.

The pressure gauge 56 is a pressure gauge that measures the pressure in the pipe from the hollow fiber filter 55 to the solenoid valve 57. The water injection pump 53 is selected to have a water pressure of, for example, 303 kPa (3 kgf / cm ² ). All pressures in this specification are expressed as gauge pressure.

  One end of the solenoid valve 57 is connected to the hollow fiber filter 55 and the pressure gauge 56 by piping, and the other is connected to the bundle preform 40 by piping. The bundle preform 40 is removable from the piping. Then, the solenoid valve 57 passes or blocks the ultrapure water sent from the water injection pump 53 to the bundle preform 40.

A supply source of nitrogen gas is connected to the pressure line 52, and piping is performed so that a pressure of, for example, 303 kPa (3 kgf / cm ² ) can be applied.

  The submicron pore filter 58 is a filter for removing nitrogen gas impurities. One of the submicron pore filters 58 is connected to the pressure line 52, and the other is connected to the solenoid valve 59 through a pipe.

One end of the solenoid valve 59 is connected to the submicron pore filter 58 via a pipe, and the other end is connected to the bundle preform 40 by a pipe common to the solenoid valve 57. The bundle preform 40 is removable from the piping.
The strength retaining material 60 is a retaining material that covers the periphery of the bundle preform.

One end of the solenoid valve 61 is connected to the bundle preform via a pipe common to the solenoid valve 57. Bundle preforms should be removable from the piping. Also, the solenoid valve 61 connects the other to the pressure gauge 62 and the solenoid valve 63 via piping.
The pressure gauge 62 is a pressure gauge that measures the pressure in the piping to the aspirator 64.

  One end of the solenoid valve 63 is connected to the solenoid valve 61 and the pressure gauge 62 by piping, and the other is connected to the aspirator 64 by piping. The solenoid valve 63 is opened when the aspirator 64 sucks.

  The aspirator 64 sucks the ultrapure water in the bundle preform 40 through the solenoid valve 61, the solenoid valve 63 and the pipe. An aspirator 64 is connected to the decompression line 65, and piping is performed so that the pressure can be reduced to −80.8 kPa (−608 Torr) or less by the pressure gauge 62.

Hereinafter, operations 1 to 7 of the cleaning device 50 will be shown according to the procedure. In each operation, the open / close state of the solenoid valve is as shown in Table 1. Although the solenoid valve may be controlled manually, program control is more desirable. The following shows the operation method based on program control.

<Procedure 1> In-Bundle Decompression The gap between single-core fibers in the bundle is decompressed using an aspirator. The solenoid valves to be opened are 61 and 63, and all other solenoid valves are closed. If the ultimate pressure of the pressure gauge 62 can be reduced to -80.8 kPa (-608 Torr) or less, the process moves to step 2.

<Operation 2> Ultra pure water injection The ultra pure water stored in the ultra pure water tank is pressurized by the injection pump and injected into the bundle preform 40. At this time, it is necessary to make ultra pure water flow in the bundle preform 40 through the hollow fiber filter so that extra pure water without foreign matter flows in. For example, the inflow was 100 cc. The solenoid valves to be opened are 57 and 54, and all other solenoid valves are closed. When the ultimate pressure of the pressure gauge 62 rises to 40.4 kPa (0.4 kgf / cm ² ), the operation moves to operation 3.

<Operation 3> Stopping water injection Stop the ultra pure water being injected in operation 2. The solenoid valves are all closed.

<Operation 4> Ultra pure water drainage The water accumulated in the bundle preform 40 is drained by depressurizing. The solenoid valves to be opened are 61 and 63, and all other solenoid valves are closed. If the pressure of the pressure gauge 62 becomes 0 Pa (0 kgf / cm ² ) or less, the operation moves to operation 5. At the completion of the operation 4, ultrapure water remains between single-core fiber strands in the bundle preform.

<Operation 5> Nitrogen gas injection Ultrapure water remaining between single-core fiber strands in a bundle preform is removed by injecting nitrogen gas. The impact force expels foreign matter from the inside of the bundle preform 40. The solenoid valves to be opened are 59, 61 and 63, and all other solenoid valves are closed. The nitrogen gas injection time may be, for example, about 1 to 10 seconds.

<Operation 6> Drainage complete Drain the ultrapure water accumulated under the single-core fiber strand of the bundle preform 40. The solenoid valves to be opened are 61 and 54, and all other solenoid valves are closed. If the ultimate pressure of the pressure gauge 62 can be reduced to -80.8 kPa (-608 Torr) or less, the procedure 7. Move to

<Operation 7> Drainage stop All solenoid valves are closed.

The operations 1 to 7 for the water stream cleaning are repeated 2000 times. By performing the operations in the order of operations 1 to 7, it is possible to alternately repeat the injection and the drainage one or more times alternately in the bundle preform 40 by the pressurizing means and the depressurizing means, and the surfactant and foreign matter are It can be cleaned and discharged. The water flowing into the bundle container can have a larger pressure difference when the cleaning liquid is injected if the bundle preform 40 is previously depressurized. The pressure reduction state can be grasped by the pressure gauge 62, and the pressure degree can be grasped by the pressure gauge 56. Further, the pressure difference between the pressure gauges 56 and 62 is the pressure of water flowing into the bundle container. When the water pressure is, for example, 303 kPa (3 kgf / cm ² ) and the ultimate pressure of the aspirator 64 is -80.8 kPa (-608 Torr), 303-(-80.8) = 383.8 kPa. The pressure difference is 250 kPa or more, preferably 300 kPa or more, and more preferably 350 kPa or more.

  The washing of the bundle preform 40 can be performed using a washing solution. The cleaning solution may be any one that does not damage the single-core fiber strand 35 and can remove foreign substances between the single-core fiber strands and any component such as a surfactant and a temporary adhesive used as needed. Water (hereinafter, also referred to as washing water) is preferable as the washing liquid in order to suppress the adhesion of extra components to the bundle preform 40 anew. As the washing water, pure water with few impurities is preferable, and ultrapure water with the amount of impurities of 0.01 μg / L or less is particularly preferable.

  Then, the surfactant is removed by flowing the cleaning solution from the bundle preform. However, in order to remove the foreign matter between single-core fiber strands, the foreign matter may not be sufficiently removed simply by flowing the cleaning solution.

  Therefore, in the present embodiment, the pressurized cleaning fluid is caused to flow into the bundle preform 40, and the foreign matter is removed from the bundle preform 40 by the force of pressure. Further, in step S13, if the bundle preform 40 is depressurized in advance, the pressure difference can be further increased when the cleaning liquid is injected. In addition, by injecting the pressurized gas instantaneously while the cleaning liquid is being filled between the single-core fiber strands of the bundle preform 40, it is possible to apply an impact force to the foreign matter, and similarly, the foreign matter is It can be expelled from within the bundle preform 40.

  Thereafter, the pressure of the bundle preform 40 is reduced to recover wash water and foreign matter from the bundle preform 40. Contamination foreign matter between single-core fiber strands in the bundle preform 40 is cleaned and discharged by alternately repeating the liquid injection and the drainage one or more times in the bundle preform 40 by the pressurizing means and the pressure reducing means. be able to.

The pressurizing means for the cleaning solution is preferably an inert gas, for example, nitrogen gas is more preferable. The pressure to be applied is preferably large, but preferably about 303 kPa (3 kgf / cm ² ) in consideration of the adhesive strength of the bundle preform container. A vacuum pump can be used as the pressure reducing means, and it is desirable to reduce the pressure to approximately −80.8 kPa (−608 Torr) or less.

  The bundle preform 40 after cleaning is heated in a reduced pressure atmosphere, preferably in a vacuum atmosphere, to integrate the whole, and then subjected to the next step of wire drawing.

  In addition, the pressure and heating temperature of a pressure-reduced atmosphere, preferably a vacuum atmosphere can use a well-known method.

  Next, in step S14 of FIG. 1, a PIF 70, which is a multicore fiber, is formed. FIG. 9 is a schematic view showing an example of a multi-core fiber manufacturing apparatus according to the present embodiment.

  In FIG. 9, a multicore fiber forming apparatus 80 includes holding means (not shown), heating means 81, wire drawing means 82, and a vacuum pump 83.

  The holding means holds the bundle preform 40 and adjusts its position.

  The heating means 81 heats the tip of the bundle preform 40. For example, the heating means 81 are a pair of heaters disposed to face each other with the tip of the bundle preform 40 interposed therebetween.

  The drawing means 82 draws the tip of the heated bundle preform 40. For example, the wire drawing means 82 is a pair of pressure rollers for pressing and holding the tip portion of the heated bundle preform 40.

  In the multicore fiber forming apparatus 80, the PIF 70 is manufactured under a reduced pressure atmosphere by a vacuum pump, preferably under a vacuum atmosphere, in order to bring the core and the clad of the PIF 70 into close contact with each other.

  As shown in FIG. 9, the tip of the bundle preform 40 is heated by the heating means 81 in a reduced pressure atmosphere, preferably in a vacuum atmosphere, and then drawn by the drawing means 82. PIF 70 is manufactured by these series of processes.

  In the step of drawing, the pressure in the reduced pressure atmosphere, preferably the vacuum atmosphere and the heating temperature are the same as in the known method.

  The produced multicore fiber is shown in FIG. FIG. 10 is a cross-sectional view of a multicore fiber. As shown in FIG. 8, in the PIF 70, the air gap existing in the bundle preform 40 disappears, and the cladding layer 42 of the plurality of single-core fiber strands 35 and the second cladding pipe 43 are fused and integrated with each other. The cladding 72 is formed. In the cross-sectional view, a PIF 70 having a sea-island structure in which a plurality of cores 71 are formed in an island shape is manufactured in the clad 72 which is a sea portion.

  The manufacturing method of the above-mentioned multi-core fiber can also be realized by a manufacturing device combining the devices of FIG. 4, FIG. 8 and FIG. FIG. 11 is a block diagram showing the configuration of the multi-core fiber manufacturing apparatus of the present embodiment. In FIG. 11, the multicore fiber manufacturing apparatus 90 includes a single core fiber forming part 91, a bundle preform forming part 92, a cleaning part 93, and a multicore fiber forming part 94.

  The single-core fiber forming portion 91 inserts the core rod 21 into the hollow portion of the first clad pipe 22 to form a single-core clad / core composite material 23, and the reduced-pressure atmosphere of the single-core clad / core composite material 23 The core rod 21 and the clad pipe 22 are integrated by heating under the bottom, preferably under a vacuum atmosphere, and wire drawing and cutting are performed. For example, the single core fiber forming unit 91 is preferably the single core fiber forming apparatus of FIG. 4 described above.

  The bundle preform forming unit 92 inserts a single-core fiber strand whose core is covered with a cladding layer into the hollow portion of a cladding pipe made of the same material as the cladding layer to obtain a bundle preform.

  The cleaning unit 93 cleans the bundle preform and removes the surfactant and foreign matter between single-core fiber strands in the bundle preform. For example, the cleaning unit 93 preferably has the configuration of FIG. 8 described above.

  The multicore fiber forming unit 94 heats the bundle preform 40 in a reduced pressure atmosphere, preferably in a vacuum atmosphere, and then draws the bundle preform 40. For example, the configuration of FIG. 9 described above is preferable for the multicore fiber forming part 94.

  Thus, when bundling single-core fiber strands by feeding a cleaning solution between single-core fiber strands in the formed bundle preform and cleaning the multi-core fiber manufacturing apparatus of the present embodiment, The surfactant used and foreign matter between single-core fiber strands can be removed, and variations in optical signals between cores can be reduced.

Next, Examples and Comparative Examples according to the present invention will be described.
Example 1
First, prepare a core rod made of polystyrene (PS, refractive index 1.59) with an outer diameter of 53 mm, and a first clad pipe made of polymethyl methacrylate (PMMA, refractive index 1.494) with an inner diameter of 55 mm and an outer diameter of 70 mm. did. Next, as shown in FIG. 2, the core rod was inserted into the hollow portion of the first clad pipe to obtain a single core clad / core composite material.

In the single core clad / core composite material, the distribution of the refractive index nd in one direction (x direction) from the central axis toward the outer periphery is such that the refractive index nd in the core rod is in the x direction as shown in FIG. It was uniform, and the refractive index nd of the first cladding pipe was uniform in the x direction.
Next, as shown in FIG. 4, the obtained single-core clad / core composite material was heated in a vacuum atmosphere, drawn, and cut to obtain a single-core fiber strand. .

The obtained single-core fiber strand had a core diameter sa = 0.68 mm, a cladding layer thickness st = 0.10 mm, an outer diameter sd = 0.88 mmφ, a core area ratio sE = 60%, and a length = 200 mm. .
5200 single-core fiber strands described above were prepared.

Next, as shown in FIG. 6, 5200 single-core fiber strands were bundled in a 0.5% by mass sodium lauryl sulfate (SLS) aqueous solution to obtain a fiber strand bundle.
Next, as shown in FIG. 7, the obtained fiber strand is inserted into the hollow portion of a second clad pipe made of polymethyl methacrylate (PMMA, refractive index 1.494) having an outer diameter of 70 mm and a thickness of 2 mm. I got a bundle preform.

Next, the obtained bundle preform was washed with water using ultrapure water (maximum resistance: 18.2 MΩ) obtained by sequentially passing tap water through a filter having an opening diameter of 0.2 μm and an ion exchange membrane. . Water washing is the procedure 2. To operation 10. Was repeated 2000 times. The water pressure was 303 kPa (3 kgf / cm ² ), the ultimate pressure of the aspirator 64 was -80.8 kPa (-608 Torr), and the pressure difference was 303-(-80.8) = 383.8 kPa. By this water washing, the surfactant attached to the bundle preform and the foreign matter mixed in the single-core fiber strand were removed. The above-mentioned cleaning device 50 was used for cleaning.

  Using the apparatus shown in FIG. 9, the tip of the bundle preform was heated by a heating means in a reduced pressure atmosphere, preferably in a vacuum atmosphere, and then drawn by a drawing means to obtain PIF. The length of PIF was 2 m. When cross-sectional observation with an optical microscope was carried out on the obtained PIF, dark defects and missing pixels were 0.1% or less of all pixels.

The cross-sectional photograph by an optical microscope is shown in FIG. 12 is a cross-sectional photograph of the optical microscope of Example 1. FIG. Main production conditions and evaluation results are shown in Table 2. The obtained PIF has pixel number N (core number) = 5200, core diameter ma (pixel diameter) = 3.4 μm, core pitch mp = 4.4 μm, virtual cladding layer thickness mt = 0.5 μm, core area ratio mE = The effective diameter D1 was 328 μm, and the outer diameter D2 was 340 μm. In addition, although ma, mp, and mt were made into the average value of ten places chosen at random, the dispersion | variation by a measurement location was not seen.

(Example 2)
Operation of water flow cleaning 2. To operation 10. Are the same as Example 1 except repeating 1000 times. When cross-sectional observation with an optical microscope was performed on the obtained PIF, dark defects of about 5% of the total number of pixels were observed. The cross-sectional photograph by an optical microscope is shown in FIG. FIG. 13 is a cross-sectional photograph of the optical microscope of Example 2. Main production conditions and evaluation results are shown in Table 2.

(Example 3)
Operation of water flow cleaning 2. To operation 10. Are the same as Example 1 except for repeating 10 times. When cross-sectional observation with an optical microscope was performed on the obtained PIF, a dark defect of about 10% of the total number of pixels was observed. The cross-sectional photograph by an optical microscope is shown in FIG. FIG. 14 is a cross-sectional photograph of the optical microscope of Example 3. Main production conditions and evaluation results are shown in Table 2.

(Example 4)
The same as Example 1 except that in place of the 0.5% by mass sodium lauryl sulfate (SLS) aqueous solution, fiber strands were bundled in pure water. When cross-sectional observation with an optical microscope was performed on the obtained PIF, dark defects of about 1% of the total number of pixels were observed. The proportion of the number of pixels in the hexagonal close-packed array was 50% or less.

(Comparative example 1)
The same as Example 1 except that the pressure of nitrogen gas in the pressurizing line was not applied and the cleaning was performed without using a water injection pump. The water pressure is 20.2 kPa (0.2 kgf / cm ² ), the ultimate pressure at aspirator 64 is -80.8 kPa (-608 Torr), and the pressure difference is 20.2-(-80.8) = 101 kPa. The When cross-sectional observation with an optical microscope was performed on the obtained PIF, a dark defect of about 20% of the total number of pixels was observed. The cross-sectional photograph by an optical microscope is shown in FIG. FIG. 15 is a cross-sectional photograph of the optical microscope of Comparative Example 1. The main manufacturing conditions and the evaluation results are shown in Table 3.

(Comparative example 2)
The pressure was the same as in Example 1 except that the pressure of nitrogen gas in the pressure line was 121.2 kPa (1.2 kgf / cm ² ) and the pressure of the water injection pump was 121.2 kPa (1.2 kgf / cm ² ). . The pressure difference was 121.2 − (− 80.8) = 202 kPa. When cross-sectional observation with an optical microscope was performed on the obtained PIF, a dark defect of about 15% of the total number of pixels was observed. The cross-sectional photograph by an optical microscope is shown in FIG. FIG. 16 is a cross-sectional photograph of the optical microscope of Comparative Example 2. The main manufacturing conditions and the evaluation results are shown in Table 3.

(Comparative example 3)
Example 1 is the same as Example 1 except that the water washing is not performed. When cross-sectional observation with an optical microscope was performed on the obtained PIF, a dark defect of about 50% of the total number of pixels was observed. The cross-sectional photograph by an optical microscope is shown in FIG. FIG. 17 is a cross-sectional photograph of the optical microscope of Comparative Example 3. The main manufacturing conditions and the evaluation results are shown in Table 3.

(Comparative example 4)
It is the same as Comparative Example 1 except that instead of the 0.5% by mass sodium lauryl sulfate (SLS) aqueous solution, fiber strands are bundled in pure water. When cross-sectional observation with an optical microscope was performed on the obtained PIF, dark defects of about 5% of the total number of pixels were observed. The proportion of the number of pixels in the hexagonal close-packed array was 50% or less.

  As described above, foreign matter can be cleaned and discharged by alternately repeating the pouring and drainage in the bundle preform by the pressurizing means and the depressurizing means. If the pressure difference is small, foreign matter can not be removed even if the number of washings is large. Even if the pressure difference is large, foreign matter can not be removed as well if the number of times of cleaning is small.

  The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the scope of the present invention. For example, in each of the above-mentioned embodiments, although a plastic image fiber which can exhibit superiority in flexibility is described, the material of the image fiber itself is not particularly limited.

  As shown in FIG. 6, the single-core fiber strand 35 is one in which one core 41 formed from the core rod 21 is covered with a cladding layer 42 formed from the first cladding pipe 22.

In the single-core fiber strand 35, the core diameter is sa, the cladding layer thickness is st, the outer diameter of the single-core fiber strand 35 is sd, and the core area ratio is sE. The outer diameter sd and the core area ratio sE of the single-core fiber strand 35 are represented by the following formulas (1) and (2).
sd = sa + 2 x st (1)
sE (%) = (sa / sd) ² x 100 (2)

  In the manufacturing method of the present embodiment, although the whole is thinned in the step of drawing the bundle preform 40, the area ratio between the individual cores and the cladding layer covering this does not change. Moreover, in this specification, the outer edge part is excluded in calculation of the core area ratio mE of PIF70. Therefore, the core area ratio sE of the single-core fiber strand 35 used for manufacture and the core area ratio mE of the PIF 70 are basically the same.

  Therefore, at the time of production of the single-core fiber strand 35, the core area ratio sE of the single-core fiber strand 35 may be designed to a desired value of the core area ratio mE of the PIF 70. As described above, considering the balance of brightness and crosstalk, the core area ratio mE of PIF 70 is preferably 50 to 62%, more preferably 53 to 60%. As described above, since the core area ratio sE of the single core fiber strand 35 is basically the same as the core area ratio mE of the PIF 70, the core area percentage sE of the single core fiber strand 35 is the core area ratio of the PIF 70 Similar to mE, it is preferably 50 to 62%, more preferably 53 to 60%.

  The core area ratio sE of the single-core fiber strand 35 is correlated with the core diameter sa of the single-core fiber strand 35, the cladding layer thickness st, and the outer diameter sd of the single-core fiber strand 35. In addition, various parameters of the PIF 70 to be manufactured depend on the parameters of the single-core fiber strand 35. Therefore, according to the various parameter design of PIF70, the various parameters of single core fiber strand 35 are designed within the desirable range.

The core diameter sa of the single-core fiber strand 35 is preferably 3.2 to 3.6 mm.
The clad layer thickness st of the single-core fiber strand 35 is preferably 0.4 to 0.6 mm.
The outer diameter sd of the single-core fiber strand 35 is preferably 4.0 to 4.8 mm.

  In the manufacturing method of the present embodiment, since it is not necessary to use a composite cap, it is possible to flexibly cope with changes in product specifications such as pixel diameter (core diameter ma), pixel number N (core number), and core area ratio mE.

  In the manufacturing method of the present embodiment, since the pixel diameter (core diameter ma), the number of pixels N (number of cores), the core area ratio mE, etc. can be freely designed, the average brightness and crosstalk of the lit pixels The PIF 70 can be designed to a suitable range and has excellent optical quality.

  In the manufacturing method of the present embodiment, a plurality of single-core fiber strands 35 are bundled using a solution (preferably, an aqueous solution) containing a surfactant to improve slippage between the multiple single-core fiber strands 35. The plurality of single-core fiber strands 35 can be prevented from rubbing against each other and scratching each other. Thereby, the dark defect of PIF70 resulting from the damage | wound etc. which were attached to the single-core fiber strand 35 is suppressed.

  Moreover, since the slippage between the plurality of single-core fiber strands 35 is improved, they can be naturally arranged neatly. As a result, pixel omission of the PIF 70 is suppressed. In addition, since the pixel arrangement is orderly, it is possible to transmit a high definition image using the PIF 70.

  As shown in FIG. 10, the PIF 70 of the present embodiment is a plastic fiber having a clad 72 and a plurality of cores 71 formed in the clad 72, and the individual cores 71 constitute plastic pixels. It is an image fiber. The PIF 70 has a sea-island structure in which a plurality of cores 71 are formed in an island shape in a clad 72 which is a sea portion in a cross sectional view.

  In the PIF 70, light passes into the individual cores 71. In order to confine light in the individual cores 71 and to guide the light well, it is necessary that the refractive index of the cores 71 be relatively larger than the refractive index of the cladding 72.

  The core 71 is made of a translucent polymer having a relatively high refractive index, and the cladding 72 is constructed of a translucent polymer having a relatively low refractive index.

As a combination of core material / cladding material,
Polystyrene (PS, for example, a refractive index of about 1.59) / polymethyl methacrylate (PMMA, for example, a refractive index of about 1.494),
Polybenzyl methacrylate (PBzMA, for example, about 1.57 refractive index) / polymethyl methacrylate (PMMA, for example, about 1.494 refractive index), and
Polymethyl methacrylate (PMMA, for example, a refractive index of about 1.494) / 2,2,2-trifluoroethyl methacrylate (for example, a refractive index of about 1.42) or the like is preferable.

  The PIF 70 may be a step index type in which the refractive index distribution in the core 71 is uniform, or may be a graded index (GI) type in which the refractive index distribution in the core 71 changes gradually. Good.

  The PIF 70 has an outer edge portion made of cladding material which does not contribute to image transmission. The portion excluding the outer edge portion is an effective portion substantially contributing to image transmission. In FIG. 10, a minimum imaginary circle 43 including all pixels (core 71) is drawn with the center of PIF 70 as the center point. The diameter of the imaginary circle 43 is defined as the effective diameter D1 of the PIF 70, and the sectional area of the imaginary circle 43 is defined as the effective sectional area of the PIF 70. In the figure, the code D2 is the outer diameter of the PIF 70.

  In FIG. 10, a symbol ma indicates a core diameter, and a symbol mp indicates a core pitch (pixel pitch). In the PIF 70, the number of cores is N. These parameters are designed according to the desired specifications. In FIG. 10, for simplification, the number of cores is illustrated less than the actual number.

  In the PIF 70, there is a cladding layer covering the individual cores 71 around the individual cores 71, but the individual cladding layers covering the individual cores 71 and the cladding layer of the outer edge portion are integrated with each other, respectively. Can not be clearly identified.

  However, in FIG. 10, the individual cladding layers covering the individual cores 71 are illustrated as "virtual cladding layers 42". The “virtual cladding layer 42” may be simply referred to as a cladding layer for the convenience of description.

In FIG. 10, the separation distance between two adjacent cores 71 is illustrated as 2 × mt.
Here, mt is the thickness of the virtual cladding layer 42 covering the individual cores 71 (virtual cladding layer thickness). In PIF 70, one pixel consists of one core 71 and a virtual cladding layer 42 covering it. The pixel diameter is ma + 2 × mt. The core 71 is a substantial lighting part in one pixel. The number of pixels N (number of cores) of the PIF 70 is designed according to the application and the like. The higher the number of pixels N, the higher the definition.

  In applications such as endoscopes, the number of pixels N is preferably 2000 or more, more preferably 5200 or more, more preferably 10000 or more, more preferably 20000 or more, more preferably 30000 or more, particularly preferably 40000 or more. In general, in the PIF 70, if the pixel diameter (core diameter) and the number of pixels (number of cores) are the same condition, the average brightness of the lit pixels (average brightness of the lit core and the cladding layer covering the same) The degree of blurring of the image, referred to as and) and crosstalk is correlated with the core area ratio mE.

  The larger the core area ratio mE, the smaller the proportion of the cladding layer, so the average brightness of the lit pixels is improved, but the degree of blurring of the image is increased by crosstalk and the image quality tends to be degraded. On the other hand, the smaller the core area ratio mE, the larger the ratio of the cladding layer, so crosstalk is suppressed and the degree of blurring of the image is reduced and the image quality is improved, while the average brightness of the lit pixels is reduced. Tend.

  The core area ratio mE in PIF 70 is the ratio of the total cross sectional area of all cores 71 to the effective cross sectional area of PIF 70 (area of imaginary circle 42), and the general formula: [total cross sectional area of all cores] / [PIF Effective cross-sectional area of

  As described above, the PIF 70 has an outer edge portion (outer portion than the imaginary circle 42) made of cladding material that does not contribute to image transmission, but the outer edge portion is excluded in calculating the core area ratio mE. . This allows the preferred range of parameters to be discussed, focusing specifically on the effective part contributing to image transmission. In the PIF 70, the cores 71 are arranged in a hexagonal close-packed order in cross section.

  Although the details will be described later, according to the manufacturing method according to the present invention, even if the number N of pixels is 5200 or more, a plurality of pixels can be arranged hexagonally and densely in order. The ratio of the number of the plurality of pixels arranged in a hexagonal close-packed manner can be 90% or more, 95% or more, or 100%.

  In the manufacturing method according to the present invention, even if the number N of pixels is 10000 or more, 20000 or more, 30000 or more, or 40000 or more, the number of a plurality of pixels arranged hexagonally densely in cross section with respect to the number N of pixels. The percentage of can be 90% or more, 95% or more, or 100%.

  In the present embodiment, since the plurality of cores 71 can be naturally arranged neatly, there is almost no variation in the core diameter ma, the core pitch mp, the virtual cladding layer thickness mt, and the core area ratio mE in the cross section of the PIF 70 .

Therefore, the core area ratio mE correlates with the core diameter ma, the thickness of the virtual cladding layer 42 covering the individual cores 71 (virtual cladding layer thickness) mt, and the core pitch mp, and the following equations (3) and (4) It is determined by
mE (%) = (ma / mp) ² x 100 (3)
mp = ma + 2 x mt (4)

  In consideration of the balance of brightness and crosstalk, the core area ratio mE of PIF 70 is preferably 50 to 62%, more preferably 53 to 60%. Moreover, in PIF70, an outer diameter is designed according to a use etc.

  For example, in a medical application, since the PIF 70 is inserted into the inside of a catheter tube or the like in an endoscope or the like, the outer diameter is designed to be smaller than the inner diameter of the catheter tube or the like. In the PIF 70, it is necessary to increase the number of pixels N (the number of cores) in order to achieve high definition under the same outer diameter condition. In this case, the core diameter ma becomes smaller. Here, if the core diameter ma is reduced while the core area ratio mE is the same, the head tends to generate crosstalk. Therefore, in order to suppress the crosstalk, it is necessary to reduce the core area ratio mE.

  That is, from the viewpoint of achieving high definition and suppressing crosstalk, it is preferable that the core diameter ma be small and the core area ratio mE be small. The core diameter ma of PIF 70 is preferably 20 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less, and particularly preferably 5 μm or less. In consideration of ease of manufacture, the core diameter ma of PIF 70 is preferably 1 μm or more, more preferably 1.5 μm or more, still more preferably 2 μm or more, and particularly preferably 3 μm or more.

  The virtual cladding layer thickness mt of PIF 70 is designed according to the desired core diameter ma and the desired core area ratio mE. The virtual cladding layer thickness mt of PIF 70 is preferably 0.3 to 1.0 μm, and more preferably 0.5 to 0.7 μm. The effective diameter D1 of the PIF 70 is designed according to the desired pixel diameter (core diameter ma), the desired number of pixels N (number of cores), and the desired core area ratio mE.

  Under the same conditions for the pixel diameter (core diameter ma) and the pixel number N (core number), the outer diameter of the PIF 70 can be made smaller if the thickness (= (D2-D1) / 2) of the outer edge portion is thinner, preferable. However, if the thickness (= (D2−D1) / 2) of the outer edge portion is too small, the light confinement effect by the cladding may be insufficient. The thickness (= (D2-D1) / 2) of the outer edge portion of PIF 70 is preferably 10 to 30 μm.

  In the manufacturing method of the present embodiment, when the surfactant is used, even if the number N of pixels is 5200 or more, a plurality of pixels can be arrayed orderly, and hexagonally densely arranged in cross section with respect to the number N of pixels The ratio of the number of the plurality of pixels can be 90% or more, 95% or more, or 100.

  In the manufacturing method of the present embodiment, when the surfactant is used, even if the number N of pixels is 10000 or more, 20000 or more, 30000 or more, or 40000 or more, they are hexagonally arranged densely in cross section with respect to the number N of pixels. It is possible to set the ratio of the number of pixels to 90% or more, 95% or more, or 100.

  In the present invention, whether or not a certain pixel (G1) is arranged in a hexagonal close-packed manner is judged based on the following criteria. First, in a cross sectional view, six pixels (G2 to G7) present in the recent surroundings as viewed from a certain pixel (G1) are selected. Here, although there are cases where six pixels do not exist around a certain pixel (G1) (for example, the outermost pixels are equivalent), the pixels are counted as not arranged in a hexagonal close-packed manner. Therefore, the ratio of the number of the plurality of pixels which are hexagonally densely arranged in cross sectional view with respect to the number of pixels N is not necessarily 100%.

  Regarding the six pixels (G2 to G7) selected as described above, assuming that the distance between the core belonging to G1 and the pixel pitch of the core belonging to Gi is mpi, the values of mp2 to mp7 are all average values of mp2 to mp7 When the pixel (G1) is in the range of 90% or more and 110% or less of the pixel number, it is counted as being hexagonally densely arranged in the cross sectional view.

Here, the average value of mp2 to mp7 is a value defined by the following equation (5).
(Mp2 + mp3 + mp4 + mp5 + mp6 + mp7) / 6 (5)

  As described above, according to the present embodiment, it is possible to flexibly cope with changes in product specifications such as the pixel diameter (core diameter ma), the number of pixels (number of cores) N, and the core area ratio mE. It is possible to provide a manufacturing method of PIF 70 in which pixel omission is suppressed, a plurality of pixels are aligned in order, and an image can be transmitted with high accuracy.

  In the above embodiment, a single core fiber is formed by covering the core with a cladding layer to form a single core fiber, and a plurality of single core fiber strands are inserted into the hollow portion of the cladding pipe made of the same material as the cladding layer. Although a bundle preform is obtained, a bundle preform may be obtained using a single-core fiber whose core is already coated with a cladding layer.

  The multifilamentary fiber and the multifilamentary fiber production method of the present invention can be preferably applied as a plastic image fiber to medical uses such as endoscopes and industrial uses such as industrial fiberscopes.

Reference Signs List 21 core rod 22 clad pipe 23 core composite material 30 single core fiber forming device 31, 81 heating means 32, 82 wire drawing means 33 cutting means 34 vacuum pump 35 single core fiber strand 40 bundle preform 41 core 42 clad layer 43 clad pipe 44 Air gap 45 Fiber wire bundle 50 Cleaning device 51 Ultra pure water tank 52 Pressure line 53 Water injection pump 54, 57, 59, 61, 63 Solenoid valve 55 Hollow fiber filter 56, 62 Pressure gauge 58 Submicron pore filter 60 Strength retaining material 64 Aspirator 65 Decompression line 71 Core 72 Clad 80 Multi-core fiber forming device 90 Multi-core fiber manufacturing device 91 Single-core fiber forming part 92 Bundle preform forming part 93 Cleaning part 94 Multi-core fiber forming part

Claims (6)

In a method of manufacturing a multi-core plastic fiber having a cladding and a plurality of cores formed in the cladding,
A bundle preform forming step of obtaining a bundle preform by inserting a plurality of single-core plastic fiber strands covered with a cladding layer in a hollow portion of a cladding pipe made of the same material as the cladding layer;
Under a reduced pressure atmosphere to heat the tip of the bundle preform, and drawing, cladding and, the multi-core plastic fiber formation to form a multi-core plastic fiber having a plurality of cores formed in said cladding A method of manufacturing a multi-core plastic fiber, comprising:
In the method of manufacturing the multi-core plastic fiber, a liquid is supplied to a space between the plurality of single-core plastic fiber strands in the bundle preform and the cladding pipe between the bundle preform forming step and the multi-core fiber forming step. A method for producing a multi-core plastic fiber, comprising a washing step of pressurized delivery and washing by applying a pressure difference of 250 kPa or more. The multi-core according to claim 1, wherein in the bundle preform forming step, the plurality of single-core plastic fiber strands are inserted into the hollow portion of the clad pipe in a solution containing a surfactant to obtain a bundle preform. Method of manufacturing plastic fiber. Wherein in the washing step, the manufacturing method of the multi-core plastic fiber according to claim 1 or 2 is repeated two or more times the liquid exhaust and delivery of gas to the pressurized pumping bundle-flops preform after out alternately. A bundle preform forming portion for obtaining a bundle preform by inserting a single-core plastic fiber strand having a core coated with a cladding layer into a hollow portion of a cladding pipe made of the same material as the cladding layer;
Under a reduced pressure atmosphere to heat the tip of the bundle preform, and drawing, a multi-core plastic fiber manufacturing apparatus having a multi-core plastic fibers forming portion for forming a multi-core plastic fibers, and
The multi-core plastic fiber manufacturing apparatus issues an liquid pressurizing pumping into the space (gap) between the multiple single-core plastic fiber in said bundle preform formed in bundle preform forming portion and the clad pipe Has a washing unit to wash,
The multi-core plastic fibers forming unit, multi-core plastic fiber manufacturing apparatus characterized by forming the multi-core plastic fibers from the bundle preform that has been cleaned in the cleaning section. The multi-core method according to claim 4, wherein the bundle preform forming unit inserts the plurality of single-core plastic fiber strands into the hollow portion of the clad pipe in a solution containing a surfactant to obtain a bundle preform. Plastic fiber manufacturing equipment. The apparatus for manufacturing a multi-core plastic fiber according to claim 4 or 5 , wherein the cleaning unit alternately repeats the gas delivery and the exhaust twice or more alternately in the bundle preform.

Images