JP2009198728A - Hollow fiber and method for fabricating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow fiber that attains improvement in fracture threshold value and excels in long-term stability and mechanical strength as well as manufacturing efficiency. <P>SOLUTION: The hollow fiber 1 has: a hollow glass capillary 11 made of quartz; an Ag film 12 which is formed in a thin film shape as a reflection film by sintering Ag nano particles inside the glass capillary 11; and a polyimide layer 13 which is coated so as to cover the outer periphery of the glass capillary 11. This hollow fiber 1 is configured to propagate light into a hollow region 14 provided inside the Ag film 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hollow fiber and a manufacturing method thereof.

  As a conventional hollow waveguide, a hollow fiber formed of a quartz material and having a hollow structure is known. A hollow fiber is a pulse laser beam having a high peak power, or an infrared wavelength band having a wavelength of 2 μm or more, which cannot be used with a solid optical fiber using a silica-based material as a transmission medium. It is used as a transmission line.

  In order to increase the light transmittance in such a hollow fiber, a hollow fiber in which a metal film is coated on the inner surface of a hollow structure has been proposed (for example, see Non-Patent Document 1).

  In the hollow fiber described in Non-Patent Document 1, a silver solution in which silver nitrate is dissolved and a reducing solution containing glucose as a reducing agent are simultaneously sucked and mixed by a vacuum pump, and flows into a glass capillary serving as a base material of the hollow fiber. As a result, silver particles are deposited on the inner wall to provide a silver thin film.

As another hollow fiber, there is one in which a thin film of aluminum is formed on the inner wall of a glass capillary by MOCVD (Metal Organic Chemical Vapor Deposition) method using DMEAA (dimethylethylamine alane) as a raw material (for example, see Non-Patent Document 2). ).
Satoshi Kubota and 6 others, “Production of low-loss thin hollow glass waveguides by silver mirror reaction method”, Laser Research, Laser Society, June 1997, Vol. 25, p438-441 Yuji Matsuura, 1 other "Aluminum hollow fiber for excimer laser", Optical Alliance, Nihon Kogyo Shuppan, July 1999, p20-22

  However, according to the conventional hollow fiber, when using a laser beam having a higher peak power, the stress load due to the laser beam irradiation cannot be ignored depending on the metal particle diameter constituting the metal film formed on the inner wall. Therefore, there is a problem of lowering the fracture threshold of the hollow fiber.

  Accordingly, an object of the present invention is to provide a hollow fiber that realizes an improvement in the fracture threshold, is excellent in stability and mechanical strength over a long period of time, and is excellent in manufacturing efficiency, and a manufacturing method thereof.

  In order to achieve the above object, the present invention comprises a hollow tube and a reflective film formed on the inner wall of the hollow tube, and the reflective film has a metal film obtained by sintering metal nanoparticles. A hollow fiber is provided.

  In order to achieve the above object, the present invention includes a step of injecting a solution in which metal nanoparticles are dispersed in a solvent inside the hollow tube, and attaching the solution to the inner wall of the hollow tube and The step of discharging the excess solution from the inside of the empty tube, the step of drying the solution adhering to the inner wall of the hollow tube, and subjecting the hollow tube dried from the solution to heat treatment and sintering. And a step of forming a metal film on the inner wall of the hollow tube.

  According to the present invention, it is possible to provide a hollow fiber that realizes an improvement in the fracture threshold, is excellent in stability and mechanical strength over a long period of time, and is excellent in manufacturing efficiency, and a manufacturing method thereof.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing a hollow fiber according to a first embodiment of the present invention. The hollow fiber 1 includes a hollow glass capillary 11 made of quartz, an Ag film 12 provided in a thin film as a reflective film by sintering silver (Ag) nanoparticles inside the glass capillary 11, a glass capillary 11 and a polyimide layer 13 that is coated so as to cover the outer peripheral surface. The hollow fiber 1 is configured to propagate light in a hollow region 14 provided inside the Ag film 12.

  The glass capillary 11 has a smooth inner wall and is excellent in optical characteristics and heat resistance. In the first embodiment, a quartz glass capillary having an inner diameter of 500 μm and an outer diameter of 650 μm is used, and the flexibility is excellent.

  The Ag film 12 preferably has an average particle size of Ag nanoparticles before sintering of 10 nm or less, and is formed using Ag nanoparticles having a particle size of 3 to 5 nm in the first embodiment. . Production techniques for metal nanoparticles having such particle diameters have already been established for Ag, Au, and Cu. Further, the film thickness of the Ag film 12 is thicker than the skin depth in the wavelength band of light propagating through the hollow fiber 1 and is preferably 100 nm or less, and is formed to be approximately 50 nm in the first embodiment.

  The polyimide layer 13 is provided in advance so as to cover the outer peripheral surface of the glass capillary 11 as a protective layer. The polyimide layer 13 is exposed to a high-temperature atmosphere in the sintering process for forming the Ag film 12, but has heat resistance enough to withstand this sintering temperature.

  FIGS. 2A to 2D are views showing a method for manufacturing a hollow fiber as a hollow waveguide according to the first embodiment of the present invention. In FIG. 2, a part of the syringe 20 and the glass capillary 11 and the like are shown in cross section for easy explanation. Below, manufacture of the hollow fiber 1 is demonstrated, referring FIG.1 and FIG.2 (a)-(d).

  First, as shown in FIG. 2A, the tip of a syringe 20 having a piston 21 is attached to a base 11 </ b> A provided on the upper part of the glass capillary 11. The syringe 20 includes a columnar piston 21 and a cylindrical main body 22, and constitutes a syringe pump capable of driving the piston 21 with high accuracy. The main body 22 contains a predetermined volume of Ag nanoparticle solution 23 in which the above Ag nanoparticles are dispersed in hexane as a solvent. In the first embodiment, the Ag nanoparticle solution 23 having an Ag content of 35 w% and a viscosity of 10 to 50 mPa · s was used.

  Next, as shown in FIG. 2B, the piston 21 of the syringe 20 is driven in the pushing direction at a constant speed. The Ag nanoparticle solution 23 is discharged from the main body 22 at a constant speed based on the pushing drive of the piston 21 and is injected under pressure into the glass capillary 11.

  The glass capillary 11 adheres to the inner wall as the Ag nanoparticle solution 23 injected into the tube moves downward, and excess Ag nanoparticle solution 23 is discharged from the lower end of the glass capillary 11 as shown in FIG. It is discharged into the container 24. The amount of the Ag nanoparticle solution 23 attached to the inner wall of the glass capillary 11 depends on the viscosity of the Ag nanoparticle solution 23 and the flow rate of the Ag nanoparticle solution 23 in the capillary.

  Next, as shown in FIG. 2 (d), the glass capillary 11 with the Ag nanoparticle solution 23 adhered to the inner wall is accommodated in an electric furnace 25, and subjected to high-temperature heat treatment while nitrogen gas is inserted, whereby Ag nanoparticles are obtained. The solution 23 is dried, and after drying, further heat treatment is performed and sintering is performed.

  In the first embodiment, the heat treatment temperature for sintering the Ag nanoparticle solution 23 is 150 to 350 ° C. This is because at a temperature lower than the above-described temperature range, the density of the Ag film 12 obtained after sintering is low, and sufficient optical properties, mechanical strength, and adhesive force cannot be obtained. Further, at a temperature higher than the above-described temperature range, Ag nanoparticles were aggregated and the particle diameter tended to be coarse.

  Based on this high temperature heat treatment, an Ag film 12 is formed on the inner wall of the glass capillary 11. The thickness of the Ag film 12 after sintering depends on the Ag content, but if the Ag content exceeds 40 wt% or the viscosity of the Ag nanoparticle solution 23 exceeds 100 mPa · s, the Ag film 12 is uniform. It is difficult to provide a desired film thickness with high accuracy. In the temperature range of 150 to 350 ° C., the polyimide layer 13 that is coated on the outer surface of the glass capillary 11 in advance as a protective layer can withstand sufficiently.

(Effects of the first embodiment)
According to the hollow fiber of the first embodiment described above, the Ag film was sintered and formed by attaching an Ag nanoparticle solution 23 in which Ag nanoparticles were dispersed in a solvent to the inner wall of the glass capillary and performing a high-temperature heat treatment. Therefore, the difference in roughness of Ag particles between the surface in contact with air and the surface in contact with the inner wall of the glass capillary can be reduced without using a large apparatus, and an Ag film having a uniform film thickness composed of nano-order Ag particles can be obtained. It is done. As a result, the optical characteristics in high peak power laser light transmission are stabilized, the light transmittance is improved, and the mechanical strength characteristics resulting from the particle diameter of the Ag particles constituting the Ag film can also be improved. .

  In addition, even for laser light with very high peak power in space or time, such as high-power, short-pulse laser light, the breakdown threshold is remarkably high, and long-term stability and mechanical strength are excellent. A hollow fiber can be manufactured with higher manufacturing efficiency while suppressing an increase in manufacturing cost as compared with a manufacturing method using a conventional manufacturing apparatus, and is useful in fields such as medical treatment, industrial processing, measurement, analysis, and chemistry.

  In the first embodiment described above, the configuration of the hollow fiber using Ag nanoparticles having a particle diameter of 3 to 5 nm has been described. By using metal nanoparticles having such a particle diameter, a glossy surface can be obtained. A metal film having a uniform thickness can be obtained.

  Moreover, in the manufacturing method shown in FIG. 2, the Ag nanoparticle solution 23 discharged to the waste liquid container 24 is small, and since the discharged Ag nanoparticle solution 23 can be recovered and injected again, The utilization efficiency of the Ag nanoparticle solution 23 is remarkably high, and an increase in manufacturing cost can be suppressed even when an expensive material such as Au is used as well as Ag.

  In the first embodiment described above, the glass capillary 11 made of quartz is used as the base material of the hollow fiber. However, the present invention is not limited to this, and other hollow tubes such as a polymer resin tube and a stainless steel pipe may be used. Good. The polymer resin tube is inferior in heat resistance to the quartz glass capillary 11 but has excellent flexibility and a low risk of breakage. A hollow fiber using stainless steel lacks flexibility, but is strong, impact-resistant and has almost no risk of breakage. Moreover, since it has an excellent heat transfer rate, it is suitable for high-power laser light transmission.

  In the first embodiment described above, nitrogen gas is used as a gas to be inserted when the glass capillary 11 is subjected to high-temperature heat treatment. However, the present invention is not limited to this, and a gas such as air, argon gas, or helium gas is used. May be.

  Further, the metal material formed on the inner wall of the glass capillary 11 is not limited to Ag described above, and may be Cu or Au. Metal thin films formed using these materials have high reflectivity and thus excellent optical characteristics. Although Au is an expensive material, it is chemically stable and excellent in stability without corrosion or discoloration.

  In the first embodiment, hexane is used as the solvent for dispersing the Ag nanoparticles, which is relatively quick to dry the Ag nanoparticle solution 23 attached to the inner wall surface of the glass capillary 11. However, the present invention is not limited to this. Alternatively, a solvent such as toluene or tetradecane can be used.

  In the first embodiment, the thickness of the Ag film 12 is 100 nm or less. However, if the thickness exceeds this, the particle diameter of the Ag film 12 increases, and the mechanical stress load on the glass capillary 11 is ignored. It was not possible to confirm that the mechanical strength of the hollow fiber 1 deteriorated. The above Ag film 12 is a lossy medium, and light energy does not penetrate deeply into the Ag film 12. Therefore, optically, the effect of forming the Ag film 12 appears by making the thickness of the Ag film 12 thicker than the skin depth. Here, the skin depth is defined by a film thickness d at which light energy attenuates to exp (−1), and d = λ / (4πk) (where λ is the wavelength of light and k is the extinction coefficient of the material). It is represented by

For example, at 10.6 μm which is the wavelength of the CO ₂ laser, the extinction coefficient of Ag is 75 and the skin depth is about 11 nm. In the first embodiment, the thickness of the Ag film 12 is set to about 50 nm, which is sufficiently thicker than the skin depth and does not affect the mechanical strength.

(Second Embodiment)
FIG. 3 shows a hollow fiber manufacturing apparatus according to the second embodiment of the present invention. In FIG. 3 as well, a part of the syringe 20 and the glass capillary 11 are shown in cross section for easy explanation. Moreover, in the following description, the same code | symbol is attached | subjected about the part which has the same structure and function as 1st Embodiment.

  In the manufacturing apparatus of the second embodiment, a branch pipe 16 capable of injecting an Ag nanoparticle solution 23 into a plurality of glass capillaries 11 is provided between the syringe 20 and the glass capillaries 11 described in the first embodiment. Have a configuration.

  The branch pipe 16 has a syringe 20 connected to the inlet side cap 16 </ b> A, and a plurality of discharge sides connected to the caps 11 </ b> A of the glass capillaries 11. The nanoparticle solution 23 is configured to be injected.

(Effect of the second embodiment)
According to the second embodiment described above, the Ag nanoparticle solution 23 can be simultaneously injected into the plurality of hollow fibers 1, and the manufacturing efficiency of the hollow fibers 1 can be increased.

(Third embodiment)
FIG. 4 shows a hollow fiber manufacturing apparatus according to the third embodiment of the present invention. In FIG. 4, the container 26 and the waste liquid container 24 are shown in cross-section for easy explanation. In the manufacturing apparatus of the third embodiment, a cylindrical container 26 that receives the Ag nanoparticle solution 23 is connected to a base 11A provided on the introduction side (upper side) of the glass capillary 11 via the discharge side (lower side). ) Is provided with a pipe 27 having elasticity. The pipe 27 is provided with a peristaltic pump 28, and the end of the pipe 27 downstream from the peristaltic pump 28 is provided so as to be located in the waste liquid container 24.

  The peristaltic pump 28 feeds the Ag nanoparticle solution 23 by applying an external force to the pipe 27 with a roller or the like and contracting it in a wave shape. In FIG. 4, the peristaltic pump 28 is connected to the downstream side of the glass capillary 11, and the Ag nanoparticle solution 23 is sucked from the container 26 into the glass capillary 11 under reduced pressure by reducing the pressure inside the glass capillary 11 and the pipe 27. It is configured as follows.

(Effect of the third embodiment)
According to the third embodiment described above, the Ag nanoparticle solution 23 may be sucked from the container 26 by reducing the pressure inside the glass capillary 11 and the pipe 27 using the peristaltic pump 28. Similarly to the pressure injection, the Ag nanoparticle solution 23 can be uniformly attached to the inner wall of the glass capillary 11.

(Fourth embodiment)
FIG. 5 is a view showing a hollow fiber manufacturing apparatus according to the fourth embodiment of the present invention. In FIG. 5, the container 26 and the waste liquid container 24 are shown in cross-section for easy explanation. In the manufacturing apparatus of the fourth embodiment, the configuration on the introduction side (upper side) of the glass capillary 11 is the same as that of the second embodiment, but the base 11B is disposed on the discharge side (lower side) of the glass capillary 11. A merging pipe 17 is provided. The junction pipe 17 joins the Ag nanoparticle solution 23 discharged from each glass capillary 11 and leads it to the pipe 27. The configuration from the pipe 27 to the waste liquid container 24 is the same as that of the third embodiment.

(Effect of the fourth embodiment)
According to the fourth embodiment described above, in addition to the preferable effects of the second and third embodiments, the adhesion of the Ag nanoparticle solution 23 to the inner walls of the plurality of glass capillaries 11 and the waste liquid container 24 are improved. The recoverability of the discharged Ag nanoparticle solution 23 can be improved.

(Fifth embodiment)
FIG. 6 is a cross-sectional view showing a hollow fiber according to a fifth embodiment of the present invention. This hollow fiber 1A is provided with a dielectric film 15 made of a transparent dielectric material in the wavelength band of light propagating through the hollow region 14 inside the Ag film 12 of the hollow fiber 1 described in the first embodiment. Thus, in the fifth embodiment, the dielectric film 15 made of an olefin resin is provided for the purpose of transmitting an Er · YAG laser or a CO ₂ laser.

(Effect of 5th Embodiment)
According to the fifth embodiment described above, the dielectric film 15 that is transparent in the wavelength band of the light propagating through the hollow region 14 is further provided inside the Ag film 12 of the hollow fiber 1 described in the first embodiment. By forming, transmission loss can be reduced. The effect is particularly remarkable in the infrared wavelength region, and is effective for transmission of an Er / YAG laser or a CO ₂ laser.

Further, the hollow fiber 1A on which the dielectric film 15 is formed can be used in combination with an Er · YAG laser, a CO ₂ laser, or the like that has an improved breakdown threshold and is effective for laser light transmission having a higher peak power. Has stable characteristics.

In the hollow fiber 1A described above, the configuration using the olefin resin as the dielectric film 15 has been described. However, a polyimide resin is used for transmitting an Nd / YAG laser having a shorter wavelength than the Er / YAG laser or the CO ₂ laser. You can also

[Other embodiments]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from or changing the technical idea of the present invention.

FIG. 1 is a cross-sectional view showing a hollow fiber according to a first embodiment of the present invention. FIGS. 2A to 2D are views showing a method for manufacturing a hollow fiber according to the first embodiment of the present invention. FIG. 3 shows a hollow fiber manufacturing apparatus according to the second embodiment of the present invention. FIG. 4 shows a hollow fiber manufacturing apparatus according to the third embodiment of the present invention. FIG. 5 is a view showing a hollow fiber manufacturing apparatus according to the fourth embodiment of the present invention. FIG. 6 is a cross-sectional view showing a hollow fiber according to a fifth embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A ... Hollow fiber, 11 ... Glass capillary, 11A, 11B ... Base, 12 ... Ag film, 13 ... Polyimide layer, 14 ... Hollow region, 15 ... Dielectric film, 16 ... Branch pipe, 16A ... Base, 17 ... Junction pipe, 17A ... cap, 20 ... syringe, 21 ... piston, 22 ... main body, 23 ... Ag nanoparticle solution, 24 ... waste liquid container, 25 ... electric furnace, 26 ... container, 27 ... piping, 28 ... peristaltic pump

Claims (9)

A hollow tube,
And a reflective film formed on an inner wall of the hollow tube, the reflective film having a metal film obtained by sintering metal nanoparticles.   The hollow fiber according to claim 1, wherein the metal film has an average particle diameter of 10 nm or less before the metal nanoparticles before sintering.   2. The hollow fiber according to claim 1, wherein the reflection film has a dielectric film that is transparent in a wavelength band of light propagating through a hollow region of the hollow tube on an inner wall of the metal film. Injecting a solution in which metal nanoparticles are dispersed in a solvent inside the hollow tube;
Attaching the solution to the inner wall of the hollow tube and discharging the excess solution from the inside of the hollow tube;
Drying the solution adhering to the inner wall of the hollow tube;
Forming a metal film on the inner wall of the hollow tube by subjecting the hollow tube dried from the solution to a heat treatment and sintering the hollow tube.   5. The hollow fiber according to claim 4, wherein the solution in which the metal nanoparticles are dispersed in a solvent has a content of the metal nanoparticles of 40% by weight or less and a viscosity of 100 mPa · s or less. Production method.   The method for producing a hollow fiber according to claim 4, wherein the step of injecting the solution comprises injecting a solution in which the metal nanoparticles are dispersed in any one of toluene, hexane, and tetradecane.   5. The method for producing a hollow fiber according to claim 4, wherein the step of forming a metal film on the inner wall of the hollow tube is performed at a temperature of 150 to 350 ° C. while flowing a gas inside the hollow tube. .   The step of forming a metal film on the inner wall of the hollow tube is performed by controlling any one of a content of the metal nanoparticles in the solution, a viscosity, and a speed of the solution passing through the hollow tube. 5. A method for producing a hollow fiber according to 4.   5. The method for producing a hollow fiber according to claim 4, wherein the step of injecting the solution is performed by pressure injection of the solution into the hollow tube or vacuum suction of the solution into the hollow tube.

Images