JPH07267669A - Production of multiple structure material - Google Patents

Abstract

PURPOSE:To easily and stably produce a multiple structure material having a thin core diameter, small variation of the diameter in longitudinal direction and high roundness of the cross-section by placing a core material on a coating material having larger size and extruding the materials while restricting the flow of the core material in radial direction. CONSTITUTION:A molding material produced by placing a core material 2 on a coating material 4 having a dimension larger than that of the core material is put into a material holding part 1 of an extruder, softened by heating and pressed with a plunger 5 from an end of the extruder to extrude a multiple structure material composed of a core material 2 covered with the coating material 4 from the other end of the extruder. The extrusion is carried out by parallelly pressing each upper face of the core material 2 and the coating material 4 from the start of extrusion while restricting the flow of the core material 2 toward the side wall. For example, a ring-shaped material 3 holding a core material 2 fitted to the central opening part is placed on the upper face of a coating material 4 and both materials are pressed at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multiple structure. INDUSTRIAL APPLICABILITY The method for manufacturing a multiple structure of the present invention is used for manufacturing an optical fiber preform, an optical fiber, an optical component, an optical structure, and the like.

[0002]

2. Description of the Related Art A preform for a single mode optical fiber, which is a multiple structure having an extremely fine core (axial core) diameter, has at least a double structure in which the extremely fine core is covered with a thick cladding layer. ing. The rod-in-tube method is one of the methods for producing a preform having such a structure. The rod-in-tube method is a method of manufacturing a preform by processing a thin core rod and a thick clad tube having elongated holes, and then inserting the core rod into the clad tube. The drawback of this method is that it is technically extremely difficult to process a thick tube having elongated holes, and the processing cost is high.

Therefore, there has been proposed an extrusion molding method of a preform for a single mode optical fiber in which a core and a clad can be integrated without requiring tube processing. As a disclosure of this method, JP-A-4-132632 (hereinafter referred to as Prior Art 1) and JP-A-4-13263 are disclosed.
There is Japanese Patent Laid-Open No. 3 (hereinafter referred to as Prior Art 2). These methods set a more compact core glass cylinder at the center of the clad glass cylinder, press the core glass body into the clad glass body with an extrusion plunger after heating and softening, and then extrude both glass bodies at the same time. Is a method for obtaining a double-structured preform having an extremely fine core glass in the center of the clad glass.

The above-mentioned prior arts and methods 2 are excellent in that the drawbacks of the conventional rod-in-tube method are eliminated, and a preform for optical fibers can be obtained without the need for thick tube processing as glass for cladding. Is the way.

[0005]

However, in the method of the prior art 1 described above, the diameter of the core glass cylinder, which is the starting material for extrusion molding, is smaller than the diameter of the clad glass cylinder, and the core glass cylinder is clad. When set in the center of the glass columnar body, the core glass columnar body is sandwiched between the plunger and the clad glass columnar body so that the periphery of the core glass is hollow. Therefore, in the initial stage of extrusion molding, the core glass is pressed into the clad glass body in a flattened state where it is crushed and deformed, so the core shape of the obtained preform is not a perfect circle but an elliptical shape. Many of them have a polygonal shape or the like, and the variation of the core diameter in the length direction of the obtained preform is large.

Further, in the method of the above-mentioned prior art 2,
By introducing a sub-container and a sub-plunger, the problem due to the hollow state around the core glass recognized in the method of the prior art 1 is solved, but the core glass body is clad glass from the sub-container side with the sub-plunger. It will be pushed into the body, and at this time, due to the frictional resistance of the contact surfaces of the two glass bodies, the cross-section of the pushed core glass may become a distorted cylindrical body such as a drum shape.

The object of the present invention is that (i) the diameter of the core (axial core) is small and the fluctuation in the longitudinal direction is small, and (ii) the cross-sectional shape of the core (axial core) has a high roundness. A multiple structure having
It is to provide a method that can be stably manufactured by a simple process.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and is a molding in which a shaft core material is placed on a coating material having a size larger than that of the shaft core material. The material is stored in the material storage part of the extrusion molding machine, and the molding material of the multilayer structure softened by heating is pressed from one end of the extrusion molding machine by the plunger, and for the shaft core coated with the coating material from the other end. In a method of manufacturing a multi-structured body made of a material by extrusion molding, in a state in which the flow in the lateral direction of the axial core material is regulated, the upper surfaces of the axial core material and the coating material are parallel to each other from the start of extrusion. The gist is a method of manufacturing a multi-layer structure characterized by pressing.

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

FIG. 1 shows a mode in which an annular body is used as a means for regulating the lateral flow of the molding material for the shaft core. In this mode, FIG. 1 (a) shows a state immediately before pressing, in which the annular body 3 sliding on the inner peripheral surface of the material storage portion 1 and fitted with the shaft core material 2 at the central opening is It is placed on the upper surface of the coating material 4 having a size larger than that of the coating material 2.

A heating heater (not shown) in which the shaft core material 2 and the coating material 4 are provided around the material accommodating portion 1
When the axial core material 2 is directly pressed by the plunger 5 and the coating material 4 is simultaneously pressed by the annular body 3 after being heated by the annular body 3 as shown in FIG. Material for shaft core 2 with flow to
Begin to flow into the coating material 4. Then, when the pressing by the plunger 5 is further continued, the shaft core material 2 becomes a shaft core shape as shown in FIG. 1C, and flows down at a higher speed than the coating material 4, and finally in FIG. As shown in (d), a double structure having a small diameter of the shaft core, uniform in the length direction, and a high roundness of the cross-sectional shape of the shaft core can be obtained.

FIG. 2 uses an annular body as in FIG.
It shows a mode in which the diameter of the opening of the annular body 3 is enlarged toward the outlet, that is, as it approaches the coating material 4. According to this aspect, the annular body 3 retains the function of restricting the flow of the shaft core material 2 in the lateral direction, and facilitates the inflow of the shaft core material 2 into the coating material 4 by pressing. In addition to the advantages obtained in the mode of FIG. 1, the advantage is obtained that the length of the portion where the axial core is formed in the obtained multiple structure is long and the yield is high.

FIG. 3 and FIG.
It shows an aspect integrated with. That is, in these aspects, a concave portion corresponding to the shape of the shaft core material 2 and capable of accommodating the shaft core material 2 is formed in the plunger 5 by perforation, and the convex portion around the recess is the annular body 3. Becomes

In the embodiment of FIG. 3, the diameter of the central opening of the annular body 3 is the same from the inlet to the outlet, that is, from the plunger side to the coating material side, but in the embodiment of FIG. The diameter of the central opening increases towards the outlet, i.e. closer to the coating material 4.

FIG. 5 shows an embodiment in which the annular body 3 has a central opening having a step structure. In this embodiment, the shaft core material 2 is fitted in the central opening portion of the annular body 3 having a small diameter. On the other hand, coating material 4
Consists of an inner coating (inside cladding) material 4i and an outer coating (outside cladding) material 4o,
The inner coating material 4i is fitted into the large-diameter central opening portion of the annular body 3, and the outer coating material 4o is contained below the inner coating material 4i and the annular body 3. By forming the annular body 3 into the shape as described above and disposing the shaft core material 2 and the coating material 4 (the inner coating material 4i and the outer coating material 4o) as described above, the core, the inside cladding, and the outside A triple structure composed of the side cladding can be obtained.

The annular body having a stepped central opening is
It is also possible to combine and form a pair of annular members each having a small-diameter and a large-diameter central opening.

In FIG. 6, a cylindrical shaft core material 2 is closely fitted with an annular inner coating material 4i around it, fitted into the central opening of the annular body 3, and further below it. This figure shows an embodiment in which an inner coating material 4i and an outer coating material 4o are arranged, and this embodiment also has three layers of a core (axial core), an inside cladding (inside coating), and an outside cladding (outer coating). A triple structure is obtained.

[0018]

The present invention will be described in more detail with reference to the following examples.

[Embodiment 1] In this embodiment, the wavelength is 1.55 μm.
It is an example of producing a preform of triple structure for m single mode optical fiber.

7 (a) to 7 (d) show a three-layer glass body (hereinafter referred to as a three-layer billet) to a triple structure (hereinafter referred to as a triple rod) using a stainless annular body that slides on the inner peripheral surface of the material storage portion. That is, it shows the flow state of the glass when it is molded. In FIG. 7A, 1 is a material storage unit, 2 is
Is a glass disk for core, 3 is a stainless steel ring, 4
i is a glass cylinder for inside cladding, and 4o is a glass cylinder for outside cladding.

As the extrusion molding die, one having a material storage portion 1 having an inner diameter of 50 mm and a nozzle die 6 having an outlet diameter of 8.0 mm was used. As the stainless steel ring 3, one having an outer diameter of 50 mm, an inner diameter of 20 mm and a thickness of 0.4 mm was used. Further, as the glass body, PbO, SiO
Three types of lead glass containing ₂ as a main component and having a composition adjusted according to the refractive index required for the core, the inside cladding, and the outside cladding were used.

In a preform for a single mode optical fiber having a wavelength of 1.55 μm, standard dimensions of the core diameter, the inside cladding diameter and the outside cladding diameter are set as follows, and each glass in a unit length of the preform is set. The result of obtaining the volume of is shown below.

Core Inside Clad Outside Clad Diameter (mm) 0.66 6.20 8.00 Volume per unit length (mm ³ / mm) 0.342 29.849 20.075

Next, the volumes of the core, the inside cladding and the outside cladding in the preform having a length of 300 mm are shown below.

Core Inside Clad Outside Clad Length 300mm Volume (mm ³ ) 102.6 8954.7 6022.5

The following should be taken into consideration when deciding the required core, inside cladding and outside cladding billet volumes based on the above respective volumes.

(1) The glass that has been softened during extrusion molding remains in the mold cavity at its contact portion with the inner surface of the mold cavity even after the completion of extrusion molding. The material loss therefor is about 5-30%.

(2) In the extrusion molding process using a three-layer billet, only the glass for outside clad is extruded first, then the double structure part of the inside clad and the outside clad is extruded, and then the core and the inside. A triple structure composed of a triple structure including a clad and an outside clad comes to be extruded.
Only the triple structure part can actually be used as a preform. Therefore, the loss of glass for inside cladding and glass for outside cladding is about 10-4.
It is 0%.

The volume of the core, inside clad and outside clad billet necessary for the above two factors was determined as follows.

Core Inside Clad Outside Clad Billet Volume (mm ³ ) 123 12,435 12,447

Further, in order to obtain a preform having a uniform and thin core diameter, the geometry and dimensions of the core billet are important. From experience, it is appropriate that the thickness is 1 mm or less and the aspect ratio is 0.1 or less.

Based on the above examination results, the aspect ratio of the core billet was set to 0.02. The aspect ratio of the inside clad billet and the outside clad billet does not need to be set in advance because the billet height can be obtained from the container inner diameter φ50 mm and the volume of each billet.

The dimensions of each molding material (billet) are as follows.

Billet Dimension (mm) Core Material: φ20 × h0.4 Inside Clad Material: φ50 × h6.34 Outside Clad Material: φ50 × h6.34

In FIG. 7A, an inside clad billet 4i is set on the outside clad billet 4o after double-side polishing, and the core billet 2 is made of stainless steel having an inner diameter of 20 mm, an outer diameter of 50 mm and a thickness of 0.4 mm. After being fitted to the ring 3, the glass is placed on the upper surface of the inside cladding billet 4i and housed in the extrusion molding container 1 and heated at a heating temperature of 550 ° C. for 1.5 hours. Plunger 5 after reaching ⁸ ps
Then, the core billet 2 was directly pressed, and the inside cladding billet 4i and the outside cladding billet 4o were simultaneously pressed via the stainless steel ring 3 to obtain a triple rod of uniform diameter. The flow state of glass during extrusion molding is as shown in FIGS.
The flow velocity of the glass body at the center of the container 1 is faster than that of the surrounding glass body, and the core billet 2 placed on the upper portion is elongated and elongated as the extrusion molding progresses.
As shown in (d), a rod having a triple structure of a core, an inside cladding, and an outside cladding was finally obtained.

The rod having a triple structure thus obtained was cut at 100 mm intervals in the length direction, and the cross section thereof was measured for the core diameter and the inside cladding diameter by an optical microscope, and for the outside cladding diameter. Checked with a micrometer. The results of these measurements are shown in FIG. As shown in this figure, the diameter variation of each layer of the preform is very small and almost coincides with the standard dimension value, and the outside cladding diameter is 8.0 mm in the portion where the length (L1) of the triple structure is 300 mm. , Inside cladding diameter is 6.2mm, core diameter is 0.66m
Since it is m, it has been clarified that this portion can be used as a preform of a single mode optical fiber having a wavelength of 1.55 μm. The roundness of the core (radius difference between the circumscribed perfect circle and the inscribed perfect circle of the circle to be measured) was measured by an optical microscope, and was 0.83 μm, which was good.

[Examples 2 to 3] In Examples 2 and 3, the materials, volumes and the like of the glass billet for core, inside clad and outside clad, and extrusion molding conditions were the same as in Example 1.

The results of examining the diameter of each layer of the rod having the triple structure obtained in Example 2 are shown in FIG. The core portion had a length of 300 mm and an average diameter of 0.67 mm. The diameter of the inside clad portion and the diameter of the outside clad portion were 6.3 mm and 8.2 mm, respectively, which were almost the same as the standard value.

The results of examining the diameter of each layer of the rod having the triple structure obtained in Example 3 are shown in FIG. The core portion had a length of 300 mm and an average diameter of 0.66 mm. The diameter of the inside clad and the diameter of the outside clad are 6.2 mm and 8.1 mm, respectively.
And was in good agreement with the standard value.

The roundness of the cores in the triple rods obtained in these examples are both 0.62 μm or less,
It was extremely accurate.

[Example 4] The same glass material as in Example 1 was used, and the target diameters of the core of the preform and the outside cladding were the same as those in Example 1, but the inside cladding diameter was 2.2 mm. I decided to make it thinner. In this case, not only the core billet but also the inside clad billet must have a small diameter.

The volume of each billet and the aspect ratio representing the geometric shape of each billet were set as follows in the same manner as in Example 1.

Core Inside Cladding Outside Cladding Volume (mm ³ ) 188.5 1,924 19,635.3 Aspect Ratio 0.04 0.06 0.4

According to the above volume and aspect ratio, the size of each billet was determined as follows.

Core Inside Clad Outside Clad Diameter (mm) 20 35 50 Thickness (mm) 0.6 2.0 20

11 (a) to 11 (d) show the manufacturing process of the triple structure.

The core billet 2 having the above-mentioned dimensions is attached to the outer diameter 5
Inside clad billet 4i is fitted to a stainless ring 3a having a diameter of 0 mm, an inner diameter of 20 mm and a thickness of 0.6 mm.
Was fitted to another stainless steel ring 3b having an outer diameter of 50 mm, an inner diameter of 35 mm and a thickness of 2.0 mm. Next, the inside clad billet 4i fitted to the annular body 3b and the core billet 2 fitted to the annular body 3a were placed in this order on the upper surface of the outside clad billet 4o and stored in the container 1. Then, the glass was heated at 550 ° C. for about 1.5 hours so that the glass had a viscosity of 10 ⁸ ps and then extruded. The flow state of the glass during molding is shown in FIG.
It changed as shown in (c) and (d). FIG. 12 shows the result of examining the variation of the diameter of each layer of the triple rod thus obtained. The diameter of each layer is uniform and the fluctuation is extremely small, and the length is 300 mm and the core diameter is 0.66 mm.
It was possible to obtain a preform for a single-mode optical fiber having a triple structure. The roundness of the inside cladding of the preform obtained in this example was 1.3 μm, and the roundness of the core was 0.33 μm, which were very good.

[Embodiment 5] As shown in FIG. 2, a stainless steel ring 3 having a central opening whose diameter is enlarged toward the outlet.
A core glass 2 having a trapezoidal cross section is fitted in the central opening of the core, and the core glass 2 is placed on the clad glass 4 and then extrusion molded to form a double structure for a single mode optical fiber having a wavelength of 0.85 μm. The preform of was produced. The standard dimensions of each layer of this preform are as follows.

[0049]

This preform has a relatively small outer diameter,
Extrusion molding conditions differ from the above examples. First, since the inner diameter of the material storage portion 1 used for extrusion molding is 35 mm and the diameter of the nozzle 6 is 2.5 mm which is the same as the outer diameter of the preform, the extrusion ratio is 196. Similar to Example 1,
The volume and geometrical dimension of the core and the clad billet were obtained by the above equations. The results are shown below.

Core-clad billet volume (mm ³ ) 314 9620 Billet cross-sectional dimension (mm) φ22 (max) × 1.0 (thickness) φ35 × 10 (thickness) φ18 (min) Aspect ratio 0.05 0.286

Further, the dimensions of the stainless steel ring 3 in which the diameter of the central opening is enlarged toward the outlet are as follows: outer diameter 35 mm, inner diameter 22 mm (maximum), 18 mm (minimum), thickness 1.0 m.
It was m.

FIG. 13 shows the result of investigation on the variation of the diameter of the actually prepared double preform. A preform having a target size is obtained, and the effective length of the preform is 1200 mm, which is considerably longer than that of any of the examples. It was confirmed that the fiber drawn by using this preform showed a single mode. Further, the roundness of the preform was extremely high, and was almost round.

[Comparative Example 1] The same glass material and the same molding conditions as in Example 2 were used except that the core billet and the inside clad billet were hollow without using a metal ring. A triple preform for a single mode optical fiber of 0.55 μm was produced. FIG. 14 shows the results of an examination of the variation in the diameter of each layer of the preform thus obtained. It was revealed that the diameter variation of the core and the inside cladding was extremely large when the stainless ring was not used.

[Comparative Example 2] Only the core billet was fitted in the metal ring, and the thickness of the inside clad billet was set to 2.
mm, diameter 5 same as outside clad billet
FIG. 15 shows the results of examining the diameter variation of a preform extruded after heat-softening after stacking it on a three-layer billet having a thickness of 0 mm. As a result, it was clarified that the fluctuation of the diameter of the inside cladding was extremely large.

The method of manufacturing the multiple structure of the present invention is as follows.
It can also be used for forming materials other than glass, such as ceramics, plastics, semiconductors, electronic materials, and the like.

Further, the material of the annular body is not limited to metal, and any mold material and the same type of coating material for molding can be used.

[0058]

EFFECTS OF THE INVENTION According to the present invention, there are advantages that (i) the core (axial core) diameter is small and the fluctuation is small, and (ii) the cross-sectional shape of the core (axial core) is high in roundness. Provided is a method capable of stably manufacturing a structure by a simple process.

[Brief description of drawings]

FIG. 1 is a diagram showing changes in the flow state of glass in the production of a double structure.

FIG. 2 is a second diagram immediately before extrusion molding in the production of the double structure.
FIG.

FIG. 3 is a third diagram immediately before extrusion in the production of the double structure.
FIG.

FIG. 4 is a fourth diagram immediately before extrusion in the production of the double structure.
FIG.

FIG. 5: Fifth time immediately before extrusion in the production of the double structure
FIG.

FIG. 6 is a sixth diagram immediately before extrusion in the production of the double structure.
FIG.

FIG. 7 is a diagram showing changes in the flow state of glass in the production of the triple structure in Example 1.

FIG. 8 is a diagram showing changes in the diameter length direction of the core, the inside cladding, and the outside cladding of the triple structure obtained in Example 1.

FIG. 9 is a diagram showing changes in the diameters of the core, the inside cladding, and the outside cladding of the triple structure obtained in Example 2 in the length direction.

FIG. 10 is a diagram showing changes in the diameters of the core, the inside cladding, and the outside cladding of the triple structure obtained in Example 3 in the length direction.

FIG. 11 is a view showing the flow state of glass in the production of the triple structure in Example 4.

FIG. 12 is a diagram showing changes in the diameters of the core, the inside cladding, and the outside cladding of the triple structure obtained in Example 4 in the length direction.

FIG. 13 is a diagram showing changes in the diameters of the core, the inside cladding, and the outside cladding of the triple structure obtained in Example 5 in the length direction.

FIG. 14 is a diagram showing changes in the diameters of the core, the inside cladding, and the outside cladding of the triple structure obtained in Comparative Example 1 in the length direction.

FIG. 15 is a diagram showing changes in the diameters of the core, the inside cladding, and the outside cladding of the triple structure obtained in Comparative Example 2 in the length direction.

[Explanation of symbols]

 1 Material Storage Section 2 Shaft Core Material 3 Annular Body 4 Coating Material 4i Inner Coating Material 4o Outer Coating Material 5 Plunger 6 Outlet

Claims (12)

[Claims] 1. A multi-layer structure in which a molding material in which an axial core material is placed on a coating material having a size larger than that of the axial core material is accommodated in a material accommodating portion of an extruder and softened by heating. By pressing the molding material from one end of the extrusion molding machine with a plunger, from the other end, in the method of manufacturing a multi-structure body made of the material for the shaft core covered with the coating material by extrusion molding, A method for producing a multi-layer structure, comprising pressing the respective upper surfaces of the shaft core material and the coating material in parallel from the start of extrusion in a state where the flow in the lateral direction is restricted. 2. An annular body, which slides on the inner peripheral surface of the material storage portion and has a shaft opening material fitted in the central opening, is placed on the upper surface of the coating material to directly mount the shaft core material. And the coating material is pressed simultaneously via the annulus. 3. The method according to claim 2, wherein the diameter of the opening of the annular body is enlarged toward the outlet. 4. The method according to claim 2, wherein the annular body is integrated with the plunger. 5. The method according to claim 2, wherein the annular body has a central opening having a step structure. 6. The method according to claim 5, wherein the annular body having the stepped central opening comprises a pair of annular bodies each having a small diameter large opening and a large diameter central opening. 7. An axial core material is fitted into a small diameter central opening portion of an annular body having a stepped central opening portion, and an inner coating material is fitted into a large diameter central opening portion,
7. The method according to claim 5, wherein the molding material placed on the outer coating material is pressed to obtain a triple structure. 8. A cylindrical shaft core material, a ring-shaped first coating material which is closely arranged around the shaft core material, is fitted into the central opening of the ring-shaped body, and the column-shaped second core material is fitted. The method according to claim 2, wherein the triple structure is obtained by pressing the molding material placed on the coating material. 9. The annular first coating material is an inner coating material, and the cylindrical second coating material is a two-layer body of an inner coating material and an outer coating material. The method according to 8. 10. The method according to claim 1, wherein the mandrel material and the covering material are glass. 11. The method according to claim 1, wherein the material for the core and the material for the coating are glass for the core and glass for the clad of the optical fiber, respectively. 12. The method according to claim 11, wherein the cladding glass comprises an inside cladding glass and an outside cladding glass.