JP2594552B2 - Method for manufacturing flexible optical waveguide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the manufacture of a flexible optical waveguide having a high-refractive-index transparent rubber-like elastic body as a core and a low-refractive-index rubbery elastic body as a cladding. In particular, the method is to make the interface between the core and the clad sufficiently smooth, and to advantageously improve the transparency of the core.

(Prior Art) As a conventionally known method of manufacturing this kind of flexible optical waveguide, there is, for example, a method disclosed in Japanese Patent Application Laid-Open No. 61-259202.

In this manufacturing method, the respective liquid polymers for forming the core and the clad are allowed to flow down from the concentric nozzle as the core forming liquid polymer as the inner layer, and the cladding forming liquid polymer as the outer layer. The two liquid polymers are simultaneously cross-linked by irradiation with radiation or ultraviolet light, or by heating. According to this method, a long elastomer optical fiber having at least a core having rubber-like elastic properties is produced. .

(Problems to be Solved by the Invention) However, in this conventional technique, both the liquid polymer for forming the core and the liquid polymer for forming the clad are simultaneously cross-linked by one cross-linking means. When heating is used as the crosslinking means, the time required for crosslinking is considerably long, so that the liquid polymer for forming the core and the liquid polymer for forming the clad are mixed with each other. There is a problem that a transition region or unevenness occurs at the interface portion of the optical fiber and the optical transmission loss increases, and in addition, there is another problem that the dimensional control of the optical fiber is extremely difficult. On the other hand, when the heating temperature is increased for the purpose of shortening the crosslinking time, thermal deterioration occurs in the core and the clad, and the temperature difference between the inner and outer portions in the radial direction becomes considerably large. By performing homogeneous crosslinking,
There was a problem that an optical fiber having excellent transparency could not be manufactured.

Further, when a crosslinking reaction is caused by irradiation of radiation or ultraviolet light, although effective shortening of the crosslinking time is realized, radiation and ultraviolet light are
Since it is relatively difficult to pass through the liquid polymer, there is a problem that the cross-linking state of the core becomes uneven in the radial direction, and the sensitizer mixed into the liquid polymer to absorb radiation. However, there is a problem that an optical transmission loss is increased.

The present invention advantageously solves such a problem of the prior art, and makes the interface between the core and the cladding sufficiently smooth, and eliminates the need to mix a sensitizer into the core material, thereby effectively reducing the optical transmission loss. Another object of the present invention is to provide a method for manufacturing a flexible optical waveguide which makes it easy to control the dimensions of an optical waveguide by rapid crosslinking of a clad material, and further, provides uniform crosslinking of a core material.

(Means for Solving the Problems) The method for manufacturing a flexible optical waveguide according to the present invention is,
First, each of the liquid core material and the clad material is simultaneously extruded from each concentrically arranged nozzle, and then the clad material of the outer layer is cross-linked by irradiation of radiation, electron beam or ultraviolet light, and then the clad material is formed inside the clad material. The core material in contact is crosslinked by heating.

(Operation) According to this method, the clad material is firstly rapidly crosslinked by the irradiation beam at a position immediately below the concentric nozzle, so that the core material and the clad material are mixed and the boundary surface thereof is disturbed. Is sufficiently prevented, and the outer diameter of the optical waveguide is specified to the expected value.

For this reason, here, the interface between the core and the clad is sufficiently smoothed, the optical transmission loss is effectively reduced, and the dimensional control of the optical waveguide becomes easy and reliable.

Further, in this method, the core material is cross-linked by heating at a relatively low temperature to prevent thermal deterioration of the core, and to cross-link the core material sufficiently uniformly and completely throughout the radial direction. So you can
It is not necessary to mix a sensitizer for absorbing the radiation into the core material, and an increase in optical transmission loss due to the sensitizer can be completely eliminated.

(Examples) The present invention will be described below based on illustrated examples.

FIG. 1 is a sectional view of an essential part showing an embodiment of the present invention. In FIG. 2 shows an inner storage tank and an outer storage tank, respectively.

Here, a liquid core material 5 is placed in the inner storage tank 3,
A liquid clad material 6 is stored in the outer storage tank 4, and these two liquid materials 5, 6 are supplied from the respective nozzles 1, 2 under pressure or based on the weight of the materials 5, 6. At the same time, the cladding material 6 as the outer layer is rapidly crosslinked by ultraviolet rays from a mercury lamp 7 disposed below the nozzles 1 and 2 at a position where the outer diameter of the cladding material 6 becomes uniform. The core material 5 inscribed in the clad material 6, more precisely, the core material 5 inscribed in the clad 6 a resulting from crosslinking the clad material 6.
Is crosslinked at a relatively low temperature by a heating furnace 8 disposed below the mercury lamp 7, so that a high-refractive-index rubber-like elastic body is used as the core 5a and a low-refractive-index rubber-like elastic body is used as the clad 6a. To manufacture a flexible optical waveguide.

Here, the flexible optical waveguide thus manufactured is wound on a winding drum 10 via a pulley 9.

Here, the core material 5 that causes a crosslinking reaction by heating is preferably a liquid rubber such as a liquid silicone rubber, a liquid polyurethane rubber, a liquid butadiene rubber, or the like, and is crosslinked by any of ultraviolet irradiation, radiation irradiation or electron beam irradiation. As the clad material 6 that causes a reaction, a liquid rubber such as a liquid silicon rubber, a liquid polyurethane rubber, a liquid fluorine rubber, or the like is preferable.

Here, the core material 5 has a phenyl group content of 5 to 5.
35% dimethyldiphenylpolysiloxane or phenylmethylpolysiloxane as a main component, an addition-reaction liquid silicone rubber, and as a cladding material 6
When an ultraviolet-crosslinkable liquid silicone rubber containing dimethylpolysiloxane as a main component is selected, the production speed of the flexible optical waveguide can be sufficiently increased because the crosslinking speed of the clad material 6 is extremely high. And
The adhesive strength between the core 5a and the clad 6a is increased, and a flexible optical waveguide having stable mechanical and optical characteristics can be obtained within a wide temperature range from a low temperature range to a high temperature range.

According to the method described above, the clad material 6 is quickly crosslinked to form the clad 6a before the turbulence occurs at the interface between the clad material 6 and the core material 5 as well as the interface between the two materials 5,6. Since it is guided to the heating furnace 8 while maintaining its shape, the optical transmission loss can be extremely effectively reduced, and the dimensional control of the optical waveguide can be leveled to achieve the expected dimensions. At the same time, dimensional variations can be sufficiently prevented.

Also, the core material 5 is cross-linked sufficiently homogeneously by heating it at a relatively low temperature in the heating furnace 8 without having to incorporate a sensitizer for absorbing radiation into the core material. Core 5a, the core 5a caused by high-temperature heating.
Can be effectively prevented from thermal degradation, heterogeneous cross-linking reaction, and the like, and these can also advantageously reduce optical transmission loss.

In the above description, the mercury lamp 7 as a means for cross-linking the clad material 6 is of course obtained as a radiation irradiator or an electron beam irradiator. 8 can be formed integrally.

Here, when the bridging means of the clad material 6 and the heating furnace 8 are integrally formed, it is preferable to cool the clad material bridging means or to thermally insulate the clad material 6 from the heating furnace 8. Preferably, radiation from the material bridging means is guided into the furnace via a quartz fiber or other optical waveguide.

Further, in the illustrated example, a method for manufacturing a flexible optical waveguide including only the core 5a and the clad 6a is shown, but a coating process of a primary coat material, a buffer coat material, a cover material, or the like is performed before the heating furnace 8 or It can be provided at a later stage, and in the latter case, it is preferable to provide a curing furnace further later in the coating step.

[Test Example] A light transmittance test of a flexible optical waveguide manufactured by the method of the present invention will be described below.

Here, the core material has a phenyl group content of 25%
The addition reaction type liquid phenylmethylsilicon rubber is used as the cladding material, and the UV-crosslinking type liquid dimethylsilicon rubber is used.
Each material was co-extruded from concentric nozzles so that the ratio became 80:20, and four 25-cm mercury lamps (output 80
W / cm) and a 100cm long heating furnace (temperature 200 ° C), 5m
/ min sequentially.

As a result, a flexible optical waveguide is obtained in which both the core and the clad are completely and uniformly cross-linked in the radial direction, and the dimensional variation is extremely small.
The transmittance at a length of 1 m was 92%.

(Effects of the Invention) Therefore, according to the present invention, a thermally crosslinked core material having a high refractive index and exhibiting rubber-like elastic properties after crosslinking, and a low refractive index, which also exhibit rubber-like elasticity after crosslinking. Co-extrusion of ultraviolet, radiation or electron beam cross-linkable cladding material, which exhibits properties, from a concentric nozzle, first cross-linking the cladding material by irradiation with ultraviolet light, radiation or electron beam and then heating the core material Accordingly, a flexible optical waveguide having extremely small optical transmission loss, having the expected dimensions, and further having a core whose cross-linking state is sufficiently uniform in the radial direction can be provided.

[Brief description of the drawings]

 FIG. 1 is a sectional view showing a main part of an embodiment of the present invention. 1,2 ... Nozzle, 5 ... Core material 5a ... Core, 6 ... Clad material 6a ... Clad, 7 ... Mercury lamp 8 ... Heating furnace

Claims (1)

(57) [Claims] 1. A transparent rubber-like elastic body having a high refractive index as a core,
In manufacturing a flexible optical waveguide having a low-refractive-index rubber-like elastic material as a clad, first, each of a liquid core material and a clad material is simultaneously extruded from respective concentrically arranged nozzles, and then the outer layer clad is formed. A method for manufacturing a flexible optical waveguide, comprising: crosslinking a material by irradiation of radiation, an electron beam, or ultraviolet light, and thereafter crosslinking a core material inscribed in a clad material by heating.