JPH0527082B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a light guide, and more particularly to a light guide suitable for use when the incident end is exposed to high temperatures such as sunlight.

(Prior Art) Light guide wires include plastic clad optical fiber (PCF), multicomponent optical fiber, quartz optical fiber, and plastic fiber.

A light guide is made by bundling a large number of these fibers together, attaching a cap to the terminal, and polishing the end face.

Recently, from the viewpoint of energy saving, a method of condensing sunlight through a Fresnel lens 1 as shown in FIG. 1 and introducing it indoors with a light guide 2 has been attracting attention.

In this case, the energy-saving density at the input end of the light guide becomes extremely large, reaching a temperature of several hundred degrees Celsius, so quartz-based optical fiber or plastic-clad optical fiber (PCF) with a quartz core is used as the light guide wire. . Considering both of these optical fibers from the viewpoint of fiber NA and fiber price, which one is suitable as a light guide fiber?
Become a PCF.

(Problem to be solved by the invention) However, the heat resistance of silicone resin, which is generally used as a cladding material for PCF, is only about 200°C, so if PCF is used as it is as a light guide fiber, the terminal part The silicone resin burns, producing silicon dioxide flakes that cover the core end face and prevent light from passing through.

Therefore, when using PCF as a light guide fiber, the silicone resin at the end is peeled to expose the core (quartz), which is inserted into the base 3 as shown in Figure 2.

Methods for removing silicone resin include mechanical removal using a stripper and chemical removal using a stripping agent containing an alkaline amine as a main component. However, in the former method, the core may be damaged or the fibers may break, and silicone resin may remain on the surface of the core.

In the latter method, since the heat treatment is performed at a temperature of 100° C. or higher, the core deteriorates due to alkali, and there are also problems in that it is harmful to the human body.

Also, regardless of whether the former or latter method is used,
Normally, processing the 100 fiber terminals required for a bundle is labor intensive and yields are low.

(Means for Solving the Problems) In order to solve these problems, the present invention provides a method for manufacturing a light guide in which the cladding 4 is formed of fluorine resin and the ends thereof are removed by thermal decomposition.

As the fluorine resin, vinylidene fluoride resin (for example, Kynar, a trademark of Pennwalt Co., Ltd., USA) is used.
or a copolymer of fluorine resin and fluorine rubber (for example, Asahi Glass Co., Ltd. product Eight Seal). All of these materials contain fluorine, which lowers the refractive index, so they have a lower refractive index than quartz, and simply coating the quartz (core) 6 creates a complete waveguide structure (optical fiber).

The thermal decomposition of Kynar (product name) and Eight Seal (product) begins at 300℃ for Kynar and around 350℃ for Eight Seal.
Both completely decompose at 500℃. In fact, when optical fibers clad with these resins were heated to 500°C in an air atmosphere, a clean surface with no residue on the core surface was obtained. Even when laser light (He-Ne) was incident from the terminal for confirmation, no scattering from the core due to residual decomposition residue was observed.

The core 6 of the light guide fiber in the present invention is preferably made of quartz. Further, the light guide wire according to the present invention, which is obtained by thermally decomposing the fluorine-containing resin at the input end, has an air cladding on the input end side and a fluorine-containing resin cladding on the input end side.

(Example) Example 1 The above Kynar was dissolved in dimethylacetamide heated to 80°C to form a paint (resin concentration 20°C).
%). This is then shaped into a quartz rod using the usual method.
A fiber drawn to 150 μm is coated and baked to produce the light guide wire 5. This fiber is cut into 20 m increments to prepare 500 fibers, and their input terminals are combined and heated at 500°C over a length of 10 cm. The crud at the input terminal was completely thermally decomposed by inserting it into an electric furnace for 5 minutes. This terminal was densely packed into the base 3 and polished to produce a light guide with an air-clad entrance end.

Example 2 A quartz rod was drawn to have an outer diameter of 200 μm using the usual method, and then the Eight Seal F-20 described above was immediately drawn on it.
Coating and baking light guide wire 5
and cut it into 10m long pieces for 500
This sample was prepared, and a length of 5 cm on the incident side was inserted into an electric furnace at 500°C for 5 minutes to completely thermally decompose the crud on the incident side. This was treated in the same manner as in Example 1 to produce a 10 m long light guide.

Example 3 The light guide wires 5 prepared in Examples 1 and 2 were each cut to a length of 10 m, 500 of each wire 5 was prepared, and the cladding on the incident side was sheathed without removing it by thermal decomposition. The cap was covered with a thin film, and the cap was filled with fine particles, which was then polished and used as a light guide.

When this light guide was attached to the condensing device shown in Fig. 1 and sunlight was incident on it, the cladding on the incident side instantaneously thermally decomposed. In this case, the reduction in light transmission effect was about 5%, which did not have a significant effect in practical terms.

(Effects of the Invention) As described above, in the present invention, the crud is formed from a fluorine-containing resin and the crud on the incident end side is removed by thermal decomposition, making the crud removal work easier and faster than in the conventional method. can be done efficiently. It used to take one person 200 minutes to process the terminals of 500 bare fibers, but now it takes about 10 minutes.

In addition, in the present invention, since the cladding can be removed without incidentally touching the light guide strand, the cladding removal process does not damage or break the cladding, and therefore the yield rate due to breakage is reduced. It also improves.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an application example of a solar light guide, FIG. 2 is an explanatory diagram showing an example of a light guide according to the present invention, and FIG. 3 is a cross-sectional view of a light guide wire. 2 is the light guide, 3 is the base, 4 is the cladding,
5 is a light guide wire, and 6 is a core.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a light guide in which the end portions of a large number of light guide wires are densely packed into a base, in which the cladding of the light guide wires is formed of a fluorine-containing resin, and the light guide A method for manufacturing a light guide, which comprises heating the incident end side of a wire to thermally decompose and remove fluorine-containing resin, thereby forming an incident end without a cladding at the end. 2. The method of manufacturing a light guide according to claim 1, wherein the cladding at the end of the light guide wire is removed by thermal decomposition before the incident end of the light guide wire is densely packed into the base. 3. The method of manufacturing a light guide according to claim 1, wherein the incident end side of the light guide wire is minutely packed into the base, and then the cladding at the same end is removed by thermal decomposition.