JPH0894871A - Optical transmission tube - Google Patents

Abstract

PURPOSE: To prevent the swelling of a clad by a silicone oil, consequently the infiltration of air induced by the swelling and the deterioration of strength of the clad even with the use of silicone oil as a core, to give stable optical transmission property for a long time and to enable to introduce the large quantity of light with a large opening angle. CONSTITUTION: In the optical transmission tube provided with the transparent core 2 and the clad 1 having lower refraction factor than the core 2, the core 2 is composed of the silicone oil, the clad 1 is composed of one made by forming a fluoro-rubber layer at least on the inner surface of a rubber elastic body in contact with the core and both opening parts of the clad is sealed with sealing plugs 3a, 3b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission tube having flexibility and good optical transmission characteristics for a long period of time.

[0002]

2. Description of the Related Art Conventionally, an optical transmission tube including a transparent core and a clad having a refractive index lower than that of the core has been used for various optical transmission applications. In this case, as the core, solid and liquid ones are known, but especially when the core has a large diameter and efficiently transmits a large amount of light, the rigid solid one is not flexible, Liquid cores are often used.

Various liquid cores have been proposed, for example, a siloxane polymer has been proposed (Japanese Patent Laid-Open Nos. 63-253303 and 63-63303).
However, when silicone oil is used as the core, swelling occurs depending on the type of the clad. For example, silicone rubber has excellent performance as a clad material in terms of heat resistance, cold resistance, flexibility, etc., but the silicone rubber clad swells due to the silicone oil core, and the clad becomes brittle, and the inner volume of the clad is large. It may happen that the air enters. Further, when the silicone rubber clad is used, there is a problem that a large amount of light is scattered due to the poor smoothness of the inner surface.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a flexible optical transmission tube which exhibits good optical transmission characteristics without swelling of the clad with silicone oil.

[0005]

Means for Solving the Problems and Modes for Carrying Out the Invention As a result of intensive studies to achieve the above object, the present inventor has found that a fluororubber layer is formed on at least the inner surface of a rubber elastic body such as silicone rubber which is in contact with the core. When the silicone oil is used for the core, the clad that has been formed has no swelling of the clad, and exhibits stable and good optical transmission characteristics for a long period of time. Since the opening angle is expanded, a large amount of light can be taken in, and the inner surface smoothness is improved even when a rubber elastic body having poor inner surface smoothness such as silicone rubber is used as the clad main body. The present invention has been completed based on the knowledge that light scattering at the interface between the cladding and the core can be prevented as much as possible.

Therefore, according to the present invention, in an optical transmission tube having a transparent core and a clad having a refractive index lower than that of the core, the core is made of silicone oil, and the clad is at least a core of a rubber elastic body. Provided is an optical transmission tube characterized in that a fluororubber layer is formed on the inner surface in contact with the cladding, and the openings at both ends of the clad are sealed by sealing plugs.

The present invention will be described in more detail below. As shown in FIG. 1, the optical transmission tube of the present invention is as follows.
The hollow tubular clad 1 is filled with the transparent liquid core 2, and the openings at both ends of the tubular clad 1 are sealed by the sealing plugs 3a and 3b. In the present invention, the liquid core material is silicone oil. Is used.

Here, the silicone oil is not particularly limited, and for example, dimethyl silicone oil, methylphenyl silicone oil, alkyl-modified silicone oil, fluorosilicone oil and the like can be used, but it is called heat resistance and high refractive index. From this point, a silicone oil containing 5 mol% or more, particularly 10 to 60 mol% of all organic groups having a phenyl group bonded to a silicon atom is preferably used.

Further, in the optical transmission tube of the present invention, as shown in FIG. 1, the cladding 1 has a structure in which a fluororubber layer 1b is formed on the inner surface of a tubular rubber elastic layer 1a.

In this case, the rubber elastic layer 1a may be composed of the fluororubber layer 1b itself or may be formed of another rubber material. Other rubber materials include, for example, dimethyl silicone rubber, methylphenyl silicone rubber,
Silicone rubbers such as fluorosilicone rubber, butyl rubber, halogenated butyl rubber, butyl rubbers such as saturated butyl rubber, EPDM, acrylic rubber, nitrile rubber,
Further, thermoplastic elastomers such as SBS, SEBS, SIS and the like are used, and a single layer structure or a multi-layer structure of two or more layers thereof can be used. However, vulcanized rubber of silicone rubber type, butyl rubber type, EPDM type is used. Preferred are also thermoplastic elastomers. Among these, silicone rubbers are preferably used from the viewpoint of heat resistance and the like, and butyl rubbers and EPDMs are preferably used from the viewpoint of gas barrier properties against water vapor and the like.

On the other hand, as the fluororubber for forming the inner surface layer, vinylidene fluoride (VDF) -hexafluoropropylene (HFP) binary copolymer, VDF-HFP
-VD fluororubber such as tetrafluoroethylene (TFE) terpolymer, propylene-tetrafluoroethylene fluororubber, tetrafluoroethylene-perfluoroalkyl vinyl ether fluororubber, thermoplastic fluororubber, and the like. Among them, VD type fluororubber is preferably used.

As a method of forming a fluororubber layer on the inner surface of the rubber elastic body using the fluororubber, a method of coextruding the fluororubber with the rubber elastic body material (in this case,
It may be extruded into a mandrel), or a method in which a fluororubber extruded into a tubular shape is coated with the above rubber elastic material, but the inner surface of the tubular rubber elastic body can be treated with an organic solvent solution of fluororubber. A coating method is preferable, and by adopting this inner surface coating method, a fluororubber layer having excellent smoothness can be formed.

The fluororubber layer formed in this manner can be used without vulcanization, but in order to impart shape-retaining property (especially at high temperature), wrinkles of the fluororubber layer due to volume expansion and contraction, and tubes It is desirable to vulcanize it in order to prevent peeling from the core and to prevent dissolution in the core liquid.
In this case, the vulcanization method may be polyol vulcanization or polyamine vulcanization, but radical vulcanization methods such as peroxide vulcanization, electron beam vulcanization, and photocrosslinking are preferable from the viewpoint of less coloring of the vulcanized fluororubber layer. Adopted by.

When peroxide vulcanization is carried out, examples of the peroxide include ketone peroxides, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters and the like.

Specifically, 2,5-dimethylhexane-
2,5-dihydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,
Di-t-butyl peroxide, t-butyl cumyl peroxide, 2,2-bis (t-butylperoxy) butane, 2,2-bis (t-butylperoxy) octane, 1,1-bis (t -Butylperoxy) cyclohexane, t-butylperoxybenzate, benzoyl peroxide, lauroyl peroxide, 2,4-
Dichlorobenzoyl peroxide, 1,1-bis (t
-Butylperoxy) -3,3,5-trimethylcyclohexane, n-butyl-4,4-bis (t-butylperoxy) palerate, dicumyl peroxide, α,
Examples include α'-bis (t-butylperoxyisopropyl) benzene and 2,5-dimethyl-2,5-di (t-butylperoxy) hexane. Among these, decomposition products are said to be less colored. From the point of view, peroxides having an aliphatic or alicyclic structure containing no aromatic ring, such as 2,5-dimethylhexane-2,5-dihydroperoxide and 2,5-dimethyl-2,5-di (t -Butylperoxy) hexyne-3, di-t-butylperoxide, 2,2-bis (t-butylperoxy) butane,
2,2-bis (t-butylperoxy) octane, 1,
1-bis (t-butylperoxy) cyclohexane, lauroyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane,
2,5-Dimethyl-2,5-di (t-butylperoxy) hexane is preferred.

Although the amount of the above-mentioned peroxide used is appropriately selected, it is preferably 0.1 to 10 parts, more preferably 0.5 to 100 parts by weight of fluororubber (the same applies hereinafter).
5 parts, more preferably 2 to 4 parts. If the amount of peroxide is too small, vulcanization cannot be performed sufficiently and the rubber physical properties cannot be sufficiently expressed, and unvulcanized fluororubber is eluted into the core, which causes light scattering in the core and the formation of the core and the clad. Scattering at the interface deteriorates the optical transmission characteristics. Further, the residual halogen compound in the fluororubber is released at a high temperature and deteriorates the light transmission characteristics. On the other hand, when the amount of peroxide is large, the compatibility between the fluororubber and the peroxide is generally poor, and therefore the peroxide aggregates and causes foaming during vulcanization. Therefore, light scattering may increase at the interface between the core and the clad, or the silicone oil core may penetrate into the rubber elastic body through the pinhole formed in the clad and swell it. In addition, since the peroxide decomposed products and unreacted products are increased, the optical characteristics are deteriorated.

At the time of peroxide vulcanization, it is preferable to add a crosslinking aid in order to increase the crosslinking efficiency of the fluororubber. As the crosslinking aid, an acryloxy group-containing compound, a methacryloxy group-containing compound, or an aryl group-containing compound can be added. Acrylic acid or methacrylic acid derivatives such as esters thereof can be used as the compound provided for this purpose.

Examples of the alcohol residue of the ester include a cyclohexyl group, a tetrahydrofurfuryl group and an aminoethyl group in addition to an alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a dodecyl group, a stearyl group and a lauryl group. , 2-hydroxyethyl group, 3-hydroxypropyl group, 3-chloro-2-hydroxypropyl group and the like. Furthermore, esters with polyfunctional alcohols such as ethylene glycol, triethylene glycol, and polyethylene glycol can be similarly used.

As the aryl group-containing compound, diallyl phthalate, diallyl fumarate, diallyl maleate, triallyl isocyanurate and triallyl cyanurate are preferably used.

The amount of these used is preferably 0.1 to 20 parts, particularly 0.5 to 5 parts, per 100 parts of fluororubber.

Further, an adhesion aid can be added to the fluororubber to improve the adhesion with the rubber elastic layer. In this case, the adhesion aid can be selected depending on the type of rubber elastic material, and for example, when the rubber elastic layer is made of silicone rubber, it is desirable to add a silane coupling agent. Known silane coupling agents provided for this purpose, for example, γ-chloropropylmethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris (β-methoxyethoxy).
Silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-ethoxycyclohexyl) ethyl-
Trimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ
-Aminopropyltrimethoxysilane and the like can be mentioned. Particularly, a silane coupling agent having a methacrylic group or a vinyl group at the end is preferable from the viewpoint of less coloring.

It is sufficient that the amount of these adhesion aids is 5 parts or less per 100 parts of fluororubber.

Further, if necessary, a colorant, an ultraviolet absorber, an antiaging agent, a discoloration preventing agent and the like can be added.

Here, when performing peroxide vulcanization,
As the fluororubber, one having a halogen atom as a radical active site in its molecule is used. This is because the halogen atom in the molecule is desorbed by the radical from peroxide,
It becomes a highly active radical and vulcanization proceeds as shown in the following formula. In addition, as the position of the halogen atom, in the main chain,
It may be located at any of the side chain and the end of the main chain, but is particularly preferably at the end of the main chain.

[0025]

[Chemical 1]

As the halogen atom in the molecule, bromine is mainly used because of its high reactivity, but according to the study of the present inventor, the fluororubber having a bromine atom in the molecule is often colored. Therefore, even if the reactivity is somewhat low, those having an iodine or chlorine atom in the molecule are suitable as the clad material from the viewpoint of less coloring, and from this point, the fluororubber clad of the present invention by radical crosslinking is suitable. It is preferable to use a radical-crosslinked fluororubber having an iodine or chlorine atom in the molecule, but by adopting the method for reducing residual halogen compounds described below,
A fluororubber having a bromine atom in the molecule can also be effectively used.

Although the peroxide vulcanization conditions vary depending on the peroxide species, for example, Perhexa 25B
When (2,5-dimethyl-2,5-di (t-butylperoxy) hexane) is used, it is usually 140 to 160.
After primary vulcanization at 10 ° C. for 1 minute to 1 hour, secondary vulcanization is performed at 160 to 200 ° C. for 1 to 20 hours. For vulcanization, a press, an oven, an autoclave, or the like is used. In the case of an oven or an autoclave, in order to prevent crosslinking inhibition by oxygen, replacement with an inert gas such as N ₂ or steam,
Vacuuming or the like is needed as appropriate. Regarding the vulcanization temperature and time, if the temperature is too low or the time is too short, not only the vulcanization of the rubber may not proceed sufficiently, but also the adhesion may be insufficient. Decomposition or adhesion of rubber (especially when silane coupling agent is used)
May be seen.

In the case of electron beam vulcanization, a radical is generated by an electron beam without using the above-mentioned peroxide, and triallyl isocyanurate (TAIC), α-TMPT,
Crosslinked using TMPT etc., in this case 0.5
The irradiation dose is preferably -20 Mrad, more preferably 2-10 Mrad, and is preferably carried out in an atmosphere of an inert gas such as nitrogen gas. The amount of the crosslinking aid used is the same as above.

Also in the case of electron beam vulcanization, the unvulcanized fluororubber to be used is preferably one having a bromine atom, an iodine atom or a chlorine atom in the molecule, particularly at the terminal, in terms of less coloring.

Further, after vulcanizing the fluororubber, it is subjected to solvent washing treatment, heat treatment, depressurization treatment, etc., so that the content of the residual halogen compound in the vulcanized fluororubber is 80 ppm or less, preferably 30 ppm or less as a halogen atom. It is recommended to use a vulcanized fluororubber whose content is 5 ppm or less. In this case, the residual halogen compound means an atom, a molecule, an ion or a compound with another atom or a molecule, and is mainly in a molecular state or a hydrogenated state.

Here, as a method of washing the vulcanized fluororubber with a solvent, a solvent which dissolves a halogen compound such as iodine or bromine, particularly a halogen molecule and does not attack the fluororubber, for example, a lower alcohol, a ketone or an aroma is used. Group hydrocarbons, water, fluorine-based solvents, silicones, petroleum-based solvents, phosphate ester-based solvents, and the like, or a mixed solvent of two or more thereof,
Preferred is a method of washing with ethanol or water. As the cleaning method, a method of dipping treatment, a method of steaming in steam (steam stripping), or the like can be adopted.

In order to accelerate the sublimation and evaporation of halogen molecules, a method of heat treatment at a high temperature, preferably above the melting point of halogen molecules is also effective, and the halogen molecules can be depressurized or vacuumed using a vacuum oven or the like. The method of removing is also suitable.

In this case, the solvent washing treatment, the heat treatment and the depressurization treatment may be carried out individually or in combination, and for example, the heat treatment and the depressurization treatment can be carried out simultaneously in parallel.

In the present invention, the vulcanized fluororubber has a residual halogen compound content of 80 as a halogen atom.
Although it is preferable to use one having a content of ppm or less, the residual halogen compound content means a value measured by the following method.

Crosslinked rubber containing the above-mentioned peroxide or containing peroxide and a crosslinking aid (including electron beam crosslinked products)
Is distilled off with alcohol (especially methanol is suitable in this case) (with a trap of AgNO ₃ solution) to extract the residual halogen, and an aqueous solution of AgNO ₃ is added to this to precipitate the residual halogen as silver halide (AgX). Then, the amount of AgX is determined by filtration and weighing (including high-temperature drying) (precipitate is washed with water and then with methanol and methyl ethyl ketone to remove impurities such as unreacted AgNO ₃ and dissolved fluororubber, etc., and high purity. belongs to).

Further, the halogen species (species X) of silver halide (AgX) are determined by XMA (X-ray microanalysis), converted into the amount of halogen, and the content in the sample is determined by the following formula. Is. The halogen X here mainly targets Br, iodine, and chlorine, but can be applied to other halogens.

[0037]

[Equation 1]

Further, the residual halogen compound in the vulcanized fluororubber layer and / or the rubber elastic body layer may be incorporated into the vulcanized fluororubber layer and / or the rubber elastic material layer to trap the residual halogen compound in the vulcanized fluororubber layer. It is effective in reducing coloring substances.

As the trapping agent for the residual halogen compound, any substance can be used as long as it is a substance that traps the halogen compound, for example, activated carbon, silica,
Adsorbents such as silica gel, alumina, molecular sieves, and other zeolite-based adsorbents, magnesium oxide, calcium carbonate, silver nitrate, and other compounds that have high reactivity with halogens, ion-exchange resins, and the like, one of which is used alone Or a combination of two or more kinds can be used.

These trapping agents are, in addition to the above residual halogen compounds, other coloring substances, clads, and other components contained in the optical transmission tube, for example, crosslinking agents such as peroxides, crosslinking aids, and other various additives. Although a decomposed product, an unreacted product, a thermally deteriorated product at a high temperature and the like can be captured, a zeolite-based adsorbent such as molecular sieves is preferable from the viewpoint of effectively capturing such various coloring substances. The zeolite adsorbent is also effectively used for removing water.

It should be noted that in order to accelerate the capture, UV, EB
It is possible to enhance the interaction with the trapping agent by irradiating the halogen compound to an active state such as ionization or radicals.

In this case, the content of the trapping agent in the fluororubber or rubber elastic layer is preferably 0.01 to 20% by weight. If the content of the trapping agent is too small, the effect of reducing the residual halogen compound is not exhibited, and if it is too large, the adhesive strength or the smoothness of the fluororubber surface is reduced,
The refractive index increases.

Here, the trapping agent is contained in a coating material described later, a coating layer of the trapping agent is formed by covering the clad, and a protection tube is further provided so as to surround the clad to protect it. A trapping agent can be filled between the tube and the clad, and the same effect as above can be obtained by this.

Although the particle size of the trapping agent is appropriately selected, it is preferably 10 μm or less, particularly 1 μm or less.

The inner surface vulcanized fluororubber layer can be constructed as described above, and the thickness of the fluororubber layer is 5 to 0.0.
It is preferably 01 mm, particularly 1 to 0.01 mm.

In the light transmission tube of the present invention, as the sealing plug, when it is used as a window material for light, the material forming the sealing plug needs to be transparent. Specific examples of the material include quartz glass, Pyrex glass, multi-component glass, sapphire, inorganic glass such as crystal, polyethylene, polypropylene, ABS resin, acrylonitrile / styrene copolymer resin, styrene / butadiene copolymer, acrylonitrile / EPDM.・
Styrene terpolymer, styrene / methyl methacrylate copolymer, (meth) acrylic resin, epoxy resin, polymethylpentene, allyl diglycol carbonate resin, spirane resin, amorphous polyolefin, polycarbonate, polyamide, polyarylate, polysulfone, poly Organic glass such as allyl sulfone, polyether sulfone, polyether imide, polyimide, polyethylene terephthalate, diallyl phthalate, fluororesin, polyester carbonate, and silicone resin and plastic transparent materials can be mentioned. Among them, the inorganic glass such as quartz glass, Pyrex glass, and multi-component glass is excellent not only in transparency but also in heat resistance, and is also chemically stable, so that the core contacting at its inner end surface and its outer end surface It does not chemically react with the gas or moisture that comes into contact with and can provide excellent performance for a long time.

Here, it is preferable to use a window material (sealing plug) having a refractive index substantially equal to that of the core. In addition, it is preferable to provide an antireflection film for at least the light wavelength range to be transmitted on the end surface of the window material (sealing plug) on the light incident side. Further, when the incident light contains ultraviolet rays or infrared rays, an ultraviolet ray and / or infrared ray cut film is optionally provided in a window material (sealing material) in order to prevent deterioration of the core due to ultraviolet rays and to prevent temperature rise due to infrared rays. It can be provided on the incident end face of the stopper. Window material (sealing stopper)
You may use what has itself UV and / or IR absorptivity.

When transparency is not required, metal or ceramics can be used.

Although not shown, in sealing the clad end portion with a sealing plug, heat shrink treatment, adhesive treatment, hose band fastening, winding with wire wire, fixing with shape memory alloy, sleeve, O -Mechanical fastening, such as fastening via rings or packing, can be carried out as required. Among them, stainless steel, aluminum, copper, copper alloys such as brass, steel, T
It is preferable that a metal sleeve made of i, Ni, or the like is fitted to the outer peripheral portion of the clad so as to cover the clad, and the sealing plug is fixed to the clad by a caulking method of compressively deforming the sleeve.

In the present invention, if necessary, the clad may be coated with an appropriate coating material for the purpose of protecting the optical transmission tube. The coating material can be selected from plastic, metal, glass and inorganic materials.

Specifically, polyamide, epoxy resin,
The clad can be coated with a polymer material such as polyvinyl chloride, polycarbonate, polystyrene, fluororesin, polyethylene, polypropylene, polyurethane, etc. by coating, extrusion molding, winding a tape-like material, heat shrinking treatment, or the like.

Further, metal materials such as SUS, aluminum, copper, iron, etc., or the above-mentioned polymer materials can be used in the form of pipes, bellows,
You may insert the clad which covered the core in what was shape | molded in the shape of a spiral wire. Furthermore, the metal film can be coated by plating a metal material on the outer periphery of the clad by plating, vapor deposition, sputtering, or the like.

These coating materials can be used alone or as a composite with other materials.

The above-mentioned coating material can be provided not only for the protection of the light transmission tube but also for the purpose of blocking light or causing only the required portion to emit light. For example, when a hole is formed in a required portion of the above covering material or the portion is made transparent, light leaks out from the portion to form a large number of spot-shaped or line-shaped light emitters.

[0055]

EXAMPLES The present invention will be specifically described below by showing experimental examples, examples and comparative examples, but the present invention is not limited to the following examples.

[Experimental Example 1] As a fluororubber, a VDF-HFP binary copolymer having an iodine atom at its terminal (Dayer G801) and a VDF-HF having a bromine atom at its terminal were used.
P binary copolymer (Viton VTR7085) was used, and 100 parts of it were added with 0.75 parts of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and 2 parts of triallyl isocyanurate. The ingredients were blended and kneaded to prepare a fluororubber composition.

This rubber composition was molded into a sheet having a thickness of 1 mm and press-vulcanized at 160 ° C. for 30 minutes.

Next, the transmittance of the vulcanized rubber is 400 nm.
Was measured at the wavelength of.

For comparison, VDF-H was used as fluororubber.
FP binary copolymer (Daiel G201, DAIEL G70
4) was used to carry out polyamine vulcanization and polyol vulcanization, respectively. Table 1 shows the above results.

[0060]

[Table 1]

[Experimental Example 2] As a fluororubber, a VDF-HFP binary copolymer having an iodine atom at the terminal (Dayer G901) and a VDF-HF having a bromine atom at the terminal were used.
P binary copolymer (Viton VTR7085) is used, and 100 parts thereof are added with 1.5 parts of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and 4 parts of triallyl isocyanurate. The ingredients were blended and kneaded to prepare a fluororubber composition.

This rubber composition was molded into a sheet having a thickness of 1 mm, press-vulcanized as primary vulcanization at 160 ° C. for 30 minutes, and then as secondary vulcanization in an oven at 180 ° C., 5
Peroxide vulcanization was performed in time.

Next, the vulcanized rubber was treated under the following conditions. The ethanol washed vulcanized rubber was immersed in ethanol and immersed at 20 ° C. for 100 hours. Heated and depressurized vulcanized rubber is put in a vacuum oven and heated at 140 ° C, 10 Tor
It was treated with r for 10 hours.

The residual halogen atom content and the transmittance at wavelengths of 400 nm and 500 nm of the untreated and the above-mentioned treated vulcanized rubber were measured. The results are shown in Table 2. The residual halogen atom content was measured by the above method.

[0065]

[Table 2]

[Experimental Example 3] As the fluororubber, a VDF-HFP binary copolymer having an iodine atom at the end (Dayer G901) and a VDF-HF having a bromine atom at the end were used.
P binary copolymer (Viton VTR7085) was used, and 100 parts thereof contained 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (1.5 parts) and triallyl isocyanurate (4 parts). The trapping agents shown in Table 3 were blended and kneaded to prepare a fluororubber composition.

This rubber composition was molded into a sheet having a thickness of 1 mm, press-vulcanized as primary vulcanization at 160 ° C. for 30 minutes, and then as secondary vulcanization at 180 ° C. in an oven at 5 ° C.
Peroxide vulcanization was performed in time.

Next, the transmittance of the above vulcanized rubber was measured.
In this case, the transmittance was measured at a wavelength of 500 nm in the case of a binary copolymer having an iodine atom at the terminal and at a wavelength of 400 nm in the case of a binary copolymer having an bromine atom at the terminal. The above results are shown in Table 3.

[0069]

[Table 3]

[Experimental Example 4] V having an iodine atom at the terminal
Using 100 parts of DF-HFP binary copolymer as fluororubber, the amount of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane was set as shown in Table 4, and triallyl isocyanurate 2 was used. Parts were mixed and kneaded to prepare a fluororubber composition.

This rubber composition was molded into a sheet having a thickness of 1 mm, press-vulcanized as primary vulcanization at 160 ° C. for 30 minutes, and then as secondary vulcanization in an oven at 180 ° C., 5
Peroxide vulcanization was performed in time.

Next, the transmittance of the vulcanized rubber is set to 500 nm.
Was measured at the wavelength of. The above results are shown in Table 4.

[0073]

[Table 4]

Example 1 As a fluororubber, a VDF-HFP binary copolymer having an iodine atom at its end was used, and 100 parts of 2,5-dimethyl-2,5-di (t
-Butylperoxy) hexane 0.75 parts, triallyl isocyanurate 2 parts and silane coupling agent (γ-
0.5 parts of methacryloxypropyltrimethoxysilane) was mixed and kneaded to prepare a fluororubber composition.

This was dissolved in methyl ethyl ketone to obtain a 25% by weight solution of the above fluororubber, and the inner surface of a dimethyl silicone rubber tube having an inner diameter of 10 mm, an outer diameter of 12 mm and a length of 1 m was coated.

Next, after the solvent was dried and removed, primary vulcanization (160 ° C. × 30 minutes, in an oven) and secondary vulcanization (180 ° C. × 5 hours, N ₂ substitution) were carried out, and the inner surface was thickened. A tube (clad) having a vulcanized fluororubber layer of 0.1 mm was obtained.

Methylphenyl silicone oil (27% phenyl group content) was filled in the clad, and both ends of the clad were sealed with Pyrex glass sealing plugs.

The obtained optical transmission tube was stored at 120 ° C. for 20 minutes.
No swelling of the clad was observed even after standing for a day, and good optical transmission performance was maintained.

Comparative Example 1 An optical transmission tube was obtained in the same manner as in Example 1 except that the inner surface was coated with an addition reaction type silicone rubber having a refractive index of 1.405 and a viscosity of 600 cp instead of the inner surface coated with fluororubber.

The results of the swelling rate and light transmittance are shown below. Swelling rate Example: The dimensional change of the light tube was short. Comparative Example: The length of the light tube was increased by about 11%. Further, air was contained in the tube for about 20 cm. The light transmission spectrum in the wavelength range of 400 to 700 nm was measured using a Hitachi spectrophotometer UV7000. The average light transmittance of 400 to 700 nm was determined from the data.

[0081]

[0082]

The optical transmission tube of the present invention uses silicone oil as a core, but the swelling of the clad due to the silicone oil does not occur, so that the air intrusion caused by the swelling and the strength of the clad are reduced. In addition to having a stable optical transmission characteristic for a long period of time, it has a large aperture angle and can introduce a large amount of light.

[Brief description of drawings]

FIG. 1 is a partially omitted sectional view showing an example of a light transmission tube of the present invention.

[Explanation of symbols]

 1 clad 1a rubber elastic body layer 1b fluororubber layer 2 cores 3a, 3b sealing plug

Claims (8)

[Claims] 1. An optical transmission tube comprising a transparent core (2) and a cladding (1) having a refractive index lower than that of the core (2), wherein the core (2) is made of silicone oil, and The clad (1) is made of a rubber elastic body having a fluororubber layer (1b) formed on at least the inner surface in contact with the core, and the openings at both ends of the clad are sealed by sealing plugs (3a, 3b). An optical transmission tube characterized in that. 2. The optical transmission tube according to claim 1, wherein the fluororubber layer is formed by coating the inner surface of the rubber elastic body. 3. The rubber elastic body is a vulcanized rubber of silicone rubber type, butyl rubber type or EPDM type.
The described light transmission tube. 4. The light transmission tube according to claim 1, wherein the rubber elastic body is a thermoplastic elastomer. 5. The fluorinated rubber layer is vulcanized.
The optical transmission tube according to claim 1. 6. The light transmission tube according to claim 5, wherein the vulcanization is crosslinking by radical reaction. 7. The optical transmission tube according to claim 6, wherein the crosslinking by radical reaction is peroxide crosslinking. 8. The optical transmission tube according to claim 1, wherein the content of the residual halogen compound in the fluororubber layer is 80 ppm or less as a halogen atom.