JPH0894862A - Optical transmission tube - Google Patents

Abstract

PURPOSE: To obtain an optical transmission tube using a fluoro-rubber, which is prevented from the deterioration of optical transmission property as much as possible, as a clad material by incorporating a trapping agent for a residual halogen compound in the clad material. CONSTITUTION: The trapping agent for the residual halogen compound is incorporated in a vulcanized fluoro-rubber and/or rubber elastic body in the clad 2 made by forming the inner surface at least in contact with a core 3 out of the vulcanized fluoro-rubber. Since bromine atom is better than iodine atom in the view point of reactivity though iodine atom is more preferable than bromine atom in the view point of coloring, the vulcanized fluoro-rubber made by vulcanizing the fluoro-rubber having intramolecular bromine atom inferior in the view point of coloring is effectively used as the clad of the optical transmission tube by removing a residual bromine compound from the vulcanized fluoro-rubber obtained by vulcanizing the fluoro-rubber having bromine atom in the molecule. And since the trapping agent captures also decomposed materials of a vulcanizer, a cross-linking agent or various additives in the rubber elastic body, the deterioration of optical transmission property is prevented.

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 using fluororubber as a clad material.

[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, solid cores and liquid cores are known as cores, and various types of clads for coating the cores are selected according to the type of the core. According to the results of the study, it was found that when a liquid core, particularly silicone oil is used as the core, it is effective that the inner surface of the clad which is in contact with the core is at least fluororubber in terms of swelling property.

However, when fluororubber is used as the clad, it is found that the optical transmission characteristics are deteriorated during long-term use. Therefore, it is possible to prevent the optical transmission characteristics from being deteriorated even after long-term use. A new solution problem arose.

The present invention has been made to solve the above problems, and provides an optical transmission tube using fluororubber as a clad material in which deterioration of optical transmission characteristics is prevented as much as possible even after long-term use. The purpose is to

[0006]

Means for Solving the Problems and Modes for Carrying Out the Invention As a result of intensive studies to achieve the above-mentioned object, the present inventor has found that an optical transmission tube using fluororubber as a clad material can transmit the optical transmission over time. It was found that the cause of the deterioration of the properties was that the coloring component in the clad was eluted into the core, and as a result of further study to obtain a fluororubber clad with little coloring, the clad coloring was It is greatly affected by the residual halogen compound, and the trapping agent for the residual halogen compound is contained in the clad or in the coating material layer covering this clad, or a protective tube filled with the trapping agent is provided outside. Moreover, it has been found that it is effective to form a coating layer of the trapping agent on the outer peripheral surface of the clad.

Particularly, when vulcanizing an unvulcanized fluororubber, peroxide vulcanization is preferable from the viewpoint of coloring, and when performing peroxide vulcanization, a fluororubber having a halogen atom in the molecule is used, The radical from the peroxide is used to eliminate the halogen atom in the molecule to form a highly active radical, which promotes vulcanization.
At this time, it was found that the iodine atom is more preferable than the bromine atom as the halogen atom in the molecule, but in any case, the residual halogen compound remains in the fluororubber and the residual halogen compound is removed. It was found that this is effective from the viewpoint of preventing coloration. In this case, as the intramolecular halogen atom, as described above, the iodine atom is more preferable than the bromine atom in terms of coloring, but the bromine atom is superior in terms of reactivity, and bromine By removing the residual bromine compound from the vulcanized fluororubber obtained by vulcanizing the fluororubber having atoms, the vulcanized fluororubber obtained by vulcanizing the fluororubber having an intramolecular bromine atom which is inferior in coloring It can be effectively used as a clad for a transmission tube, and by using a residual halogen compound trapping agent as described above, the optical transmission characteristics of the optical transmission tube are maintained for a long period of time, and an optical transmission tube in which coloring is prevented is provided. It was found that it can be obtained.

Further, in this case, in addition to the residual halogen compound in the fluororubber, the causative substance (coloring substance) that lowers the light transmittance is a vulcanizing agent, a cross-linking aid, a decomposed product of various additives, and unreacted. In the case where a rubber elastic body and a fluororubber formed on the inner peripheral surface thereof are used to form the clad material and the clad, a vulcanizing agent and a cross-linking agent in the rubber elastic body, decomposed products / unreacted materials of various additives, and It was found that there are also heat-deteriorated products at high temperatures, but the trapping agent also acts effectively to capture such coloring substances, and it was found that the light transmission characteristics are effectively exhibited over a long period of time. The present invention has been completed.

Therefore, according to the present invention, (1) in an optical transmission tube having a transparent core and a clad having a refractive index lower than that of the core, at least the inner surface of the clad in contact with the core is made of vulcanized fluororubber. The optical transmission tube characterized by containing a trapping agent for residual halogen compounds in the cladding,
(2) In an optical transmission tube including a transparent core and a clad having a refractive index lower than that of the core, at least the inner surface of the clad which is in contact with the core is made of vulcanized fluororubber and covers the clad. An optical transmission tube characterized in that a coating material layer is formed by containing a trapping agent for a residual halogen compound in the coating material layer, and (3) a transparent core and a refractive index lower than that of the core. In an optical transmission tube having a clad, at least the inner surface of the clad which is in contact with the core is formed of vulcanized fluororubber, and a trapping agent for residual halogen compound is directly provided on the outer side of the clad or through a coating material layer. An optical transmission tube characterized by arranging a protective tube filled therein, and (4) a transparent core and a cladding having a lower refractive index than the core. In the optical transmission tube including, at least the inner surface of the clad in contact with the core is formed of vulcanized fluororubber, and the coating layer of the trapping agent for the residual halogen compound is formed to cover the clad. A characteristic optical transmission tube is provided.

Hereinafter, the present invention will be described in more detail.
As shown in FIG. 1, an optical transmission tube 1 according to the first aspect of the present invention is formed by covering a core 3 with a hollow tubular clad 2 (note that 4a and 4b are sealing plugs). However, in the present invention, at least the inner surface of the clad 2 in contact with the core 3 is formed of vulcanized fluororubber. In this case, the clad 2 may be entirely formed of vulcanized fluororubber, or the clad main body may be formed of a rubber elastic body other than vulcanized fluororubber, and a vulcanized fluororubber layer may be formed on the inner surface thereof. May be.

In the first aspect of the present invention, the above-mentioned clad, that is, vulcanized fluororubber and / or rubber elastic body, contains a trapping agent for residual halogen compounds.
The residual halogen compounds include halogen molecules, H
I, HBr, and the like, which are compounds with atoms, molecules, ions, or other atoms or molecules, are mainly in a molecular state or a hydrogenated state.

Here, as the fluororubber, VD type fluorine such as vinylidene fluoride (VDF) -hexafluoropropylene (HFP) binary copolymer and VDF-HFP-tetrafluoroethylene (TFE) ternary copolymer are used. Examples thereof include rubber, propylene-tetrafluoroethylene-based fluororubber, tetrafluoroethylene-perfluoroalkylvinylether-based fluororubber, and thermoplastic fluororubber.

The optical transmission tube of the present invention uses the above-mentioned vulcanized fluororubber as the clad material. In this case, the method for crosslinking the unvulcanized fluororubber is not particularly limited. In addition to radical cross-linking methods such as peroxide vulcanization and electron beam vulcanization, polyamine vulcanization and polyol vulcanization can be adopted, but the radical cross-linking method is preferable because of less coloring.

A typical example of the radical crosslinking method is a peroxide vulcanization method. When peroxide vulcanization is performed, the peroxides include ketone peroxides, hydroperoxides and 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. In addition, the residual halogen in the fluororubber is released at a high temperature, deteriorating 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, the light scattering at the interface between the core and the clad becomes large, and especially in the case of a liquid core such as silicone oil, the liquid core penetrates into the rubber elastic body through the pinhole formed in the clad and swells it. There are cases in which In addition, since the peroxide decomposed products and unreacted products are increased, the optical characteristics are deteriorated.

Further, 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.

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.

[0022]

[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, as the vulcanized fluororubber itself, those having an iodine atom in the molecule are suitable as the clad material from the viewpoint of less coloring, but in the present invention,
The use of the trapping agent removes the residual halogen compound and reduces the coloring, so that a fluororubber having a bromine atom in the molecule can be effectively used.

The peroxide vulcanization conditions vary depending on the peroxide species, but 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, especially at the terminal, because it causes less coloring.

In the present invention, when the clad is composed of a rubber elastic body and a vulcanized fluoro rubber formed inside thereof, examples of the rubber elastic body include dimethyl silicone rubber, methylphenyl silicone rubber, fluorosilicone rubber and the like. Butyl rubbers such as silicone rubbers, butyl rubbers, halogenated butyl rubbers and saturated butyl rubbers, EP
DM, acrylic rubber, nitrile rubber, SBS, SE
Although thermoplastic elastomers such as BS and SIS are used, and these can have a single layer structure or a multilayer structure of two or more layers, silicone rubber type, butyl rubber type, EP
DM-based vulcanized rubber is preferable, and thermoplastic elastomer is also preferable. 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.

In the first invention of the present invention, the vulcanized fluororubber and / or the rubber elastic body is made to contain a trapping agent for the residual halogen compound. The trapping agent for the residual halogen compound is a halogen compound. Any substance can be used as long as it is a substance to be captured, for example, activated carbon, silica, silica gel, alumina, adsorbents such as molecular sieves and other zeolite-based adsorbents, ion exchange resins, and highly reactive with halogen. Examples thereof include compounds such as magnesium oxide, calcium carbonate and silver nitrate, and one of them can be used alone or two or more of them can be used in combination.

These trapping agents are, in addition to the above residual halogen compounds, other coloring substances (yellowing substances), clads, and other components contained in the optical transmission tube, for example, crosslinking agents such as peroxides, crosslinking aids, etc. Although it is possible to capture decomposed products of various additives, unreacted products, thermally deteriorated products at high temperature, etc., in effectively capturing such various colored substances,
Zeolite-based adsorbents such as molecular sieves are preferred. The zeolite adsorbent is also effectively used for removing water.

In this case, the content of the trapping agent in the fluororubber or the rubber elastic body (clad) is preferably 0.01 to 20% by weight. If the content of the trapping agent is too small, the effect of reducing free halogen will not be exerted, and if it is too large, the refractive index of the clad will increase and the surface smoothness of the fluororubber will deteriorate. The particle size of the trapping agent is appropriately selected, but is preferably 10 μm or less, particularly 1 μm or less.

The trapped halogen state is not limited to an atom, but may be an ion, a molecule, or a bonded state with another atom. U to facilitate capture
It is possible to irradiate V, EB or the like to ionize the residual halogen compound or to activate it in another active state to enhance the interaction with the trapping agent.

In the optical transmission tube of the present invention, the core material is not particularly limited, and a solid, liquid or fluid transparent material having a higher refractive index than the clad material is used.

In this case, as the solid transparent material, acrylic resins and methacrylic resins are preferably used, and examples thereof include alkyl acrylates such as methyl acrylate and methyl methacrylate, homopolymers and copolymers of alkyl methacrylates, and monomers and co-polymers thereof. The thing which copolymerized other acrylate and methacrylate which can obtain a transparent polymer which can be polymerized can be mentioned. Specific examples of the liquid or fluid transparent material include aqueous solutions of inorganic salts, polyhydric alcohols such as ethylene glycol and glycerin, silicone oils such as polydimethylsiloxane and polyphenylmethylsiloxane, polyethers, polyesters, liquid paraffin. Hydrocarbons, etc.
Halogenated hydrocarbon such as trifluorochloroethylene oil,
Examples thereof include phosphoric acid esters such as tris (chloroethyl) phosphate and trioctylphosphate, and polymer solutions prepared by diluting the polymer with a suitable solvent.

Among these, a liquid or fluid core,
Silicone oil is particularly effective for the purpose of the present invention.

The sealing plug may be used even if the core material is solid, but it is necessary especially when the core material is liquid or fluid, and in this case, as a light window material. When operating, the material forming the sealing plug needs to be transparent, and specific examples of the material of the sealing plug include inorganic materials such as quartz glass, Pyrex glass, multi-component glass, sapphire, and quartz. Glass, polyethylene, polypropylene, ABS resin, acrylonitrile
Styrene copolymer resin, styrene-butadiene copolymer,
Acrylonitrile / EPDM / styrene terpolymer,
Styrene / methyl methacrylate copolymer, methacrylic resin, epoxy resin, polymethylpentene, allyl diglycol carbonate resin, spirane resin, amorphous polyolefin, polycarbonate, polyamide, polyarylate, polysulfone, polyallylsulfone, polyethersulfone, poly Examples thereof include organic glass and plastic transparent materials such as ether imide, polyimide, polyethylene terephthalate, diallyl phthalate, fluororesin, polyester carbonate and silicon resin. Among these, quartz glass, Pyrex glass, inorganic glass such as multi-component glass is not only transparent, but also excellent in heat resistance, and also chemically stable,
It does not chemically react with the core material that comes into contact with its inner end surface and the gas or moisture that comes into contact with its outer end surface, and can provide excellent performance for a long period of 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 shrinkage 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, as shown in FIG.
The cladding 2 may be coated with an appropriate coating material 5 for the purpose of protecting the light transmission tube. The coating material can be selected from plastic, elastomer, metal, glass, and inorganic material.

Specifically, polyamide, epoxy resin,
Polymers such as polyvinyl chloride, polycarbonate, polystyrene, fluororesin, butyl rubber, halogenated butyl rubber, polyethylene, polypropylene, polyurethane, hydrochloric acid rubber, natural rubber, polyisoprene rubber, polybutadiene rubber, chloroprene rubber, acrylic rubber, EPDM, fluororubber The material can be coated, extruded, wrapped with a tape-shaped material, heat-shrinked or the like to cover the clad.

Further, a metal material such as SUS, aluminum, copper, iron or the like, or the above-mentioned polymer material is pipe-shaped, bellows-shaped,
You may insert the clad which coat | 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 protecting the light transmission tube but also for the purpose of blocking light or causing only a 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.

Here, in the second aspect of the present invention, the coating material layer 5 contains the trapping agent. In this case, the type of the trapping agent is the same as above, and the content of the trapping agent can be contained in a large amount because there is no disadvantage in light transmission. Therefore, 1 to 100% by weight in the coating material layer 5, Preferably 1 to 50% by weight, more preferably 1 to
It can be 30% by weight.

Furthermore, in the third invention of the present invention, as shown in FIG. 3, the cladding 1 is removed and a protective tube 6 is disposed, and the protective tube 6 is filled with the trapping agent 7. Is. In this case, the clad 2 may be coated with a coating material as shown in FIG. 2, the protection tube 6 may be disposed so as to cover the cladding 2, and the trapping agent 7 may be filled in the interior thereof. 8 in the figure
Is a mounting member (base) for the protective tube 6.

Further, in the fourth aspect of the present invention, as shown in FIG. 4, the coating layer 9 of the trapping agent is formed on the outer peripheral surface of the clad 2. In this case, it is preferable to form the covering material layer 5 so as to cover the coating layer 9.

The objects of the present invention can be achieved by the second, third and fourth inventions.

In this case, it is not essential to add a trapping agent to the vulcanized fluororubber, but it is more preferable to use a vulcanized fluororubber containing a trapping agent.

[0049]

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

[Experimental Example] As a fluororubber, a VDF-HFP binary copolymer having an iodine atom at the end (Dayer G901) and a VDF-HFP having a bromine atom at the end are used.
Binary copolymer (Viton VTR7085) was used, and 100 parts thereof contained 1.5 parts of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 4 parts of triallyl isocyanurate, and The trapping agent shown in Table 1 was 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 peroxide vulcanized at 180 ° C. for 5 hours in an oven as secondary vulcanization. Sulfurized.

Next, the transmittance of the above vulcanized rubber was measured.
In this case, the iodine atom terminal copolymer has a wavelength of 500.
nm, bromine atom-terminated copolymer was measured for transmittance at a wavelength of 400 nm. The results are shown in Table 1.

[0053]

[Table 1]

Example 1 Experiment No. Using the fluororubber composition of No. 3, this was molded into a tube having an inner diameter of 10 mm, an outer diameter of 12 mm and a length of 1 m, and vulcanized.

This tube was filled with silicone oil, and both ends were sealed with Pyrex glass (diameter: 10 m).
m × length 20 mm) was attached to prepare an optical transmission tube.

Example 2 Experiment No. Using the fluororubber composition of No. 7, this was molded into a tube having an inner diameter of 10 mm, an outer diameter of 12 mm and a length of 1 m, and vulcanized.

This tube was filled with silicone oil, and both ends were sealed with a Pyrex glass sealing plug (diameter: 10 m).
m × length 20 mm) was attached to prepare an optical transmission tube.

Example 3 Experiment No. 3 was formed on the inner surface of a dimethyl silicone tube containing 30 phr of silica gel and having an inner diameter of 10 mm and an outer diameter of 12 mm. 7 fluororubber layer 50
μm was formed, and this was vulcanized to prepare an optical transmission tube in the same manner as above.

Example 4 The optical tube of Example 1 was replaced with a stainless steel spiral tube (inner diameter 14 mm, outer diameter 16 mm).
Coated with. 10 g of alumina having an average particle size of 1 μm was dispersed in the space between the clad material and the spiral tube.

The optical transmission tube obtained above had good optical transmission characteristics for a long period of time without substantially coloring the core.

[0061]

The optical transmission tube of the present invention is capable of preventing the deterioration of the optical transmission characteristics even if it is used for a long period of time.

[Brief description of drawings]

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

FIG. 2 is a partially omitted sectional view showing another example of the optical transmission tube of the present invention.

FIG. 3 is a partially omitted sectional view showing another example of the optical transmission tube of the present invention.

FIG. 4 is a partially omitted sectional view showing still another example of the optical transmission tube of the present invention.

[Explanation of symbols]

 1 Optical Transmission Tube 2 Clad 3 Cores 4a, 4b Sealing Plug 5 Covering Material Layer 6 Protective Tube 7 Trap Agent 8 Mounting Member 9 Coating Layer

Claims (7)

[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 at least the inner surface of the cladding (1) in contact with the core is added. An optical transmission tube, which is formed of fluorinated fluororubber and contains a trapping agent for a residual halogen compound in the clad. 2. 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 at least the inner surface of the cladding (1) in contact with the core is added. The coating material layer (4) is formed of fluorinated fluororubber and covers the clad (1), and the coating material layer (4) contains a trapping agent for the residual halogen compound. Characteristic light transmission tube. 3. The optical transmission tube according to claim 2, wherein the clad contains a trapping agent for residual halogen compounds. 4. 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 at least the inner surface of the cladding (1) in contact with the core is added. A protective tube (5) made of fluororubber and having a trapping agent for a residual halogen compound directly or through a coating material layer (4) is provided outside the clad (1). A light transmission tube. 5. The optical transmission tube according to claim 4, wherein the cladding contains a trapping agent for a residual halogen compound. 6. An optical transmission tube comprising a transparent core and a clad having a refractive index lower than that of the core, wherein at least the inner surface of the clad in contact with the core is formed of vulcanized fluororubber and the clad is formed. An optical transmission tube, characterized in that a coating layer of a residual halogen compound trapping agent is formed so as to cover the. 7. The light transmission tube according to claim 6, wherein a coating material layer is formed so as to cover the coating layer of the trapping agent.