JPH0416084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plastic optical fiber, and more particularly to a plastic optical fiber that can be used for optical fiber cords, optical fiber cables, and the like.

[Conventional technology]

Conventionally, inorganic glass optical fibers have been known to have excellent optical transmission properties over a wide range of wavelengths, but they are not only difficult to process and have low bending stress, but also are expensive. , optical fibers based on plastic have been developed and put into practical use.

This plastic optical fiber consists of a core layer made of a polymer such as polymethyl methacrylate (PMMA) or polycarbonate (PC), which has a high refractive index and good light transmittance, and The basic structural unit is a sheath material layer (clad) made of a transparent polymer such as a fluorine-containing polymer with a low refractive index as a base material. The product forms of these core-clad type optical fibers include bulk fibers such as optical fibers and cored optical fibers coated with a functional protective layer, and optical fibers. There are optical fiber coats in which wires are coated with jacket materials, and optical fiber cables in which bulk fibers or collective fibers, which are aggregates of bulk fibers, are combined with tension members and the like.

Conventionally, low-density polyethylene and ethylene-vinyl acetate copolymers have been used as coating materials for optical fiber cords and as base materials for protective layers of optical fiber cores, but these polymers have low softening points and high heat resistance. It cannot withstand use in high temperature areas. When processing cables using optical fiber cores, it is not possible to process cables using cable sheathing materials with higher heat resistance, and because the heat shrinkage rate is high, it is difficult to process optical fibers at temperatures above 100℃, for example. When used in high-temperature areas, there was a problem in that optical transmission loss increased significantly due to fiber contraction.

Therefore, in order to eliminate these problems, it has been proposed to form a crosslinked polyethylene layer by, for example, crosslinking polyethylene by electron beam irradiation or heat application. is extremely impractical.

In order to eliminate such inconvenience, the present inventors
Previously, we proposed to improve the heat resistance, coating processability at high temperatures, optical transmission loss, etc. of plastic optical fibers by coating the outer layer of core-clad optical fibers with water-crosslinked polyolefin.

[Problems to be solved by the invention]

However, when coating with water-crosslinked polyolefin, there is a problem that low molecular weight alcohols such as methanol and ethanol produced during the crosslinking reaction of water-crosslinked polyolefin migrate into the interior of the fiber. There was a problem in that it affected the cladding material, lowered the bending resistance of the cladding material, and significantly lowered the repeated bendability of the optical fiber. The present invention has been made to solve this problem.

[Means for solving problems]

That is, the plastic optical fiber of the present invention, which has been found to solve the above problems, has a core
A plastic optical fiber comprising a clad optical fiber whose outer layer is coated with water-crosslinked polyolefin, characterized in that at least one alcohol-resistant protective layer is interposed between the clad and the water-crosslinked polyolefin coating layer. That is.

〔Example〕

The present invention will be explained in detail with reference to Examples below.

1 to 7 are cross-sectional views illustrating examples of the structure of the plastic optical fiber of the present invention.

FIG. 1 shows a core-clad optical fiber comprising a core material layer (core) 1 and a sheath material layer (cladding) 2, and an alcohol-resistant protective layer 3 according to the present invention is disposed on the outer layer of the cladding 2. is provided, and a coating layer 4 made of water-crosslinked polyolefin is provided via this protective layer 3. The optical fiber in Figure 1 is
For example, it can be used as an optical fiber core wire.

The example shown in FIG. 2 has basically the same structure as the example shown in FIG. 1, but the thickness of the water-crosslinked polyolefin coating layer 4 is increased so that it can be used as is as an optical fiber cord or optical fiber cable.

The same elements as in Fig. 1 are represented by the same symbols, and consist of a core 1, a cladding 2, and a functional protective layer 5 made of a thermoplastic resin such as polymethyl methacrylate or polycarbonate or a thermosetting resin such as silicone rubber. An alcohol-resistant protective layer 3 according to the present invention is provided on the optical fiber core, and a coating layer 4 made of water-crosslinked polyolefin is provided via this protective layer 3.

The examples shown in Figures 4 and 5 basically have the same configuration as the example shown in Figure 3, with tension members made of steel, FRP, etc. placed at appropriate locations within the fiber. There is. In the example shown in FIG. 4, tension members 6, 6, . . . are arranged approximately concentrically within the functional protective layer 5, and in the example shown in FIG. Tension members 7, 7... are arranged along the line. The shape, location, number, etc. of the tension members are not limited to the illustrated example, and can be arbitrarily determined as desired.

The example shown in FIG. 6 has basically the same configuration as the examples shown in FIGS. 3 to 5, but wrapping with a thin metal plate such as aluminum thin plate is applied along the outer peripheral surface of the water-crosslinked polyolefin coating layer 4. It is an optical fiber coat or optical fiber cable provided with a moisture-proof layer 8 made of metal plating, metal tube, or the like.

In the example shown in FIG. 7, a plurality of optical fiber cores 9 consisting of a core 1', a cladding 2', and an alcohol-resistant protective layer 3' according to the present invention are coated with a water-crosslinked polyolefin coating layer 4' according to the present invention. The example in FIG. 8 is a group of fibers used as optical fiber coats, optical fiber cables, etc. The optical fiber 10 shown in FIG.
It is an optical fiber cable constructed by arranging a plurality of... around a tension member 11.

In the examples shown in FIGS. 1 to 8, one or two layers of the alcohol-resistant protective layer according to the present invention are used, but there is no particular restriction on the number of layers, and the number of layers can be changed as desired depending on the structure of the fiber. The number of layers can be selected.

As the base material for the cores 1 and 1', amorphous transparent polymers are suitable, such as homopolymers or copolymers of methyl methacrylate (70% by weight or more of the starting monomers are methyl methacrylate, 30% by weight) % or less is preferably a monomer copolymerizable with methyl methacrylate. Examples of monomers copolymerizable with methyl methacrylate include vinyl monomers such as methyl acrylate and ethyl acrylate.), methacrylic acid cyclohexyl, t-butyl methacrylate, isobornyl methacrylate,
Copolymers of methacrylic acid esters such as adamantyl methacrylate, benzyl methacrylate, phenyl methacrylate, naphthyl methacrylate and monomers copolymerizable with these, polycarbonates,
Polystyrene, styrene-methacrylic acid ester copolymers, deuterated polymers in which all or some of the hydrogen atoms of these polymers are replaced with deuterium atoms, etc. can be used, and of course, other transparent polymers can be used. , transparent core polymers, and transparent blends can also be used.

As the base material for the cladding 2, 2', a substantially transparent polymer having a refractive index smaller than the refractive index of the core component by 0.01 or more is used, but usually the difference in refractive index from the core component is 0.01 to 0.01. It is best to choose from those within the range of 0.15. There is no particular restriction on the type of polymer constituting the sheath material layer, and conventionally known polymers may be used, but
For example, when the core material is a homopolymer or copolymer of methyl methacrylate,
Esters consisting of methacrylic acid and fluorinated alcohols as disclosed in Japanese Patent Publication No. 56-8321, Japanese Patent Publication No. 56-8322, Japanese Patent Publication No. 56-8323, and Japanese Patent Publication No. 53-60243, etc. It is possible to use polymerized products of the same type. Further, when polycarbonate or polystyrene is used as the core material, for example, polymethyl methacrylate can be used as the sheath material. Other specific examples of the sheath material include vinylidene fluoride polymers such as those described in Patent Publication No. 43-8978 or Patent Publication No. 53-42260, and other vinylidene fluoride polymers. -Hexafluoropropylene copolymers, methacrylic acid ester polymers other than the polymethyl methacrylate, and methylpentene polymers can also be used as the sheath material.

The base material of the alcohol-resistant protective layer 3, 3' according to the present invention may be one that does not dissolve in alcohols generated by the water-crosslinking reaction of the water-crosslinked polyolefin coating according to the present invention, and does not allow alcohols to penetrate.
Examples include organic polymers that do not cause decomposition or deformation due to chemical changes. Specific examples of organic polymers having such effects include polyethylene, ethylene copolymers, ionomers, polypropylene, polyolefins such as poly4-methylpentene-1, polyvinylidene fluoride, vinylidene fluoride copolymers, Halogen-containing polymers such as polytetrafluoroethylene, tetrafluoroethylene copolymers, polyvinyl chloride, polyvinylidene chloride, polyesters, polyamides,
Examples include polycarbonate, polyacetal, ABS, styrene-butadiene, rubber, etc.

The alcohol-resistant protective layers 3, 3' according to the present invention are
In addition, it may be constructed by wrapping with a thin metal plate such as aluminum foil, a metal plating layer, a vapor deposited layer, or the like.

The thickness of the alcohol-resistant protective layer according to the present invention is not particularly limited, but sufficient effects can be expected by setting it within the range of, for example, 2 to 1000 μm, preferably 5 to 300 μm, and more preferably 5 to 100 μm. can.

Ice-crosslinked polyolefin used in the present invention 4,
As 4', an alkoxysilane grafted or copolymerized to a polyethylene or polypropylene chain reacts with water etc. to form -Si-O-Si through condensation.
- Types that crosslink by forming bonds are common; for example, commercially available water-crosslinked polyethylene or water-crosslinked polypropylene is manufactured by Mitsubishi Yuka Co., Ltd.
Co., Ltd., trade name: Linkron, Copper Linkron-X, etc.

Base polymers for water-crosslinked polyolefin include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, isotactic polypropylene, as well as their copolymers, block copolymers, blends, etc. Can be used as required.

For example, in water-crosslinked polyethylene, an alkoxysilane grafted onto a polyethylene chain reacts with water etc. to cause -Si-O-Si-
A type of polyethylene that crosslinks by forming bonds is generally used. For example, a commercially available water-crosslinked polyethylene includes a product manufactured by Mitsubishi Yuka Co., Ltd. under the trade name Linkron-X. Base polymers for water-crosslinked polyethylene include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene. It is necessary to use water-crosslinked polyethylene with a medium density or higher (density 0.935 g/cm ³ or higher). Density 0.935
Water-crosslinked polyethylene below g/mm ³ has a low heat distortion temperature, causing fiber deformation and increased optical transmission loss. Further, by using water-crosslinked polyethylene having a density of 0.935 g/mm ³ or more, not only heat resistance but also properties such as oil resistance and gasoline resistance, which are problems in automobiles or ships, are improved.
By exposing these water-crosslinked polyolefins to the atmosphere after forming the fibers, a crosslinking reaction can gradually occur from the interface with the atmosphere to the inside of the layer due to the action of moisture in the atmosphere. .

Hot steam can also be used to accelerate the crosslinking reaction.

In addition to the anti-aging agent, the water-crosslinked polyolefin layers 4, 4' can also be filled with an inorganic or organic filler such as carbon black, talc, glass fiber, aromatic polyamide fiber, carbon fiber, or the like.

Typical methods for manufacturing the plastic optical fiber of the present invention include spinning alone and methods combining spinning with extrusion, coating, etc. For example, the optical fiber core shown in FIG. 1 is manufactured. In this case, a method using only spinning involves blending the base materials of the core 1, cladding 2, alcohol-resistant protective layer 3, and water-crosslinked polyolefin layer 4 in a molten state through a special nozzle, and discharging the mixture to shape it. It is preferable to use a composite spinning method. In addition, as a method of combining spinning and coating processing, for example, only the core 1 and the cladding 2 are spun, or the core 1, the cladding 2, and the alcohol-resistant protective layer are spun and shaped, and if necessary, tension is applied. A method is used in which this excipient is sequentially coated with other constituent layers such as a water-crosslinked polyolefin coating layer using a member.

Example 1 The optical fiber core illustrated in FIG. 1 was produced by the following method, and its characteristics were evaluated.

100 parts of methyl methacrylate and 0.40 parts of t-butyl mercaptan were produced by continuous bulk polymerization using a volatile separation device consisting of a reaction tank equipped with a spiral ribbon type stirrer and a twin-screw pent type extruder.
A monomer mixture consisting of 0.00017 parts of di-t-butyl peroxide was reacted at a polymerization temperature of 155°C and an average residence time of 4.0 hours, and then the temperature of the vent extruder was adjusted to 260°C in the bend part, 250°C in the extrusion part, and 250°C in the extrusion part. The volatile part was separated under a partial vacuum of 4 mmHg, and the component polymer of core 1 was supplied to a core-sheath-protective layer three-component composite spinning head at 230°C via a gear pump section maintained at 230°C.

On the other hand, methacrylic acid chloride and 2,2,3,
100 parts of 2,2,3,3,3-pentafluoropropyl methacrylate prepared from 3,3-pentafluoropropanol and 1 part of methacrylic acid were mixed with a small amount of n-
Polymerized in the presence of octyl mercaptan, refractive index
A component polymer of Clad 2 of 1.417 was obtained. This sheath component polymer was supplied to a composite spinning head at 230°C via a gear pump in a screw melt extruder set at 220°C.

Further, a commercially available ethylene/ethyl acrylate copolymer was supplied to a composite spinning head at 230°C via a gear pump in a screw melt extruder set at 230°C.

The melted polymers of the core, cladding and protective layer were fed at the same time through a spinneret (nozzle opening diameter: 3 mmφ).
was discharged at 230℃, and after cooling and solidifying, 3
Pick up, wind, and core material diameter at a speed of m/min.
A plastic optical fiber core having a thickness of 500 μm, a sheath part thickness of 8 μm, and an ethylene/ethyl acrylate copolymer layer thickness of 242 μm was obtained. Using this core wire, an optical fiber cord (optical fiber cord) was coated with water-crosslinked polyethylene (Linkron MF-700A (ρ = 0.945 g/mm ³ ) manufactured by Mitsubishi Yuka Co., Ltd.) using a crosshead coating machine to a thickness of 0.6 mm. (outer diameter 2.2mm). The processing conditions were an extrusion temperature of 175°C and a linear speed of 50 m/min.
The obtained optical fiber cord was water-crosslinked with boiling water at 100°C for 3 hours. The water-crosslinked polyethylene and ethylene/ethyl acrylate copolymer were peeled off from the obtained optical fiber cord so as not to damage the fiber portion, and the clad portion was observed under a microscope.
No abnormality was observed in Clad.

Comparative Example 1 An optical fiber having a core diameter of 984 μm and a sheath thickness of 8 μm was obtained in the same manner as in Example 1 except that the protective layer polymer was not used. This strand was coated with water-crosslinked polyethylene in the same manner as in Example 1, and when the water-crosslinked polyethylene was similarly peeled off and the cladding portion was observed under a microscope, numerous cracks were observed in the cladding.

〔Effect of the invention〕

According to the present invention, the water-crosslinked polyolefin coating allows cable processing with a coating material that has excellent heat resistance and higher heat resistance at high temperatures.
In addition, the present invention provides a plastic optical fiber with less optical transmission loss due to heat shrinkage, and in which damage to the fiber constituent layers, especially the cladding, due to alcohols produced by the crosslinking reaction of water-crosslinked polyolefin is well prevented.

[Brief explanation of drawings]

1 to 8 are diagrams for explaining configuration examples of the plastic optical fiber of the present invention. 1,1'...core, 2,2'...clad, 3,
3'...Alcohol-resistant protective layer, 4,4'...Water-crosslinked polyethylene layer, 5...Functional protective layer, 6,7...
...Tension member, 8...Moisture-proof layer.

Claims (1)

[Claims] 1 A plastic optical fiber comprising a core-clad optical fiber whose outer layer is coated with water-crosslinked polyolefin, with at least one alcohol-resistant protective layer interposed between the cladding and the water-crosslinked polyolefin coating layer. A plastic optical fiber characterized by: