JPS61278807A - Production of plastic optical fiber - Google Patents

Abstract

PURPOSE:To improve heat resistance, thermal shrinkage and optical transmission loss at a high temp. by using a 3-layered type optical fiber core consisting of core, sleeve and protective layer and coating the outside thereof with a water crosslinking type polyolefin at 160-230 deg.C working temp. CONSTITUTION:The optical fiber core having the three-layered structure is produced by a method known as a combined spinning system consisting in discharging the respective base materials for the core material, 1, the sleeve material 2 and the protective layer 3 from a special nozzle in a molten state thereby molding these materials. The coating layer is formed on such core by a melt molding method. The coating temp. is required to be iota160 deg.C and about >=1704oC is more preferably adopted. The upper limit of the coating temp. is made preferably about 230 deg.C, more preferably about 220 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] 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 core cables, and the like.

[Conventional technology]

Conventionally, inorganic glass optical fibers have been known as optical fibers, which have excellent optical transmission properties over a wide range of wavelengths, but they have poor workability, bending stress of only 5°, and are expensive. There is power in being.

Since then, optical fibers based on plastic have been developed.
It has been put into practical use.

This plastic optical fiber is made of polymethyl methacrylate (PMMA), which has a high refractive index (and good light transmission).
), a core material layer (core) made of a polymer such as polycarbonate (PC), and a sheath material layer (core) made of a transparent polymer such as a fluorine-containing polymer with a lower refractive index than the core material (
The basic structural unit is cladding). These core
The product form of clad-type optical fiber (optical fiber bare wire) includes bulk fibers such as optical fiber wires, optical fiber wires such as Hikari 7-Ibar core wire coated with a functional protective layer, and optical fiber wires. There are optical fiber cords coated with a sheathing material (jacket material), and optical fiber cables that combine bulk fibers or collective fibers that are aggregates of bulk fibers with tension members and the like.

Conventionally, low-density polyethylene and ethylene-vinyl acetate copolymers have been used as the coating material for the plastic optical fiber cord and the protective layer base material for the optical fiber core.
These polymers have a low softening point and poor heat resistance, so they cannot withstand use in high-temperature areas.When processing cables using optical 7-iper fibers, it is necessary to use cable covering materials with higher heat resistance. In addition, the thermal shrinkage rate is high, so when optical fibers are used in high-temperature areas such as 115°C or higher, which is required for automotive applications, optical transmission loss increases due to fiber shrinkage. remarkable,
There were some problems.

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 by applying heat using an organic peroxide as a crosslinking agent. , the optical transmission loss of the optical fiber due to electron beams and heat is significant, making it impractical.

On the other hand, in the field of electric wire coating, methods of coating electric wires with water-crosslinked polyethylene have been known, but usually low-density water-crosslinked polyethylene with insufficient heat resistance is used.

Furthermore, a method of coating a plastic fiber wire consisting of two layers, a core and a sheath, with water-crosslinked polyolefin is described in JP-A-60-21012 and JP-A-56-30209. Since the heat resistance of the plastic fiber itself to be coated is insufficient, the coating temperature must be set at a low temperature of around 120°C, and a coating material with a low processing temperature (softening point) is used. As a result, the resulting coated plastic optical fiber has insufficient heat resistance.

[Problem that the invention seeks to solve]

The present invention solves the problems that conventional plastic optical fibers have, namely (1) the heat resistance of the plastic optical fiber to be coated is insufficient, and (2) the coating temperature cannot be raised. We are trying to solve the problems such as not being able to coat with a coating material with good heat resistance (3ν, therefore, the heat resistance of the finished optical fiber with coating material is insufficient, and the optical transmission loss is significant in a high temperature atmosphere. It is something.

[Means for solving problems]

As a result of investigation, the above problems can be solved by using a three-layer optical fiber core, a core, a sheath, and a protective layer, and coating the outside with water-crosslinked polyolefin at a processing temperature of 160 to 230°C. It was discovered that

The plastic optical fiber to be coated in the present invention has a three-layer structure of a core, a sheath, and a protective layer, or is currently under application by the present applicant. It is possible to prevent destruction of the sheath layer. Moreover, as the water-crosslinked polyolefin, one having excellent heat resistance is used.

The present invention will be explained in more detail below with reference to the drawings.

Figure 1 shows the outer layer of a core-clad-sheath type optical fiber (optical fiber core), which consists of a core material layer (core) 1, a sheath material layer (cladding) 2, and a protective layer (sheath) 3. This figure shows a cross-sectional structure of an optical fiber cord or coated optical fiber in which layer 3 is coated with a water-crosslinked polyolefin layer 4.

Although FIG. 2 basically has the same configuration as the example shown in FIG. 5
This figure shows a cross-section of an optical fiber cord or coated optical fiber wire. The shape, location, number, etc. of the tension members are not limited to the illustrated example, and can be arbitrarily determined as desired.

FIG. 3 shows an example in which the configuration is basically the same as the example in FIG. FIG. 2 is a cross-sectional view of a fiber cord or optical fiber cable.

FIG. 4 shows the structure of an assembled fiber in which a plurality of core-clad-sheath type optical fiber strands are coated with water-crosslinked polyolefin 4, and is used as an optical fiber cord or the like.

FIG. 5 shows a cross section of an optical fiber cable in which a plurality of core-clad-sheath type optical fibers are bundled together and combined with a tension member 5'.

In the plastic optical fiber core of the present invention consisting of three layers: a core material layer (core), a sheath material layer (cladding), and a protective layer (sheath), the base material of the core 1 is a non-quality transparent polymer. For example, a homopolymer or copolymer of methyl methacrylate (at least 70% by weight of the starting material is methyl methacrylate and 30% by weight or less is a monomer copolymerizable with methyl methacrylate). Preferred examples of monomers copolymerizable with methyl methacrylate include vinyl monomers such as methyl acrylate and ethyl acrylate), cyclohexyl methacrylate, t-butyl methacrylate, inbornyl methacrylate, adamantyl methacrylate, Copolymers of methacrylic esters such as benzyl methacrylate, phenyl methacrylate, and 7-tyl methacrylate and monomers copolymerizable with these, polycarbonate, polystyrene, styrene-methacrylic ester copolymers, or hydrogen of these polymers. Deuterated polymers in which all or some of the atoms are substituted with deuterium atoms can be used, and mochi, ron, and other transparent polymers, transparent core type polymers, and transparent blends can also be used. be.

The cladding 20 base material has a refractive index of 0.
A substantially transparent polymer having a refractive index as low as 01 or more is used, but usually the difference in refractive index with the core component is o, oi
It is preferable to select from those in 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. For example, when a homopolymer or copolymer of methyl methacrylate is used as the core material,
No. 8978, Special Publication No. 56-8321, Special Publication No. 56-8
No. 322, Japanese Patent Publication No. 56-8323, and Japanese Patent Publication No. 53-6
It is possible to use polymerized esters of methacrylic acid and fluorinated alcohols as disclosed in No. 0243 and the like. 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 as described in Japanese Patent Publication No. 43-8978 or Japanese Patent Publication No. 53-42260. Vinylidene chloride-hexafluoropropylene copolymers, methacrylate ester polymers other than the polymethyl methacrylate, and methylpentene polymers are also used as the sheath material.

be able to.

Furthermore, polymerized esters of α-fluoroacrylic acid and fluorinated alkyl alcohol can also be used.

As the base material for the protective layer (sheath) 30, polymethyl methacrylate, polycarbonate, edelene-ethyl acrylate copolymer, polypropylene, polyester, polyamide, polyvinylidene fluoride, polysulfone, polyacetal, polyoxymethylene, polybutene, etc. may be used. I can do it.

The polyolefin used for coating is JP-A-56-30.
209 and 60-21012, but in the present invention, the density is 0.935 to 0.970 J'/cI.
It is preferable to use a base polymer such as high-density polyethylene, polypropylene, or ethylene-propylene copolymer with alkoxysilane grafted or copolymerized to a base polymer such as high-density polyethylene, polypropylene, or ethylene-propylene copolymer. to generate a -5t-O~Si- bond.

Furthermore, since these water-crosslinked polyolefins have a high melting temperature, if they are processed at a temperature below 160° C., the surface of the coating layer will become rough (which is not preferable).

Therefore, the coating processing temperature needs to be 160°C or higher, but in order to obtain a product with low thermal shrinkage or a smooth surface, a higher temperature, for example, 170°C or higher, is used. It is more preferable.

Further, coating at a high temperature of 230° C. or higher is not preferable because the coated fiber is affected by the heat during processing and the optical fiber is damaged.

The upper limit of the coating temperature is preferably about 230°C, more preferably about 220°C.

In the present invention, a particularly preferable coating temperature is 180 to 2
The temperature range is 10°C.

When these water-crosslinked polyolefins are exposed to the atmosphere after being shaped into fibers, a crosslinking reaction can gradually occur from the interface with the atmosphere into the layer due to the action of moisture in the atmosphere. Moreover, hot water or steam can also be used to promote the crosslinking reaction.

In addition to the anti-aging agent, the water-crosslinked polyolefin layer 4 can also be filled with inorganic or organic fillers such as carbon black, Merck, glass fiber, aromatic polyamide fiber, carbon fiber, and the like.

A typical method for manufacturing the plastic optical fiber of the present invention is a method that combines spinning, extrusion, coating, etc. For example, when manufacturing the optical fiber core shown in FIG. A three-layer optical fiber core is manufactured using a so-called composite spinning method in which the respective base materials of the sheath material 2 and the protective layer 3 are discharged in a molten state through a special nozzle and shaped, and the coating layer is formed using a melt-forming device. A method of coating is used.

〔Example〕

Specific examples are shown below, but the embodiments of the present invention are not limited thereto.

Example 1 The stone layer is a polymethyl methacrylate layer with a diameter of 900 μm,
Methacrylic acid 2, 2, 3, 3. The sheath material layer has a thickness of 10 μm.
Using a plastic optical fiber core wire with a three-layer structure in which the copolymer layer of 3-pentafluoropropyl and methacrylic acid and the protective layer are an ethylene and ethyl acrylate copolymer layer with a thickness of 40 μm, crosshead cable processing was performed using iK. Water-crosslinked polyethylene graft-polymerized with alkoxysilane (density: 0,945 JP/cWL", M F
R; 1.5 J'/10m1n (190°C)
An optical fiber cord with an outer diameter of 2.2 mm was manufactured by coating the fiber to a thickness of 0.6 dew at a coating temperature of 180°C and a linear speed of 50 m/1 nin, and then soaked in hot water at 98°C for 30 minutes. Water crosslinking treatment was performed by immersing the sample for a period of time.

The heat resistance and optical transmission loss of the obtained optical fiber cord were evaluated by the following evaluation method. The results are shown in the table.

〔Evaluation methods〕

(1) Measure 15 ffl of the optical fiber core wire at a temperature when the light amount is halved, and measure the middle part 10 f.
Put the fl into the dryer, take out 2.5 m of each end from the wall hole of the dryer, and attach a 650 nm or 770 nm film to one end.
Attach a wavelength light source and a photodetector at one end. The temperature of the dryer was raised at a rate of 2°C/mln, and the temperature at which the amount of light emitted from the optical fiber became half of the initial light amount at room temperature was measured.

(2) Thermal shrinkage rate An optical fiber cord with a total length of 80 cyt (Lo) was hung in a circulating hot air dryer, and the length L) after being held at 115° C. for 20 hours was calculated using the following formula.

(3) Optical transmission loss Measured by the method disclosed in Japanese Unexamined Patent Publication No. 58-7602. The measurement wavelength is 650 nm or 770 nm.

Comparative Example 1 Using the same three-layer optical fiber core and water-crosslinked polyethylene as in Example 1, the coating was performed at a coating temperature of 155°C, and the other conditions were the same as in Example 1. The surface shape of the obtained optical fiber cord was rough and the optical transmission loss was poor.

Moreover, the light amount half-life temperature also showed a lower value as shown in the table when compared with Example 1.

Comparative Example 2 Low-density water-crosslinked polyethylene (density:
0.923 J' 7cm3, MFR; 0.7 J'
/ 10 min), a three-layer core wire consisting of a core, a sheath and a protective layer was coated at 180° C. in the same manner as in Example 1 to obtain an optical fiber cord.

The evaluation results are shown in the table, and compared to Example 1, the light amount change temperature was low (and the thermal shrinkage rate was large).

Example 2 The core material layer is a polymethyl methacrylate layer with a diameter of 900 μm,
Methacrylic acid 2, 2, 3, 3. The sheath material layer has a thickness of 10 μm.
Water-crosslinked polyethylene (density: 0.955!/cI!L”, MFR;2.
4]/10m1o CI 90℃]) coating processing temperature 1
Coating was carried out to a thickness of 0.611111 at 90°C and a line speed of 50 m/min to obtain an optical fiber cord with an outer diameter of 2° and 2 electric φ, which was subjected to water crosslinking treatment in the same manner as in Example 1 and its performance was evaluated. .

Example 3 The core material layer is a polycarbonate layer with a diameter of 900 μm, the sheath material layer is a methacrylic acid 2,2°3.3,3,3-pentafluoropropyl and methacrylic acid copolymer layer with a thickness of 10 μm, and the protective layer is 40 μm in thickness. Water-crosslinked polypropylene (density: 0,912 P/cIIL", M
An optical fiber cord was obtained under the same conditions as in Example 1 except that the coating temperature was 220° C. and the performance was evaluated.

Comparative Example 3 An optical fiber cord was manufactured under the same conditions as Example 3, except that the coating temperature was 240''C, but the outer diameter of the cord was 2.2±0.3 tn, which was highly uneven. Moreover, the optical transmission loss also showed a large value.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a jacketed plastic optical fiber that has excellent heat resistance, low thermal shrinkage, and low optical transmission loss at high temperatures.

[Brief explanation of the drawing]

1 to 5 illustrate examples of the cross-sectional structure of the plastic optical fiber of the present invention, and the symbols in the figures are as follows: 1 core material layer 2 sheath material layer (cladding) ) 3 Protective layer (sheath) 4 Covering layer (jacket) 5 Tension member 6 Moisture-proof layer 1 unit + f Figure Blue 2 Diagram 3 Nose 3 concave

Claims (2)

[Claims] (1) One layer of water-crosslinked polyolefin is added to the plastic optical fiber core, which has a three-layer structure of a core, sheath, and protective layer.
A method for producing a jacketed plastic optical fiber, characterized in that coating is performed at a temperature of 60 to 230°C. (2) The method for manufacturing a plastic optical fiber according to claim 1, wherein the coating temperature is 180 to 210°C.