JP2001324626A - Heat resistant plastic optical fiber and cable made by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastics optical fiber cable with excellent mechanical strength and with little pistoning even when used under high temperature surroundings for a long period. SOLUTION: The cable is made by multicomponent spinning of a core composed of a polymethyl methacrylate resin, a first sheath layer composed of a resin composition consisting of a vinylidene fluoride resin and a polymethyl methacrylate resin and a second sheath layer composed of a copolymer consisting of vinylidene fluoride, hexafluoropropene and tetrafluoroethylene and by coating the outside with nylon-12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile cable,
Provided are a plastic optical fiber and a cable having excellent heat resistance, which can be used as a domestic cable, a factory wiring, and a cable for a photoelectric sensor.

[0002]

2. Description of the Related Art In recent years, various plastic optical fibers have been developed in the communication field. For example, Japanese Patent Publication No. 63-67164 discloses a sheath layer made of a vinylidene fluoride homopolymer or a resin composition comprising a copolymer containing vinylidene fluoride as a main component and a polymethylmethacrylate copolymer. Are disclosed. Further, the present inventors formed a first sheath layer using a resin composition comprising a copolymer containing vinylidene fluoride as a main component and a resin containing methyl methacrylate as a main component, and formed a second sheath layer. A plastic optical fiber formed by using a resin containing vinylidene fluoride as a main component and having a lower refractive index than the resin composition constituting the first sheath layer was first disclosed in JP-A-9-243836. Proposed. Further, the present inventor has found that the resin constituting the second sheath layer is composed of 30 to 92 mol% of a vinylidene fluoride component, 0 to 55 mol% of a tetrafluoroethylene component, and 8 to 25 mol% of a hexafluoropropene component. Japanese Unexamined Patent Publication No. Hei.
No. 1-101915. The same publication also proposes that the covering material is nylon 12.

[0003]

In recent years, the speed of plastic optical fibers has been increased, and the accompanying problem of heat generation of LEDs requires plastic optical fibers that can be used for a long time under high temperature conditions of about 100 to 105 ° C. Have been.
At the same time, in the processing method of the terminal of the plastic optical fiber, conventionally, the tip of the fiber was pressed against a hot plate to enlarge the fiber, thereby preventing the fiber from being retracted from the ferrule of the connector. Has been omitted. Therefore, it has become necessary to extremely reduce the extent to which the fiber shrinks due to heat during use and enters the coating (hereinafter referred to as "pistoning").
This is because if the pistoning is large, there is an inconvenience that the light loss at the time of coupling between the LED and the fiber, the fiber and the fiber, and the fiber and the PD becomes large. In order to reduce fiber shrinkage and pistoning, the orientation of the fiber may be adjusted. However, as a result, the fiber becomes mechanically very brittle and is not practical.

An object of the present invention is to provide a heat-resistant plastic optical fiber cable which has a small pistoning even when left at a high temperature of 100 to 105 ° C. for a long time and has sufficient mechanical strength, and a fiber used therefor.

[0005]

The first aspect of the present invention is to form a first sheath layer around a core and further form a second sheath layer around the first sheath layer.
A heat-resistant plastic optical fiber comprising a sheath layer, wherein the core is made of a polymethyl methacrylate polymer containing 90% by weight or more of methyl methacrylate as a monomer component, and the first sheath layer is vinylidene as a monomer component. A mixture of 60 to 90% by weight of a vinylidene fluoride-based resin containing 95 mol% or more of fluoride and 10 to 40% by weight of a polymethyl methacrylate-based resin,
The second sheath layer is made of a resin composition having a refractive index of 1.43 to 1.45 and a melting point of 140 to 180 ° C. at a sodium D line, wherein the second sheath layer has a vinylidene fluoride component of 25 to 50 mol% and a hexafluoropropene component. 10 to 15 mol%, 38 to 64 mol% of a tetrafluoroethylene component, a refractive index at sodium D line of 1.34 to 1.37, and a melting point of 140 to 1.
A heat-resistant plastic optical fiber comprising a copolymer at 180 ° C.

A second aspect of the present invention is a heat-resistant plastic optical fiber cable comprising the above-mentioned heat-resistant plastic optical fiber of the present invention as a bare wire and a nylon 12 coating around the bare wire. The gap between the bare wire and the nylon 12 coating layer at the end when left for 500 hours in an environment of 0.06 mm or less,
It has a bending resistance of 1000 times or more when bent at ± 20 ° at a bending radius of 5 mm at −20 ° C. Moreover, it is preferable that the cable of the present invention is left at 110 to 120 ° C. for 1 hour or more after covering the bare wire with nylon 12.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A plastic optical fiber according to the present invention is a bare wire comprising a core, a first sheath layer formed around the core, and a second sheath layer formed around the first sheath layer. In the plastic optical fiber cable of the present invention, the bare wire is coated with nylon 12.

[0008] The core of the plastic optical fiber of the present invention is:
As the core resin, a polymethyl methacrylate (PMMA) -based resin containing 90% by weight or more of methyl methacrylate (MMA) as a monomer component is used. Such P
In the MMA resin, as a monomer component other than MMA,
It can contain other copolymerizable monomers such as other acrylates and methacrylates, or acrylic acid and methacrylic acid.

The first sheath resin forming the first sheath layer of the plastic optical fiber of the present invention may be a vinylidene fluoride resin containing from 95 to 90% by weight of vinylidene fluoride as a monomer component. , PM
A resin composition obtained by mixing 10 to 40% by weight of the MA resin is used. In the vinylidene fluoride resin, tetrafluoroethylene, trifluoroethylene, hexafluoropropene, hexafluoroacetone, and the like can be used as monomer components other than vinylidene fluoride. Above all, the vinylidene fluoride resin is PMM
When mixed with the A-based resin to form a resin composition, the vinylidene fluoride component is preferably high, and a homopolymer is particularly preferable, since it has high transparency and does not become cloudy even under high temperature and heat.

The PMMA resin mixed with the vinylidene fluoride resin includes, in addition to MMA homopolymer (PMMA), monomers copolymerizable with MMA such as methyl acrylate and ethyl acrylate. Copolymers with acrylates, ethyl methacrylate, maleimides such as isopropylmaleimide, and the like are included. When a copolymer is used, it is desirable to contain MMA as a monomer component in an amount of 50% by weight or more.

The above vinylidene fluoride resins 60 to 9
0% by weight and 10 to 40% by weight of the PMMA-based resin are sufficiently kneaded so as to be completely compatible with each other to obtain a resin composition. In the present invention, among the resin compositions, particularly, the melting point is 140 to 18.
Since a substance having a very high temperature of 0 ° C. is effective for preventing pistoning and shrinkage, the substance having a high melting point is selected and used. This high melting point resin composition is transparent in the indoor state,
Furthermore, transparency is maintained even in a state of 85 ° C. and 95% humidity, which is particularly preferable in the present invention. It is also a very important combination because it is compatible with the core made of PMMA resin and adheres integrally, and has high mechanical strength.

That is, when the orientation of the fiber is suppressed to suppress the pistoning, the first sheath layer adheres firmly to the core made of the PMMA resin to prevent the mechanical strength from remarkably decreasing. It is important that the sheath layer itself keeps its shape without causing deformation flow.

Further, the first sheath resin used in the present invention has a refractive index at a sodium D line (hereinafter, "refractive index" indicates a refractive index at a sodium D line) of 1.43-1.
A relatively high optical fiber of 45 is used, and the NA of the plastic optical fiber is set to about 0.35 to 0.43 to cope with heat-resistant high-speed communication applications.

Next, as the second sheath resin for forming the second sheath layer of the plastic optical fiber of the present invention, 25 mol% to 50 mol% of a vinylidene fluoride component and 10 mol% to 15 mol% of a hexafluoropropene component are used. Mol%, a copolymer comprising 38 to 64 mol% of a tetrafluoroethylene component, having a melting point of 140 to 180 ° C. or higher and a refractive index of 1.34 to
1.37 transparent resin is used.

In the present invention, the first purpose of providing the second sheath layer made of the second sheath resin is to first bring the second sheath layer into close contact with the first sheath layer and integrate it as a bare wire. .
Further, the second object is that when the cable of the present invention is constructed, the integrated bare wire and the nylon 12 coated thereon are adhered to each other with a very strong adhesive force, and even at a high temperature of about 105 ° C. This is to prevent pistoning for a long time. Therefore, the second sheath resin requires high heat resistance having a melting point of 140 ° C. to 180 ° C. and strong adhesion to nylon 12.

Further, when the first sheath layer alone causes a large optical loss when the fiber is bent and is difficult to use in a high communication band, by providing such a second sheath layer, the refractive index of the second sheath resin becomes 1. .34 to 1.37, which is very low,
The bending effect is eliminated by the second sheath layer, and when the length is about several meters, the effect that light passing through the second sheath layer can be used for communication can be obtained. In order to obtain this effect, the second sheath resin itself is transparent so that light can be totally reflected, and the transparency of the first sheath resin is impaired at the interface between the first sheath layer and the second sheath layer. There is no significant interaction.

According to the method for producing a plastic optical fiber of the present invention, a core resin in a molten state, a first sheath resin, and a second sheath resin are supplied to a three-layer composite spinning die, and the diameter of the core is approximately 1.0.
When the thickness is set to mm, the supply amount of each resin is adjusted such that the thickness of the first sheath layer is about 2 μm to 25 μm, and the thickness of the second sheath layer is also about 2 μm to 25 μm. In this way, the bare yarn is obtained by the composite spinning, and the raw yarn is continuously in the range of 130 to 25.
It is stretched about 1.3 to 3 times at a temperature of 0 ° C. for several seconds to several tens of seconds, imparts mechanical strength to the fiber, and then continuously heat-treated at the same temperature for several tens of seconds or less at the same temperature to obtain orientation. Eliminates distortion to provide dimensional stability.

The plastic optical fiber of the present invention has a thickness of about 50 .mu.m to 1.0 mm as a protective coating around the ethylene-vinyl alcohol copolymer, a polyamide resin, a polyester resin, a polypropylene resin, and a polyvinylidene fluoride. It can be used as a cable by coating with a system resin or the like. For low temperature applications, any of these cables can be used as is,
Above all, the plastic optical fiber cable of the present invention in which the coating material is nylon 12 can suppress the pistoning to a small value even when used at a temperature of about 100 to 105 ° C. for a long time. In particular, it is preferable that the cable is aged for a long time.

The reason why the long-term aging treatment is preferable is that PMM
The glass transition point (Tg) of the A-based resin is about 110 ° C., whereas the melting points of the first sheath resin and the second sheath resin according to the present invention are greatly separated from 140 ° C. to 180 ° C. It is difficult or inadequate to perform a short-time treatment by continuous heating, which has been performed by the conventional manufacturing method, as a method for appropriately taking the orientation distortion of the sheath layer or the second sheath layer and the orientation distortion of the core. It is. That is, when the treatment is performed in a short time and at a high temperature condition, the mechanical strength of the core is reduced, and when the treatment is performed at a low temperature condition in accordance with the core, the sheath layer cannot be distorted, so that the shrinkage occurs. Occurs. Therefore, when manufacturing the heat-resistant plastic optical fiber cable of the present invention, a long-time heat treatment of about 0.1 hour to about 50 hours under a temperature condition of about 100 ° C. to about 120 ° C. around Tg of the PMMA-based resin is preferable. . This temperature is 1 when humidity is added.
It is effective even at a low temperature of about 0 ° C. More preferable conditions are 11
1 hour or more at 0 to 120 ° C for 1 hour to 24 hours is desirable. If the temperature is too high, the strength of the fiber decreases. Therefore, the conditions may be set as appropriate while actually confirming the effect in the above range.

The reason why nylon 12 is used as the coating layer of the plastic optical fiber cable of the present invention is that, as described above, the adhesive force with the second sheath layer is strong, the pistoning of the cable after the heat treatment is small, and the dimensional stability is high. And high hardness. From the viewpoint of heat resistance, the thickness of the nylon 12 coating layer is 0.1 mm to 0.6 mm.
mm is preferable because it has sufficient holding power.

A particularly important performance of the plastic optical fiber cable of the present invention is low pistoning and high mechanical strength. As described above, the pistoning is a retraction or protrusion of the bare wire that occurs between the bare wire and its direct coating layer, and as a measurement method,
Both ends of a 50 cm cable are cut vertically, left in a test environment for a predetermined time, and then retracted or jumped out is observed with a microscope. The nylon 12 coated cable according to the present invention has a pistoning of 0.06 mm or less when left at 105 ° C. for 500 hours. Moreover, the mechanical strength of the cable at that time is as follows:
When bending at ± 90 ° with a bending radius of 5mm at 20 ° C,
It has bending resistance that does not break even when it is bent 1000 times or more.

[0022]

EXAMPLES As a core resin, the weight average molecular weight is 100,000 and M
MA 99.5% by weight and methyl acrylate 0.5% by weight
Was used. Refractive index of this resin
(N _d20) Was 1.49.

Further, 70% by weight of a homopolymer of vinylidene fluoride having a melt flow index at 230 ° C. and a load of 3.8 kg (hereinafter referred to as “melt flow index” under the above conditions) being 20 g / 10 min. A transparent resin composition obtained by melting and mixing 30% by weight of the same PMMA resin as the core resin was used as the first sheath resin. The refractive index of the first sheath resin was 1.44, the melting point was 170 ° C., and the melt flow index was 18 g / 10 minutes.

The second sheath resin is a copolymer comprising 40 mol% of a vinylidene fluoride component, 48 mol% of a tetrafluoroethylene component and 12 mol% of a hexafluoropropene component, having a refractive index of 1.36 and a melting point of Is 155 ° C,
A transparent resin having a melt flow index of 7 g / 10 minutes was used.

The above core resin, first sheath resin and second sheath resin were melted, and three layers were simultaneously subjected to composite spinning. In this fiber spinning step, drawing is performed at a draw ratio of 2 times, and a large orientation removal process is performed by heating continuously at 150 ° C. for a short time of several tens of seconds to obtain a core diameter of 970 μm and a first sheath. Layer thickness 7 μm, second sheath layer thickness 8 μm, outer diameter 1.00 m
m plastic optical fiber bare wires were obtained. Then, nylon 12 was applied to the bare plastic optical fiber with a thickness of 25.
A cable covered with 0 μm and having an outer diameter of 1.5 mm was wound around a metal bobbin. Thereafter, the bobbin was placed in an oven at 115 ° C. for 15 hours and aged to obtain a plastic optical fiber cable of the present invention.

The transmission loss of the cable 50m was measured. Measured using monochromatic light with an incident NA of 0.15, 65
It was 180 dB / km at 0 nm. The transmission loss after storing the cable at 105 ° C. for 500 hours is 1
It was 85 dB / km. Similarly, the transmission loss when stored at 85 ° C. and 95% humidity for 1000 hours is 210 dB /
At km, the theoretical loss of OH absorption due to moisture absorption increased and it was stable.

The pistoning of the cable was measured. That is, 50 cm of the cable was vertically cut off with a new razor, and the pistoning after storage at 105 ° C. for 500 hours and the shrinkage of the cable were measured. As a result, the pistoning was 0.03 mm, the bare wire was retracted into the coating, and the cable shrinkage was only 0.2%.

The mechanical strength of this cable is 1500 when it is bent at ± 90 ° at a bending radius of 5 mm at −20 ° C.
The wire was disconnected at times. Further, the cable after storage at 105 ° C. for 500 hours showed a strong strength of 1,300 times.

The light retention due to the bending of the cable was measured. The measurement was performed using an LED light source with an incident NA of 0.6, and the light loss when it was wound once around a rod having a bending radius of 10 mm was 1.6 dB, which was an allowable level.

When the transmission band of this fiber was measured by the measuring pulse method, the band of 20 m was 170 MHz with an incident NA of 0.65.

[0031]

As described above, according to the present invention,
A heat resistant plastic optical fiber cable with a low level of pistoning for a long time even under high temperature conditions and excellent mechanical strength is provided.It is very useful for various types of wiring, especially for high temperature conditions. is there.

Claims (3)

[Claims] 1. A heat-resistant plastic optical fiber comprising a first sheath layer formed around a core and a second sheath layer formed around the first sheath layer, wherein the core is a monomer component. A first sheath layer comprising 60 to 90% by weight of a vinylidene fluoride-based resin containing 95% by mole or more of vinylidene fluoride as a monomer component, and a polymethyl methacrylate-based resin containing 90% by weight or more of methyl methacrylate; A mixture of 10 to 40% by weight of a methacrylate resin has a refractive index of 1.4 at a sodium D line.
3 to 1.45, a resin composition having a melting point of 140 to 180 ° C., wherein the second sheath layer comprises a vinylidene fluoride component 2
5 to 50 mol%, hexafluoropropene component 10 to 15
Mol%, and a tetrafluoroethylene component of 38 to 64 mol%, and a refractive index at sodium D line of 1.34 to 1.3.
7. A heat-resistant plastic optical fiber comprising a copolymer having a melting point of 140 to 180 ° C. 2. A plastic optical fiber cable comprising the heat-resistant plastic optical fiber according to claim 1 as a bare wire and a nylon 12 coating around the bare fiber, wherein said cable is 50 cm in an environment of 105 ° C. for 500 hours. The displacement between the bare wire and the nylon 12 coating layer at the end when left to stand is 0.06 mm or less, and the bending radius is 5 at -20 ° C.
A heat-resistant plastic optical fiber cable having a bending resistance of 1000 times or more when bent at ± 90 ° in mm. 3. After covering the bare wire with nylon 12, 11
The heat-resistant plastic optical fiber cable according to claim 2, which is left at 0 to 120 ° C for 1 hour or more.