JP2011075751A - Heat-resistant plastic optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-resistant plastic optical fiber which maintains sufficient transmission performance over a long period of time, even in severe high temperature and high humidity surroundings. <P>SOLUTION: The heat-resistant plastic optical fiber consists of a core section and a sheath section. The core section is formed of a resin which contains an alicyclic polyolefin resin, and of which the glass transition temperature is 150°C or more. The sheath section is formed of a composition having an amorphous fluorine resin as a refractive index adjusting agent, contained in the resin for forming the core section, in such an amount that a refractive index of the sheath section becomes lower than that of the core section. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat-resistant plastic optical fiber, and more particularly to a heat-resistant plastic optical fiber used for optical signal transmission such as in-vehicle wiring, mobile wiring, and FA equipment wiring, and a photoelectric sensor.

  As a heat-resistant plastic optical fiber, a plastic optical fiber having a core made of polycarbonate resin, polyarylate resin, polycycloolefin resin, or the like is well known. However, as a core that can withstand the use as an in-vehicle wiring, which is one of the harshest use environments, the temperature is about 125 ° C required in the engine room of a gasoline vehicle, and further in the engine room of a diesel vehicle. It must be able to withstand the required temperature of about 150 ° C., and the polycarbonate resin is insufficient in heat resistance. Polycarbonate resins and polyarylate resins have a relatively large birefringence, so there is optical loss due to them, and because they are hydrolyzable due to their molecular structure, they are durable for long-term use. There are concerns. Therefore, development of an optical fiber having a polycycloolefin resin having a small birefringence and a low hygroscopic property as a core is widely desired.

  The material of the clad (sheath part) of the optical fiber having a polycycloolefin resin as a core is limited to a fluorine-based or silicon-based resin having a refractive index lower than that of a polycycloolefin-based resin that originally has a small refractive index. Therefore, an α-fluoro-fluoroalkyl acrylate copolymer, a blend of vinylidene fluoride resin and polymethyl methacrylate resin, a copolymer of vinylidene fluoride, hexafluoroacetone and tetrafluoroethylene, silicon Resin, etc. are used. However, in any case, the performance is insufficient in terms of heat resistance and adhesion to the core, and the modification of the clad resin, peeling between the core and the clad, and the like occur. Therefore, it does not endure long-term use in in-vehicle wiring applications.

  In order to improve the problems related to the clad, for example, in Patent Document 1, a flexible composition is arranged in the clad to improve adhesion to the core, and the brittle thermal and mechanical characteristics of the clad are compensated. Therefore, an optical fiber having a protective layer provided on the outer layer of the cladding has been proposed. However, as the number of layers increases, production facilities and devices increase, which is a concern in terms of production cost and quality control. Even if the cost and quality are unquestioned, the heat resistance of the optical fiber described in Patent Document 1 is about 140 ° C. (paragraph 0023) and does not reach the heat resistance exceeding 150 ° C.

  As another polycycloolefin-based heat-resistant optical fiber, Patent Document 2 proposes an optical fiber having at least a core formed of a polycycloolefin-based resin. This Patent Document 2 describes that by introducing a polar group into a cycloolefin monomer, the adhesion between the core and the sheath, or between the sheath and the outer coating can be improved. ing. However, by introducing a polar group, the low hygroscopicity, which is one of the advantages of using a polycycloolefin-based resin as a heat-resistant optical fiber, is impaired. For this reason, it is difficult to say that a polar group-introduced one is suitable for long-term use in an automobile engine room that can be humid for a long time.

JP 2000-275448 A JP-A-4-365003

  The important physical properties desired for the resin of the sheath part of the plastic optical fiber using the alicyclic polyolefin resin as the thermoplastic heat-resistant transparent resin as the core part are heat resistance, moisture resistance, transparency, appropriate refractive index, Examples thereof include adhesion to the core. However, nothing that satisfies all these physical properties has yet been found.

  An object of the present invention is to provide a heat-resistant plastic optical fiber that can maintain a sufficient transmission performance over a long period of time even under a severe high temperature and high humidity environment.

The object of the present invention is achieved by the following configurations.
(1) Consists of a core part and a sheath part, the core part is formed of a resin containing an alicyclic polyolefin resin and having a glass transition temperature of 150 ° C. or more, and the sheath part forms the core part. The resin is made of a composition containing an amorphous fluororesin as a refractive index adjusting agent in such an amount that the refractive index of the sheath part is lower than the refractive index of the core part. Features heat-resistant plastic optical fiber.

  (2) The heat resistant plastic optical fiber according to (1), wherein the amorphous fluororesin is a perfluoro resin.

  (3) The heat-resistant plastic optical fiber according to (1) or (2), wherein the deflection temperature under load of the alicyclic polyolefin resin in the core is 140 ° C. or higher.

  (4) The heat-resistant plastic optical fiber according to any one of (1) to (3), wherein the refractive index of the sheath is 3 to 15% lower than the refractive index of the core.

  The heat-resistant plastic optical fiber of the present invention uses an alicyclic polyolefin resin as a core part, and uses the same resin as the core part in the sheath part to improve the adhesion with the core part, thereby forming a refractive index difference. By incorporating an amorphous fluororesin into the sheath resin, sufficient transmission and excellent heat resistance can be achieved without impairing the heat resistance, transparency, and low hygroscopic properties of the core alicyclic polyolefin resin. And stable productivity can be realized.

  That is, according to the present invention, the optical fiber is composed mainly of a core part formed of a transparent thermoreversible resin having a glass transition temperature of 150 ° C. or higher, and the same resin as the core part, and has a refractive index higher than that of the core part. Therefore, the heat resistance is increased, the flexibility is high, and the mass productivity can be improved as compared with the conventional plastic optical fiber.

  Furthermore, according to the present invention, a plastic optical fiber having sufficient transmission performance and heat resistance can be obtained, and can be used for a long time with high reliability even in a high temperature and high humidity environment.

  The resin forming the core of the heat-resistant plastic optical fiber of the present invention has a glass transition temperature (Tg) of 150 ° C. or higher, preferably 160 ° C. or higher, and contains an alicyclic polyolefin resin. The deflection temperature under load of the resin is preferably 140 ° C. or higher. The alicyclic polyolefin resin is an amorphous resin, but preferably does not have a polar functional group. Specifically, “ZEONEX”, “ZEONOR” and the like of ZEON Corporation can be listed. In addition, “TOPAS” manufactured by Nippon Polyplastics Co., Ltd. and “APEL” manufactured by Mitsui Chemicals, Inc. can be mentioned. Since these products have heat resistance, moisture resistance, and transparency, by using these products, a heat-resistant plastic optical fiber having such performance can be obtained.

  The composition of the sheath part of the heat-resistant plastic optical fiber of the present invention is made of an amorphous fluororesin as a refractive index adjusting agent in the same resin as the core part, and the refractive index of the sheath part is lower than the refractive index of the core part. It is contained in such an amount. Specifically, the composition of the sheath part preferably contains the amorphous fluororesin in such an amount that the refractive index of the sheath part is 3 to 15% lower than the refractive index of the core part, In addition, it is preferable that the amorphous fluororesin is good and uniformly dispersed.

  As described above, the base resin of the sheath portion needs to be the same resin as the core portion, and the sheath portion is preferably melt-molded simultaneously with the core portion. By forming the sheath part with the same resin as the core part, it is possible to ensure the adhesiveness of the core-sheath interface, which is another important characteristic required for the sheath part, by the compatibility between the core part and the sheath part. This is because it becomes possible.

  In the present invention, an amorphous fluororesin is used as described above as a refractive index adjusting agent to be added in order to make the refractive index of the sheath part smaller than that of the core part. Among these, an amorphous perfluoro resin is preferable. Fluorocarbon resins have a low refractive index, and perfluororesins in which all hydrogen atoms are substituted with fluorine atoms have a particularly low refractive index.

  In general, a crystalline resin is not suitable for an optical material because optical uniformity is impaired by unevenness of crystallinity. In order for total reflection for transmitted light to be performed uniformly over the entire length of the optical fiber, ideally, the optical fiber needs to be formed by a core portion and a sheath portion that do not have a crystal phase or density fluctuation. In the present invention, in order to achieve this at the highest possible level, both the core part and the sheath part are made of an amorphous resin, and an amorphous substance is selected even for the refractive index lowering agent added to the sheath part. It is a feature.

  The content of the amorphous fluororesin is preferably such that the refractive index of the sheath part is smaller than the refractive index of the core part by 3% or more and 15% or less. If it is less than 3%, the refractive index difference between the core and the sheath is small, so that the transmission loss at the time of bending increases, and the flexibility, which is one of the characteristics of the plastic optical fiber, may be lowered. Further, the refractive index difference between the core portion and the sheath portion has no upper limit in principle, but it is preferable that the upper limit is 15% as described above. This is because, without adding a high refractive index agent to the core part, when the amorphous fluororesin is contained as a refractive index lowering agent for the sheath part so that the refractive index difference exceeds 15%, the core part Because the fraction of amorphous fluororesin that is incompatible with other alicyclic polyolefins becomes excessive, there is a high possibility that not only the adhesion between the core and sheath but also melt moldability will be lost. is there.

  In forming a refractive index difference between the core portion and the sheath portion, it is possible to add a high refractive index agent to the resin of the core portion. In that case, the core portion may have a higher refractive index with an upper limit of 5%. A known agent may be used as the high refractive index agent in that case. However, it is preferable that the core portion through which the transmission light passes does not include impurities, substances that cause impurities, density fluctuations of the resin, etc., as well as impurities, so as not to reduce transmission loss. Therefore, it is preferable to form a difference in refractive index only by adding a refractive index lowering agent to the sheath, rather than adding a high refractive index agent to the core resin.

  In the present invention, the adhesiveness between the core and the sheath is imparted by compatibility based on the fact that both are mainly composed of the same resin, so the addition amount of other agents having different compatibility is possible. The smaller number is preferable.

  In the optical fiber of the present invention, the outer diameter of the core part is usually 20 μm to 10 mm, preferably 60 μm to 5 mm, and the thickness of the sheath part is usually 5 μm to 1 mm, preferably 10 μm to 0.5 mm. The optical fiber of the present invention can be used as it is, or it can be used as a cable with an outer coating (jacket) of a thermoplastic resin such as polyethylene, polyvinyl chloride, polyurethane, nylon, or polypropylene. It is also possible to do.

  The optical fiber of the present invention can be produced by a known method. For example, after forming a core part by heating and melting polycycloolefin resin and making it into fiber while pulling, using a method of attaching the sheath part or a two-layer composite spinning die, the resin of the core part and the sheath part Examples thereof include a method in which both the core and the sheath are formed at the same time by composite spinning. The latter production method in which the core portion and the sheath portion are in close contact in a molten state is more preferable in terms of adhesiveness.

  The addition method of the amorphous fluororesin is not particularly limited. However, because it is incompatible and heat resistant grade, it melts sufficiently in a multi-screw extruder or a high L / D extruder in order to disperse it well and uniformly in a highly viscous alicyclic polyolefin resin. It is preferable to knead. After melt-kneading and pelletizing into a master batch, it may be added to the melt-extrusion molding system, may be added directly at the time of extrusion molding, or may of course be added during the polymerization process.

  The optical fiber of the present invention can be used for purposes such as information transmission and optical transmission, such as light guide, light cable, fiberscope, fiber plate, microchannel plate, optical fiber cable, optical fiber cord, image fiber, sensor head, etc. It can be suitably used for various applications.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
[Example]
As the alicyclic polyolefin resin used for the core, “ZEONOR 1600” (glass transition temperature (Tg) 171 ° C., deflection temperature under load 161 ° C., refractive index 1.53) made by Nippon Zeon Co., Ltd., which is a norbornene resin, was used. As the composition of the sheath, the above-mentioned “ZEONOR 1600”, as a refractive index reducing agent, an amorphous fluororesin “Teflon (registered trademark) AF1600” (refractive index 1.31) manufactured by Mitsui DuPont Fluorochemical Co., Ltd. What was added by 22 mass% dry blend was used.

And after melt | dissolving the resin of a core part, and the composition of a sheath part individually with a single screw extruder and a twin screw extruder, a sheath part is extruded on the outer periphery of a core part using a two-layer compound spinning die. did. Further, this was solidified by water cooling and wound up by a winder to produce a prototype of a plastic optical fiber. The outer diameter of the optical fiber can be determined by the extrusion amount of the core part and the sheath part and the speed of the winder. The prototype optical fiber has a fiber diameter of about 1 mm and a sheath part thickness of about 20 μm. Met. The refractive index of the composition of the sheath was 1.482, which was 3.2% lower than the refractive index of the core.
The light source used for the measurement of optical characteristics was an LED having a light emission wavelength of 660 nm (manufactured by Stanley: FH511), and the output light from the optical fiber was measured with a power meter (manufactured by Ando Electric: AQ-1135). The evaluated environment was a dry state of 140 ° C.

  As a result, while the initial transmission loss was 900 dB / km, the value after leaving for 2000 hours in the high temperature environment of 140 ° C. was 910 dB / km, and almost no deterioration was observed. Furthermore, when left in a high temperature and high humidity environment of 95% at 85 ° C. for 1000 hours and 2000 hours, sufficiently stable values of 950 dB / km and 1150 dB / km were shown, respectively. When the flexibility was evaluated by a bending loss value at a bending radius of 5 mm, the loss value was about 0.3 dB.

[Comparative Example 1]
The same norbornene-based resin as in the example was used for the core, and polyvinylidene fluoride (made by Kureha Chemical Industries, trade name “KF # 850”, refractive index 1.42) was used for the sheath resin. An optical fiber was prototyped in the same way as the example. The refractive index difference between the core and the sheath was 0.09 (6.9%).

  As a result of performing the same measurement as that of the example for this optical fiber, the initial transmission loss is 1170 dB / km, the value after being left at 140 ° C. for 2000 hours is 1200 dB / km, the temperature is 85 ° C., and the humidity is 95%. When left for 1000 hours and 2000 hours, they were 1250 dB / km and 1500 dB / km, respectively, which were relatively stable values, but inferior to the examples. The loss value at a bending radius of 5 mm was 3.2 dB, and peeling occurred at a part of the core-sheath interface.

[Comparative Example 2]
The same norbornene-based resin as in the example was used for the core. The resin for the sheath is a solid solution composed of polyvinylidene fluoride (same as Comparative Example 1) and polymethyl methacrylate (manufactured by Sumitomo Chemical Co., Ltd., trade name “Sumipec LO”). A material having a mass fraction of 70/30 was used. Then, an optical fiber was prototyped by the same method as in the example. The refractive index of the composition of the sheath was 1.44, and the refractive index difference from the core was 0.07 (5.3%).

  As a result of performing the same measurement as in the example, the transmission loss of this optical fiber was 1.44 dB / m. The bending loss was about 1.3 dB when the bending radius was 10 mm, and the transmission loss of the output light after standing for 160 minutes in a thermostatic bath was about 0.4 dB.

[Comparative Example 3]
Various characteristics were measured using an optical fiber manufactured by Fujitsu Kasei. This optical fiber uses a polycarbonate resin (trade name “Panlite” manufactured by Teijin Kasei Co., Ltd., refractive index: 1.58) for the core, and a solid solution made of a composition of polyvinylidene fluoride and polymethyl methacrylate for the sheath. (Same as Comparative Example 2). The refractive index difference between the core and the sheath was 0.14 (8.9%).

  As a result of performing the same measurement as in the example, the transmission loss of this optical fiber was 1.40 dB / m. The bending loss was about 0.4 dB when the bending radius was 10 mm.

[Comparative Example 4]
Various characteristics were measured using an optical fiber manufactured by Mitsubishi Rayon Co., Ltd. (trade name “Esca Extra, EH4001”). The optical fiber used was a core portion polymethyl methacrylate resin (refractive index 1.49) and a sheath portion using fluorinated acrylate (refractive index 1.42). The refractive index difference was 0.07 (4.7%).

  As a result of performing the same measurement as in the example, the transmission loss of this optical fiber was 0.3 dB / m. The bending loss was about 3.2 dB when the bending radius was 10 mm.

Claims (4)

  Consists of a core part and a sheath part, the core part is formed of a resin containing an alicyclic polyolefin resin and having a glass transition temperature of 150 ° C. or higher, and the sheath part is formed of a resin that forms the core part. The amorphous fluororesin as a refractive index adjusting agent is formed of a composition containing an amount such that the refractive index of the sheath portion is lower than the refractive index of the core portion. Heat-resistant plastic optical fiber.   2. The heat-resistant plastic optical fiber according to claim 1, wherein the amorphous fluororesin is a perfluoro resin.   The heat-resistant plastic optical fiber according to claim 1 or 2, wherein the deflection temperature under load of the alicyclic polyolefin resin in the core is 140 ° C or higher.   The heat-resistant plastic optical fiber according to any one of claims 1 to 3, wherein the refractive index of the sheath is 3 to 15% lower than the refractive index of the core.