JPH0518401B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to optical fibers, optical fiber cores,
The present invention relates to a plastic optical fiber that can be used as an optical fiber cord or optical fiber cable. [Prior Art] Inorganic glass optical fibers, which have excellent optical transmission properties over a wide range of wavelengths, have been known as optical fibers for optical transmission, but they have poor workability and are susceptible to bending stress. Plastic optical fibers based on synthetic resin have been developed because they are relatively expensive. Synthetic resin optical fibers have a core-sheath structure, with a core made of a polymer with a high refractive index and good light transmittance, and a sheath made of a transparent polymer with a lower refractive index. obtained by doing. The polymer useful as a core component with high light transparency is preferably an amorphous material, and polymethyl methacrylate or polystyrene is generally used. Among these, polymethyl methacrylate has excellent transparency, mechanical properties, weather resistance, etc., and is used industrially as a core material for high-performance plastic optical fibers. However, the glass transition temperature (Tg) of polymethyl methacrylate is 100℃ for plastic optical fibers with a core of polymethyl methacrylate, and when the environmental conditions of use exceed 100℃, the optical transmission properties decrease rapidly. This limitation in heat resistance limits the applications of plastic optical fibers. Furthermore, various types of optically transmitting fibers with polycarbonate cores have been proposed, but they have poor optical transmission characteristics, are not fully satisfactory in terms of heat resistance, and do not suffer from optical transmission loss at high temperatures. It was extremely inferior. For this reason, for example, in JP-A-58-18608, it was proposed to improve the mechanical properties and heat resistance by providing a three or more layer structure with an additional protective layer around the sheath material. However, even if the fiber is manufactured using a high-temperature structure, optical transmission loss deteriorates at high temperatures due to molding distortion during fiber manufacturing and distortion due to heat shrinkage. It was extremely difficult to use it as a means of communication or a means of optical sensor. [Problems to be Solved by the Invention] The purpose of the present invention is to solve the problems associated with conventional plastic optical fibers, to provide excellent heat resistance and optical transmission characteristics, and to provide good performance even when used under high temperature conditions. An object of the present invention is to provide a plastic optical fiber that can exhibit excellent optical transmission characteristics and a method for manufacturing the same. [Means for Solving the Problems] The plastic optical fiber of the present invention, which has been found to achieve the above object, is a plastic optical fiber whose basic constituent units are a core material layer and a sheath material layer, and which has the above-mentioned features. The core material layer is made of transparent polycarbonate having an intrinsic viscosity (in methylene chloride, 20°C) of 0.25 dl/g or more and less than 0.40 dl/g, and a glass transition temperature of 140 to 150°C. . [Embodiment] FIGS. 1 to 4 are cross-sectional views for explaining an example of the structure of the plastic optical fiber of the present invention. The example shown in FIG. 1 is an optical fiber wire composed only of the basic structural units of a core material layer (core) 1 and a sheath material layer (cladding) 2 used in the present invention. Hereinafter, the same elements as in FIG. 1 will be represented by the same reference numerals. The example in FIG. It is. The example shown in FIG. 3 is an optical fiber cable having a four-layer structure including a core 1, a cladding 2, a protective layer 3 made of an organic polymer, and a covering layer 4 made of a jacket material made of an organic polymer. In the example shown in FIG. 4, a plurality of optical fiber cores 5 having a three-layer structure consisting of a core 1, a cladding 2, and a protective layer 3 made of an organic polymer are coated with a coating layer 4 of a jacket material made of an organic polymer. It is a multi-core optical fiber cord. The structure of the plastic optical fiber of the present invention is not limited to the examples shown in FIGS. 1 to 4, but it is sufficient that at least the basic structural unit is composed of the core and cladding used in the present invention. Furthermore, it is also possible to adopt a fiber structure, for example, by incorporating a tension member made of steel or FRP or a metal coating into the optical fiber, or by adding a desired number and weight of the coating to five or more layers. It may also be a configuration. A suitable polycarbonate for forming the core 1 has the general formula

[Formula], where R ₁ is

【formula】

Alicyclic polycarbon represented by [Formula] Bonato,

【formula】

【formula】

【formula】

【formula】

Examples include aromatic polycarbonates represented by the formula: Copolymers of these and dioxy compounds such as 4,4'-dioxydiphenyl ether, ethylene glycol, P-xylylene glycol, and 1,6-hexanediol can also be used; From the point of view the glass transition temperature is 140-150
℃ is preferred. Note that the glass transition temperature of the polycarbonate used in the present invention can be measured using, for example, a differential thermal balance. The feature of the present invention is that the polycarbonate has an intrinsic viscosity (in methylene chloride at 20°C) of 0.25.
The purpose is to selectively use transparent polycarbonate with a dl/g or more and less than 0.40 dl/g. intrinsic viscosity
If less than 0.55 dl/g of polycarbonate is used, the above-mentioned conventional drawbacks become apparent and satisfactory properties are not obtained in terms of mechanical properties and light transmission properties at high temperatures. As the polycarbonate, those produced by conventionally known polymerization methods can be used, and those prepared by bulk polymerization methods are usually preferred. Further, a desired intrinsic viscosity value can be obtained by controlling polymerization conditions such as polymerization temperature, selectively using a polymerization initiator, chain transfer agent, etc., and controlling the degree of polymerization in a conventional manner. In the conventional manufacturing method for optical fibers using polycarbonate as a core material, polycarbonate with an intrinsic viscosity of less than 0.40 dl/g has a low melt viscosity when spun at a spinning temperature of 230 to 250°C for optical fibers using polycarbonate as a core material. The incidence of excessive fiber spots was high, and it was not possible to create an optical fiber with good optical transmission properties of 1500 dB/Km or less. By using spinning temperature conditions that are higher by 25 to 40 degrees Celsius, we were able to create an optical fiber with extremely low occurrence of yarn spots and excellent light transmission properties with optical transmission characteristics of 1500 dB/Km or less. be. Here, the crystallization temperature of polycarbonate is the temperature at which the degree of crystallinity is maximum, and is usually in the range of 180 to 185°C. For Clad 2, from the optical refractive index of the core component,
A polymer with good transparency and a refractive index as low as 0.01 or more is used, but it is usually preferable to select one having a difference in refractive index from the core component in the range of 0.01 to 0.15. There is no particular restriction on the type of polymer constituting the cladding, and conventionally known polymers may be used. Specific examples include the following. Polymethyl methacrylate (n=1.49), styrene/methyl methacrylate copolymer (n=
1.50-1.58), poly4-methylpentene 1 (n=
1.46), ethylene-acetate copolymer (n=1.46~
1.50), polycarbonate (n=1.50~1.57), fluorine-containing polymethyl methacrylate (n=1.38~
1.45), vinylidene fluoride polymer (n=1.38~
1.42), vinylidene fluoride/hexafluoropropylene copolymer (n=1.38-1.42), methyl methacrylate/styrene, vinyltoluene or α-
Methylstyrene/maleic anhydride terpolymer or quaternary copolymer (n=1.50-1.58), etc. In order to improve the delamination strength of the basic structural units, these polymers include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, glycidyl acrylate or methacrylate, and β-
Unsaturated glycidyl monomers such as methylglycidyl acrylate or methacrylate, hydrophilic monomers such as acrylamide, methacrylamide and derivatives thereof, hydroxyalkyl acrylate or methacrylate may be copolymerized. Among these polymers, those with high versatility include methacrylic polymers such as polymethyl methacrylate, and, for example, Japanese Patent Publication No. 43-8978,
Special Publication No. 56-8321, Special Publication No. 56-8322, Special Publication No. 1983
It is possible to use polymerized esters of methacrylic acid and fluorinated alcohols as disclosed in Japanese Patent Application Laid-Open No. 53-8323 and JP-A-53-60243. Specific examples of these esters include:
For example, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3,3 methacrylate
-pentafluoropropyl and the like. Furthermore, using one or more of these fluorine-containing methacrylic esters, for example,
-7311, fluorine-containing methacrylic acid ester, as described in JP-A-59-116702, etc.
A copolymer consisting of a vinyl monomer that can be copolymerized with this ester and a vinyl monomer that can be formed with a hydrophilic homopolymer may be used. In the structural examples of the plastic optical fiber of the present invention shown in FIGS. 1 to 4, the organic polymers constituting the protective layer 3, the coating layer 4, etc. have the characteristics that are intended to be improved by the present invention. They can be selected as desired with the aim of improving the properties of the plastic optical fiber. For example, in order to improve the heat resistance, heat shrinkage resistance, and mechanical properties of the optical fiber, the protective layer 3 can be made of an organic polymer having a heat distortion temperature of 100° C. or higher. Examples of organic polymers with a heat distortion temperature of 100°C or higher include polyester, polyamide, and poly(4).
-Methylpentene-1, polyvinylidene fluoride,
So-called engineering plastics such as polyacetal, polysulfone, polyethylene terephthalate, polypropylene, polyoxymethylene, polybutene, polytetramethylene terephthalate, ABS, polyphenylene oxide, and polycarbonate can be used. The jacket material constituting the covering layer 4 can be appropriately selected from organic polymers that can be used in the protective layer 3, including polyolefin resins such as polyethylene and polypropylene. . Further, for example, water-crosslinked polyolefin can be selectively used for the purpose of improving the heat resistance, heat shrinkage resistance, light transmission characteristics, etc. of the optical fiber. In addition, the polymers used for the protective layer 3 to the coating layer 4 include carbon black, talc, glass fiber,
It is also possible to fill with inorganic or organic fillers such as aromatic polyamide fibers and carbon fibers. Typical methods for shaping the plastic optical fiber of the present invention include a method using only spinning and a method using a combination of spinning and coating. For example, when shaping the fiber shown in Figure 1, the core 1 and cladding 2, and when shaping the fiber shown in Figure 2,
It is best to use a so-called composite spinning method in which the base materials of the core 1, cladding 2, and protective layer 3 are blended and discharged in a molten state through a special nozzle. In addition, when shaping the fiber shown in Fig. 3, core 1,
It is possible to form the cladding 2 and the protective layer 3 by a composite spinning method, and then cover the jacket material 4 thereon by extrusion, coating, or the like. The composite spinning method is a labor-saving and energy-saving process that has high productivity and can simplify equipment. Furthermore, it has advantages such as being able to produce optically transmitting fibers with a wide range of thicknesses and easy process control, making it an extremely advantageous method from an industrial perspective. It is possible to manufacture For example, when the fibers shown in FIGS. 1 and 2 are shaped by a composite spinning method, a core layer component melt extrusion machine,
It is produced by a composite spinning machine consisting of a sheath material layer component melt extruder and, in the case of three layers, a protective layer component melt extruder. The core component is melted by a melt extruder and fed in a fixed amount to the spinning head by a metering pump.
The sheath component and, in the case of three layers, the protective layer component are each fed to the spinning head in the same way. The material is formed into a two- or three-layer structure using a spinneret in a spinning head and discharged, and after being cooled and solidified, it is wound up and optionally subjected to stretching or annealing treatment. FIG. 5 shows a spinneret for forming a three-layer structure, in which the core material layer component is supplied from A, the sheath material layer component is supplied from B, and the protective layer component is supplied from C, and is discharged from D. In addition, for example, if the core material layer components and the protective layer components are the same,
These components are fed through the same route to the spinning head,
For example, the spinneret shown in FIG. 6 can be used for distribution. In FIG. 6, the core material layer component and the protective layer component are supplied from E, distributed within the nozzle, shaped into a three-layer structure together with the sheath material layer component from B, and discharged from D. When producing the plastic optical fiber of the present invention, in such a composite spinning method, melt extrusion is carried out at a temperature of 20 to 20°C above the crystallization initiation temperature of polycarbonate.
By carrying out at a temperature 50°C higher, preferably 200 to 225°C, more preferably 210°C to 225°C,
The properties targeted by the present invention, including optical transmission properties at high temperatures, are further improved. At temperatures below 200°C, optical transmission loss increases due to crystallization, and at temperatures above 225°C, optical transmission loss increases due to an increase in thread patterns. By performing such high-temperature melt extrusion, it is possible to undergo a thermal history of nearly 200°C when making optical fibers into cables, making it possible to select and use coating materials with higher heat resistance. Another effect is that the selection range of covering materials is widened. Core layers 11 and 2 in the optically transmitting fiber of the present invention
1. The thickness and thickness of the sheath material layers 12, 22 and the protective layers 13, 23 are appropriately set according to the intended use of the optical transmission fiber. For example, in the spinneret shown in FIG. 2 or 3, the thickness and diameter can be controlled by changing the diameter and length of the orifice at each feed port. Hereinafter, the present invention will be explained in detail with reference to Examples. Note that parts in the examples indicate parts by weight. The optical transmission performance was evaluated by measuring according to the method disclosed in Japanese Unexamined Patent Publication No. 7602/1983. The measurement light wavelength is 770nm. Examples 1 to 4, Comparative Examples 1 to 9 Polycarbonate having a crystallization start temperature of 182°C and an intrinsic viscosity shown in Table 1, with _R1 having a bisphenol A skeleton, was heated to 215°C through a gear pump section maintained at 215°C. The core-sheath protective layer was melted and supplied to the core spinning head of a three-component composite spinning machine. On the other hand, a fluorinated methacrylate polymer with a refractive index of 1.417 was melted at 220°C as a polymer for forming a sheath component and supplied to the sheath component spinning head of a composite spinning machine.
A polymer prepared by mixing 0.2% by weight of carbon black with polycarbonate having an intrinsic viscosity of 0.50 was melted at 225°C and supplied to a spinning head for forming a protective layer of a composite spinning machine. The molten polymers of the core material layer, sheath material layer, and protective material layer that were supplied at the same time were discharged at the temperature shown in Table 1 using a spinneret with a nozzle diameter of 3 mm, and after cooling and solidifying, they were withdrawn at a speed of 3 m/min. , core diameter 900μ
A plastic optical fiber with an outer diameter of about 1.0 mm and a sheath thickness of 10 μm and a protective layer thickness of 40 μm was obtained. Optical transmission loss of the obtained optical fibers left at room temperature and heat treated at 130℃ for 2000 hours
The results measured at 770 nm are shown in Table 1. Also,
The thread pattern of the obtained optical fiber was measured, and the results are also shown in Table 1.

【table】

〔Effect of the invention〕

According to the plastic optical fiber and its manufacturing method of the present invention, the problems associated with conventional plastic optical fibers are solved, and the plastic optical fiber has excellent heat resistance, excellent optical transmission characteristics, and is good even when used under high temperature conditions. It can exhibit optical transmission characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the construction of a two-layer plastic optical fiber according to the present invention. Second
The figure is a cross-sectional view showing the structure of a three-layer plastic optical fiber according to the present invention. FIG. 3 is a cross-sectional view showing the construction of a four-layer plastic optical fiber according to the present invention. FIG. 4 is a cross-sectional view showing the construction of a two-core plastic optical fiber according to the present invention. 5 and 6 are cross-sectional views of a spinneret of a composite spinning head used in producing the plastic optical fiber of the present invention. 1... Core material layer (core), 2... Sheath material layer (cladding), 3... Protective layer, 4... Covering layer.

Claims (1)

[Scope of Claims] 1. A plastic optical fiber having a core material layer and a sheath material layer as basic structural units, wherein the core material layer has an intrinsic viscosity (in methylene chloride, 20° C.) of 0.25 dl/g or more, and Less than 0.40dl/g, glass transition temperature 140~
A plastic optical fiber characterized by being made of transparent polycarbonate at 150°C. 2 Intrinsic viscosity (in methylene chloride, 20℃) is 0.25
dl/g or more and less than 0.40 dl/g as a core material, and a highly transparent organic polymer having a refractive index that is 0.01 or more smaller than the optical refractive index of the polycarbonate as a core material, and crystallization of the polycarbonate. 1. A method for producing a plastic optical fiber characterized by performing composite spinning at a temperature 20 to 50°C higher than the above temperature.