JPH0568682B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a plastic light transmitting fiber with excellent heat resistance. Conventionally, inorganic glass optical fibers have been known as optical fibers that have excellent optical transmission properties over a wide range of wavelengths, but they have poor processability, are susceptible to bending stress, and are expensive. Light transmitting fibers made of synthetic resin have been developed. Optical transmission fibers made of synthetic resin have 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.
It is obtained by producing fibers with a sheath structure. 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°C, and the plastic light transmitting fiber with polymethyl methacrylate as its core cannot be used at all if the operating environment exceeds 100°C. Limited heat resistance limits the use of plastic light transmitting fibers. Furthermore, various optically transmitting fibers with polycarbonate cores have been proposed, but they have not been put into practical use because polycarbonate has a large optical transmission loss and a sheath material with excellent heat resistance has not been developed. . The present inventors have conducted extensive studies aimed at developing a plastic light transmitting fiber with excellent heat resistance and durability that overcomes the weaknesses of such conventional plastic light transmitting fibers, and as a result has arrived at the present invention. That is, the present invention has a core 1 made of polycarbonate, a sheath 2 made of a substantially transparent polymer having a refractive index lower than the refractive index of the core by 0.01 or more, and a polycarbonate having a heat distortion temperature of 110° C. or more. This plastic light transmitting fiber is characterized in that the light transmitting fiber comprising the protective layer 3 is produced by a composite spinning method with a core spinning draft in the range of 1.1 to 100. The light transmitting fiber of the present invention has a structure as shown in FIGS. 1 and 2, and the light 4 incident at an incident angle θ ₃ is transmitted while being totally reflected at the interface between the core 1 and the sheath 2. Also, the light 5 incident at an incident angle θ ₄ is transmitted while being totally reflected at the interface between the core 1 and the sheath 2, resulting in a light-transmitting fiber that does not generate noise. Furthermore, when the protective layer 3 is a transparent polymer, the refractive index of the protective layer 3 is preferably greater than the refractive index of the sheath 2. This is because the refractive index of the protective layer 3 is greater than the refractive index of the sheath 2, so the light 6 incident from the outside of the protective layer 3 is totally reflected at the interface between the protective layer 3 and the sheath 2, and does not enter the core of the fiber, causing noise. will not be detected as such. Therefore, it is made of plastic light transmission fiber with excellent light transmission properties. Polycarbonate, which has excellent transparency and excellent heat resistance, is used as the polymer forming the core 1 and protective layer 3 of the optically transmitting fiber of the present invention. The general formula for polycarbonate suitable for use as a core is

Represented by [formula] thing, where R is

【formula】

【formula】 Aliphatic polycarbonate represented by

【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 this point of view, those having a heat distortion temperature of 120° C. or higher are preferable. Here, heat distortion temperature is ASTMD−648, load 4.6
Measured value in Kg/ ^cm2 . As the light transmitting fiber sheath 2 of the present invention, a substantially transparent polymer having a refractive index that is 0.01 or more lower than the refractive index of the core is used. Assuming that the refractive index of the core 1 is n ₁ and the refractive index of the sheath 2 is n ₂ , if a light transmitting fiber with a core-sheath structure is manufactured using a combination of polymers such that n ₁ − _{n 2} is less than 0.01, the light will not be incident on the core. The total reflectance of light at the optical core-sheath interface decreases, making it impossible to obtain a light transmitting fiber with low light transmission loss. The larger the value of n ₁ −n ₂ is, the more preferable it is, but it is usually in the range of 0.01 to 0.15. The thickness of the sheath layer of the present invention is not particularly limited, but with conventional optically transmitting fibers, it was not possible to make it very thin from the viewpoints of handling and durability, but in the present invention, it is 1 to 30 μm, and even 1 to 30 μm. Even if it is made as thin as 10 μm, there will be no inconvenience in terms of optical transmission, durability, ease of handling, etc. Furthermore, by covering with the protective layer 3 having a heat deformation temperature of 110° C. or higher, the range of application of the sheath polymer becomes very wide. In other words, the heat resistance of the sheath polymer does not need to be as high as that of the core 1 or the protective layer 3, and even if the heat distortion temperature is 110°C or lower, 100°C or lower, or even 50°C or lower, the present invention can be applied. If the structure is followed, it is possible to ensure sufficient heat resistance and durability. Specific examples of polymers used as the sheath include the following: Polymetal methacrylate (n=1.49), styrene/methyl methacrylate copolymer (n=
1.50-1.58), 4-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 ternary or quaternary copolymer (n=1.50-1.58). In order to improve the delamination strength between the core-sheath-protective layer, these polymers include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, unsaturated glycidyl acrylates such as glycidyl acrylate or methacrylate, and unsaturated glycidyl acrylates such as β-methylglycidyl acrylate or methacrylate. Hydrophilic monomers such as monomers, acrylamide, methacrylamide and derivatives thereof, hydroxyalkyl acrylates or methacrylates may be copolymerized. The protective layer 3 of the light transmitting fiber of the present invention must be made of a polymer having a heat deformation temperature of 110° C. or higher.
If the heat distortion temperature is less than 110°C, the effect of improving heat resistance and durability, which is the objective of the present invention, will be small. That is, under severe conditions such as in the engine room of an automobile, surface fusion of the light transmitting fibers or disturbance of the core-sheath interface occurs, resulting in a significant increase in light transmission loss. Polycarbonate for forming the core 1 is used as the polymer for the protective layer 3 of the photoconductive fiber of the present invention, and if a spinning nozzle as shown in FIG. 4 is used, polycarbonate having the same composition as the core can also be easily used as the protective layer. It can be used for. The thickness of the protective layer of the optically transmitting fiber of the present invention is 1 to 1.
Even with a very thin protective layer of 30 μm, the effect of improving heat resistance, which is the objective of the present invention, can be sufficiently exhibited, but depending on the purpose, the protective layer may be thicker than 30 μm. In order to manufacture the optically transmitting fiber of the present invention, it is preferable to form it by melt spinning, but when polycarbonate is used as the core, it is necessary to reduce the transmission loss to a practical level and to form it at high temperatures. In order to maintain heat resistance and durability, it is necessary to shape the core polycarbonate so that the molecular orientation is as small as possible, and the spinning draft of the core component polymer must be in the range of 1.1 to 100. When the spinning draft exceeds 100, the molecular orientation becomes extremely large, and not only does the transmission loss decrease, but when a durability test is performed at high temperatures, the transmission loss tends to change due to the relaxation of the molecular orientation. Furthermore, if the spinning draft is less than 1.1, disturbances occur at the core-sheath interface, resulting in extremely poor transmission loss. For these reasons, it is preferable in the present invention that the stretching treatment, which is normally carried out in the production of plastic optical transmission fibers, is not carried out.On the contrary, it is preferable to carry out the annealing treatment at a temperature equal to or higher than the glass transition point of the core polymer. In addition, in producing the optically transmitting fiber of the present invention, if composite spinning is performed using a nozzle as shown in FIGS. 3 and 4, core/sheath/
Simultaneous shaping of the holding layer becomes possible, which is very advantageous industrially. FIG. 3 is a cross-sectional view of an example of a composite spinning nozzle for producing light transmitting fibers of the present invention, each having a different composition. of polymer is supplied and taken out from the discharge port D. FIG. 4 is a cross-sectional view of another example of a composite spinning nozzle.
Polymer is supplied from the sheath material supply port A and the core material supply port B, and the polymer for the core material is divided into the core material and the protective layer for composite spinning, and is taken out from the discharge port D. Since the optical transmission fiber of the present invention has improved heat resistance and durability, high molding temperatures are required in the optical fiber cable processing process, where conventional optical transmission fibers melt the sheath material and disturb the core-sheath interface. The heat-resistant jacket polymer has great advantages in improving heat resistance, such as being able to be easily used for cable processing without damaging the light transmitting fibers, and the significance of the present invention is extremely large. The light transmitting fiber of the present invention is very suitable for controlling light in moving bodies such as automobiles, especially in parts such as engine compartments that have severe environmental conditions. Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 A polycarbonate having a refractive index (n _D ) of 1.58 and a heat distortion temperature of 133° C. was obtained by reacting bisphenol A with phosgene, and this was used as a core material polymer. On the other hand, methacrylic acid chloride and 2,2,2-
2,2,2-trifluoroethyl methacrylate prepared from trifluoroethanol was polymerized in the presence of a small amount of n-octyl mercaptan using azobisisobutyronitrile as a catalyst, and the refractive index
Obtained a polymer of 1.413 and 230 as a polymer for sheath material.
The mixture was supplied to a core-sheath composite spinning head at 230°C via a gear pump in a screw melt extruder set at 230°C. The molten polymer for forming the core, sheath and protective layer that was supplied at the same time was discharged at 230°C using the spinneret shown in No. 4 (nozzle diameter 1.5mmφ), and after cooling and solidifying, it was withdrawn at a speed of 3m/min. Ivy. At this time, the spinning draft was 2.25, and the obtained light transmitting fiber was a concentric light transmitting fiber with a core diameter of 970 μm, a sheath layer thickness of 5 μm, a protective layer thickness of 10 μm, and an outer diameter of 1000 μm. Ta. The transmission loss of this optical transmission fiber was 1500 dB/Km for light with a wavelength of 690 mm, and the light transmitted sufficiently over a length of 10 m could be detected. Comparative Example 1 A core-sheath two-layer optical transmitting fiber was obtained in exactly the same manner as in Example 1 except that a normal core-sheath two-layer nozzle nozzle was used. Core material diameter
986μm, sheath material thickness is 7μm, optical transmission loss is
It was 1750dB/Km. Example 2 The two types of optical transmission fibers obtained in Example 1 and Comparative Example 1 were evaluated for heat resistance and durability under various conditions as shown in Table 1. Transmission loss was measured using light at a wavelength of 690 nm.

[Table] As shown in Table 1, the optically transmitting fiber of the present invention is
No increase in transmission loss was observed even when heated to 140°C or 100 hours at 130°C, whereas the light transmitting fiber of Comparative Example 1 had the same core material. When the temperature exceeded 110℃, the transmission loss increased rapidly. Examples 2 to 6, Comparative Examples 2 to 3 Light transmitting fibers were obtained in exactly the same manner as in Example 1, except that the diameter of the spinning nozzle or the spinning speed was variously changed. Table 3 shows the performance and heat resistance durability test results of the obtained light transmitting fiber.

[Table] In Examples 2 to 6, which were spun with a spinning draft within the range of the present invention, no large increase in transmission loss was observed even after heat treatment, but in Comparative Example 2, where the spinning draft exceeded 100, even before heat treatment. The loss is slightly large, but the transmission loss deteriorates even further with heat treatment. Comparative Example 3 is an example in which the spinning draft is too small, and the core-sheath interface is not smoothed. Example 7 Using the light transmitting fibers obtained in Example 1 and Comparative Example 1, polyester elastomer containing carbon black was produced at a die temperature of 190°C and a take-up speed of 40 m/min.
Cable coating processing was carried out at min. The transmission loss of the optical cable obtained using the optical transmission fiber of Example 1 did not change at all, whereas the transmission loss of the optical transmission fiber of Comparative Example 1 was 1750 dB/Km.
After cable processing, the transmission loss significantly increased to 7900dB/Km. When the cross section was observed under a microscope, irregularities were observed at the core-sheath interface.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the optically transmitting fiber of the present invention, FIG. 2 is a schematic diagram showing the optical transmittance of the optically transmitting fiber of the present invention, and FIGS. FIG. 2 is a cross-sectional view of an example of a spinning nozzle used in producing light transmitting fibers.

Claims (1)

[Claims] 1 Optical transmission properties consisting of a core 1 made of polycarbonate, a sheath 2 made of a substantially transparent polymer having a refractive index 0.01 or more smaller than the refractive index of the core, and a protective layer 3 made of polycarbonate. The spinning draft of the fiber and core component is 1.1
100, and is characterized in that it is produced by a composite spinning method.