JPH0644085B2 - Plastic optical fiber and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plastic optical fiber having excellent heat resistance, moisture resistance and self-extinguishing property, and further having an optical transmission loss suitable for optical transmission, and a method for producing the same. .

[Prior Art] Plastic optical fibers are increasingly used for short-distance optical communication, data links, sensors and the like. The reason is that the plastic optical fiber has a larger aperture and numerical aperture than quartz and multi-component glass-based fibers, easy connection with a light source and connection between fibers, excellent flexibility and flexibility, It is easy to process and wire, and the price is low.

However, conventional plastic optical fibers have the drawback of low heat resistance. For example, the heat distortion temperature of polymethylmethacrylate (PMMA) is 98 ° C, and the normal use temperature is up to 70 ° C. Methyl α with improved heat distortion temperature
-The heat distortion temperature of the fluoromethacrylate polymer core fiber is 110 ° C, and the heat resistance is still insufficient.
(See JP-A-60-118808).

Heat resistance is required for moving objects and sensors,
When used in the engine room of an automobile, it is necessary to withstand a temperature of 120 ° C.

Further, the conventional polymethylmethacrylate core plastic optical fiber has a problem that the moisture resistance is not sufficient and the transmission loss increases due to moisture absorption.

Moreover, the conventional polymethylmethacrylate core plastic optical fiber does not have self-extinguishing property.

[Structure of the Invention] One aspect of the present invention resides in a plastic optical fiber including a polymer of a monomer containing methyl α-chloroacrylate as a core and a polymer having a refractive index lower than that of the core as a clad. The plastic optical fiber of the present invention is characterized in that the core is formed of a polymer of a monomer containing methyl α-chloroacrylate. The core is obtained from a polymer obtained from a monomer consisting of methyl α-chloroacrylate alone, or a monomer composition of methyl α-chloroacrylate and an alkyl methacrylate or an alkyl acrylate (for example, methyl methacrylate or methyl acrylate). It may be a copolymer. The weight ratio of the monomers in the monomer composition depends on the kind of the monomers.

The cladding can be any transparent polymer having a lower refractive index than the core polymeric material, such as fluorine-containing alkyl methacrylate polymers, vinylidene fluoride-tetrafluoroethylene copolymers, and polymers thereof. May be a blend of

Another subject matter of the present invention is a process for producing a plastic optical fiber having a polymer of a monomer containing methyl α-chloroacrylate as a core and a polymer having a refractive index lower than that of the core as a clad, and providing a core polymer. Monomers are purified in a substantially oxygen-free closed system, polymerized, melted while maintaining a closed state, extrusion-spun, drawn, and then a clad is formed in a plastic optical fiber. It depends on the manufacturing method.

Each step of the manufacturing method of the present invention will be described below.

(1) Purify the core monomer in a closed system that is substantially oxygen free. The oxygen concentration in the closed system is preferably 5 ppm or less. The core monomer is usually purified by distillation.

(2) After purification, polymerization is carried out while maintaining a closed state. It is preferable to sufficiently remove dissolved oxygen before carrying out the polymerization. The dissolved oxygen can be removed, for example, by blowing nitrogen gas. After the dissolved oxygen is sufficiently removed, the polymerization initiator and, if necessary, a chain transfer agent are added while maintaining the closed state to polymerize the core monomer. The polymerization initiator may be any conventional initiator, for example, an azo-based polymerization initiator or a peroxide-based polymerization initiator. If desired, the chain transfer agent added may be any conventional chain transfer agent, such as mercaptan.

(3) After polymerization, the core is melted, extrusion-spun, and drawn to form a fiber. Then, a clad is formed around the core. The clad can be formed by melt coating or melt coating.

EFFECTS OF THE INVENTION The plastic optical fiber of the present invention has a high heat distortion temperature of the core material of 135 to 141 ° C. and is excellent in heat resistance as compared with the conventional plastic optical fiber. Although the water absorption of PMMA is about 0.3%, the core material of the present invention has a small water absorption of about 0.1% and is excellent in moisture resistance. While PMMA is not self-extinguishing, the core material of the present invention is self-extinguishing.

The plastic optical fiber of the present invention can be used in the form of an optical fiber cord or cable, or an optical power composite cable, and is useful in a data link.

[Examples] Examples and comparative examples are shown below.

Examples 1 to 4 and Comparative Example 1 The purified monomer was distilled under reduced pressure using a vacuum distillation, polymerization and fiberizing device having an oxygen concentration of 1 ppm or less, and a polymerization initiator azoisobutyronitrile 0.01 mol%, chain Transfer agent
0.3 mol% of n-dodecyl mercaptan was added, dissolved in a monomer, transferred to a polymerization vessel, heated at 50 ° C. for 5 hours, then heated at a rate of 10 ° C. for 1 hour, and kept at 140 ° C. for 2 hours, Polymerization was carried out.

Furthermore, the temperature is raised under reduced pressure and nitrogen gas is introduced at 190 ° C.,
After returning to normal pressure, the molten polymer was extruded under a nitrogen pressure of 4 kg / cm ² , stretched, and coated with a fluorine-containing polymer solution to give a plastic optical fiber with a core diameter of 0.5 mm and a cladding thickness of 0.08 mm. Got fiber.

Table 1 shows Tg of the obtained core polymer, self-extinguishing property of fiber and loss. As is clear from Table 1, the plastic optical fiber of the present invention is particularly excellent in heat resistance and self-extinguishing property.

Claims (4)

[Claims] 1. A plastic optical fiber comprising a polymer of a monomer containing methyl α-chloroacrylate as a core and a polymer having a refractive index lower than that of the core as a clad. 2. The plastic optical fiber according to claim 1, which has a core of a polymer of a monomer consisting only of methyl α-chloroacrylate. 3. The plastic optical fiber according to claim 1, which has a core of a copolymer of a monomer composition containing not only methyl α-chloroacrylate but also alkyl methacrylate or alkyl acrylate. 4. A method for producing a plastic optical fiber, comprising a polymer of a monomer containing methyl α-chloroacrylate as a core, and a polymer having a refractive index lower than that of the core as a clad. A method for producing a plastic optical fiber, which comprises purifying in a closed system substantially free of oxygen, polymerizing, melting while keeping a closed state, extrusion spinning, stretching, and then forming a clad,