JPH09178961A - Production of plastic optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for production capable of obtaining a plastic optical fiber which is low in transmission loss at a low cost. SOLUTION: This process for production is composed of a stage for manufacturing the plastic optical fiber of a prescribed outside diameter by drawing and spinning a preform having a prescribed refractive index distribution and a stage for forming a protective layer on the surface of the plastic optical fiber. In such a case, the preform is previously arranged within a cylindrical body consisting of a thermoplastic resin compsn. Both are simultaneously drawn and spun, by which the protective layer consisting of the thermoplastic resin compsn. is formed on the surface of the plastic optical fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a plastic optical fiber having a protective layer on its surface (for example, a multimode gradient index plastic optical fiber), and more particularly to a plastic optical fiber having a small transmission loss. The present invention relates to a manufacturing method that can be obtained at low cost.

[0002]

2. Description of the Related Art A plastic optical fiber having both a core and a clad made of a plastic material is more flexible than a silica-based optical fiber and has a large diameter, which facilitates end face treatment and connection treatment. Recently, various applications as an optical signal medium such as LAN and ISDN have been studied because of its low price. Among them, for example, the core as disclosed in Japanese Patent Laid-Open No. 5-241036 is disclosed. A multi-mode gradient index plastic optical fiber (hereinafter abbreviated as "GI type plastic optical fiber") having a refractive index profile in which the refractive index gradually decreases from the center of It is regarded as important as an optical signal medium in the concept of communication networks.

Generally, in this type of GI type plastic optical fiber, a base material having a predetermined refractive index distribution is continuously introduced into a heating furnace provided in a heat drawing device (drawing device) at a constant speed. A plastic optical fiber having a predetermined outer diameter is produced by drawing and spinning the softened and melted base material at a constant speed, and then using an extruder on the surface of the obtained plastic optical fiber. It is produced by extrusion coating a protective layer made of a thermoplastic resin composition. Here, the protective layer is formed for the purpose of preventing entry of ambient light, mechanical protection, and the like.

[0004]

However, the plastic optical fiber manufactured by such a method has a problem that the heat, the pressure of the molten resin and the flow of the molten resin when the protective layer is formed on the surface of the fiber by extrusion coating. There is a problem that the transmission loss due to microbending increases due to the influence of nonuniformity. The GI type plastic optical fiber originally has a characteristic that the numerical aperture is lower than that of the step index type plastic optical fiber (SI type plastic optical fiber) and transmission loss due to microbending is likely to occur. Therefore, protection by extrusion coating is performed. The formation of layers has been a factor that further increases the transmission loss.

Another problem is that the material loss of the plastic optical fiber is large. That is, it takes time to set the extrusion conditions at the start of extrusion when the protective layer is extrusion-coated on the surface of the plastic optical fiber, which causes a problem that material loss of the plastic optical fiber occurs. Especially this kind of G
In the I-type plastic optical fiber, the length of the plastic optical fiber obtained is limited depending on the size of the base material used, and thus such material loss is a great negative factor in terms of cost. Further, as described above, the conventional manufacturing method is composed of two steps, that is, a step of drawing and spinning a base material to produce a plastic optical fiber, and a step of forming a protective layer on the surface of the plastic optical fiber. Therefore, there is also a problem that production efficiency is low.
The low productivity has been a major factor in raising the cost of the plastic optical fiber in combination with the above-mentioned problem of material loss.

To solve this problem, for example, a method of reducing the influence of heat or pressure by extrusion coating a thermoplastic resin composition at a high speed, or at a low temperature as a constituent material of a protective layer is used. A method of using a resin material (polyethylene having a melting point of 120 to 170 ° C.) capable of extrusion coating, thereby reducing the influence of heat (for example,
Methods disclosed in Japanese Patent Laid-Open No. 59-9603) and the like are conceivable. However, all of these methods are based on the premise that the protective layer is formed by extrusion coating. It is impossible to completely prevent the influence of heat and pressure, and it is impossible to obtain any effect on the occurrence of material loss and the reduction of productivity.

As described above, in the current manufacturing method, a plastic optical fiber having a small transmission loss and a low cost has not been obtained.

[0008]

As a result of various studies to solve the above-mentioned problems of the conventional technique, the present inventors have formed a protective layer, which has been conventionally performed after manufacturing a plastic optical fiber. It was found that a plastic optical fiber having a small transmission loss and a low cost can be obtained by simultaneously performing the above-mentioned process at the time of manufacturing the plastic optical fiber (at the time of drawing and spinning), and completed the present invention.

That is, the method for producing a plastic optical fiber according to the present invention comprises a step of producing a plastic optical fiber having a predetermined outer diameter by drawing and spinning a base material having a predetermined refractive index distribution, and a step of forming a plastic optical fiber on the surface of the plastic optical fiber. In the method for producing a plastic optical fiber, which comprises a step of forming a protective layer, the base material is placed in advance in a cylinder made of a thermoplastic resin composition, and the plastic optical fiber is produced by simultaneously drawing and spinning the base material. A protective layer made of a thermoplastic resin composition is formed on the surface of the fiber.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The base material for a plastic optical fiber used in the present invention is not particularly limited in its constituent material, length, outer diameter and the like as long as it has a GI type refractive index distribution. Since various kinds of constituent materials have been conventionally known, they may be appropriately selected and used. As an example, JP-A-5-241036
Polymethylmethacrylate (PM) as disclosed in Japanese Patent Publication No. WO93 / 08488, etc.
Examples thereof include a resin mainly composed of MA) doped with a high refractive index compound for controlling the refractive index.

The cylindrical body on which the above-mentioned base material is arranged is made of a thermoplastic resin composition. The thermoplastic resin composition is not particularly limited as long as it can be processed into a linear shape without being decomposed by heat during drawing and spinning. For example, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-α olefin copolymer, ethylene-propylene copolymer, polyvinyl chloride, polyamide, vinyl chloride-vinyl acetate copolymer. Polymer, polyurethane, urethane-
Examples thereof include those in which a conventionally known additive such as an antioxidant, a processing aid, and a colorant is appropriately blended with a simple substance such as a vinyl chloride copolymer or a mixture of two or more kinds thereof, and the like. It should be noted that, for example, when carbon black or the like is used as the colorant to color it black, it is effective in preventing the entry of ambient light into the plastic optical fiber obtained by the present invention.

The inner diameter of the cylindrical body may be such that the base material can be arranged, but is preferably 2 times the outer diameter of the base material.
It is within a factor of 2, and more preferably within a factor of 1.5. If it exceeds 2 times, it becomes difficult to carry out drawing and spinning at the same time as the base material. Incidentally, in order to prevent the displacement of the base material at the time of drawing and spinning, it is possible to attach an appropriate spacer to one end of the base material.

The base material placed in the cylindrical body is continuously introduced into a conventionally known hot drawing apparatus (drawing apparatus), and the base material and the cylindrical body are simultaneously drawn and spun to have a predetermined outer diameter, A plastic optical fiber having a protective layer formed of a thermoplastic resin composition on the surface is completed. According to such a manufacturing method, the extrusion coating step for forming the protective layer, which has conventionally been a factor of increasing the transmission loss due to microbending, can be omitted, so that a plastic optical fiber with a small transmission loss can be obtained. . Further, by omitting the extrusion coating step, the occurrence of material loss is eliminated and the productivity is improved, so that the cost can be significantly reduced.

[0014]

EXAMPLES Examples of the present invention will be described below together with comparative examples.

Example First, an outer diameter of 16.4 mm having a GI type refractive index distribution,
Base material with a length of 300 mm, outer diameter 30 mm, inner diameter 22 mm
It was inserted into the polypropylene pipe, and the upper part was fixed with a spacer. Then, these are introduced into the drawing furnace main body maintained at 230 ° C. at a speed of 4.2 mm / min,
A plastic optical fiber (outer diameter: 1.5 mm, optical fiber diameter: 0.75 mm) having a polypropylene protective layer formed on its surface is drawn by spinning at a speed of 2.0 m / min.
40 m was manufactured. Thus, the transmission loss of the obtained plastic optical fiber was measured and found to be 0.2 dB.
/ M (660 nm). This value was the same as the value of the plastic optical fiber having no protective layer, which was produced by drawing and spinning without using the polypropylene pipe in the above-mentioned example.

Comparative Example A plastic optical fiber 14 produced by drawing and spinning without using a polypropylene pipe in the above example.
The surface of 0 m (transmission loss: 0.2 dB / m, 660 nm) was extrusion-coated with polypropylene at a temperature of 180 ° C. using an extruder to form a protective layer. The transmission loss of the thus obtained plastic optical fiber was measured and found to be 0.55 dB / m. That is, since the protective layer was formed by extrusion coating, the transmission loss increased by 0.35 dB / m. The material loss of the plastic optical fiber obtained by this method was about 100 m.

[0017]

As described above in detail, according to the present invention, a protective layer is formed on the surface of a plastic optical fiber at the same time when the base material is drawn and spun, so that a plastic optical fiber with a small transmission loss can be obtained. Obtainable.
Further, by omitting the extrusion coating step, the occurrence of material loss is eliminated and the productivity is improved, so that the cost can be significantly reduced.

Claims (1)

[Claims] 1. A process comprising: drawing a base material having a predetermined refractive index distribution to draw a plastic optical fiber having a predetermined outer diameter; and forming a protective layer on the surface of the plastic optical fiber. In the method for producing a plastic optical fiber according to the above, the base material is preliminarily placed in a cylinder made of a thermoplastic resin composition, and a thermoplastic resin composition is formed on the surface of the plastic optical fiber by simultaneously drawing and spinning them. A method of manufacturing a plastic optical fiber, which comprises forming a protective layer.