JP2000098143A - Production of plastic optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of an optical fiber by which a plastic optical fiber of a large diameter with small bending loss can be produced at a low cost. SOLUTION: In this producing method of a plastic optical fiber, a noncrystalline thermoplastic resin compsn. is formed while polymerized around a preform having specified distribution of refractive index which is disposed in the center. Then the preform with the resin together is drawn into a fiber to obtain the plastic optical fiber having a coating made of the noncrystalline thermoplastic resin compsn. which does not contribute to transmission of light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multimode gradient index plastic optical fiber having a coating on its surface made of an amorphous thermoplastic resin composition.
The present invention relates to a method for manufacturing a plastic optical fiber having a small bending loss and a large diameter at a low cost.

[0002]

2. Description of the Related Art A plastic optical fiber in which both a core and a clad are made of a plastic material has excellent flexibility as compared with a silica-based optical fiber and has a large diameter, so that end face processing and connection processing are easy. In recent years, various applications for optical signal media such as LAN and ISDN have been studied because of their low cost. Among these, for example, a multimode refractive index distribution type plastic optical fiber having a refractive index distribution such that the refractive index gradually decreases from the center of the core as disclosed in Japanese Patent Application Laid-Open No. 5-21036 (hereinafter, referred to as Japanese Patent Application Laid-Open No. H5-241036) , "GI plastic optical fiber") is regarded as important as an optical signal medium in a next-generation communication network concept because of its large transmission capacity.

Generally, a GI type plastic optical fiber of this kind is prepared by first filling a core liquid in a cylindrical polymerization vessel made of a clad material, as disclosed in Japanese Patent Application Laid-Open No. H5-241036. Then, while the polymerization vessel is rotated at an appropriate speed by a rotating device, a polymerization reaction proceeds from the periphery to produce a base material having a predetermined refractive index distribution,
Then, these are continuously introduced into a heating furnace provided in a hot drawing device (drawing device) at a constant speed and heated, and the softened and molten base material is drawn and spun at a constant speed. ing.

In such a plastic optical fiber, a transmission loss due to bending (hereinafter, abbreviated as "bending loss") may occur during actual use depending on the laying state. Generally, when it is necessary to reduce bending loss, it is effective to use a plastic optical fiber with a small core diameter drawn and spun with a small outer diameter, but a plastic optical fiber with a small core diameter is effective. However, there is a problem that the heat resistance is inferior and the ease of work due to the large diameter, which is an advantage of the plastic optical fiber, is lost. Therefore, in order to reduce the bending loss of the plastic optical fiber without sacrificing its workability, it is necessary to reduce only the core diameter without changing the outer diameter.

[0005] Means for reducing the core diameter alone include, for example, (1) a method of extrusion-coating a thermoplastic resin composition on the surface of a drawn and spun plastic optical fiber having a small outer diameter, and (2) a method of drawing a thinner outer diameter. A method of applying an ultraviolet curable resin to the surface of the spun plastic optical fiber and then curing the ultraviolet curable resin; (3) forming a thick clad material by coating with a thermoplastic resin composition or the like; To prepare a base material by allowing the polymerization reaction to proceed and draw and spin the base material. (4) A method in which the base material is placed in a cylinder made of a thermoplastic resin composition, and then these are simultaneously drawn and spun. ,and so on.

[0006]

However, first of all,
In the case of the method of extrusion-coating a thermoplastic resin composition on the surface of a plastic optical fiber, the transmission loss due to microbending increases due to the effect of heat at the time of extrusion coating, and the core becomes uneven due to uneven thickness at the time of extrusion coating. There is a problem of eccentricity.

In the case of applying and curing an ultraviolet curable resin on the surface of a plastic optical fiber having a thin outer diameter, a thickness of about 50 to 100 μm is required in order to exhibit an effect of reducing bending loss. A resin layer is required, but in order to form such a thick resin layer,
Since it is necessary to apply and cure the coating several times, productivity is significantly reduced. In addition, eccentricity of the core is also expected as in the case of the extrusion coating method described above.

In the case of a method of drawing and spinning a base material obtained by using a thick clad material, if the thickness of the clad material is large, heat conduction becomes poor, and it is difficult to control a polymerization reaction. Therefore, as the diameter of the base material is increased in order to enhance mass productivity, more strict control of the reaction is required, and the production cost is increased.

In the case of a method in which a base material is placed in a cylindrical body made of a thermoplastic resin composition and they are simultaneously drawn and spun, the drawing conditions (drawing temperature, drawing speed, diameter of the base material and the size of the cylindrical body) are set. If the setting of the thickness ratio, etc.) is not performed precisely, the optical fiber may not be able to be applied to the optical fiber due to the difference in the shrinkage, especially when the cylindrical body is made of a crystalline thermoplastic resin composition having a high molding shrinkage. The necessary stress is applied,
There is a risk that transmission loss will increase. Further, when the cylindrical body is composed of a thermoplastic resin composition having high adhesion to the clad material, foaming may occur at the interface between the base material and the cylindrical body during drawing and spinning due to both decomposition gases and the like. .

[0010] The present invention has been made based on such a point, and an object of the present invention is to reduce bending loss,
Another object of the present invention is to provide a manufacturing method capable of obtaining a large-diameter plastic optical fiber at low cost.

[0011]

In order to achieve the above object, a method for manufacturing a plastic optical fiber according to the present invention comprises:
After being molded while polymerizing the amorphous thermoplastic resin composition around the base material having a predetermined refractive index distribution arranged in the center, by simultaneously drawing and spinning these, even if not involved in light transmission around, The present invention is characterized in that a plastic optical fiber having a good amorphous thermoplastic resin composition is obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The constituent material, length, outer diameter and the like of the base material used in the present invention are not particularly limited as long as the base material has a GI type refractive index distribution. Since various kinds of constituent materials have been known in the art, they may be appropriately selected and used. For example, Japanese Patent Application Laid-Open No. H5-241036, International Publication No. W
As disclosed in O93 / 08488 and the like, a resin obtained by doping a resin mainly composed of polymethyl methacrylate with a compound having a high refractive index for controlling a refractive index can be used.

In the present invention, first, an amorphous thermoplastic resin composition is molded around the base material while being polymerized. As a molding method, for example, (1) after disposing a base material in the center of a cylindrical polymerization container having a predetermined inner diameter, filling a reaction liquid between the base material and the polymerization container, and then heating from the periphery, Alternatively, a method of irradiating energy rays (ultraviolet rays, infrared rays, etc.) to cause the polymerization reaction to proceed, (2) after disposing the base material at the center of a cylindrical polymerization vessel having a predetermined inner diameter, Filling, and then heating from one end of the polymerization vessel or irradiating with energy rays (ultraviolet rays, infrared rays, etc.) to allow the polymerization reaction to proceed. After that, the reaction liquid is gradually supplied from the bottom into the polymerization vessel and heated, or at the same time, the polymerization reaction is advanced by irradiating energy rays (such as ultraviolet rays and infrared rays).

The reaction solution to be used may be any as long as it is polymerized by irradiation of heat or energy rays (such as ultraviolet rays and infrared rays) to form an amorphous thermoplastic resin composition. Examples thereof include those obtained by adding a thermal initiator and a chain transfer agent to methyl methacrylate, styrene, vinyl acetate, and the like, and those obtained by adding an ultraviolet curing agent to urethane acrylate and the like.

Conventionally, in the case of a method in which a base material is placed in a cylinder made of a thermoplastic resin composition and they are simultaneously drawn and spun, the cylinder is made of a thermoplastic resin composition having high adhesion to a clad material. If it had been, when drawing and spinning, there was a risk that foaming due to both decomposed gas and the like at the interface between the base material and the cylindrical body, but in the case of the present invention, when such a material is used Also, since the above reaction solution is molded while being polymerized, the interface between the base material and the resin composition disappears, and foaming is suppressed.

Next, the base material is continuously introduced into a conventionally known hot drawing apparatus (drawing apparatus), and the base material and the amorphous thermoplastic resin composition are simultaneously drawn and spun to obtain a predetermined outer shape. A plastic optical fiber having a diameter and having on its surface a coating made of an amorphous thermoplastic resin composition which may not be involved in light transmission is completed.

[0017]

EXAMPLES Examples of the present invention will be described below together with comparative examples. In the following examples, the final finish outer diameter was 0.7
This is an example in which a plastic optical fiber is manufactured to have a length of 5 mm. Further, as a constituent material of the base material, a resin mainly composed of polymethyl methacrylate,
A material doped with a compound having a high refractive index for controlling the refractive index was used. Further, as a reaction liquid constituting the amorphous thermoplastic resin composition molded around the base material, a reaction liquid obtained by adding a thermal initiator and a chain transfer agent to methyl methacrylate was used.

[0018] Example First, an outer diameter 22mm having a refractive index profile of the GI-type, core diameter 13.2 mm, the base material of length 500 mm, internal diameter 50m
m, fixed at the center of a cylindrical polymerization vessel having a length of 450 mm. Next, a reaction liquid [methyl methacrylate: lauroyl peroxide: 1-dodecanethiol = 100: 0.2: 1.5 (weight ratio)] was added little by little to the gap between the base material and the polymerization vessel.
Is supplied at a rate of 3 ml / min.
In a silicone oil bath at a rate of 0.2 mm / min. Next, this was introduced into a drawing furnace main body maintained at 200 ° C. at a speed of 0.45 mm / min, and drawn and spun at a speed of 2.0 m / min to form an outer surface provided with a coating of polymethyl methacrylate on the surface. 0.7 diameter
A plastic optical fiber having a diameter of 5 mm and a core diameter of 0.20 mm was manufactured. The bending loss of the obtained plastic optical fiber was 0.2 dB at a radius of 25 mm and bending at 180 °, and 0.4 dB at a radius of 15 mm and bending at 180 °.

COMPARATIVE EXAMPLE A GI type refractive index distribution having an outer diameter of 22 mm and a core diameter of 1
A base material having a length of 3.2 mm and a length of 500 mm was drawn and spun to produce a plastic optical fiber having an outer diameter of 0.75 mm and a core diameter of 0.45 mm. The bending loss of the obtained plastic optical fiber was 25 mm in radius, 180 mm in this way.
増 加 Increase in bending 0.7dB, radius 15mm, 180
増 加 The increase loss was 1.2 dB in bending.

[0020]

As described above in detail, according to the production method of the present invention, an amorphous thermoplastic resin composition is preliminarily molded on a base material before drawing and spinning, and these are formed. By simultaneously drawing and spinning, a plastic optical fiber having only a small core diameter can be obtained by a simple method without requiring precise control of polymerization conditions. Therefore, a plastic optical fiber having a small bending loss and a large diameter can be obtained at low cost.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masaki Takahashi 4830 Takatsuka-cho, Hamamatsu-shi, Shizuoka Pref.

Claims (1)

[Claims] The present invention relates to a method of forming an amorphous thermoplastic resin composition around a base material having a predetermined refractive index distribution arranged in the center while polymerizing the amorphous thermoplastic resin composition. A method for producing a plastic optical fiber, characterized by obtaining a plastic optical fiber provided with a coating made of an amorphous thermoplastic resin composition, which does not have to be concerned.