JP2000047040A - Production of plastic optical fiber mother material and reaction cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a reaction cell for producing the plastic optical fiber mother material exhibiting low loss and stable transmission characteristics. SOLUTION: The reaction cell is a cylindrical or test tube-like reaction cell 10 which is used for producing the plastic optical fiber mother material. A polymerizable liquid is filled inside 11 the reaction cell 10 and then polymerized. The cell 10 has a thermal conductivity of >=1.0×10-2 cal/sec. deg.C when the thermal conductivity is measured between inside and outside its wall. It becomes possible to supply a sufficient amount of heat to the polymerizable liquid to accelerate the polymerization reaction and to rapidly remove the reaction heat, by allowing the cell to have a thermal conductivity of >=1.0×10-2 cal/sec. deg.C. Accordingly, the polymerization reaction can be carried out while keeping the polymerization liquid at a prescribed temp.

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 plastic optical fiber preform having low loss and stable transmission characteristics, and a reaction vessel used for the production.

[0002]

2. Description of the Related Art Plastic optical transmission bodies having a predetermined refractive index distribution are used as rod lenses, plastic optical fibers, and the like. Since the plastic optical fiber is made of a plastic material for both the core and the cladding, for example, when compared to a silica-based optical fiber as a broadband plastic optical fiber, it is excellent in flexibility and has a large diameter, so that the end face processing and the connection processing are performed. In recent years, LAN, IS
Various applications as an optical signal medium such as a DN have been studied. Among these, for example, JP-A-9-230145
The multi-mode refractive index type plastic optical fiber having a distribution such that the refractive index gradually decreases in the radial direction from the center of the core as disclosed in Japanese Patent Publication No. Has been regarded as important as an optical signal medium.

As a method for manufacturing such a plastic optical transmission medium, for example, as disclosed in Japanese Patent Application Laid-Open No. H08-110419, first, a certain amount of a polymerizable material is poured into a cylindrical container, While rotating the cylindrical container, the polymerizable material is polymerized while heating the cylindrical container from the outside. When the polymerizable material hardly flows, the rotation is stopped to produce a clad pipe. Then
The polymerizable material for a core is poured into a cylindrical container and polymerized, and the same operation is repeated thereafter to produce a plastic optical fiber preform in which polymerized layers having different refractive indexes are laminated inside the cylinder. Then, a plastic optical fiber is obtained by drawing the preform.

In the production method described in Japanese Patent Application Laid-Open No. 9-269424, a clad pipe is first prepared by the same method as described above, and then a polymerizable compound for swelling and dissolving the clad pipe is used. In this method, a core solution composed of a mixture with a neutral compound is filled in a clad pipe, and the core solution is polymerized under pressure by an inert gas.

[0005]

Problems to be Solved by the Invention
In the manufacturing method described in Japanese Patent Application Laid-Open No. 9-26, since a polymer layer having different refractive indexes is laminated in the radial direction, a desired refractive index distribution is easily obtained.
The manufacturing method described in Japanese Patent No. 4 has an advantage that the manufacturing time is shortened.

[0006] However, the reaction vessel used in the conventional production method, particularly in the case of a glass vessel, tends to have a large wall thickness of the glass in order to secure mechanical strength. Therefore, there is a problem that air bubbles are easily generated in the base material, and the optical fiber obtained by drawing the base material has a large scattering loss.

Accordingly, an object of the present invention is to investigate a method for producing a preform obtained by charging a polymerizable solution into a reaction vessel and polymerizing the same, and to find a plastic optical fiber preform having low loss and stable transmission characteristics. And a reaction vessel used for the method.

[0008]

SUMMARY OF THE INVENTION A method of manufacturing a plastic optical fiber preform according to the present invention comprises supplying a polymerizable solution into a cylindrical or test tube-shaped reaction vessel and promoting a polymerization reaction of the polymerizable solution. A method for producing a plastic optical fiber preform in which heat is fed to perform polymerization, wherein the polymerization reaction is performed in a reaction vessel having a thermal conductivity of 1.0 × 10 ⁻² cal / sec · ° C. or more. The heat generated by the polymerization reaction is released through the outer wall surface of the reaction vessel.

According to the method for producing a plastic optical fiber preform according to the present invention, a polymerizable solution is filled in a reaction vessel and polymerized to produce a plastic optical fiber preform. Since the thermal conductivity propagating between the wall and the wall is 1.0 × 10 ^-2 cal / sec · ° C or higher, the supplied heat necessary to promote the polymerization reaction is controlled at a predetermined temperature. And the reaction heat generated by the polymerization reaction can be rapidly released. Therefore, the polymerization solution can be maintained at a predetermined temperature and a certain polymerization reaction can be performed. On the other hand, the thermal conductivity is 1.0 × 10 ^-2 cal / sec
If the temperature is lower than ° C., the ability to release reaction heat is particularly reduced, and the reaction heat is stored, and the temperature is locally increased, the degree of polymerization is increased, and bubbles are generated, which causes transmission loss.

The reaction vessel according to the present invention is a reaction vessel for manufacturing a plastic optical fiber preform by filling a polymerizable solution in a cylindrical or test tubular vessel and polymerizing the polymerizable solution. The thermal conductivity propagating between the inner wall surface and the outer wall surface of the container is 1.0 × 10 ⁻² cal / sec · ° C. or more.

According to the reaction vessel of the present invention, the thermal conductivity between the inner wall surface and the outer wall surface of the vessel is 1.0 × 10 ⁻² cal / sec ·
℃ or more, the supply heat for accelerating the polymerization reaction is controlled to a predetermined temperature and sent to the polymerizable solution,
Further, the reaction heat generated when the polymerizable solution is polymerized is quickly released via the reaction vessel. Therefore, the polymerization reaction can be performed while maintaining the predetermined temperature of the polymerizable solution. In contrast, the thermal conductivity of the reaction vessel was 1.0
If the temperature is lower than × 10 ⁻² cal / sec · ° C., even if the controllable heat is supplied to the predetermined temperature and the polymerizable solution tries to maintain a constant temperature, it is not enough to release the reaction heat generated by the polymerization reaction. Temperature inconsistency occurs due to lack of ability. As a result, the heat of reaction is accumulated, and the degree of polymerization locally increases, causing a local change in the degree of polymerization. This causes an increase in loss due to irregular refractive index distribution, and also causes bubbles.

In the reaction vessel of the present invention, the reaction vessel is preferably formed by coating a thin layer of silicon carbide on the inner surface of a graphite vessel. Both graphite and silicon carbide have excellent thermal conductivity, and silicon carbide has good releasability from monomers, so that the base material after polymerization is easy to handle.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a plastic optical fiber preform according to a first embodiment of the present invention; In addition,
In the description of the drawings, the same elements are denoted by the same reference numerals,
A duplicate description will be omitted.

First, the configuration of the reaction vessel used in the present embodiment will be described with reference to FIGS. FIG. 1 shows a reaction vessel 1 in which a wall 10 is formed by a cylindrical plate made of the same material, and has a columnar space 11 in the center. The wall 10 is made of quartz glass having high thermal conductivity or metal such as copper or stainless steel having high thermal conductivity and high mechanical strength.

FIG. 2 shows a plurality of walls 10 made of different materials (FIG. 2).
In this case, the reaction vessel 3 is formed in such a manner that the surfaces of two types of cylindrical plates 10-1 and 10-2 are in close contact with each other and has a columnar space 11 at the center. The inner side 10-2 of the wall 10 has a large thermal conductivity and is made of quartz glass, silicon carbide or the like which has good releasability from the monomer, and the outer side 10-1 has a large thermal conductivity and a mechanical property. Metals such as copper and stainless steel, and graphite, etc., having high mechanical strength are used.

Next, a method for manufacturing a plastic optical fiber preform according to the present embodiment will be described with reference to FIGS. FIG. 3A is a diagram illustrating a method for producing a first tubular polymer formed outside the optical fiber preform, and FIG. 3B is a diagram illustrating the first tubular polymer polymerized in a reaction vessel. FIG. FIG. 4 (a) is a diagram illustrating a method for producing a second tubular polymer formed inside the first tubular polymer, and FIG. 4 (b) is a diagram illustrating the second tubular polymer formed inside the first tubular polymer. It is a figure which shows a two-tube polymer. FIG. 5 is a view showing a plastic optical fiber preform manufactured according to this embodiment.

In this embodiment, first, the first tubular polymer 2
0 is produced. The first tubular polymer 20 constitutes the outermost layer of the plastic optical fiber preform as shown in FIG. 5, and is a cylindrical polymer having a predetermined refractive index, a predetermined inner diameter and an outer diameter. is there.

The first tubular polymer 20 is shown in FIG.
As shown in (a), a cylindrical reaction vessel 1 is arranged horizontally, and a polymerizable polymer containing at least one kind of monomer, a polymerization initiator and a chain transfer agent and / or a high refractive index dopant in the reaction vessel 1 is provided. Charge solution A. By operating a heating means such as a ring heater 2 while rotating the opening of the reaction vessel 1 around a central axis X in a sealed state (using a constant temperature bath or an oil bath instead of the ring heater 2). A polymerization reaction is performed. The first tubular polymer 20 thus formed inside the reaction vessel 1 is shown in FIG.

The above-mentioned monomer is not particularly limited as long as it is transparent to transmitted light after polymerization. For example, methyl methacrylate, diphenyl sulfide, 2,2,2-
Trifluoroethyl methacrylate, styrene and the like are used. As the polymerization initiator, for example, perbutylΙ,
Benzoyl peroxide and the like are used, and as the chain transfer agent, for example, mercaptan-based chain transfer agents such as n-butyl mercaptan and n-octyl mercaptan are used. Benzyl benzoate or the like is used as the high refractive index dopant.

The second tubular polymer 21 is shown in FIG.
As shown in (a), a reaction vessel 1 having a first tubular polymer 20 is disposed horizontally, and a polymerizable solution B having a higher refractive index than the polymerizable solution A is charged into a hollow portion of the first tubular polymer 20. I do. The opening of the reaction vessel 1 is sealed with the central axis X
The polymerization reaction is carried out by operating the heating means such as the ring heater 30 while rotating around the ring. The second tubular polymer 2 thus formed inside the first tubular polymer 20
1 is shown in FIG.

As a result, as shown in FIG. 5, a second tubular polymer 21 having a higher refractive index is formed on the inside, and a first tubular polymer having a lower refractive index than the second tubular polymer 21 is formed around the second tubular polymer 21. A plastic optical fiber preform consisting of 20 is obtained. By drawing this base material, a plastic optical fiber can be manufactured.

When the transmission loss of the plastic optical fiber obtained by drawing the preform prepared by using the reaction vessel in this way is measured, the optical fiber tends to contain air bubbles, and the loss is reduced. It turned out to be limited. Therefore, the present inventors have conducted intensive studies on this point, and as a result, even if the externally supplied heat is controlled to be constant,
If the heat generated when the polymerizable solution reacts was not smoothly released, it was presumed that temperature unevenness would occur, and the polymerization would rise locally and bubbles would be trapped. The most effective way to quickly release the heat of reaction is to increase the thermal conductivity of the reaction vessel 1. Therefore, the present inventor selected the material and thickness of the reaction vessel to change the thermal conductivity, to produce a plastic optical fiber preform based on the above embodiment,
The relationship between the thermal conductivity of the reactor and the transmission loss was studied.

[0023]

Embodiment 1 FIG. 6 is a view showing a reaction vessel used in this embodiment. The reaction vessel 1-1 has a thickness t:
1.0mm, an inner diameter D _i: 27mm, outer diameter D _o: 29mm,
2. A length L: formed of a quartz glass tube having a length of 60 cm, and the heat conductivity of the tube wall of the quartz glass at normal pressure (hereinafter the same).
1 × 10 ^-2 cal / sec · ° C. A solution containing 0.15% by weight of methyl methacrylate as a monomer, 0.15% by weight of n-butyl mercaptan as a chain transfer agent, and 0.5% by weight of perbutyl II as a polymerization initiator is placed in the reaction vessel 1-1, and the opening is sealed. The polymerization was carried out horizontally while rotating at 1500 rpm for 20 hours in the air at 75 ° C. Inside the reaction vessel 1-1, an outside diameter of 27 mm and an inside diameter of 10
Thus, a clad made of the first tubular polymer 10 mm was obtained.

Next, in the hollow portion of the first tubular polymer 10 formed inside the reaction vessel 1-1 as described above, methyl methacrylate and diphenyl sulfide as monomers are chain-transferred at a weight ratio of 5: 1. A mixed solution of 0.15% by weight of n-butyl mercaptan as an agent and 0.5% by weight of perbutyl II as a polymerization initiator was added. After that, the opening is sealed, placed horizontally, and placed in an atmosphere at 85 ° C. for 20 hours, 1
Polymerization was performed while rotating at 500 rpm to produce a core made of the cylindrical polymer 11. As a result, the outer diameter is 27 m.
m, a cylindrical plastic optical fiber preform having an inner diameter of 7 mm was obtained.

This cylindrical preform was stretched at 50 g while being heated to produce a plastic optical fiber having a diameter of 0.75 mm. The transmission loss of this optical fiber was measured using a white light source and a spectrum analyzer.
At 0 nm, a very low loss of 150 dB / km was obtained.

(Embodiment 2) Next, a case where a plastic optical fiber preform is manufactured using the reaction vessel 1-2 will be described. The reaction vessel 1-2, in the configuration shown in FIG. 6, the thickness t: 2.5 mm, inner diameter D _i: 27 mm, outer diameter D _o: 32 mm, Length L: is formed by a quartz glass tube of 60cm, quartz glass The thermal conductivity of the tube wall is 1.2 × 10 ^-2
cal / sec · ° C. Using this reaction vessel 1-2, the cladding and the core were polymerized in the same manner as in Example 1 to obtain an outer diameter of 27.
A cylindrical plastic optical fiber preform having a diameter of 7 mm and an inner diameter of 7 mm was produced.

This cylindrical preform was stretched at 50 g while being heated to produce a plastic optical fiber having a diameter of 0.75 mm. The transmission loss of this optical fiber was measured using a white light source and a spectrum analyzer.
At 0 nm, a low loss of 160 dB / km was obtained.

(Embodiment 3) Next, a case where a plastic optical fiber preform is manufactured using the reaction vessel 1-3 will be described. The reaction vessel 1-3, in the configuration shown in FIG. 6, the thickness t: 2.5 mm, inner diameter D _i: 27 mm, outer diameter D _o: 32 mm, Length L: is formed by 60cm stainless steel tube, the tube of stainless steel The thermal conductivity of the wall is 7.2 × 10 ^-2
cal / sec · ° C. Using this reaction vessel 1-3, the clad and the core were polymerized in the same manner as in Example 1 to obtain an outer diameter of 27.
A cylindrical plastic optical fiber preform having a diameter of 7 mm and an inner diameter of 7 mm was produced.

This cylindrical preform was stretched at 50 g while heating to produce a plastic optical fiber having a diameter of 0.75 mm. The transmission loss of this optical fiber was measured using a white light source and a spectrum analyzer.
At 0 nm, a very low loss of 150 dB / km was obtained.

(Embodiment 4) Next, a case where a plastic optical fiber preform is manufactured using the reaction vessel 1-4 will be described. In the configuration shown in FIG. 7, the reaction vessel 1-4 has a thickness t _{i of} 1.0 mm, an inner diameter d _{i of} 27 mm,
Outer diameter d _o: 29 mm, Length L: is formed by a quartz glass tube of 60cm, inner diameter to the outer periphery of the quartz glass tube D _i: 29.
It is a configuration covered with a copper tube having a diameter of 4 mm, an outer diameter D _{o of} 39.4 mm, and a length L of 60 cm. The thermal conductivity of the quartz glass and copper tube walls is 3.1 × 10 ⁻² cal / sec · ° C. and 4.9 × 10 ⁻¹ cal / sec · ° C., respectively. This reaction vessel 1
Using No. 4, a clad and a core were produced in the same manner as in Example 1 to obtain a cylindrical plastic optical fiber preform having an outer diameter of 27 mm and an inner diameter of 7 mm.

The cylindrical preform was stretched at 50 g while being heated to produce a plastic optical fiber having a diameter of 0.75 mm. The transmission loss of this optical fiber was measured using a white light source and a spectrum analyzer.
At 0 nm, the loss was as low as 150 dB / km.

(Example 5) Next, a case where a plastic optical fiber preform is manufactured using the reaction vessel 1-5 will be described. The reaction vessel 1-5, in the configuration shown in FIG. 7, the outer thickness t _o: 1 mm, inner diameter D _i: 28mm, outer diameter D _o: 29 mm, Length L: is formed by 60cm graphite tube, the graphite The inner surface of the tube is coated with silicon carbide having a thickness t _{i of} 0.5 mm. The thermal conductivities of the graphite and silicon carbide tube walls are 3.5 × 10 ⁻² cal / sec · ° C. and 4.8 × 10 ⁻¹ cal / sec · ° C., respectively. This reaction vessel 1
Using No. 5, the cladding and the core were polymerized in the same manner as in Example 1 to prepare a cylindrical plastic optical fiber preform having an outer diameter of 27 mm and an inner diameter of 7 mm.

This cylindrical preform was stretched at 50 g while being heated to produce a plastic optical fiber having a diameter of 0.75 mm. The transmission loss of this optical fiber was measured using a white light source and a spectrum analyzer.
At 0 nm, the loss was as low as 150 dB / km.

(Comparative Example 1) Next, a case where a plastic optical fiber preform is manufactured using the reaction vessel 1-6 will be described. The reaction vessel 1-6, in the configuration shown in FIG. 6, the thickness t: 3.5 mm, inner diameter D _i: 27 mm, outer diameter D _o: 34 mm, Length L: is formed by a quartz glass tube of 60cm, quartz glass The thermal conductivity of the tube wall is 0.9 × 10 ^-2
cal / sec · ° C. Using this reaction vessel 1-6, the clad and the core were polymerized in the same manner as in Example 1 to obtain an outer diameter of 27.
A cylindrical plastic optical fiber preform having a diameter of 7 mm and an inner diameter of 7 mm was produced.

This cylindrical preform was stretched at 50 g while being heated to produce a plastic optical fiber having a diameter of 0.75 mm. The transmission loss of this optical fiber was measured using a white light source and a spectrum analyzer.
At 0 nm, it was remarkably large at 220 dB / km.

(Comparative Example 2) Next, a case where a plastic optical fiber preform is manufactured using the reaction vessel 1-7 will be described. The reaction vessel 1-7, in the configuration shown in FIG. 6, the thickness t: 5.0 mm, inner diameter D _i: 27 mm, outer diameter D _o: 37 mm, Length L: is formed by a quartz glass tube of 60cm, quartz glass The thermal conductivity of the tube wall is 0.6 × 10 ^-2
cal / sec · ° C. Using this reaction vessel 1-7, the cladding and the core were polymerized in the same manner as in Example 1 to obtain an outer diameter of 27.
A cylindrical plastic optical fiber preform having a diameter of 7 mm and an inner diameter of 7 mm was produced.

This cylindrical preform was stretched at 50 g while heating to produce a plastic optical fiber having a diameter of 0.75 mm. The transmission loss of this optical fiber was measured using a white light source and a spectrum analyzer.
It increased to 350 dB / km at 0 nm, and could not be used as a transmission line.

[0038]

According to the method for producing a plastic optical fiber preform according to the present invention, the thermal conductivity propagating between the inner wall surface and the outer wall surface of the reaction vessel is set to 1.0 × 10 ⁻² cal / sec · ° C. or more. , The heat of reaction generated by the polymerization reaction can be quickly released. Therefore, the polymerization solution can be maintained at a predetermined temperature and a certain polymerization reaction can be performed.

In the reaction vessel of the present invention, since the thermal conductivity of the vessel is 1.0 × 10 ⁻² cal / sec · ° C. or higher, it is possible to supply heat for promoting the polymerization reaction to the polymerizable solution. And the heat of reaction is released quickly. Therefore, the polymerization reaction can be performed while maintaining the polymerizable solution at a predetermined temperature.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a reaction vessel used in the present embodiment.

FIG. 2 is a diagram showing another configuration of the reaction vessel used in the present embodiment.

FIG. 3 (a) is a diagram illustrating a method for producing a first tubular polymer, and FIG. 3 (b) is a diagram illustrating a first tubular polymer polymerized by this method.

FIG. 4 (a) is a diagram illustrating a method for producing a second tubular polymer, and FIG. 4 (b) is a diagram illustrating a second tubular polymer polymerized by this method.

FIG. 5 is a view showing a plastic optical fiber preform manufactured according to the embodiment.

FIG. 6 is a diagram showing a configuration of a reaction vessel in the present example.

FIG. 7 is a diagram showing another configuration of the reaction vessel in the present embodiment.

[Explanation of symbols]

1, 2, 3 ... reaction vessel, 10 walls, 11 hollow parts, 20 ...
1st tubular polymer, 21 ... second tubular polymer, 30 ... ring heater, A, B ... polymerizable solution, X ... central axis, d, D
... diameter, L ... length, t ... thickness

Claims (3)

[Claims] 1. A method for producing a plastic optical fiber preform in which a polymerizable solution is filled in a cylindrical or test tubular reaction vessel, and supplied heat for promoting a polymerization reaction of the polymerizable solution is polymerized. The polymerization reaction has a thermal conductivity of 1.0 × 10 ⁻² cal / sec ·
A method for producing a plastic optical fiber preform, wherein the reaction is performed in a reaction vessel having a thermal conductivity of not less than ° C., and heat generated by the polymerization reaction is released through an outer wall surface of the reaction vessel. 2. A reaction vessel for filling a polymerizable solution into a cylindrical or test tubular container and polymerizing the polymerizable solution to produce a plastic optical fiber preform. A reactor having a thermal conductivity propagating between a wall surface and an outer wall surface of 1.0 × 10 ⁻² cal / sec · ° C. or more. 3. The reaction vessel according to claim 2, wherein the reaction vessel is formed by coating a thin layer of silicon carbide on an inner surface of a graphite vessel.