JPH0875931A - Plastic optical fiber preform and its production - Google Patents

Abstract

PURPOSE: To obtain a plastic optical fiber preform from which fibers can be drawn with good workability by forming such a plastic optical fiber preform comprising a core and a clad having a lower refractive index than that of the core by polymerizing core-forming monomers in the clad having a hollow revolution body shape to obtain a specified range of weight average mol.wt. by GPC. CONSTITUTION: The optical fiber preform 10 consists of a core 11 and a clad 12 having lower refractive index than that of the core 11. The weight average mol.wt. measured by GPC(gel permeation chromatography) of polymers which constitute the core 11 and the clad 12 is specified to between 10000 and 300000. In the mol.wt. is <10000, cutting of the preform during drawing is easily caused and this makes drawing difficult. If the mol.wt. exceeds 300000, the preform is too hard even during heating, which makes drawing difficult. From the viewpoint of workability for drawing, the weight average mol.wt. is preferably between 30000 and 250000, and more preferably 50000 and 200000.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic optical fiber preform and its manufacturing method.

[0002]

2. Description of the Related Art A plastic optical fiber whose core and clad are both made of plastic is used for optical transmission at a short distance between devices for transmitting and receiving optical signals (for example, between electronic devices) to the extent that transmission loss is not a substantial problem. As a transmission line, it has a feature that it is easier to use than a glass optical fiber. In addition, the plastic optical fiber is usually used as a short-distance optical transmission line because it can be generally lower in cost than the glass optical fiber. A plastic optical fiber having such characteristics is particularly suitable for LAN (local area network), ISDN (in
Its importance is increasing in the concept of next-generation communication networks such as integrated service digital networks.

As a plastic optical fiber, an optical fiber having a refractive index distribution as schematically shown in FIG. 1, that is, a step index (SI) type optical fiber has been put into practical use.

In addition, as compared with the SI type optical fiber, it is possible to send a large amount of information per time (there is a large transmission capacity), and FIG. 2 shows an optical fiber having more suitable characteristics for communication. A graded index (GI) type optical fiber having a refractive index distribution as schematically shown has also been proposed.

A conventional method for producing a plastic optical fiber preform is, for example, Japanese Patent Laid-Open No. 4-97302.
As described in Japanese Patent Laid-Open Publication No. 2004-242242, a plastic optical fiber preform is produced by utilizing a so-called "gel effect" when a core is synthesized by using a plurality of materials having different reactivities after polymerizing a clad material. A method for producing is known.

[0006]

However, according to the study of the present inventor, when the plastic optical fiber preform manufactured by such a conventional method is used, the plastic optical fiber preform is drawn even if heat is applied during drawing. There was a problem that it was difficult to do.

An object of the present invention is to provide a plastic optical fiber preform which solves the above-mentioned problems of the prior art and a manufacturing method thereof.

Another object of the present invention is to provide a plastic optical fiber preform capable of being drawn with good workability and a method for manufacturing the same.

[0009]

As a result of earnest research by the inventor of the present invention, poor workability in drawing a conventional plastic optical fiber preform is caused by adjustment of molecular weight when obtaining a clad and / or core by polymerization. Was found to be insufficient.

The method for producing a plastic optical fiber preform according to the present invention is based on the above findings, and more specifically,
A method for producing a plastic optical fiber preform including a core and a clad having a refractive index lower than that of the core, wherein the core is formed by polymerizing a core-forming monomer in the clad having a hollow rotating body shape. And the clad has a weight average molecular weight of 10,000 or more by GPC (gel permeation chromatography) of 300 or more,
000 or less of the plastic optical fiber preform is formed.

According to the present invention, a core and a clad having a refractive index lower than that of the core are further provided, and the clad and the core have a weight average molecular weight of 10,000 by GPC (gel permeation chromatography). Provided is a plastic optical fiber preform characterized in that the above is not more than 300,000.

The present invention will be described below in detail with reference to the drawings as necessary.

(Plastic optical fiber preform) FIG.
It is a schematic perspective view which shows the one aspect | mode of a structure of the plastic optical fiber preform 10 of this invention. With reference to FIG. 3, the optical fiber preform 10 includes a core 11 and a clad 12 having a refractive index lower than that of the core 11.

In the present invention, the GPC of the polymer constituting the core 11 and the clad 12 of the optical fiber preform 10 is used.
The weight average molecular weight by (gel permeation chromatography) is 10,000 or more and 300,000 or less.
If the weight average molecular weight is less than 10,000, disconnection is likely to occur during the drawing of the optical fiber preform, making it difficult to draw. On the other hand, the weight average molecular weight is 300,0.
When it exceeds 00, the base material becomes too hard even when heated, and it becomes difficult to perform good drawing. From the viewpoint of workability during drawing, the weight average molecular weight is 30,000 or more 2
50,000 or less (further 50,000 or more 200,0
00 or less) is preferable.

In the present invention, the weight average molecular weight of the polymer constituting the core 11 and the clad 12 of the optical fiber preform 10 can be measured, for example, as follows.

<Measurement Method of Weight Average Molecular Weight> The entire plastic optical fiber preform whose average molecular weight is to be measured is dissolved in tetrahydrofuran (THF) to a concentration of 0.1.
Use a THF solution of about mg / ml.

The THF solution thus obtained is passed through a membrane filter (for example, a membrane filter manufactured by Millipore), if necessary, and then introduced into a GPC measurement system to perform GPC analysis. The weight average molecular weight of the optical fiber preform is obtained based on the analysis result. This G
For PC analysis, for example, the following measurement conditions are preferably used.

GPC device: Tosoh Corp., trade name: HLC-8020 GPC column: Tosoh Corp., trade name: TSK gel 4000HXL TSK gel 2500HXL TSK gel 2000HXL (3 connected) (inner diameter 7.8 mm x length 300 mm ( Column bath temperature: 40 ° C. Mobile phase: THF Flow rate: 1.0 ml / min Detector: RI (refractive index) Data processing device: Tosoh Corp., trade name: CP-8000 In the present invention, core 11 has a weight average molecular weight (M _R ) of 10,000 or more and 300,000.
The following is preferred. Further, the weight average molecular weight (M _D ) of the polymer constituting the clad 12 is also 10,000.
It is preferably 300,000 or less. The weight average molecular weight of such core 11 or clad 12 is also
The weight average molecular weight of the whole base material 10 can be measured in the same manner.

In the present invention, the ratio M _D / M _R of the above M _R and M _D is about 0.8 to 1.2, and more preferably 0.9 to 1.2.
It is preferably about 1.1.

In the present invention, the method for obtaining the above-mentioned specific molecular weight is not particularly limited.
1 and / or the clad 12 is polymerized in the presence of a polymerization initiator and / or a chain transfer agent that terminates the polymerization reaction, thereby further adjusting the amount of the polymerization initiator and / or the chain transfer agent. Therefore, it is preferable to obtain the above-mentioned specific molecular weight.

In the present invention, as shown in FIG. 3, the diameter D ₁ of the core portion 11 is 80% or more of the cladding diameter D ₂ from the viewpoint that a desired GI type distribution can be easily obtained. Is more preferable, and 85% or more (particularly 90% or more) is more preferable.

(Method for producing optical fiber preform) Next, a preferred embodiment of the method for producing the optical fiber preform 10 having a specific molecular weight as described above (the method for producing the optical fiber preform of the present invention) will be described. To do.

In the method for producing an optical fiber preform according to the present invention, a composition containing at least a high refractive index dopant and a core (forming) monomer is polymerized in a plastic hollow rotating body corresponding to the clad portion 12. Preferably.

In such a polymerization reaction for forming a core, the chain carrier is increased due to the increase in the viscosity of the oligomer or polymer derived from the core monomer.
r; For example, based on the so-called "gel effect" in which diffusion of polymer-grown radicals is inhibited, the core monomer is preferentially subjected to polymerization, so that the polymer having a low refractive index is first (the core center part). Generated from the outside)
A core portion 11 having a GI type refractive index distribution as shown in FIG.
Can be obtained. That is, due to the gel effect, the polymerization of the core proceeds from the core / cladding interface toward the center, but at this time, the high refractive index dopant is concentrated in the center because the molecular size is larger than that of the monomer.
Based on this, a GI type refractive index distribution is formed.

In the present invention, as long as it is possible to obtain the above-mentioned "specific molecular weight" as the optical fiber preform 10, the "clad portion 12" to be used in the core forming reaction is used.
May be prepared separately from the core part 11 or may be obtained by polymerization itself. When the clad is formed by polymerization, the above-mentioned core forming reaction may be carried out separately from the clad forming reaction or may be carried out continuously with the clad forming reaction.

The clad portion 12 can be obtained, for example, by carrying out a polymerization reaction in a container having a hollow rotating body shape.

Next, an embodiment of the present invention in which both the clad 12 and the core 11 are formed by polymerization will be described.

First, a clad is formed by polymerization in a hollow cylinder (for example, a glass container). More specifically, a clad-forming composition containing at least a monomer (organic low molecular weight material) forming a clad and a polymerization initiator is injected into the hollow cylinder, and the clad is rotated while rotating the hollow cylinder. To form. The amount of the polymerization initiator used is
0.001 to the total amount of the clad-forming monomer
The amount is preferably about 1.0 part by weight, more preferably about 0.01 to 0.3 part by weight (particularly about 0.05 to 0.15 part by weight). The amount of the polymerization initiator used during the clad polymerization is 1.
If it exceeds 0 part by weight, the polymerization rate is too fast and foaming is likely to occur. On the other hand, when the amount of the polymerization initiator used is less than 0.001 part by weight, the molecular weight of the produced polymer tends to be small, and the base material is likely to be broken during the drawing and the drawing becomes difficult.

In the polymerization for forming the clad,
A chain transfer agent may be used if necessary. The chain transfer agent is used in an amount of about 0.001 to 1.0 part by weight, and more preferably 0.01 to 1.0 part by weight, based on the entire clad-forming monomer.
It is preferably about 0.3 parts by weight (particularly about 0.05 to 0.15 parts by weight). When the amount of the chain transfer agent used in the clad polymerization exceeds 1.0 part by weight, the molecular weight tends to be small and the base material is easily broken during the drawing.
It is difficult to draw a line. On the other hand, the amount of chain transfer agent used is 0.0
If it is less than 01 parts by weight, the molecular weight of the produced polymer tends to be large, and the base material is too hard to be drawn easily.

The inner diameter of the hollow cylindrical body used for forming the clad is the same as the plastic fiber base material 1 to be formed.
It depends on the outer diameter of 0. When forming a clad by polymerization, the number of rotations of the hollow cylinder is 10,000 rpm or less (further, about 100 to 5000 rpm, particularly 500 to
It is preferably about 2000 rpm).

Then, the tubular clad formed by the above polymerization is taken out from the hollow cylindrical container, and at least the core-forming monomer and the low molecular weight compound having a high refractive index (high refractive index dopant) are placed in the clad. A core-forming composition containing a polymerization initiator is injected to perform core polymerization.

The amount of the polymerization initiator used is 0.001 to 1 with respect to the entire core-forming monomer (when the high refractive index dopant described later is used, the total of (monomer + high refractive index dopant)). 0.0 parts by weight, more preferably 0.01 to
It is preferably about 0.3 parts by weight (particularly about 0.05 to 0.15 parts by weight). When the amount of the polymerization initiator used in the core polymerization exceeds 1.0 part by weight, the polymerization rate is too fast and foaming is likely to occur. On the other hand, when the amount of the polymerization initiator used is less than 0.001 part by weight, the molecular weight of the produced polymer tends to be small, and the base material is liable to be broken during the drawing, and continuous drawing (drawing) is performed. Becomes difficult.

In the polymerization for forming the core, a chain transfer agent may be used if necessary. The amount of the chain transfer agent used is 0.001 to 1.0% by weight with respect to the whole core-forming monomer (the whole of (monomer + high-refractive-index dopant) when a high-refractive-index dopant described later is used). It is preferably about 0.1 part by weight, more preferably about 0.01 to 0.3 part by weight (particularly about 0.05 to 0.15 part by weight). When the amount of the chain transfer agent used in the core polymerization exceeds 1.0 part by weight, the molecular weight tends to be small, and the base material is easily broken during the drawing, which makes the drawing difficult. on the other hand,
When the amount of the chain transfer agent used is less than 0.001 part by weight, the molecular weight of the produced polymer tends to be large, and the base material is too hard to be drawn easily.

The number of revolutions of the clad (which functions as a container for forming the core) at the time of forming the core is 10,000 rp.
m or less (further, about 100 to 5000 rpm, especially 5
It is preferably about 00 to 2000 rpm).

(Polymer for Clad) In the present invention, the polymer A (refractive index: N _a ) which should constitute the clad 12 is used.
As the above, it is possible to use a known transparent polymer without particular limitation. For example, a homopolymer of methyl methacrylate (polymethyl methacrylate: PMMA),
Polycarbonate (PC); or a transparent copolymer of methyl methacrylate and another monomer can be used. Examples of such "other monomers" include monofunctional (meth) acrylates, fluorinated alkyl (meth) acrylates, polyfunctional (meth) acrylates,
Acrylic monomers such as acrylic acid and methacrylic acid; styrene monomers such as styrene and chlorostyrene can be preferably used.

Among the above-mentioned polymers, polymethylmethacrylate (refractive index n = 1.490) or polycarbonate (n = 1.59) can be particularly preferably used.

(Polymer for Core) In the present invention, as the polymer B (refractive index: N _b ) which constitutes the core 11, a known transparent polymer is particularly used, like the polymer for clad. Although it can be used without limitation, for example, homopolymer of methyl methacrylate (polymethyl methacrylate: PMMA), polycarbonate (P
C); Alternatively, a transparent copolymer of methyl methacrylate and another monomer can be used. Examples of such “other monomer” include monofunctional (meth) acrylates, fluorinated alkyl (meth) acrylates, polyfunctional (meth) acrylates, acrylic acid such as acrylic acid and methacrylic acid. Monomers: Styrene-based monomers such as styrene and chlorostyrene can be preferably used.

Among the above-mentioned polymers, polymethylmethacrylate (refractive index n = 1.490) or polycarbonate (n = 1.59) can be particularly preferably used.

In the present invention, the material forming the core 11 is preferably the same material as the material of the clad 12 in consideration of the adhesiveness between the clad and the core. More specifically, in such an embodiment, it is preferable to use a material containing 90% or more (more preferably 95% or more) of a component (monomer or the like) of the clad material as the base polymer constituting the core (here, , High refractive index compounds are not included.)

In such an embodiment, as the material for forming the core, a polymer having the same quality as that of the polymer A as the material for forming the clad is preferably used. here,
“Homogeneous” means that the monomer that constitutes the core polymer B is
It means that the monomer constituting the polymer A of the clad is substantially common, and more specifically, 90 mol% or more (preferably 95 mol% or more) of the monomer constituting the polymer B of the core is It is the same as the monomer that constitutes the polymer A of the clad.

In the case of a copolymer (containing two or more kinds of monomers), the monomers common to the core and the clad are M ₁ and M _2, and the monomer composition of the clad is {M ₁ (a ₁ mol) + M ₂ (b ₁ mol)}, the monomer composition of the core (meaning the base polymer, not including high refractive index compounds)
Is {M ₁ (a ₂ mol) + M ₂ (b ₂ mol)},
0.9 ≦ (a ₂ + b ₂ ) / (a ₁ + b ₁ ) ≦ 1.1, and further 0.95 ≦ (a ₂ + b ₂ ) / (a ₁ + b ₁ ) ≦ 1.
It is preferably 0.

The melting point of the material forming the core is preferably substantially equal to the melting point of the material forming the clad. More specifically, assuming that the melting point of the core material is m _R and the melting point of the clad material is m _D , | m _R −m _D | (absolute value) is 1
It is preferably 0 ° C. or lower (that is, the value of (m _R −m _D ) is within ± 10 ° C.).

(High Refractive Index Dopant) In the present invention,
As the material (high refractive index dopant) having a refractive index higher than that of the polymer B (N _b ), a material having a refractive index (N _c ) higher than that of the polymer is used without particular limitation. It is possible.

The molecular weight of the high refractive index dopant is not particularly limited, as long as it gives a desired refractive index distribution and can coexist stably with the polymer B. Further, the high refractive index dopant itself may have a polymerizable functional group (for example, an unsaturated polymerizable group such as vinyl group CH ₂ ═CH—). That is, the high refractive index dopant may be a monomer or a mixture thereof, or may be an oligomer or a polymer.

The refractive index N _b of the polymer B constituting the core,
The absolute value | N _c −N _b | of the difference from the refractive index (N _c ) of the high refractive index dopant is preferably 0.01 or more, and 0.02 or more (particularly 0.03 or more). More preferably,

In the present invention, when the polymer B is polymethylmethacrylate (PMMA) (N _a = n = 1.49), a high refractive index dopant which can be suitably used in combination with the polymer B Specific examples of phthalic acid butylbenzyl ester (N _b = n = 1.53
6), 2-phenylethyl acetate (n = 1.51), dimethyl phthalate (n = 1.515), diphenyl sulfide (n = 1.635), vinyl benzoate (n = 1.577),
Examples thereof include benzyl methacrylate (n = 1.568) and diallyl phthalate (n = 1.518). In the above specific examples, vinyl benzoate, benzyl methacrylate, and diallyl phthalate are high refractive index dopants having a polymerizable functional group.

The amount of the high-refractive-index dopant used is not particularly limited as long as a suitable GI type refractive index distribution can be formed, but normally, it is 10 with respect to the whole core-forming monomer (monomer + high-refractive-index dopant). It is preferably about 50 to 50 parts by weight (further, about 20 to 40 parts by weight).

(Initiator) The polymerization initiator which is optionally used in the polymerization of the clad and the core is a weight average molecular weight of 10,000 to 300, as the above-mentioned plastic base material.
There is no particular limitation as long as 000 is given, and it is possible to appropriately select and use from known polymerization initiators.

In the present invention, more specifically, for example, an azo compound or a peroxide can be preferably used. Examples of the azo compound include azobisisobutyronitrile (AIBN). On the other hand, as the above-mentioned peroxide, either an inorganic type or an organic type can be used, and examples thereof include benzoyl peroxide and di-tert-butyl peroxide.

(Chain Transfer Agent) The chain transfer agent which is optionally used in the polymerization of the clad and the core is a weight average molecular weight of 10,000 to 30 as the above-mentioned plastic base material.
There is no particular limitation as long as it gives 2,000, and it is possible to use it by appropriately selecting from known chain transfer agents. Such known chain transfer agents include, for example, benzene,
Examples thereof include aromatic hydrocarbons such as isopropylbenzene; halides such as chloroform and carbon tetrachloride; and mercapto compounds (compounds having a —SH group) such as butyl mercaptan.

In the present invention, among these, mercapto compounds are preferably used and include butyl mercaptan (n-C ₄ H ₉ SH) and amyl mercaptan (n-C).
₅ H ₁₁ SH) is particularly preferably used.

(Drawing Method) Next, the above optical fiber preform 1
A method of drawing 0 into an optical fiber will be described with reference to the schematic sectional view of FIG. FIG. 4 is a schematic sectional view showing a plastic optical fiber drawing device.

Referring to FIG. 4, a heater 42 and a core tube 43 are provided in the line drawing furnace main body 41. When such a drawing device is used, the resin base material (preform) 10 for optical fiber is passed through the upper opening 41a of the furnace body 41.
Is inserted, heated in a heating furnace 41, melted, and drawn or spun into a plastic optical fiber 46 having a predetermined outer diameter. The plastic optical fiber 46 thus drawn is drawn out from the lower opening portion 41b of the furnace 41, and thereafter, the outer diameter of the optical fiber 46 is measured by the outer diameter measuring device (monitor) 44 while the optical fiber 46 is being measured.
Is taken up by the take-up device 45.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[0055]

Example 1 A hollow cylindrical glass tube (inner diameter: 20 mm, outer diameter: 23)
mm, length: 400 mm) was prepared, and 100 parts by weight of methyl methacrylate (MMA) as a clad-forming monomer and azobisisobutyronitrile (AIBN) 0 as a polymerization initiator were placed in the glass tube held horizontally. and .1 part by weight, a chain transfer agent serving as butyl mercaptan (n-C ₄ H ₉
25 ml of a clad-forming composition containing 0.1 part by weight of SH) was injected, and both ends of the glass tube were sealed with vinyl tape. Then, while rotating the glass tube at 3500 rpm, the glass tube was heated at 70 ° C. for 12 hours to polymerize the above-mentioned monomer to polymethylmethacrylate (PMMA).
The clad was formed.

After the glass tube on the outside of the clad formed above was broken and removed, the clad tube obtained was held horizontally, and methyl methacrylate 7 was placed in the clad tube.
0 parts by weight, 30 parts by weight of diphenyl sulfide as a high refractive index dopant, 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator, and 0.1 parts by weight of butyl mercaptan as a chain transfer agent. Composition 100
After injecting ml and shielding with vinyl tape, 35
While rotating at 00 rpm, heating was performed at 70 ° C. for 12 hours to polymerize the above monomers to form a core made of polymethylmethacrylate (PMMA) to obtain a plastic optical fiber preform.

The entire base material thus produced was
It was dissolved in tetrahydrofuran (THF) and the concentration was adjusted to 0.
A THF solution of approximately 1 mg / ml was introduced into the following GPC measurement system for GPC analysis, and the weight average molecular weight of the optical fiber preform was determined based on the GPC analysis result.
The molecular weight was 200,000.

<GPC measurement conditions> GPC device: Tosoh Corp., trade name: HLC-8020 GPC column: Tosoh Corp., trade name: TSK gel 4000HXL TSK gel 2500HXL TSK gel 2000HXL (3 connected) (inner diameter 7.8 mm) Column length: 40 ° C Mobile phase: THF Flow rate: 1.0 ml / min Detector: RI (refractive index) Data processing device: Tosoh Corp., trade name: CP-8000 Above The plastic optical fiber preform 10 having a GI type refractive index distribution manufactured in 1 above was drawn by using a drawing device as shown in FIG. 4 to manufacture an optical fiber. At the time of this drawing, the temperature inside the furnace core tube was set to 200 ° C.
Insert the preform 10 into No. 1 and linear velocity 10m / min
Was drawn to prepare an all-plastic optical fiber (POF) having an outer diameter of 650 μm and a length of 100 m.

The refractive index distribution in the radial direction of the optical fiber thus manufactured was measured by the NFP method (measurement device: manufactured by York Co., Ltd.,
The GI as shown in the graph of FIG. 5 (the horizontal axis indicates the distance from the center of the core with a relative value with the radius of the optical fiber being 1) when measured with a product name: FCM-1000).
A mold refractive index profile was obtained.

Further, the transmission loss of the optical fiber was measured and found to be 200 dB / km at a wavelength of 650 nm.

In this transmission loss evaluation, a laser diode (LD) having a wavelength of 0.658 μm was used as a light source, and a spectroscope (trade name: FML-10 manufactured by Operex) was used.
The transmission loss was evaluated by a cutback method using a zero wavelength loss measuring instrument (including a power meter). (For this cutback method, Katsuhiko Okubo "Optical fiber technology in the ISDN era", Rikagakusha, 1989, (3-15) to (3
-16) can be referred to).

Example 2 As a clad-forming monomer composition to be injected into a hollow cylindrical glass tube, 100 parts by weight of methyl methacrylate and benzoyl peroxide (BP) as a polymerization initiator were used.
O) 0.1 part by weight and a composition comprising 0.1 part by weight of butyl mercaptan as a chain transfer agent were used to form a clad tube made of PMMA by the same method as in Example 1, and As a core-forming monomer composition to be injected into the PMMA-made clad tube, 80 parts by weight of methyl methacrylate, 20 parts by weight of diphenyl sulfide as a high refractive index dopant, and 0.
1 part by weight and 0.1 as a chain transfer agent butyl mercaptan
A plastic optical fiber preform was obtained by forming a PMMA core having a GI type refractive index profile by the same method as in Example 1 except that a composition containing 1 part by weight was used.

The weight average molecular weight of the optical fiber preform produced as described above was measured by the same method as in Example 1 and found to be 150,000.

An optical fiber was obtained by drawing the above base material in the same manner as in Example 1. The optical fiber thus manufactured had a refractive index distribution similar to that of the optical fiber obtained in Example 1. Furthermore, when the transmission loss of this optical fiber was measured by the same method as in Example 1, it was 200 dB / km at a wavelength of 650 nm.

Example 3 As a clad-forming monomer composition to be injected into a hollow cylindrical glass tube, 100 parts by weight of methyl methacrylate and azobisisobutyronitrile (AI) as a polymerization initiator were used.
BN) and 0.1 parts by weight, except for using a composition comprising a chain transfer agent serving as amyl mercaptan _{(n-C 5 H 11 SH} ) 0.15 parts by weight, PM in the same manner as in Example 1
60 parts by weight of methyl methacrylate, 40 parts by weight of diphenyl sulfide as a high-refractive index dopant, as a core forming monomer composition to be injected into the PMMA-made cladding tube Azobisisobutyronitrile (AIBN) as an initiator
0.1 parts by weight, except for using a composition comprising a chain transfer agent serving as amyl mercaptan _{(n-C 5 H 11 SH} ) 0.15 parts by weight, the refractive of the GI-type in the same manner as in Example 1 A PMMA core having a rate distribution was formed to obtain a plastic optical fiber preform.

The weight average molecular weight of the optical fiber preform thus produced was measured by the same method as in Example 1 and found to be 50,000.

An optical fiber was obtained by drawing the above base material in the same manner as in Example 1. The optical fiber thus manufactured had a refractive index distribution similar to that of the optical fiber obtained in Example 1. Furthermore, when the transmission loss of this optical fiber was measured by the same method as in Example 1, it was 200 dB / km at a wavelength of 650 nm.

Comparative Example 1 As a clad-forming monomer composition to be injected into a hollow cylindrical glass tube, 100 parts by weight of methyl methacrylate and azobisisobutyronitrile (AI) as a polymerization initiator were used.
BN) 0.2 part by weight and a chain transfer agent butyl mercaptan 0.1 part by weight except that a composition was used to form a clad tube made of PMMA by the same method as in Example 1, and As a core-forming monomer composition to be injected into the PMMA-made clad tube, 70 parts by weight of methyl methacrylate, 30 parts by weight of diphenyl sulfide as a high-refractive-index dopant, and azobisisobutyronitrile as a polymerization initiator. A PMMA core having a GI type refractive index distribution was formed by the same method as in Example 1 except that a composition consisting of 2 parts by weight and 0.1 part by weight of a chain transfer agent, butyl mercaptan, was used. As a result, a plastic optical fiber preform was obtained. In the produced preform, air bubbles 13 were observed as shown in the schematic perspective view of FIG.

The weight average molecular weight of the optical fiber preform produced as described above was measured by the same method as in Example 1 and found to be 400000.

An optical fiber was obtained by drawing the above base material in the same manner as in Example 1. The optical fiber thus manufactured had a refractive index distribution similar to that of the optical fiber obtained in Example 1. Furthermore, when the transmission loss of this optical fiber was measured by the same method as in Example 1, it was 400 dB / km at a wavelength of 650 nm.

Comparative Example 2 As a clad-forming monomer composition to be injected into a hollow cylindrical glass tube, 100 parts by weight of methyl methacrylate and 0.1 of azobisisobutyronitrile as a polymerization initiator were used.
A cladding tube made of PMMA was formed in the same manner as in Example 1 except that a composition consisting of 1 part by weight and 0.2 part by weight of butyl mercaptan as a chain transfer agent was used, and the cladding made of PMMA. 80 parts by weight of methyl methacrylate, 20 parts by weight of diphenyl sulfide as a high refractive index dopant, and 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator, as a core-forming monomer composition to be injected into a tube. P having a GI type refractive index distribution was prepared in the same manner as in Example 1 except that a composition containing 0.2 part by weight of a chain transfer agent, butyl mercaptan, was used.
A core made of MMA was formed to obtain a plastic optical fiber preform.

The weight average molecular weight of the optical fiber preform thus produced was measured in the same manner as in Example 1 and found to be 8,000.

The base material thus produced was drawn by the same method as in Example 1 to obtain an optical fiber. However, the base material became too soft due to heating during drawing, It was not possible to draw because the wire was broken during seed removal (operation of initial drawing).

Comparative Example 3 As a cladding-forming monomer composition to be injected into a hollow cylindrical glass tube, 100 parts by weight of methyl methacrylate and 0.0 of azobisisobutyronitrile as a polymerization initiator were used.
3 parts by weight and 0.1 as a chain transfer agent butyl mercaptan
A clad tube made of PMMA was formed by the same method as in Example 1 except that a composition consisting of 1 part by weight was used.
Further, as a core-forming monomer composition to be injected into the PMMA clad tube, methyl methacrylate 60 is used.
1 part by weight, 40 parts by weight of diphenyl sulfide as a high refractive index dopant, 0.03 part by weight of azobisisobutyronitrile as a polymerization initiator, and 0.1 part by weight of butyl mercaptan as a chain transfer agent. Other than that,
By the same method as in Example 1, a PMMA core having a GI type refractive index distribution was formed to obtain a plastic optical fiber preform.

The weight average molecular weight of the optical fiber preform thus produced was measured in the same manner as in Example 1 and found to be 7,000.

The above base material was drawn by the same method as in Example 1 to obtain an optical fiber. However, as in the case of Comparative Example 1, the base material was softened by heating during drawing. It was not possible to draw the wire because it was cut off when the seed was removed (operation of the initial drawing).

Comparative Example 4 As a cladding-forming monomer composition to be injected into a hollow cylindrical glass tube, 100 parts by weight of methyl methacrylate and 0.1 of azobisisobutyronitrile as a polymerization initiator were added.
Parts by weight and 0.03 as a chain transfer agent butyl mercaptan
A clad tube made of PMMA was formed by the same method as in Example 1 except that a composition consisting of 1 part by weight was used.
In addition, as the core-forming monomer composition to be injected into the PMMA clad tube, methyl methacrylate 70
1 part by weight, 30 parts by weight of diphenyl sulfide as a high refractive index dopant, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator, and 0.03 part by weight of butyl mercaptan as a chain transfer agent. Other than that,
By the same method as in Example 1, a PMMA core having a GI type refractive index distribution was formed to obtain a plastic optical fiber preform.

The weight average molecular weight of the optical fiber preform produced as described above was measured by the same method as in Example 1 and found to be 500,000.

The above base material was drawn in the same manner as in Example 1 to obtain an optical fiber. However, as in the case of Comparative Example 1, the base material was hard even when heated during drawing. It was too late to remove seeds (operation of initial drawing).

As shown in the above Examples and Comparative Examples, when manufacturing the plastic optical fiber preform,
(For example, by adjusting the amount of the polymerization initiator and / or the chain transfer agent in the clad polymerization and the core polymerization), the weight average molecular weight of the polymers constituting these is 10,000 or more 3
It has been found that by setting the amount to be less than or equal to 000, it is possible to produce a preform which can easily draw without causing bubbles in the preform.

[0081]

As described above, according to the present invention, the core and the clad having a refractive index lower than that of the core are used, and the weight average molecular weight of the clad and the core by GPC (gel permeation chromatography) is 1
There is provided a plastic optical fiber preform characterized by being in the range of 2,000 or more and 300,000 or less.

Further, according to the present invention, there is provided a method for producing a plastic optical fiber preform including a core and a clad having a refractive index lower than that of the core; A plastic optical fiber preform having a weight average molecular weight of 10,000 or more and 300,000 or less by GPC (gel permeation chromatography) of the core and the clad is formed by polymerizing a forming monomer. A method of manufacturing a plastic optical fiber preform is provided.

As a result, there is no problem in appearance (such as generation of bubbles in the fiber preform), and the plastic optical fiber preform is excellent in workability at the time of drawing, and the optical characteristics of the optical fiber are excellent. It is possible to provide an optical fiber preform that provides a fiber.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a refractive index distribution of a step index (SI) type fiber.

FIG. 2 is a schematic diagram showing a refractive index distribution of a graded index (GI) type fiber.

FIG. 3 is a schematic perspective view showing one embodiment of a plastic optical fiber preform of the present invention.

FIG. 4 is a schematic cross-sectional view showing an example of a drawing device that can be used for drawing the plastic optical fiber preform of the present invention.

5 is a graph showing the refractive index distribution in the radial direction of the optical fiber manufactured in Example 1. FIG.

6 is a schematic perspective view showing the appearance of a plastic optical fiber preform produced in Comparative Example 1. FIG.

[Explanation of symbols]

10 ... Plastic optical fiber preform, 11 ... Core, 12
... Clad, 13 ... Bubbles generated in the base material, 41 ... Drawing furnace main body, 41a ... Upper opening of the drawing furnace main body, 42 ... Heater, 43 ... Reactor tube, 44 ... Optical fiber outer diameter monitor, 4
5 ... Winding device, 46 ... Optical fiber.

Claims (13)

[Claims] 1. A method for producing a plastic optical fiber preform including a core and a clad having a refractive index lower than that of the core, wherein a monomer for forming a core is polymerized in the clad having a hollow rotating body shape. As a result, GPC (gel permeation chromatography) of the core and the clad is performed.
The weight average molecular weight is 10,000 or more 300,00
A method for producing a plastic optical fiber preform, which comprises forming a plastic optical fiber preform of 0 or less. 2. The method for producing a plastic optical fiber preform according to claim 1, wherein the clad is formed by polymerizing a clad-forming monomer in a container having a hollow rotating body shape. 3. The method for producing a plastic optical fiber preform according to claim 2, wherein the clad and core polymerization is performed in the presence of a chain transfer agent. 4. The method for producing a plastic optical fiber preform according to claim 3, wherein the chain transfer agent is a mercapto compound. 5. The method for producing a plastic optical fiber preform according to claim 4, wherein the chain transfer agent is butyl mercaptan. 6. The method for producing a plastic optical fiber preform according to claim 2, wherein the clad and core polymerization is carried out in the presence of a polymerization initiator. 7. The method for producing a plastic optical fiber preform according to claim 6, wherein the polymerization initiator is an azo compound or a peroxide. 8. The method for producing a plastic optical fiber preform according to claim 7, wherein the polymerization initiator is azobisisobutyronitrile (AIBN), benzoyl peroxide, or di-tert-butyl peroxide. 9. The chain transfer agent is used in an amount ratio of 0.05 parts by weight or more and 0.15 parts by weight or less with respect to the entire clad-forming monomer or core-forming monomer (100 parts by weight). 3. The method for producing a plastic optical fiber preform according to item 3. 10. The polymerization initiator is used in an amount ratio of 0.05 parts by weight or more and 0.15 parts by weight or less with respect to the entire clad-forming monomer or core-forming monomer (100 parts by weight). 6. The method for producing a plastic optical fiber preform according to 6. 11. A core refraction in which a high-refractive-index dopant having a higher refractive index than that of the homopolymer of the core-forming monomer is coexisted during the core polymerization, and the refractive index increases toward the central portion based on the gel effect. The method for producing a plastic optical fiber preform according to claim 1, wherein a graded index (GI) type plastic optical fiber preform is obtained by forming a rate distribution. 12. A core and a clad having a refractive index lower than that of the core, and G of the clad and the core.
A plastic optical fiber preform having a weight average molecular weight of 10,000 or more and 300,000 or less as measured by PC (gel permeation chromatography). 13. The plastic optical fiber preform according to claim 12, wherein a graded index (GI) type refractive index distribution in which the refractive index increases toward the central portion of the core is formed.