JPH09269424A - Production of plastic light transmission body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for production for obtaining a plastic light transmission body with which the complete prevention of the occurrence of cavities is made possible and which is uniform in the refractive index distribution in a longitudinal direction and high in dimensional accuracy. SOLUTION: In this process, a polymerizable raw material for a clad is packed into a pressurizable vessel consisting of a straight pipe as its essential part and a clad pipe along the longitudinal direction of the straight pipe is produced by centrifugal force. A core liquid consisting of a mixture composed of a polymerizable compd. which has the refractive index higher than the refractive index of the clad pipe and swells or dissolves this clad pipe is packed into the vessel described above. This core liquid is polymerized under pressurization by an inert gas.

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 transmission body having a predetermined refractive index distribution, and in particular, it is possible to completely prevent the generation of cavities and obtain a refractive index distribution in the longitudinal direction. The present invention relates to a manufacturing method for obtaining a uniform and highly accurate plastic optical transmission body.

[0002]

2. Description of the Related Art Among optical transmission materials, a plastic optical transmission material having a predetermined refractive index distribution is used as a rod lens or a plastic optical fiber. Since both the core and the clad of a plastic optical fiber are made of a plastic material, when compared with a silica optical fiber as a broadband plastic optical fiber, for example, it has excellent flexibility and a large diameter, so that end face treatment and connection are possible. Due to the ease of processing and the lower price, LA
Various applications as an optical signal medium such as N and ISDN have been studied. Among these, for example, JP-A-5-241
No. 036, a multimode gradient index plastic optical fiber (hereinafter referred to as [G
"I-type plastic optical fiber" is abbreviated as "optical signal medium" in the concept of next-generation communication networks because of its large transmission capacity.

As a method for manufacturing a plastic optical transmission body, for example, as disclosed in Japanese Patent Laid-Open No. 5-241036, a core liquid is filled in a cylindrical polymerization container made of a clad material, and this is rotated. By heating or irradiating energy rays (for example, ultraviolet rays, infrared rays, etc.) from the periphery while rotating at a uniform and appropriate speed by a method such as swelling and dissolving the inner wall of the polymerization container in the core liquid to proceed the polymerization reaction As disclosed in JP-A-6-194530, the core liquid is gradually supplied from above into a polymerization container made of a clad material, and the inner wall of the polymerization container is swollen and dissolved in the core liquid to carry out the polymerization reaction. There is a way to proceed.

[0004]

However, first of all,
The method disclosed in Japanese Unexamined Patent Publication No. 5-241036 has a drawback that cavities are easily formed inside the optical transmission medium due to volume contraction due to polymerization. In addition, JP-A-6-19
In the method disclosed in Japanese Patent No. 4530, it is very difficult to adjust the supply rate of the core liquid, the polymerization conditions, etc., and it takes a long time. If these adjustments are insufficient, the optical transmission medium is affected by gravity. There is a possibility that the refractive index distribution in the longitudinal direction becomes uneven, or a cavity is formed inside the optical transmission body. Furthermore, in this method, since the clad material used swells and dissolves in the core liquid, when the polymerization reaction of the core liquid is advanced by heating,
Depending on the heating conditions, the clad material may be deformed or damaged.

Therefore, when a plastic optical fiber or the like is manufactured using the plastic optical transmission body obtained by such a conventional manufacturing method, the optical transmission performance is inferior and the commercial value is impaired. Will end up.

The present invention has been made on the basis of such a point, and an object of the present invention is to completely prevent the generation of cavities and to obtain a uniform refractive index distribution in the longitudinal direction and to achieve dimensional accuracy. It is to provide a manufacturing method for obtaining a high plastic light transmission body.

[0007]

In order to achieve the above object, a method for producing a plastic optical transmission body according to the present invention comprises filling a pressurizable container having a straight pipe as an essential component with a polymerizable raw material for cladding. A mixture of a polymerizable compound and a non-polymerizable compound that produces a clad pipe along the longitudinal direction of the straight pipe by centrifugal force, has a higher refractive index than the clad pipe, and swells or dissolves the clad pipe The core liquid consisting of (3) is filled in the container, and the core liquid is polymerized under pressure with an inert gas.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As a pressurizable container used in the present invention, a straight pipe having a length comparable to that of a clad pipe and an inner diameter corresponding to the outer diameter of the clad pipe is provided as an essential component, and will be described later. Any structure may be used as long as it is provided with a pressurizing means capable of polymerizing the core liquid under pressure with an inert gas. For example, a straight pipe, a sealing lid for sealing one end of the straight pipe, and a hose connection portion that can pressurize by supplying the inert gas after replacing the residual air in the container with the inert gas. It is conceivable that it is composed of a sealing lid having the same. The constituent material is not particularly limited as long as it can withstand the heat when manufacturing the clad pipe, the heat when polymerizing the core liquid, the pressure and the like.

Examples of the polymerizable raw material for the clad used in the present invention include methyl methacrylate, ethyl methacrylate, benzyl methacrylate, phenyl methacrylate, 1,1,2-trifluoroethyl methacrylate, styrene, 4-methylcyclohexyl methacrylate. , Cyclohexyl methacrylate, furfuryl methacrylate, 1-phenylethyl methacrylate, 1-phenylcyclohexyl methacrylate, 1,
2-diphenylethyl methacrylate, o-chlorobenzyl methacrylate, diphenylmethyl methacrylate, pentachlorophenyl methacrylate, pentabromophenyl methacrylate, hexafluoroisopropyl-α-fluoroacrylate, trifluoroethyl-
α-fluoroacrylate, pentafluoropropyl-
Examples thereof include a monomer such as α-fluoroacrylate, or a mixture of two or more kinds of these monomers and three or more kinds.

In addition to these, for example, JP-A-8-58
No. 48, a monomer having a fluorine-containing alicyclic structure such as perfluoro (2,2-dimethyl-1,3-dioxole), or this monomer and tetrafluoroethylene, chlorotrifluoro. A mixture of monomers such as ethylene and perfluoro (methyl vinyl ether) to the extent that the resulting copolymer does not have crystals, perfluoro (allyl vinyl ether),
Monomers such as perfluoro (butenyl vinyl ether) (however, cyclopolymerization), or these monomers and monomers such as tetrafluoroethylene, chlorotrifluoroethylene, perfluoro (methyl vinyl ether),
The obtained copolymer is mixed to such an extent that it does not have crystals, and monomers such as perfluoro (2,2-dimethyl-1,3-dioxole), perfluoro (allyl vinyl ether) and perfluoro (butenyl vinyl ether) are used. Among them, a mixture of at least two kinds or the like can be mentioned.

The above raw materials include organic peroxides such as benzoyl peroxide, thermal polymerization radical initiators such as azobis compounds such as azobisisobutyronitrile and azobiscyclohexanenitrile, and ultraviolet rays such as benzoin methyl ether. A radical polymerization initiator, a chain transfer agent such as an alkyl mercaptan such as n-butyl mercaptan, and the like can be appropriately blended as necessary.

The core liquid used in the present invention comprises a mixture of a polymerizable compound that swells or dissolves the clad pipe and a non-polymerizable compound having a refractive index higher than that of the clad pipe. As the polymerizable compound that dissolves or swells the clad pipe, the above-mentioned polymerizable compound mainly containing the polymerizable raw material for the clad can be used. Examples of the non-polymerizable compound having a refractive index higher than that of the clad pipe include benzyl-n-butyl phthalate and 1-methoxyphenyl-1 when the polymerizable compound used is mainly composed of methyl methacrylate.
-Phenylethane, benzyl benzoate, bromobenzene, o-dichlorobenzene, m-dichlorobenzene,
1,2-dibromoethane, 3-phenyl-1-propanol and the like can be used, and the polymerizable compound used is hexafluoroisopropyl-α-fluoroacrylate, trifluoroethyl-α-fluoroacrylate or pentafluoropropyl. When the main component is -α-fluoroacrylate, phthalic acid di-n
-Butyl, diethyl phthalate and the like can be used.

When the clad pipe is made of an amorphous fluorine-containing polymer as disclosed in, for example, JP-A-8-5848, an aromatic ring such as a benzene ring is used. It is preferable to use a low molecular compound, an oligomer, a polymer or the like containing a halogen atom such as chlorine, bromine or iodine, or a bonding group such as an ether bond.

Specifically, 1,3-dibromotetrafluorobenzene, 1,4-dibromotetrafluorobenzene, 2-bromotetrafluorobenzotrifluoride, chloropentafluorobenzene, bromopentafluorobenzene, iodopentafluorobenzene and deca. Fluorobenzophenone, perfluoroacetophenone,
Oligomers consisting of monomers containing no hydrogen atom such as perfluorobiphenyl, chloroheptafluoronaphthalene, bromoheptafluoronaphthalene, tetrafluoroethylene, chlorotrifluoroethylene, dichlorodifluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ethers, and their monomers Of 2
More copolymerizable oligomer _{species, -CF 2 CF (CF 3)} O
Examples thereof include perfluoropolyether having a structural unit of — or — (CF ₂ ) nO— (n is an integer of 1 to 3).

The above core liquid contains organic peroxides such as benzoyl peroxide, thermal polymerization radical initiators such as azobis compounds such as azobisisobutyronitrile and azobiscyclohexanenitrile, and benzoin methyl ether. An ultraviolet radical polymerization initiator, a chain transfer agent such as an alkyl mercaptan such as n-butyl mercaptan, and the like can be appropriately blended as necessary.

In the present invention, first, a predetermined amount of the above-mentioned clad polymerizable raw material is filled in a straight pipe provided in a pressurizable container, and heating or energy rays (for example, from the surroundings) are applied from the periphery while applying centrifugal force to the straight pipe. , Ultraviolet rays, infrared rays, etc.) to promote the polymerization reaction to produce a clad pipe along a straight pipe. As the means for applying the centrifugal force, for example, a rotating device disclosed in Japanese Patent Laid-Open No. 5-241036 may be used. The temperature condition when the polymerization reaction proceeds by heating varies depending on the size of the obtained light transmission medium and the type of polymerizable raw material used, but, for example, when a typical methacrylate-based monomer is used. Preferably, it is 50 ° C to 150 ° C.
C, and more preferably 80 to 120 ° C. If it is lower than 50 ° C, the time required for production becomes extremely long, and if it exceeds 150 ° C, the polymerization reaction may proceed rapidly to cause foaming, which is not preferable.

Then, a clad pipe located in the container (straight pipe) is filled with a predetermined amount of the core liquid, and while being pressurized with an inert gas such as nitrogen gas or argon gas, heating or energy rays (for example, from the periphery) are used. , Ultraviolet rays, infrared rays, etc.) to accelerate the polymerization reaction.

The polymerization reaction of the core liquid proceeds while the inner wall portion of the clad pipe swells and dissolves in the core liquid. At this time, when the clad pipe used is thick and thick, the clad pipe is used. The amount of the chain transfer agent to be added to the polymerizable raw material during production is slightly increased, or as the thermal polymerization radical initiator at the time of polymerization of the core liquid, one that functions at a higher temperature is selected and added to the reaction temperature. It is preferable to promote swelling and dissolution of the inner wall of the clad pipe by raising the temperature. Incidentally, the non-polymerizable compound contained in the core liquid, although not directly involved in the polymerization reaction, since its content gradually increases from the inner wall portion of the clad pipe to the central portion throughout the polymerization reaction process,
The obtained plastic optical transmission body has a refractive index distribution in which the refractive index gradually decreases from the center of the core.

The temperature conditions for proceeding the polymerization reaction of the core liquid by heating vary depending on the size of the optical transmission medium to be obtained and the type of the core liquid used, but for example, a typical methacrylate-based monomer is used. When used, the temperature is preferably 50 ° C to 150 ° C, more preferably 80 ° C to 120 ° C. If it is lower than 50 ° C, the time required for production becomes extremely long, and if it exceeds 150 ° C, the polymerization reaction may proceed rapidly to cause foaming, which is not preferable.

The pressure applied to the core liquid varies depending on the type of the core liquid used and the size of the optical transmission medium to be obtained. For example, in the case of manufacturing a plastic optical transmission medium having an outer diameter of 26 mm and a length of 50 cm. Is preferably 0.
^{2kgf / cm 2 ~20kgf / cm 2} , more preferably in the range of ^{0.5kgf / cm 2 ~10kgf / cm 2} . If the pressure applied is less than 0.2 kgf / cm ² , the generation of cavities inside the optical transmission body cannot be prevented, and if it exceeds 20 kgf / cm ² , the cladding pipe may be damaged.

As a method for advancing the polymerization reaction of the core liquid while pressurizing, for example, JP-A-7-168028 is used.
As disclosed in Japanese Patent Laid-Open Publication No. JP-A-2004-242977, a core liquid is filled in a hollow tubular clad material having an opening at one end, and a polymerization reaction proceeds while pressurizing the liquid surface of the core liquid in the axial direction of the clad material. There is a way. In the case of this method, the clad material used is not one that swells or dissolves in the core liquid, and its purpose is also between the clad material and the core material in the optical transmission tube having a step index type (SI type) refractive index distribution. Since it is to prevent the adhesion failure of the above, the "pressurizable container having a straight pipe as an essential part" which is an essential requirement in the present invention is not required. However, when the clad pipe swells and dissolves in the core liquid as in the present invention, it is necessary to provide the above-described “pressurizable container having a straight pipe as an essential component” for dimensional accuracy. It is difficult to obtain a high plastic optical transmission medium, and the cladding pipe may be damaged even when the pressure applied is relatively low.

In the present invention, when the core liquid is polymerized, it is possible to rock the container in order to avoid the influence of gravity. As a method of rocking the container, for example, a method of causing the polymerization reaction to proceed in a state where the container is vertical or inclined and periodically inverting the container upside down is considered.

When the core liquid is polymerized as described above and taken out from the container, the generation of cavities is completely prevented, and
A plastic optical transmission body having a uniform refractive index distribution in the longitudinal direction and high dimensional accuracy can be obtained. As described above, this optical transmission body has a refractive index distribution in which the refractive index gradually decreases from the center of the core, and therefore, for example, as disclosed in Japanese Patent Laid-Open No. 5-241036. "G
It is suitable as a constituent material of "I-type plastic optical fiber". As a method for producing a GI type plastic optical fiber, in addition to the method disclosed in Japanese Patent Application Laid-Open No. 5-241036, the applicant of the present invention has a Japanese Patent Application No. 7-35042.
The method proposed in No. 5 can be adopted.

[0024]

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

Example 1 As a pressurizable container having a straight pipe as an essential component, an inner diameter 26
mm, an outer diameter of 30 mm, and a length of 50 cm were prepared, and 200 g of methyl methacrylate as a polymerizable raw material for the clad, 0.5 part by weight of benzoyl peroxide, 0.3 part of n-butyl mercaptan were prepared in the glass test tube.
Parts by weight were mixed and filled. This was rotated by a rotating device and heated to 70 ° C. while applying a centrifugal force to allow the polymerization reaction to proceed to produce a clad pipe along a glass test tube. Next, the glass test tube was placed vertically in an oil bath maintained at 90 ° C., and allowed to stand until the temperature became stable. Then, 68 g of methyl methacrylate as a core liquid and 17 g of benzyl benzoate were placed in a clad pipe in the glass test tube. 0.02 parts by weight of ditetrabutyl peroxide and 0.3 parts by weight of n-lauryl mercaptan were mixed and filled. After closing the opening of the glass test tube and replacing the remaining air with nitrogen gas, nitrogen gas was further supplied to add 0.5 kgf of core liquid.
Pressure was applied at a pressure of / cm ² , and polymerization was carried out for 24 hours while maintaining this pressurized state. Then, set the oil bath temperature to 9
The temperature was raised from 0 ° C. to 110 ° C., and the core liquid polymerization reaction was allowed to proceed for a further 48 hours. Finally, the glass test tube was taken out from the oil bath and cooled, and then the plastic optical transmission body was taken out from the inside of the glass test tube.

The thus obtained plastic optical transmission body (outer diameter 26 mm, length 50 cm) has a GI type refractive index distribution in which the refractive index gradually decreases from the center of the core. No cavities were generated, the variation of the outer diameter was 0.3%, and no deformation such as warpage was observed. Further, when the refractive index distributions were measured at positions of 10 cm from the upper end and one end of the plastic optical transmission body, respectively, both showed the same GI type refractive index distribution, and the influence of gravity was not recognized.

Example 2 As a pressurizable container having a straight pipe as an essential component, an inner diameter of 40
mm, an outer diameter of 60 mm, a length of 1 m, and a metal tube having flanges at both ends are prepared, and an opening at one end is sealed with a lid fitted to the flange, and then methyl methacrylate is used as a polymerizable raw material for the clad in the metal tube. 950 g, benzoyl peroxide 0.5 parts by weight, and n-butyl mercaptan 0.3 parts by weight were mixed and filled. This was rotated by a rotating device and heated to 70 ° C. while applying a centrifugal force to allow the polymerization reaction to proceed to produce a clad pipe along the metal pipe. Then, the metal tube was placed in an oil bath maintained at 90 ° C. at an angle of 45 ° and allowed to stand until the temperature became stable. Then, 320 g of methyl methacrylate as a core liquid in a clad pipe in the metal tube, Benzyl benzoate 80
g, ditetrabutyl peroxide 0.02 parts by weight, n
-0.3 parts by weight of lauryl mercaptan were mixed and filled.
After closing the opening of the metal tube and replacing the residual air with nitrogen gas, nitrogen gas was further supplied to add 2.0 kgf /
Pressurize with a pressure of cm ² , and while maintaining this pressurized state, 4
Polymerization was carried out for 8 hours. Then, set the oil bath temperature to 90
C. to 110.degree. C. and the polymerization reaction of the core liquid was allowed to proceed for 72 hours. In this example, since the length of the plastic optical transmission body to be manufactured is as long as 1 m, the metal tube in a tilted state is inverted and shaken every 10 minutes to avoid the influence of gravity. Moved.

Finally, after taking out the metal tube from the oil bath and cooling it, the plastic optical transmission body was taken out from the inside of the metal tube.

The plastic optical transmission body (outer diameter 40 mm, length 1 m) thus obtained has a GI type refractive index distribution in which the refractive index gradually decreases from the center of the core. No cavities were generated, and the variation of the outer diameter was 0.
It was 5%, and no deformation such as warpage was observed. Also, 10c from the top and one end of the plastic optical transmission body, respectively.
When the refractive index distribution at the position of m was measured, both showed the same GI type refractive index distribution, and no influence by gravity was recognized.

Comparative Example 1 A glass test tube having an inner diameter of 26 mm, an outer diameter of 30 mm and a length of 50 cm was prepared, and 200 g of methyl methacrylate as a polymerizable raw material for a clad, 0.5 part by weight of benzoyl peroxide, and n were prepared in the glass test tube. -Butyl mercaptan 0.3 parts by weight was mixed and filled. This was rotated by a rotating device and heated to 70 ° C. while applying a centrifugal force to allow the polymerization reaction to proceed to produce a clad pipe along a glass test tube. Then, in a clad pipe in a glass test tube, 68 g of methyl methacrylate, 17 g of benzyl benzoate, and 0.1 g of ditetrabutyl peroxide were added as core liquid.
02 parts by weight and 0.3 parts by weight of n-lauryl mercaptan were mixed and filled. Keep it horizontal in the rotator, 30r
While heating at 90 ℃ while rotating at a rotation speed of pm 24
Polymerization was carried out for a time.

The plastic optical transmission body thus obtained (outer diameter 26 mm, length 50 cm) has a GI type refractive index distribution in which the refractive index gradually decreases from the center of the core. However, a large number of cavities were generated inside the optical transmission body.

Comparative Example 2 A glass test tube having an inner diameter of 26 mm, an outer diameter of 30 mm and a length of 50 cm was prepared, and 200 g of methyl methacrylate as a polymerizable raw material for a clad, 0.5 part by weight of benzoyl peroxide, and n were prepared in the glass test tube. -Butyl mercaptan 0.3 parts by weight was mixed and filled. This was rotated by a rotating device and heated to 70 ° C. while applying a centrifugal force to allow the polymerization reaction to proceed to produce a clad pipe along a glass test tube. Next, the glass test tube was broken, the clad pipe was taken out, the opening at one end of the clad pipe was sealed, and the clad pipe was held vertically at the upper part of the oil bath maintained at 90 ° C., and the speed was set to 2 mm / min. While precipitating in an oil bath, 68 g of methyl methacrylate,
A core liquid prepared by mixing 17 g of benzyl benzoate, 0.02 part by weight of ditetrabutyl peroxide, and 0.3 part by weight of n-lauryl mercaptan was added dropwise into the clad pipe while adjusting the liquid level so as not to change.

The plastic optical transmission body thus obtained (outer diameter 26 mm, length 50 cm) has a GI type refractive index distribution in which the refractive index gradually decreases from the center of the core. Cavities were generated at three locations inside the optical transmission body, the variation of the outer diameter was 4.0%, and deformation such as warpage was also observed. Further, when the refractive index distribution was measured at a position of 10 cm from each of the upper end and one end of the plastic optical transmission medium, the refractive index distribution in the longitudinal direction of the optical transmission medium was non-uniform due to the influence of gravity. In Comparative Example 2, it was necessary to perform a test about three times until the supply rate of the core liquid and the polymerization conditions (heating conditions) were obtained, and it was very difficult to adjust the conditions.

[0034]

As described above in detail, according to the present invention, it is possible to easily manufacture a plastic optical transmission body in which the generation of cavities is completely prevented, the refractive index distribution in the longitudinal direction is uniform, and the dimensional accuracy is high. be able to. Since this plastic optical transmission body has a refractive index distribution in which the refractive index gradually decreases from the center of the core, it can be suitably used as a constituent material of a GI type plastic optical fiber.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Muramatsu 4830 Takatsuka-cho, Hamamatsu-shi, Shizuoka Prefecture Crabe Co., Ltd. (72) Inventor Masaki Takahashi 4830 Takatsuka-cho, Hamamatsu-shi, Shizuoka Prefecture Crabe Co., Ltd.

Claims (2)

[Claims] 1. A polymerizable raw material for clad is filled in a pressurizable container having a straight pipe as an essential component, and a clad pipe along the longitudinal direction of the straight pipe is manufactured by centrifugal force. Higher refractive index than, and filled in the container a core liquid consisting of a mixture of a polymerizable compound and a non-polymerizable compound that swells or dissolves the cladding pipe,
A method for producing a plastic optical transmission body, characterized in that the core liquid is polymerized under pressure with an inert gas. 2. The method for producing a plastic optical transmission article according to claim 1, wherein the container is rocked so as to avoid the influence of gravity when the core liquid is polymerized.