KR20050066213A - Method of preparing preform for step-index optical fiber - Google Patents

Abstract

The present invention relates to a method for producing a preform for a step index type plastic optical fiber, and more particularly, to prepare a plastic optical fiber preform by polymerizing a protective layer, a clad, and a core in order on a glass tube rotating by the centrifugal force. And it relates to a method of manufacturing the optical fiber by drawing it, the plastic optical fiber produced by the method of the present invention is excellent in mechanical properties such as bending, bending.

Description

Method of preparing preform for step index type plastic optical fiber {Method of preparing Preform for Step-Index Optical Fiber}

The present invention relates to a method for manufacturing a preform for a step index type plastic optical fiber, and more particularly, to a method for manufacturing a preform for a plastic optical fiber having a step-index type refractive index distribution by centrifugal force method.

Plastic optical fibers can be largely classified into step index type optical fibers having different refractive indices and clad refractive indices of cores used for lighting and display, and graded index optical fibers whose refractive indexes used for communication gradually increase from the outside to the inside. have. As described above, the step index type is most used for light transmission means, such as for lighting and display, but can also be used for signal transmission and sensors of A / V systems by greatly reducing the optical transmission loss of the plastic optical fiber. Recently, there have been attempts to use the multi-step index type for near field communication. The plastic optical fiber has a much larger diameter than the quartz optical fiber, and has a large numerical aperture due to the difference in refractive index, which is advantageous in transmitting light, and is expected to be applicable to a local area network having a large number of contacts.

Conventional step-index plastic optical fibers have generally been produced by direct radiation by continuous polymerization. In particular, a copolymer composed of polymethyl methacrylate as the core material and methyl methacrylate, methacrylate and fluoroalkyl methacrylate is used as the clad material. In addition, a protective layer (US Pat. No. 5,963,701 or Korean Patent No. 1999-014822) for protecting them uses a copolymer composed of vinylidene fluoride / tetrafluoroethylene. However, all of them produce a plastic optical fiber by melt spinning a copolymerization method and a commercially available copolymer, and thus have high initial investment costs, core and clad adhesion problems, and problems of copolymer contamination.

In order to solve the problems of the prior art as described above, the present invention is to produce a plastic optical fiber having a low loss, high numerical aperture, high mechanical strength by providing a method for producing a pre-index for the step index type plastic optical fiber using a centrifugal force.

That is, the present invention is one aspect

1) Copolymer of methyl methacrylate and tetrafluoroethylene / vinylidene fluoride, copolymer of vinylidene fluoride / hexafluoropropene and tetrafluoroethylene / vinylidene fluoride / hexafluoro Preparing a protective layer by adding an initiator and a chain transfer agent to a mixture of one selected from the group consisting of propene, injecting the same into a cylindrical glass reactor, and rotating the same to polymerize under centrifugal force;

2) after the step 1) is completed, adding a mixture of fluorinated alkyl methacrylate and methyl methacrylate to the reactor in rotation and polymerization while rotating to produce a clad; And

3) After the step 2) is completed, a method for producing a pre-index for the plastic step-index plastic optical fiber comprising the step of adding a methyl methacrylate, styrene or a copolymer thereof to the reactor and polymerized to produce a core To provide.

Another aspect of the present invention is to provide a preform manufactured according to the above method and a method for manufacturing a step index plastic fiber manufactured by stretching the same.

The present invention will be described in more detail below.

In the present invention, the pre-form of the step-index type plastic optical fiber is manufactured by the centrifugal force method rather than the conventional continuous spinning method, and the process is as follows.

Copolymer of methyl methacrylate with tetrafluoroethylene / vinylidene fluoride, copolymer of vinylidene fluoride / hexafluoropropene, and tetrafluoro as a first step in preparing a preform for plastic optical fibers of the present invention Into a mixture of one selected from the group consisting of copolymers of ethylene / vinylidene fluoride / hexafluoropropene, an initiator and a chain transfer agent were added to the cylindrical glass reactor, and then rotated and polymerized under centrifugal force. Prepare a protective layer.

Tetrafluoroethylene / vinylidene fluoride copolymers, copolymers of vinylidene fluoride / hexafluoropropene, or tetrafluoroethylene / vinylidene fluoride / commonly used for melt spinning by direct spinning The hexafluoropropene copolymer is used for the production of preforms for plastic optical fibers using centrifugal force, which not only corrects optical loss due to bending of the core / clad, but also improves mechanical properties of the plastic optical fiber.

In step 1), a copolymer of 50 to 90% by weight of methyl methacrylate with tetrafluoroethylene / vinylidene fluoride, vinylidene fluoride / hexafluoropropene copolymer, and tetrafluoroethylene A mixed solution is prepared by mixing one selected from the group consisting of copolymers of vinylidene fluoride and hexafluoropropene at 10 to 50% by weight. At this time, when the methyl methacrylate is less than 50% by weight, copolymers such as tetrafluoroethylene / vinylidene fluoride do not exist in the methyl methacrylate as a dispersed phase and the viscosity is also increased, making it difficult to apply in the process. If the acrylate exceeds 90% by weight, the amount of tetrafluoroethylene / vinylidene fluoride copolymer is too small to serve as a protective layer.

The composition of the tetrafluoroethylene / vinylidene fluoride copolymer used in the protective layer in the present invention should be composed of 60 to 90 mol% of tetrafluoroethylene, 10 to 40 mol% of vinylidene fluoride and If the composition is out of the composition it becomes difficult to exhibit the properties that can be used as a protective layer.

The copolymer of vinylidene fluoride / hexafluoropropene used in the protective layer is composed of 70 to 90 mol% of vinylidene fluoride and 10 to 30 mol% of hexafluoropropene. It is difficult to show the physical properties as a layer.

It is also possible to use a copolymer composed of tetrafluoroethylene / vinylidene fluoride / hexafluoropropene, wherein the composition of the copolymer is 60 to 90 mol% of tetrafluoroethylene and 5 to 5 vinylidene fluoride. It is 30 mol% and 1-20 mol% of hexafluoroethylene, and when it is out of the said composition, it is hard to show the physical property as a protective layer.

In polymerizing the protective layer of the first step with the mixed solution prepared as described above, at least one selected from the group consisting of BPO (benzoylperoxide) and AIBN as an initiator is added to 0.01 ~ 0.1 mol%, mercaptan as a chain transfer agent At least 1 type of compound is added, Preferably n-butyl mercaptan is added at 0.05-0.5 mol%, Then, a liquid mixture is thrown into a glass tube, and it rotates at a rotation speed of 1,000-10,000 rpm. At this time, the rotation speed is sufficient if the mixed liquid is more than enough to cover the inside of the glass tube evenly, but less than 1000rpm there is a disadvantage of uneven dispersion, if more than 10,000rpm is difficult to manufacture equipment More than that is possible.

The polymerization is carried out at a polymerization temperature of 60 ~ 150 ℃. If the polymerization temperature is less than 60 ℃ polymerization time is long, if the polymerization temperature is higher than 150 ℃ methyl methacrylate is evaporated and practically unable to polymerize.

When the protective layer polymerization of the first step is completed, as a second step for the preparation of the plastic optical fiber preform of the present invention, the mixture is composed of 50 to 90% by weight of methyl methacrylate and 10 to 50% by weight of fluorine-substituted alkyl methacrylate. In the same manner as described above, 0.01 to 0.1 mol% of at least one selected from the group consisting of BPO and AIBN is added as an initiator, and at least one of mercaptan compounds is preferably used as a chain transfer agent, preferably n-butyl mercaptan is 0.05 to 0.5. After adding it in mol%, the mixed liquid is put into a glass tube and rotated at a rotational speed of 1,000 to 10,000 rpm to polymerize the clad. The fluorine-substituted alkyl methacrylates include trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, pentafluoropropyl methacrylate, hexafluoro isomethacrylate, octafluoro pentyl methacrylate, And at least one copolymer selected from the group consisting of dodecafluoro heptyl methacrylate.

After the second stage of the clad polymerization, as a third step for the preparation of the plastic optical fiber preform of the present invention, 0.01 to 0.1 mol% of methyl methacrylate, styrene or a copolymer thereof as the same initiator, After adding 0.05-0.5 mol% as a chain transfer agent, a mixed liquid is put into a glass tube, it rotates at a rotation speed of 1,000-10,000 rpm, and polymerizes a core.

The preform for the plastic optical fiber manufactured as described above is manufactured as a step index plastic optical fiber through a drawing process.

That is, after completion of the polymerization of the core through the first step to the third step, the preform is separated from the glass tube, and then put in a vacuum oven at a temperature of 70 ~ 120 ℃, to remove the residual monomers and additives obtained as a result Drawing on the preform with heat produces a plastic optical fiber.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the following examples are for the purpose of explanation and are not intended to limit the present invention.

The bending characteristics of the optical fiber manufactured in Example were tested for how many times the fracture occurred after bending at an angle of 90 degrees and a speed of 90 times / min, and the flexibility was measured 20 times in a cylinder having various diameters. The measurement was made based on the time when no fracture occurred when wound. In addition, the measurement of the optical loss was measured by a method of cut-backing 30m optical fibers 10 times every 3m.

Example 1

AIBN 0.06 as an initiator in a dispersion consisting of 30% by weight of a copolymer of tetrafluoroethylene / vinylidene fluoride having a polymerization ratio of 20 mol% / 80 mol% and 70% by weight of methyl methacrylate in a glass tube rotated by centrifugal force. N-butyl mercaptan 0.3 mol% was added as a mole% and a chain transfer agent, followed by polymerization at 90 ° C. while rotating at a rotational speed of 3,000 rpm to prepare a protective layer. 90 wt% of methyl methacrylate and 10 wt% of trifluoroethyl methacrylate were added to the same amount as the initiator and the chain transfer agent to make a mixed solution, and the same was added to the glass tube in which the protective layer was prepared. The clad was polymerized under the conditions. Subsequently, a mixed solution in which an initiator and a chain transfer agent were added to methyl methacrylate in the same amount as above was added to a rotating glass tube through several steps to prepare a preform by polymerization under the same conditions. The prepared preform was drawn to prepare a plastic optical fiber. Physical and optical properties at this time are shown in Table 1.

Example 2

0.06 mol of AIBN as an initiator in a dispersion composed of 20 wt% of a copolymer of tetrafluoroethylene / vinylidene fluoride having a polymerization ratio of 20 mol% / 80 mol% in a glass tube rotating by centrifugal force and 80 wt% of methyl methacrylate. 0.3 mol% of n-butyl mercaptan was added as a% and a chain transfer agent, followed by polymerization at a polymerization temperature of 90 ° C. while rotating at a rotational speed of 3,000 rpm to prepare a protective layer. 90% by weight of methyl methacrylate and 10% by weight of trifluoroethyl methacrylate were added an initiator and a chain transfer agent in the same amounts as above to form a mixed solution and put into a glass tube in which the protective layer was prepared. The clad was polymerized at. Subsequently, a mixed solution in which an initiator and a chain transfer agent were added to methyl methacrylate in the same amount as described above was added to a rotating glass tube through several steps to prepare a preform by polymerization under the same conditions. The prepared preform was drawn to prepare a plastic optical fiber. Physical and optical properties at this time are shown in Table 1.

Example 3

AIBN as an initiator in a mixed solution consisting of 30% by weight of a copolymer of vinylidene fluoride / hexafluoropropene having a polymerization ratio of 88 mol% / 12 mol% and 70% by weight of methyl methacrylate in a glass tube rotating by centrifugal force. After inserting 0.06 mol% and 0.3 mol% of n-butyl mercaptans as a chain transfer agent, it superposed | polymerized at the polymerization temperature of 90 degreeC, rotating at 3,000 rpm, and the protective layer was prepared. 90% by weight of methyl methacrylate and 10% by weight of trifluoroethyl methacrylate were added an initiator and a chain transfer agent in the same amounts to form a mixed solution, and the clad was added to a glass tube in which the protective layer was prepared. The polymerization was carried out under the same conditions. In addition, a mixture obtained by adding an initiator and a chain transfer agent to methyl methacrylate in an amount equal to the above amount was added to a rotating glass tube over several steps to polymerize under the same conditions, thereby preparing a preform. The prepared preform was drawn to prepare a plastic optical fiber. The physical characteristics and optical characteristics at this time are shown in Table 1.

Example 4

30 wt% of tetrafluoroethylene / vinylidene fluoride / hexafluoropropene having a polymerization ratio of 18 mol% / 72 mol% / 10 mol% in a glass tube rotating by centrifugal force, 70 weight of methyl methacrylate 0.06 mol% of AIBN as an initiator and 0.3 mol% of n-butyl mercaptan as a chain transfer agent were added to a dispersion composed of%, followed by polymerization at a polymerization temperature of 90 ° C. while rotating at a rotational speed of 3,000 rpm to prepare a protective layer. 90% by weight of methyl methacrylate and 10% by weight of trifluoroethyl methacrylate were added an initiator and a chain transfer agent in the same amounts to form a mixed solution, and the clad was added to a glass tube in which the protective layer was prepared. The polymerization was carried out under the same conditions. In addition, a mixture obtained by adding an initiator and a chain transfer agent to methyl methacrylate in an amount equal to the above amount was added to a rotating glass tube over several steps to polymerize under the same conditions, thereby preparing a preform. The prepared preform was drawn to prepare a plastic optical fiber. The physical characteristics and optical characteristics at this time are shown in Table 1.

Comparative Example 1

N-butyl mercaptan as a initiator and 0.06 mol% of AIBN as a initiator and a chain transfer agent in a mixed solution of 90% by weight of methyl methacrylate and 10% by weight of trifluoroethyl methacrylate without preparing a protective layer in a glass tube rotated by centrifugal force After the addition of 0.3 mol% was polymerized at a polymerization temperature of 90 ℃ while rotating at a rotational speed of 3,000rpm to prepare a clad. In addition, a mixture obtained by adding an initiator and a chain transfer agent to methyl methacrylate in the same amount as described above was added to a rotating glass tube over several steps to polymerize under the same conditions to prepare a preform. The prepared preform was drawn to prepare a plastic optical fiber. Physical and optical properties at this time are summarized in Table 1.

Bend Characteristics (times) Flexibility (φ) Transmission loss (dB / km) Example 1 10 1.5 173 Example 2 8 3 175 Example 3 10 1.5 211 Example 4 8 3 228 Comparative Example 1 One 15 180

The step-index plastic optical fiber of the present invention can be polymerized using centrifugal force while copolymerizing tetrafluoroethylene and vinylidene fluoride or copolymers of tetrafluoroethylene, vinylidene fluoride and hexafluoropropene to methylmethacryl. By polymerizing and manufacturing at a rate, it is possible to provide a plastic optical fiber with significantly improved physical properties such as bending and flexibility.

1 is a schematic diagram of a method for producing a preform for a step index type plastic optical fiber under centrifugal force.

Claims (8)

1) Copolymer of methyl methacrylate and tetrafluoroethylene / vinylidene fluoride, copolymer of vinylidene fluoride / hexafluoropropene and tetrafluoroethylene / vinylidene fluoride / hexafluoro Adding an initiator and a chain transfer agent to a mixture of one selected from the group consisting of a copolymer of propene, injecting the same into a cylindrical glass reactor and rotating the polymer to rotate under centrifugal force to prepare a protective layer; 2) after the step 1) is completed, adding a mixture of fluorinated alkyl methacrylate and methyl methacrylate to the reactor and rotating to polymerize it while producing a clad; And 3) After the step 2) is completed, the step of preparing a step index-type plastic optical fiber preform comprising the step of adding a methyl methacrylate, styrene or a copolymer thereof to the reactor and polymerized. According to claim 1, wherein the copolymer of tetrafluoroethylene and vinylidene fluoride with 50 to 90% by weight of methyl methacrylate of step 1), copolymer of vinylidene fluoride and hexafluoropropene, and tetra A method for producing a preindex for a step-index plastic optical fiber, characterized in that 10 to 50% by weight of one selected from the group consisting of a copolymer of fluoroethylene, vinylidene fluoride and hexafluoropropene. According to claim 2, wherein the tetrafluoroethylene and vinylidene fluoride copolymer composition is 60 to 90 mol% of tetrafluoroethylene, 10 to 40 mol% of vinylidene fluoride is characterized in that the copolymer A method of manufacturing a preform for a step index type plastic optical fiber. The composition of the vinylidene fluoride and hexafluoropropene copolymer is 70 to 90 mol% of vinylidene fluoride, and 10 to 30 mol% of hexafluoropropene. A method of manufacturing a preform for a step index type plastic optical fiber. According to claim 2, wherein the composition of the tetrafluoroethylene, vinylidene fluoride and hexafluoropropene copolymer is 60 to 90 mol% of tetrafluoroethylene, 5 to 30 mol% of vinylidene fluoride A method for producing a preindex for a step index type plastic optical fiber, characterized in that 1 to 20 mol% of hexafluoroprolene. The method of claim 1, wherein the fluorinated alkyl methacrylate of step 2) is trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, pentafluoropropyl methacrylate, hexafluoroisomethacrylate, octa A method for producing a pre-index for a step index type plastic optical fiber, characterized in that at least one member selected from the group consisting of fluoropentyl methacrylate and dodecafluoroheptyl methacrylate. A preform for plastic optical fibers prepared according to any one of claims 1 to 6. Plastic optical fiber produced by stretching the preform of claim 7.