JP3762489B2 - Multi-step index type plastic optical fiber and manufacturing method thereof - Google Patents

Description

【００３２】
【発明の効果】
以上説明したように、本発明によれば、グレーデッドインデックス型プラスチック光ファイバに準ずるマルチステップインデックス型プラスチック光ファイバを、安定した品質で経済的に大量生産することができる。
【図面の簡単な説明】
【図１】本発明の実施例に係るＰＭＭＡ樹脂とＡＳ樹脂の混合供給工程を説明するための図である。
【図２】本発明の実施例に係る「超多層複合紡糸ダイ」を概略的に示した断面図である。
【図３】本発明の実施例に係るプラスチック光ファイバを構成する各層の屈折率を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-step index type plastic optical fiber having a multi-step graded refractive index distribution having a high band and a continuous manufacturing method thereof, in accordance with a graded index type plastic optical fiber.
[0002]
[Prior art]
A graded index (GI) optical fiber is an optical fiber having a high refractive index at the center of the fiber and a refractive index that decreases in a second order distribution toward the outside, and is characterized by a wide transmission band.
[0003]
There have been many proposals for plastic GI fiber since the Showa 40's. Among them, the excellent ones developed by Keio University's Otsuka and Koike et al. Are known.
[0004]
These GI POFs are made by polymerizing a rod called a PMMA-based preform having a refractive index distribution in advance, and stretching it with heat to form a fiber. The point is that these preforms are polymerized in a PMMA pipe so that a refractive index gradient can be obtained, and mainly MMA monomer and a high refractive index polymerizable monomer or non-polymerizable compound are allowed to stand or rotate. It is produced by polymerizing and solidifying for a long time while paying close attention. The performance of this preform determines important performance such as transmission loss and transmission band of the GI fiber.
[0005]
[Problems to be solved by the invention]
The advantage of POF is that it has a large diameter and is easy to handle, but GI-type POF by the conventional preform method is the one in which the refractive index distribution is formed using the diffusion state of the molecules in the polymerization process. Too large ones are difficult to manufacture, and if a fiber with a relatively large diameter of about 0.5 mm to 1.0 mm is drawn to maintain the merit of POF, the fiber length obtained from the preform is short. Inferior to productivity. In fact, there is no prospect of mass production of such preform rods with industrially stable quality and economical production.
[0006]
An object of the present invention is to provide a novel GI-type POF that eliminates the disadvantages of the conventional preform method and enables mass production economically with stable quality and a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
The configuration of the present invention made to achieve the above object is as follows.
[0008]
That is, the first aspect of the present invention, a PMMA resin consisting mainly of methyl methacrylate as a first component resin, is mixed to the resin and Misshiburu can form a transparent resin, refractive index nd20 ° C. is the PMMA A resin whose absolute value is 0.01 or more different from the value of the resin is used as the second component resin, and the second component resin has a styrene structural unit of 78 to 85% by weight and an acrylonitrile structural unit of 22 to 15% by weight. a coalescing, these single component resins or mixed resins, the center has the highest refractive index, so that the refractive index towards its circumference outside is reduced almost secondary distribution shape, concentrically over at least 5 layers The multi-step index type plastic optical fiber is characterized in that it is arranged in the above.
[0009]
Further, a second aspect of the present invention is a method for producing the first multi-step index type plastic optical fiber according to the first aspect of the present invention, wherein the first component resin and the second component resin in a molten state are measured and mixed. Adjust the mixing ratio of both component resins using a gear pump with transfer performance, adjust the refractive index, and supply it to the “super multi-layer composite spinning die” with at least five layers. This is a continuous manufacturing method of multi-step index type plastic optical fibers which are arranged and arranged in multi-stages and concentric circles so that the refractive index decreases substantially in a quadratic distribution toward the outer circumference.
[0010]
The conventional manufacturing method of a graded index type plastic optical fiber is a method in which a refractive index gradient is given by diffusion of a monomer during polymerization of a rod called a preform, but the multi-step index type plastic optical fiber of the present invention is used. A fiber is a product in which resins having different refractive indexes are molded into multiple layers and is mass-productive. However, the refractive index gradient of the fiber is stepped. This is not always desirable, but it allows a compromise in terms of cost performance. If the number of steps is infinite, the refractive index gradient becomes smooth, but by using five or more steps, an improvement appears in the transmission band as a plastic optical fiber.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The first component resin according to the present invention is a homopolymer of methyl methacrylate or a copolymer with 50 wt% or more of acrylic acid ester, methacrylic acid ester, or other copolymerizable component. The preferred melt flow index of the PMMA-based resin is that the orifice diameter is 2 mm, the length is 8 mm, and the range of 0.2-60 g / 10 min at 230 ° C. and 3.8 kg load can be used. The thing of 0.0-40 g / 10min is preferable. In addition, as a consideration for eliminating foreign substances contained in these PMMA resins as much as possible and suppressing coloring due to heat, the resin is produced by a continuous solution polymerization method or a continuous bulk polymerization method, and the resin mixing described later is performed. It is preferable that the spinning process is incorporated into a continuous process.
[0012]
On the other hand, as the second component resin, it is necessary to select a miscible resin that is compatible with the PMMA resin and can be mixed in a molecular form. The reason for this is that, as will be described later, the resin layer is mixed and the refractive index is changed one after another, and the resin has good compatibility and smooth refractive index on the contact surface of each layer. This is important in that a distribution can be given. In addition, a resin that becomes miscible at 250 ° C. or lower must be selected because it is mixed in a molten state or is formed by composite spinning. Moreover, as another important property of these resins, the refractive index needs to be different from that of the PMMA resin. The absolute value of the difference in refractive index needs to be 0.01 or more at a refractive index nd20 ° C. with respect to the sodium D line as a guide.
[0013]
Examples of the second component resin include AS resin which is a copolymer of acrylonitrile and styrene. In particular, a copolymer having 78 to 85% by weight of styrene structural units and 22 to 15% by weight of acrylonitrile structural units may be subjected to a treatment such as mixing AS resin with PMMA resin at 250 ° C. or lower. It is preferable because it can be mixed completely miscible. In addition, as an effective resin, methyl methacrylate, unsaturated carboxylic acid such as methacrylic acid or acrylic acid, and aromatic vinyl compound such as styrene or α-methylstyrene are copolymerized, and a six-membered cyclized product is obtained by heat dehydration reaction. The contained copolymer is also preferably a resin having excellent compatibility. In addition, a copolymer of methyl methacrylate, styrene, and maleic anhydride is also preferable because it is a resin that is well compatible with the PMMA resin and becomes transparent.
[0014]
All of the second component resins described above are resins that can be produced by continuous solution polymerization or continuous bulk polymerization, and the first component resin and second component resin are produced by continuous polymerization. It is an optically superior resin composition that can be devolatilized from stage to stage, and can continue to the process of mixing and spinning in a continuous process while the resin is in a molten state, and has little contamination and heat history. Is preferable in that is processed.
[0015]
Other second component resins include vinylidene fluoride resins such as vinylidene fluoride-hexafluoroacetone copolymers, or ternary components obtained by adding trifluoroethylene or tetrafluoroethylene to these binary components. The above copolymers are very preferred. Further, a copolymer of vinylidene fluoride and hexafluoropropylene, or a ternary copolymer obtained by adding trifluoroethylene or tetrafluoroethylene to these binary components, and further vinylidene fluoride and tetrafluoroethylene. Binary copolymers, such as binary copolymers of vinylidene fluoride and trifluoroethylene, are resins that cannot be spun in a consistent process by continuous polymerization, but can be used as a second component resin. .
[0016]
Hereinafter, the second component resin will be described in detail as an AS resin.
[0017]
The refractive index of the AS resin varies depending on the amount of the acrylonitrile component. The AS resin having an acrylonitrile component of 20% by weight has a refractive index of nd20 ° C. of 1.5747, and the acrylonitrile component of 25% by weight has a refractive index of nd20 ° C. of 1.5695. is there.
[0018]
On the other hand, the refractive index nd20 ° C. of the PMMA resin is about 1.492. When both resins are mixed, a transparent resin composition is obtained, and the refractive index can be adjusted in proportion to the blending.
[0019]
The mixing of these resins and the supply of the mixed resin to the composite spinning die are advantageous in that they have a mixing function such as a gear pump and are quantitative. As a more preferable method, the PMMA resin and AS resin are each produced by a continuous polymerization method, and volatile components such as unreacted monomers and solvents are devolatilized in a continuous process, and a measuring device is used in a molten state. The mixing ratio of the PMMA resin and AS resin is adjusted in multiple stages so that the gradient of the refractive index is mixed in multiple stages, and is supplied to the composite spinning die via a mixing supply device such as a gear pump. Continuously manufactures plastic optical fibers that are arranged in multiple stages and concentric circles in such a way that the mixed resin with the highest AS concentration and the highest refractive index is placed, and the refractive index gradually decreases to a quadratic distribution. To do. At this time, the layer width in the fiber axial direction may or may not be uniform, but what is necessary is that the refractive index distribution in the axial direction is the highest in the center and goes outward. Accordingly, a structure in which the relationship between the position and the refractive index of the place decreases in a quadratic distribution form is sufficient.
[0020]
The preferred melt flow index of the AS resin is that the diameter of the orifice is 2 mm, the length is 8 mm, and the range of 0.2 to 60 g / 10 min at 230 ° C. and 3.8 kg load can be used. Those of ˜40 g / 10 min are preferred.
[0021]
Next, a specific example of a process from mixing of PMMA resin and AS resin to spinning will be described. First, the number of gear pumps corresponding to the number of resin layers is prepared, the number of rotations of each gear pump is set to a pre-calculated value, and the melted PMMA resin is weighed. On the other hand, the molten AS resin is mixed with the PMMA resin weighed in advance by each mixing gear pump connected to the discharge line of each gear pump of the PMMA resin. The rotation speed of the mixing gear pump is controlled in proportion to the cross-sectional area of each layer.
[0022]
By the way, the setting method of the rotation speed of the gear pump of PMMA resin is calculated from the refractive index and amount of the mixed resin supplied by the mixed gear pump. That is, a mixed resin having the highest AS concentration and a high refractive index is disposed at the center of the fiber, and the refractive index distribution is set so that the refractive index decreases in a substantially quadratic distribution toward the outer circumference. The ratio of AS resin and PMMA resin is calculated | required, and the quantity of PMMA resin is calculated | required from the whole quantity of those mixed resin. Of course, the actual operation may involve fine adjustment. Here, the quantity of AS resin can also be measured using a gear pump. However, it is preferable to avoid AS resin because it is easily gelled or colored.
[0023]
In this way, the resin with the refractive index gradient designed for each layer is supplied to the “super multilayer composite spinning die” by the designed cross-sectional integral. Here, the “super multi-layer composite spinning die” is a die having five or more layers including at least a central layer. The super multi-layer composite spinning die has a die plate corresponding to the number of layers as shown in FIG. 2, and a pipe for guiding the resin of the corresponding layer is preferably attached to the die plate. The larger the number of layers of the die, the more preferable the refractive index gradient becomes smoother, but the disadvantage is that the equipment cost is increased and the amount of resin per layer is reduced, so that the resin is easily deteriorated. The number of layers is preferably about 5 to 20 layers. In this way, the resin that has been supplied to the “ultra-multilayer composite spinning die” and has a multilayer structure is drawn down and drawn into a fiber having a diameter of about 0.25 to 2.0 mm.
[0024]
【Example】
An embodiment of the present invention will be described below.
[0025]
FIG. 1 shows a mixed supply process diagram of PMMA resin and AS resin, and FIG. 2 shows a composite spinning die.
[0026]
A copolymer of 98% by weight methyl methacrylate and 2% by weight methyl acrylate, polymerized continuously in the absence of oxygen, with a nd20 ° C. of 1.492 and a melt flow index of 9 g / 10 min was removed at 210 ° C. It supplied to the gear pumps P1-P9 from the volatile extruder. The discharge pipes of the gear pumps P1 to P9 are connected to the supply sides of the mixing gear pumps P11 to P19, respectively, and the PMMA resin measured by the gear pumps P1 to P9 is supplied to the mixing gear pumps P11 to P19. The discharge amounts of the gear pumps P1 to P9 are as shown in Table 1, respectively.
[0027]
On the other hand, 80% by weight styrene copolymer and 20% by weight acrylonitrile copolymerized by continuous solution polymerization in the absence of oxygen were devolatilized and extruded at 210 ° C with a nd20 ° C of 1.575 and a melt flow index of 10g / 10min. Supplied directly from the machine to the mixing gear pumps P11 to P19. And the discharge amount of P11-P19, ie, the amount of mixed resin, was set as Table 1.
[0028]
The discharge pipes of the mixing gear pumps P11 to P19 were connected to the receiving ports H1 to H9 of the “super multilayer composite spinning die” shown in FIG. The resin temperature was kept at 210 ° C. during these steps. The strand discharged from the exit of the “ultra-multilayer composite spinning die” was stretched and stretched to obtain a plastic optical fiber having a 9-layer structure and a diameter of 1.0 mm. And this plastic optical fiber was coat | covered with black polyethylene, and the cable was obtained.
[0029]
The refractive index nd of each layer constituting the plastic optical fiber is as shown in Table 1, and this is shown in FIG. In other words, the present plastic optical fiber has the highest refractive index at the center, and the refractive index decreases in a substantially quadratic distribution toward the outer circumference.
[0030]
The transmission loss of this plastic optical fiber was 300 dB / km at 650 nm. The transmission band of this plastic optical fiber was found to be 1 GHz / 50 m or more.
[0031]
[Table 1]

[0032]
【The invention's effect】
As described above, according to the present invention, it is possible to mass-produce multi-step index type plastic optical fibers according to graded index type plastic optical fibers with stable quality and economically.
[Brief description of the drawings]
FIG. 1 is a view for explaining a mixed supply process of PMMA resin and AS resin according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically showing an “super multilayer composite spinning die” according to an embodiment of the present invention.
FIG. 3 is a diagram showing the refractive index of each layer constituting the plastic optical fiber according to the embodiment of the present invention.

Claims (2)

The PMMA resin consisting mainly of methyl methacrylate as a first component resin, is mixed to the resin and Misshiburu can form a transparent resin, refractive index nd20 ° C. is in absolute value than the value of the PMMA resin 0 A resin having a difference of 0.01 or more is used as a second component resin, and the second component resin is a copolymer having a styrene structural unit of 78 to 85% by weight and an acrylonitrile structural unit of 22 to 15% by weight. Alternatively, the mixed resin is arranged in a concentric manner in at least five layers or more so that the center has the highest refractive index and the refractive index decreases in a quadratic distribution toward the outer circumference. Step index type plastic optical fiber. A method for producing a multi-step index plastic optical fiber according to claim 1 ,
The first component resin and the second component resin in the molten state are adjusted to a refractive index by adjusting the mixing ratio of the two component resins using a gear pump having meterability, mixing property and transfer performance, and at least five layers or more. Supply to the “ultra-multilayer composite spinning die”, arrange the mixed resin with the highest refractive index in the center, and multi-stage, concentric circles so that the refractive index decreases to a secondary distribution toward the outer circumference Manufacturing method of multi-step index type plastic optical fiber placed in

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