Tape for combining coated optical fibers and optical fiber unit

Abstract

Provided are a tape for combining coated optical fibers and an optical fiber unit formed using this tape, the tape being suitable for combining by a single bunching scheme in which one tape is helically wound around a coated optical fiber bundle.　This optical fiber unit is configured by helically winding, around the outer periphery of a coated optical fiber bundle, a tape (1) for combining coated optical fibers, of which the cross section perpendicular to a longitudinal direction has a sea-island structure in which a plurality of island components (12) comprising a second thermoplastic resin having a melting point higher than that of a first thermoplastic resin by 20°C or more are scattered in a sea component (11) comprising the first thermoplastic resin, the width (w) is 3.2-5.0 mm, the thickness (t) is 0.12 mm or less, the tensile elongation is 20-50%, and the thermal shrinkage rate when heated at 100°C for three hours is 1.1-1.5%.

Description

Optical Fiber Core Wire Binding Tape and Optical Fiber Unit

[0001] The present invention relates to an optical fiber core wire binding tape for binding optical fiber core wires and an optical fiber unit bound by the binding tape.

[0002] In high-density optical fiber cables, for example, an optical fiber unit in which a large number of optical fiber core wires are bound by a tape-shaped or string-shaped bundling material is used. As the bundling material used for such an optical fiber unit, a flat sea-island type composite fiber or tape composed of two types of thermoplastic resins having different melting points has been proposed (see, for example, Patent Documents 1 to 3).

[0003] In Patent Document 1, as a material suitable for the "cross bundling method" in which two bundling materials are wound in different twisting directions and their intersection portions are heat-sealed, the heat shrinkage rate after heating at 80°C for 6 hours is 0.2% or less, and two binding fibers are crossed at an intersection angle of 90°. An optical fiber unit binding fiber having a flatness ratio of 50% or more at the intersection of the binding fibers when heat pressure-bonded and heat-sealed at 150°C and 0.0245 MPa for 20 seconds has been proposed.

[0004] Further, in Patent Document 2, as a material used for the "single bundling method" in which one bundling material is wound in a spiral shape, the melting start temperature of the sea component is 100°C or higher, the melting peak temperature is 120 to 150°C, the width is 0.5 to 3.0 mm, the thickness is 0.15 mm or less, and the heat shrinkage rate after heating at 100°C for 3 hours is 1.0% or less. An optical fiber unit binding fiber has been proposed.

[0005] Furthermore, in Patent Document 3, an optical fiber core wire binding tape having a melting point of the sea component resin of 150 to 230°C, a melting point of the island component resin of 200 to 260°C, the melting point of the island component resin being 20°C or higher than the melting point of the sea component resin, a tensile elastic modulus of 4000 to 10000 MPa, and a diameter of the island component resin of 10 to 60 μm has been proposed. On the other hand, in order to easily take out the optical fiber core wire during branching work, an optical fiber unit using a bundling material having a heat shrinkage rate of 1.03% or less has also been proposed (see Patent Document 4).

[0006] Japanese Patent Publication No. 2013-037253, International Publication No. 2014 / 024720, Japanese Patent Publication No. 2021-157175, Japanese Patent Publication No. 2014-219530

[0007] However, the conventional bundle materials mentioned above have the following problems. The bundle materials described in Patent Documents 1 and 3 are intended for cross-bunching methods, so when used in single-bunching methods, the bundle material may not be strong enough, causing the optical fiber core to protrude or the bundle material to break. On the other hand, the bundle materials described in Patent Documents 2 and 4 are applied to single-bunching methods, but because the width of the bundle material is narrow, the binding of the bundle material to the optical fiber core is strong, which tends to increase transmission loss, and further performance improvements are needed.

[0008] Therefore, the present invention aims to provide an optical fiber core bundle tape suitable for bundled optical fiber cores using a single bunching method in which a single tape is spirally wrapped around an optical fiber core bundle, and an optical fiber unit formed using this bundled tape.

[0009] The optical fiber core bundling tape according to the present invention is wound spirally around an optical fiber core bundle in a single piece. The cross-section perpendicular to the longitudinal direction has a sea-island structure in which multiple island components made of a second thermoplastic resin having a melting point 20°C or more higher than that of the first thermoplastic resin are scattered within a sea component made of a first thermoplastic resin. The tape has a width of 3.2 to 5.0 mm, a thickness of 0.12 mm or less, a tensile elongation of 20 to 50%, and a thermal shrinkage rate of 1.1 to 1.5% when heated at 100°C for 3 hours. For example, the thermal shrinkage rate of this optical fiber core bundling tape can be made 0.25 to 0.5% when heated at 80°C for 6 hours. The optical fiber core bundling tape of the present invention may be formed by bundling multiple composite fibers having a sheath-core structure in which the sheath portion is made of a first thermoplastic resin and the core portion is made of a second thermoplastic resin, and fusing the sheath portions of each composite fiber into a single unit. In this case, the total fineness can be 3000 to 5000 dTex, and the number of filaments of the composite fiber can be 50 to 500. For example, the first thermoplastic resin in the optical fiber core bundling tape of the present invention can be a thermoplastic resin with a melting point of 100 to 260°C.

[0010] The optical fiber unit according to the present invention has one optical fiber core bundling tape, as described above, spirally wrapped around the outer circumference of an optical fiber core bundle, which is made up of multiple optical fiber cores.

[0011] According to the present invention, it is possible to realize an optical fiber core bundleing tape suitable for bundleing using a single-bunching method, and an optical fiber unit that can obtain stable performance even with a single-bunching method.

[0012] This figure schematically shows the cross-sectional structure of the optical fiber core bundling tape according to the first embodiment of the present invention. This is a schematic perspective view showing the sheath-core composite fiber bundle before fusion splicing. This is a schematic perspective view showing an example of the configuration of the optical fiber unit according to the second embodiment of the present invention.

[0013] The embodiments for carrying out the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below.

[0014] (First Embodiment) First, the fiber optic core bundle tape (hereinafter simply referred to as "bunching tape") according to the first embodiment of the present invention will be described. The bundle tape of this embodiment is used for bundles using a single bunching method and is wound spirally around a bundle of fiber optic cores as a single piece when manufacturing an optical fiber unit.

[0015] [Tape Structure] Figure 1 is a schematic diagram showing the cross-sectional structure of the bonding tape of this embodiment. As shown in Figure 1, the bonding tape 1 of this embodiment has a sea-island structure in which a cross section perpendicular to the longitudinal direction contains a sea component 11 made of a first thermoplastic resin, with a plurality of island components 12 made of a second thermoplastic resin having a melting point 20°C or more higher than that of the first thermoplastic resin.

[0016] The first thermoplastic resin forming the marine component 11 is not particularly limited and may be a single-component thermoplastic resin, a copolymer thermoplastic resin, or various modified thermoplastic resins. However, from the viewpoint of improving spinning stability and production stability during tape formation, it is preferable to use a resin with a melting point in the range of 100 to 260°C. Furthermore, from the viewpoint of improving spinning stability and tape properties, a polyolefin resin is preferred.

[0017] Specifically, the first thermoplastic resin forming the marine component 11 includes ethylene polymers such as high-density, medium-density, or low-density polyethylene and linear low-density polyethylene; copolymers of propylene and other α-olefins such as propylene-butene-1 random copolymer and propylene-ethylene-butene-1 random copolymer; amorphous propylene polymers such as soft polypropylene; and poly-4-methylpentene-1. These thermoplastic resins may be used individually or in combination of two or more types.

[0018] The second thermoplastic resin forming the island component 12 is not particularly limited as long as it has a melting point at least 20°C higher than the first thermoplastic resin described above and is melt-spinnable. Specifically, crystalline polypropylene, crystalline polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamide (nylon), and aromatic polyester resins (liquid crystal polymers) can be used. Among these resins, crystalline polypropylene, polyethylene terephthalate, and polyamide are preferred from the viewpoint of improving spinnability. The thermoplastic resins described above may be used individually or in combination of two or more.

[0019] The first and second thermoplastic resins described above may be colored, and may also have weather-resistant agents, heat-resistant agents, etc., added to them. Furthermore, other additives may be added as needed, to the extent that they do not impair the effects of the present invention. Examples of other additives added to thermoplastic resins include processing heat stabilizers, light stabilizers, ultraviolet absorbers, antioxidants, lubricants, colorants, antistatic agents, flame retardants, water-repellent agents, waterproofing agents, hydrophilicity-imparting agents, conductivity-imparting agents, thermal conductivity-imparting agents, electromagnetic wave shielding-imparting agents, light transmittance modifiers, fluorescent agents, sliding-imparting agents, transparency-imparting agents, antiblocking agents, metal deactivators, and antibacterial agents.

[0020] The aforementioned bonding tape 1 can be manufactured from composite fibers with a sheath-core structure. Figure 2 is a schematic perspective view showing a bundle of sheath-core composite fibers before fusion. As shown in Figure 2, the composite fiber 2 processed into the bonding tape 1 has a sheath portion 21 made of the aforementioned first thermoplastic resin and a core portion 22 made of the aforementioned second thermoplastic resin. Multiple such composite fibers 2 with a sheath-core structure are bundled together, and the sheath portions 21 are fused together to form a single composite fiber, thereby obtaining the bonding tape 1.

[0021] The composite fibers 2 constituting the bonding tape 1 preferably have a total fineness of 3000 to 5000 dTex and 50 to 500 filaments. This results in a bonding tape 1 with good flexibility that does not apply excessive lateral pressure to the optical fiber core bundle.

[0022] [Tape width w] When bundled with optical fiber cores using a single bunching method, if the tape width w of the bunching tape 1 is less than 3.2 mm, the tape strength will be insufficient, causing the optical fiber cores to protrude or the tape to break. On the other hand, if the tape width w of the bunching tape 1 exceeds 5.0 mm, the ability to follow the optical fiber core bundle will decrease. Therefore, in this embodiment, the tape width w of the bunching tape 1 is set to 3.2 to 5.0 mm.

[0023] [Tape Thickness t] If the tape thickness t of the bundling tape 1 exceeds 0.12 mm, handling during bundling may be reduced. Therefore, in the bundling tape 1 of this embodiment, the tape thickness t is set to 0.12 mm or less.

[0024] [Tensile Elongation] If the tensile elongation of the bonding tape 1 is less than 20%, breakage or cracking may occur in the tape when bonding the optical fiber cores, leading to poor quality of the manufactured optical fiber units. Furthermore, if the tensile elongation of the bonding tape 1 exceeds 50%, the tape stretches when bonding the optical fiber cores, reducing processability. Therefore, in this embodiment, the tensile elongation of the bonding tape 1 is set to a range of 20 to 50%.

[0025] The tensile elongation of the bonding tape 1 in this embodiment can be measured by conventionally known methods. For example, when measuring with the Tensilon universal material testing machine RTG-1210 manufactured by A&D Company, Limited, the measurement can be performed under conditions of a chuck distance of 200 mm and a tensile speed of 500 mm / min.

[0026] [Thermal Shrinkage Rate] The thermal shrinkage rate of the optical fiber core bundling tape 1 of this embodiment is in the range of 1.1 to 1.5% when heated at 100°C for 3 hours. If the thermal shrinkage rate when heated at 100°C for 3 hours is less than 1.1%, the holding power of the optical fiber cores after bundling will be weak. On the other hand, if the thermal shrinkage rate when heated at 100°C for 3 hours exceeds 1.5%, the tightening of the optical fiber cores will increase due to heat when forming the outermost sheath in the optical cable manufacturing process, increasing the transmission loss. Therefore, in the bundling tape of this embodiment, by setting the thermal shrinkage rate when heated at 100°C for 3 hours to 1.1 to 1.5%, it is possible to realize an optical fiber unit with low transmission loss and high holding power of the optical fiber cores.

[0027] Furthermore, the bonding tape 1 of this embodiment preferably has a thermal shrinkage rate of 0.25 to 0.5% when heated at 80°C for 6 hours. By setting the thermal shrinkage rate within this range when heated at 80°C for 6 hours, an optical fiber unit with low transmission loss and high retention force of the optical cable core can be obtained.

[0028] The heat shrinkage rate of the conjugation tape 1 can be measured by the following method. First, a 2m sample is cut from the conjugation fiber to be measured, and markings are accurately made at 1m intervals as the inspection length. The load used during marking is precisely defined to the inspection length and is standardized to a load equivalent to 0.0393 cN / dtex, which does not stretch the fiber. Then, the test piece is placed in a dry heat oven heated to 100°C or 80°C without load and subjected to a heat treatment for 3 or 6 hours until the heat shrinkage rate reaches saturation. Then, while applying a load of 0.0393 cN / dtex to the test piece, taking care not to twist it, the length of the marked area is measured, and the rate of change in the inspection length before and after the heat treatment is calculated as the heat shrinkage rate (%).

[0029] As detailed above, the binding tape of this embodiment has a wider width than conventional products, a tensile elongation of 20-50%, and a thermal shrinkage rate of 1.1-1.5% when heated at 100°C for 3 hours. This improves processability and reduces the likelihood of cracking or breaking of the tape during the binding process. As a result, the occurrence of quality defects is suppressed when the tapes are unitized, and a binding tape suitable for single-bunching binding can be realized.

[0030] (Second Embodiment) Next, an optical fiber unit according to a second embodiment of the present invention will be described. Figure 3 is a schematic perspective view showing an example of the configuration of the optical fiber unit of this embodiment. As shown in Figure 3, in the optical fiber unit 30 of this embodiment, one optical fiber bundle tape 1 of the first embodiment is wrapped around the outer circumference of an optical fiber bundle in which a plurality of optical fiber cores 3 are bundled together.

[0031] In this embodiment, the optical fiber unit uses an optical fiber core bundlening tape 1 with excellent processability, making it less likely for the tape to crack or break during the bundlening process, thus suppressing the occurrence of quality defects. Furthermore, in this embodiment, the bundlening tape 1 is wrapped using a single-bunching method, and since the tapes do not cross each other, the problem of thickness at the intersections does not occur, and stable performance can be obtained.

[0032] The optical fiber core wire 3 used in the optical fiber unit of this embodiment includes not only optical fiber strands, but also optical fiber dyed wires having a colored layer on the outside of the optical fiber strands, optical fiber tapes made by bundling multiple optical fiber dyed wires together and forming them into a tape shape with a tape layer, and intermittently fixed tape core wires in which single optical fiber strands are intermittently bonded.

[0033] As detailed above, the optical fiber unit of this embodiment uses a bundled tape with improved strength and handling properties, and bundles optical fiber cores using a single-bunching method, resulting in low transmission loss and high retention force of the optical cable cores. As a result, it is possible to realize an optical fiber unit with good quality and stable performance.

[0034] The effects of the present invention will be specifically described below with reference to examples and comparative examples. In this example, the bonding tapes of the example and comparative example were manufactured by the method shown below, and their processability was evaluated.

[0035] <Preparation of Conjugation Tape> A sheath-core composite fiber was formed using ethylene-polypropylene random copolymer (CoPP) with a melting point of 134°C as the sheath component and polyethylene terephthalate (PET) with a melting point of 256°C as the core component. From this composite fiber (single fiber), a tape-like sea-island type fiber (conjugation tape) of a predetermined width was prepared.

[0036] <Tape Width and Thickness> Using a microtome, a sample with a cross-section perpendicular to the longitudinal direction was cut from the conjugation tape. This tape cross-section sample was fixed to a horizontal sample stage and observed from directly above and to the side using a KEYENCE digital microscope (VHX-900), and photographed with a camera fitted with an appropriate magnifying lens. Next, the captured images were imported into a computer, and the length was measured by comparing the length of an arbitrary point with a reference length. The major axis was defined as the tape width and the minor axis as the tape thickness, and these dimensions were determined.

[0037] In this process, the tape width was measured with an accuracy of 1 / 10 mm using images taken with a 50x magnifying lens. The tape thickness was measured with an accuracy of 1 / 100 mm using images taken with a 175x magnifying lens. The dimensions of each part were measured five times at 1m intervals, and the average value was calculated.

[0038] <Tensile elongation> The tensile elongation of each holding tape in the examples and comparative examples was calculated from the following formula (1) by conducting a breaking test using a tensilon universal material testing machine RTG-1210 manufactured by A&D Company, Limited. At that time, the distance L between the chucks before the start of measurement ０ was set to 200 mm, the tensile speed was set to 500 mm / min, and the distance L between the chucks at the time of breakage was measured.

[0039]

[0040] <Heat shrinkage rate> The heat shrinkage rate at 100°C was measured by taking out a tape cut to a length of 1000 mm after curing it in an oven heated to 100°C for 3 hours and measuring the length T (mm). The heat shrinkage rate at 80°C was measured by taking out a tape cut to a length of 1000 mm after curing it in an oven heated to 80°C for 6 hours and measuring the length T (mm). Then, the heat shrinkage rate was calculated from the following formula (2).

[0041]

[0042] <Evaluation of workability> The workability of each holding tape in the examples and comparative examples was evaluated by winding one holding tape around a nylon tube with a diameter of 8 mm five times in the S direction at intervals of 80 mm, and visually checking whether "breakage", "cracks", or "slack" occurred in the optical fiber core wire holding tape. Here, "cracks" refer to a state where a crack penetrates in the thickness direction and extends 3 mm or more in the longitudinal direction in the wound part. Also, "slack" refers to a state where a gap of 1.5 mm or more occurs between the wound part and the nylon tube.

[0043] As a result, those in which "breakage", "cracks", or "slack" did not occur in the holding tape were regarded as having good workability (○), and those in which "breakage", "cracks", or "slack" occurred even at one location in the holding tape were regarded as having poor workability (×). The above results are shown in Tables 1 and 2 below.

[0044] <着

[0045]

[0046] As shown in Table 2, the bonding tapes of Comparative Examples 1 to 3 had widths of 1.20 to 2.80 mm, which is narrower than the range of the present invention, resulting in fracture. On the other hand, the bonding tape of Comparative Example 4 had a width exceeding 5.0 mm and a tensile elongation of less than 20%, resulting in reduced conformability and cracking. The bonding tape of Comparative Example 5 had a thickness exceeding 0.12 mm, which is thicker than the range of the present invention, resulting in reduced conformability and cracking. The bonding tape of Comparative Example 6 had a tensile elongation exceeding 50%, resulting in sagging.

[0047] The bonding tape of Comparative Example 7 had a thermal shrinkage rate of less than 1.1% after heating at 100°C for 3 hours, resulting in weak holding power and sagging. On the other hand, the tape of Comparative Example 8 had a thermal shrinkage rate of more than 1.5% after heating at 100°C for 3 hours, causing deformation of the nylon tube due to shrinkage, raising concerns about increased transmission loss when applied to optical fiber cables.

[0048] In contrast, the bonding tapes of Examples 1 to 4, which were manufactured within the scope of the present invention, did not exhibit "breakage," "cracking," or "sagging," and had good processability.

[0049] From the above results, it has been confirmed that the present invention makes it possible to realize a conjugation tape suitable for conjugation using a single-bunching method.

[0050] 1. Bundling tape 2. Composite fiber 3. Optical fiber core 11. Sea component (first thermoplastic resin) 12. Island component (second thermoplastic resin) 21. Sheath portion 22. Core portion 30. Optical fiber unit

Claims

1. A fiber optic core bonding tape that is wound spirally around a bundle of fiber optic cores, wherein the cross section perpendicular to the longitudinal direction has a sea-island structure in which multiple island components made of a second thermoplastic resin having a melting point 20°C or more higher than that of the first thermoplastic resin are scattered within a sea component made of a first thermoplastic resin, the tape has a width of 3.2 to 5.0 mm, a thickness of 0.12 mm or less, a tensile elongation of 20 to 50%, and a thermal shrinkage rate of 1.1 to 1.5% when heated at 100°C for 3 hours.

2. The optical fiber core bundling tape according to claim 1, wherein the thermal shrinkage rate when heated at 80°C for 6 hours is 0.25 to 0.5%.

3. A fiber optic core bundle tape according to claim 1 or 2, comprising a plurality of composite fibers having a sheath-core structure in which the sheath portion is made of the first thermoplastic resin and the core portion is made of the second thermoplastic resin, the sheath portions being fused together to form a single unit, the total fineness being 3000 to 5000 dTex, and the number of filaments of the composite fiber being 50 to 500.

4. The optical fiber core bonding tape according to any one of claims 1 to 3, wherein the first thermoplastic resin has a melting point of 100 to 260°C.

5. An optical fiber unit in which one optical fiber core bundling tape according to any one of claims 1 to 4 is spirally wound around the outer circumference of an optical fiber core bundle, which is made up of multiple optical fiber cores bundled together.

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