Tapes and optical fiber units for bundled optical fiber cores

Abstract

The present invention provides an optical fiber core bundling tape suitable as a bundling material for bundling multiple optical fiber cores, winding at least two bundling materials around them in different twisting directions, and heat-sealing the intersections of each bundling material to form a unit, and an optical fiber unit formed using this bundling tape. [Solution] An optical fiber core bundling tape 1 is constructed by wrapping one or more of these tapes around the outer circumference of an optical fiber core bundle, which is made up of multiple optical fiber cores. The tape has a cross section perpendicular to the longitudinal direction, forming a sea-island structure in which multiple 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, are scattered within a sea component 11 made of a first thermoplastic resin, and has a width w of 3.2 to 5.0 mm and a CV value (standard deviation / average width) of the tape width measured every 1 m in the longitudinal direction of 3% or less.

Description

Technical Field

[0001] The present invention relates to a tape for bundling optical fiber cores that bundles optical fiber cores and an optical fiber unit bundled by the bundling tape.

Background Art

[0002] In high-density optical fiber cables, for example, an optical fiber unit in which a large number of optical fiber cores are bundled 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] Patent Document 1 proposes an optical fiber unit bundling fiber that is suitable for the "cross-banding method" in which two bundling materials are wound in different twisting directions and their crossing portions are heat-sealed. The heat shrinkage rate after heating at 80°C for 6 hours is 0.2% or less, and the two bundling fibers are crossed at an intersection angle of 90°. When heat pressure bonding and heat sealing are performed at 150°C and 0.0245 MPa for 20 seconds, the intersection flatness rate of the bundling fibers is 50% or more.

[0004] Further, Patent Document 2 proposes an optical fiber unit bundling fiber used for the "single banding 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.

[0005] Furthermore, Patent Document 3 proposes a tape for bundling optical fiber cores, in which the melting point of the marine component resin is 150-230°C, the melting point of the island component resin is 200-260°C, the melting point of the island component resin is 20°C or more higher than the melting point of the marine component resin, the tensile modulus is 4000-10000 MPa, and the diameter of the island component resin is 10-60 μm. On the other hand, an optical fiber unit using a bundle material with a thermal shrinkage rate of 1.03% or less has also been proposed to allow for easy removal of optical fiber cores during branching operations (see Patent Document 4). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2013-037253 [Patent Document 2] International Publication No. 2014 / 024720 [Patent Document 3] Japanese Patent Publication No. 2021-157175 [Patent Document 4] Japanese Patent Publication No. 2014-219530 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, the conventional bundle materials mentioned above have a problem in that poor adhesion is likely to occur at the intersections when they are bundled using the cross-bunching method.

[0008] Therefore, the present invention aims to provide an optical fiber core bundling tape suitable as a bundling material when bundling multiple optical fiber cores, winding at least two bundling materials around them in different twisting directions, and heat-sealing the intersections of each bundling material to form a unit, and an optical fiber unit formed using this bundling tape. [Means for solving the problem]

[0009] The optical fiber core bundling tape according to the present invention has a sea-island structure in which a cross section perpendicular to the longitudinal direction contains 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, with a sea component made of a first thermoplastic resin. The tape has a width of 3.2 to 5.0 mm, and the CV value (standard deviation / average width) of the width measured every 1 m in the longitudinal direction is 3% or less. This optical fiber core bundling tape can achieve a thermal shrinkage rate of 1.1-1.5% when heated at 100°C for 3 hours, and a thermal shrinkage rate of 0.25-0.5% 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 the first thermoplastic resin in the optical fiber core bundling tape of the present invention, for example, a thermoplastic resin with a melting point of 100 to 260°C can be used.

[0010] The optical fiber unit according to the present invention has one or more of the aforementioned optical fiber core bundling tapes wrapped around the outer circumference of an optical fiber core bundle, which is made up of multiple optical fiber cores bundled together. [Effects of the Invention]

[0011] According to the present invention, it is possible to realize an optical fiber unit that improves adhesion defects at the intersections of optical fiber core bundlers and bundlers, which are suitable for bundlers using the cross-bunching method. [Brief explanation of the drawing]

[0012] [Figure 1] This figure schematically shows the cross-sectional structure of the optical fiber core bundling tape according to the first embodiment of the present invention. [Figure 2] This is a schematic perspective view showing a sheath-core composite fiber bundle before fusion. [Figure 3]Figures A and B are schematic perspective views showing an example configuration of an optical fiber unit according to a second embodiment of the present invention. [Modes for carrying out the 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 "bundling tape") according to the first embodiment of the present invention will be described. The bundlening tape of this embodiment has heat-sealing properties and is used for bundlening fiber optic cores.

[0015] [Tape Configuration] 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 monoplastic thermoplastic resin, a copolymer thermoplastic resin, or various modified thermoplastic resins. However, from the viewpoint of improving adhesion at the tape intersection during conjugation, it is preferable to use a resin with a melting point in the range of 100 to 260°C, and from the viewpoint of improving spinning stability and tape properties, a polyolefin resin is preferred.

[0017] Specifically, the first thermoplastic resin forming the sea 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 alone or in combination of two or more.

[0018] The second thermoplastic resin forming the island component 12 is not particularly limited as long as its melting point is 20°C or higher than that of the first thermoplastic resin described above and it can be melt-spun. 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, from the viewpoint of improving spinnability, crystalline polypropylene, polyethylene terephthalate, and polyamide are preferable. The above-mentioned thermoplastic resins may be used alone or in combination of two or more.

[0019] The above-mentioned binding tape 1 can be manufactured from composite fibers having a sheath-core structure. FIG. 2 is a perspective view schematically showing a sheath-core composite fiber bundle before fusion. As shown in FIG. 2, the composite fiber 2 processed into the binding tape 1 has a sheath portion 21 made of the first thermoplastic resin described above and a core portion 22 made of the second thermoplastic resin described above. Then, a plurality of these sheath-core composite fibers 2 are bundled, and the sheath portion 21 is fused and integrated to obtain the binding tape 1.

[0020] The composite fiber 2 constituting the binding tape 1 preferably has a total fineness of 3000 to 5000 dTex and a number of filaments of 50 to 500. Thereby, a binding tape 1 with good flexibility and stable in the longitudinal direction can be obtained.

[0021] [Width w] The bundling tape 1 in this embodiment has a width w of 3.2 to 5.0 mm. When connecting the ends of optical fiber cables, a wider bundling tape 1 is preferable because it improves adhesion and provides sufficient holding power as a bundling material. However, if the tape width w is less than 3.2 mm, the effect of improving adhesion is not obtained, and if the tape width w exceeds 5.0 mm, the elongation decreases, making it easier for problems such as breakage during processing or reduced heat adhesion to occur. The tape width w may be measured online.

[0022] [Vacuum value] In this embodiment, the bonding tape 1 has a CV value (standard deviation / average width) of 3% or less for the width w measured every 1m in the longitudinal direction. If the variation in the tape width w in the longitudinal direction is large, narrower sections may intersect, and in that case, the adhesive area becomes smaller compared to other intersections, and the tape thickness at the intersection increases, resulting in a significant decrease in thermal adhesion. Specifically, if the CV value exceeds 3 mass%, the adhesive strength at the intersection decreases and becomes insufficient.

[0023] [Thermal shrinkage rate] The bundling tape of this embodiment preferably has a thermal shrinkage rate of 1.1 to 1.5% when heated at 100°C for 3 hours, and more preferably has a thermal shrinkage rate of 0.25 to 0.5% when heated at 80°C for 6 hours. This makes it possible to maintain flexibility during bundling and suppress cable shrinkage due to heat during cable sheathing.

[0024] As described in detail above, the bundling tape of this embodiment has a wider tape width and a lower CV value than conventional products, thereby improving adhesion. As a result, even when wrapped around an optical fiber bundle using a cross-bunching method, the occurrence of adhesion defects at intersections is suppressed.

[0025] (Second embodiment) Next, an optical fiber unit according to a second embodiment of the present invention will be described. Figures 3A and 3B are schematic perspective views showing an example of the configuration of the optical fiber unit of this embodiment. As shown in Figures 3A and 3B, the optical fiber units 30 and 31 of this embodiment have one or more optical fiber bundle tapes 1 of the first embodiment wrapped around the outer circumference of an optical fiber bundle in which a plurality of optical fiber cores 3 are bundled together.

[0026] The method of bundled optical fiber cores 3 using the bundled tape 1 is not particularly limited, but it is suitable for the so-called "cross-bunching method" shown in Figure 3B, in which two bundle materials are wound in different twisting directions and their intersections are heat-fused. Furthermore, the optical fiber unit of this embodiment is not limited to the "cross-bunching method," and can also be suitably used for the so-called "single-bunching method" shown in Figure 3A, in which a single bundle material is wound spirally.

[0027] As described in detail above, since the optical fiber unit of this embodiment uses a bundling tape with improved adhesive properties, even when the bundling tape is wrapped around the optical fiber bundle using a cross-bunching method, the occurrence of adhesion defects at the intersections can be suppressed. [Examples]

[0028] The effects of the present invention will be specifically described below with reference to examples and comparative examples. In this example, the bundled tapes of the example and comparative example were manufactured by the method shown below, and each bundled tape was wrapped around an optical fiber core bundle using a cross-bunching method to create an optical fiber unit. The adhesion of the bundled tapes at the intersections of the fabricated optical fiber unit was then evaluated.

[0029] <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) with a width of 3.2 mm was produced.

[0030] <Fabrication of optical fiber units> Six layers of intermittently connected optical fiber tapes, each consisting of 12 optical fiber cores connected in parallel, were stacked. The tapes of the example and comparative example were then wrapped around these tapes using the cross-bunning method shown in Figure 3B to create a 72-core optical fiber unit.

[0031] <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 used as the tape width and the minor axis as the tape thickness, and these dimensions were determined.

[0032] 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.

[0033] <Adhesion Evaluation> The adhesion at the intersections was evaluated using the following method and conditions. First, the optical fiber unit prepared using the method described above was heat-treated at 140°C for 10 minutes to heat-bond the tape intersections. Next, the ease with which the 20 intersections could be peeled off was checked. As a result, if the intersections peeled off easily, it was classified as "poor adhesion," and if they did not peel off easily, it was classified as "good adhesion." Samples with a good adhesion rate of 90% or more were deemed acceptable.

[0034] The results are shown in Table 1 below.

[0035] [Table 1]

[0036] As shown in Table 1 above, the samples of Examples 1 to 4 showed fewer instances of adhesion defects at intersections and improved adhesion compared to the samples of Comparative Examples 1 to 4.

[0037] From the above results, it has been confirmed that, according to the present invention, a suitable optical fiber core bundling tape can be obtained as a bundle material when bundling multiple optical fiber cores, winding at least two bundle materials around them in different twisting directions, and heat-sealing the intersections of each bundle material to form a unit.

[0038] Furthermore, the present invention may also take the following forms. [1] A 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. Width is 3.2~5.0mm, The coefficient of variation (CV) of the width measured every 1 meter along the longitudinal direction is 3% or less. Tape for bundling optical fiber cores. [2] The optical fiber core bundling tape described in [1] has a thermal shrinkage rate of 1.1 to 1.5% when heated at 100°C for 3 hours. [3] A fiber optic core bundling tape as described in [1] or [2], wherein the thermal shrinkage rate when heated at 80°C for 6 hours is 0.25 to 0.5%. [4] Multiple composite fibers with a sheath-core structure, where the sheath portion is made of the first thermoplastic resin and the core portion is made of the second thermoplastic resin, are bundled together, and the sheath portions are fused together to form a single integrated structure. Total fiber density is 3000-5000 dTex. The number of filaments in the aforementioned composite fiber is 50 to 500. A tape for bundling optical fiber cores as described in any of [1] to [3]. [5] The first thermoplastic resin is a tape for bonding optical fiber cores according to any one of [1] to [4], wherein the melting point is 100 to 260°C. [6] An optical fiber unit in which one or more optical fiber core bundling tapes described in any of [1] to [5] are wrapped around the outer circumference of an optical fiber core bundle, which is made up of multiple optical fiber cores. [Explanation of Symbols]

[0039] 1. Conjugation tape 1a intersection 2 Composite Fibers 3 Optical fiber core 11 Marine components (first thermoplastic resin) 12 Island component (second thermoplastic resin) 21 Scabbard part 22 Core 30, 31 Fiber Optic Unit

Claims

1. A 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. Width is 3.2 to 5.0 mm. The CV value (standard deviation / mean width) of the width measured every 1 meter along the longitudinal direction is 3% or less. Tape for bundling optical fiber cores.

2. The optical fiber core bundling tape according to claim 1, wherein the thermal shrinkage rate when heated at 100°C for 3 hours is 1.1 to 1.5%.

3. 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%.

4. Multiple composite fibers with a sheath-core structure, where the sheath portion is made of the first thermoplastic resin and the core portion is made of the second thermoplastic resin, are bundled together, and the sheath portions are fused together to form a single integrated structure. Total fiber thickness is 3000-5000 dTex. The number of filaments in the aforementioned composite fiber is 50 to 500. The optical fiber core bundling tape according to claim 1.

5. The optical fiber core bonding tape according to claim 1, wherein the first thermoplastic resin has a melting point of 100 to 260°C.

6. An optical fiber unit in which one or more optical fiber core bundling tapes according to any one of claims 1 to 5 are wrapped 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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